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Author SHA1 Message Date
Yosry Ahmed
b786e34cde KVM: nSVM: Drop nested_vmcb_check_{save/control}() wrappers
The wrappers provide little value and make it harder to see what KVM is
checking in the normal flow. Drop them.

Opportunistically fixup comments referring to the functions, adding '()'
to make it clear it's a reference to a function.

No functional change intended.

Co-developed-by: Sean Christopherson <seanjc@google.com>
Cc: stable@vger.kernel.org
Signed-off-by: Yosry Ahmed <yosry@kernel.org>
Link: https://patch.msgid.link/20260303003421.2185681-14-yosry@kernel.org
Signed-off-by: Sean Christopherson <seanjc@google.com>
2026-03-04 16:08:51 -08:00
Yosry Ahmed
8998e1d012 KVM: nSVM: Clear tracking of L1->L2 NMI and soft IRQ on nested #VMEXIT
KVM clears tracking of L1->L2 injected NMIs (i.e. nmi_l1_to_l2) and soft
IRQs (i.e. soft_int_injected) on a synthesized #VMEXIT(INVALID) due to
failed VMRUN. However, they are not explicitly cleared in other
synthesized #VMEXITs.

soft_int_injected is always cleared after the first VMRUN of L2 when
completing interrupts, as any re-injection is then tracked by KVM
(instead of purely in vmcb02).

nmi_l1_to_l2 is not cleared after the first VMRUN if NMI injection
failed, as KVM still needs to keep track that the NMI originated from L1
to avoid blocking NMIs for L1. It is only cleared when the NMI injection
succeeds.

KVM could synthesize a #VMEXIT to L1 before successfully injecting the
NMI into L2 (e.g. due to a #NPF on L2's NMI handler in L1's NPTs). In
this case, nmi_l1_to_l2 will remain true, and KVM may not correctly mask
NMIs and intercept IRET when injecting an NMI into L1.

Clear both nmi_l1_to_l2 and soft_int_injected in nested_svm_vmexit(), i.e.
for all #VMEXITs except those that occur due to failed consistency checks,
as those happen before nmi_l1_to_l2 or soft_int_injected are set.

Fixes: 159fc6fa3b ("KVM: nSVM: Transparently handle L1 -> L2 NMI re-injection")
Cc: stable@vger.kernel.org
Signed-off-by: Yosry Ahmed <yosry@kernel.org>
Link: https://patch.msgid.link/20260303003421.2185681-13-yosry@kernel.org
Signed-off-by: Sean Christopherson <seanjc@google.com>
2026-03-04 16:08:50 -08:00
Yosry Ahmed
69b721a86d KVM: nSVM: Clear EVENTINJ fields in vmcb12 on nested #VMEXIT
According to the APM, from the reference of the VMRUN instruction:

  Upon #VMEXIT, the processor performs the following actions in order to
  return to the host execution context:

  ...

  clear EVENTINJ field in VMCB

KVM already syncs EVENTINJ fields from vmcb02 to cached vmcb12 on every
L2->L0  #VMEXIT. Since these fields are zeroed by the CPU on #VMEXIT, they
will mostly be zeroed in vmcb12 on nested #VMEXIT by nested_svm_vmexit().

However, this is not the case when:

  1. Consistency checks fail, as nested_svm_vmexit() is not called.
  2. Entering guest mode fails before L2 runs (e.g. due to failed load of
     CR3).

(2) was broken by commit 2d8a42be0e ("KVM: nSVM: synchronize VMCB
controls updated by the processor on every vmexit"), as prior to that
nested_svm_vmexit() always zeroed EVENTINJ fields.

Explicitly clear the fields in all nested #VMEXIT code paths.

Fixes: 3d6368ef58 ("KVM: SVM: Add VMRUN handler")
Fixes: 2d8a42be0e ("KVM: nSVM: synchronize VMCB controls updated by the processor on every vmexit")
Cc: stable@vger.kernel.org
Signed-off-by: Yosry Ahmed <yosry@kernel.org>
Link: https://patch.msgid.link/20260303003421.2185681-12-yosry@kernel.org
[sean: massage changelog formatting]
Signed-off-by: Sean Christopherson <seanjc@google.com>
2026-03-04 16:08:50 -08:00
Yosry Ahmed
f85a6ce06e KVM: nSVM: Clear GIF on nested #VMEXIT(INVALID)
According to the APM, GIF is set to 0 on any #VMEXIT, including
an #VMEXIT(INVALID) due to failed consistency checks. Clear GIF on
consistency check failures.

Fixes: 3d6368ef58 ("KVM: SVM: Add VMRUN handler")
Cc: stable@vger.kernel.org
Signed-off-by: Yosry Ahmed <yosry@kernel.org>
Link: https://patch.msgid.link/20260303003421.2185681-11-yosry@kernel.org
Signed-off-by: Sean Christopherson <seanjc@google.com>
2026-03-04 16:08:49 -08:00
Yosry Ahmed
5d291ef058 KVM: nSVM: Triple fault if restore host CR3 fails on nested #VMEXIT
If loading L1's CR3 fails on a nested #VMEXIT, nested_svm_vmexit()
returns an error code that is ignored by most callers, and continues to
run L1 with corrupted state. A sane recovery is not possible in this
case, and HW behavior is to cause a shutdown. Inject a triple fault
instead, and do not return early from nested_svm_vmexit(). Continue
cleaning up the vCPU state (e.g. clear pending exceptions), to handle
the failure as gracefully as possible.

From the APM:

  Upon #VMEXIT, the processor performs the following actions in order to
  return to the host execution context:

  ...

  if (illegal host state loaded, or exception while loading host state)
      shutdown
  else
      execute first host instruction following the VMRUN

Remove the return value of nested_svm_vmexit(), which is mostly
unchecked anyway.

Fixes: d82aaef9c8 ("KVM: nSVM: use nested_svm_load_cr3() on guest->host switch")
CC: stable@vger.kernel.org
Signed-off-by: Yosry Ahmed <yosry@kernel.org>
Link: https://patch.msgid.link/20260303003421.2185681-10-yosry@kernel.org
Signed-off-by: Sean Christopherson <seanjc@google.com>
2026-03-04 16:08:48 -08:00
Yosry Ahmed
1b30e75517 KVM: nSVM: Triple fault if mapping VMCB12 fails on nested #VMEXIT
KVM currently injects a #GP and hopes for the best if mapping VMCB12
fails on nested #VMEXIT, and only if the failure mode is -EINVAL.
Mapping the VMCB12 could also fail if creating host mappings fails.

After the #GP is injected, nested_svm_vmexit() bails early, without
cleaning up (e.g. KVM_REQ_GET_NESTED_STATE_PAGES is set, is_guest_mode()
is true, etc).

Instead of optionally injecting a #GP, triple fault the guest if mapping
VMCB12 fails since KVM cannot make a sane recovery. The APM states that
a #VMEXIT will triple fault if host state is illegal or an exception
occurs while loading host state, so the behavior is not entirely made
up.

Do not return early from nested_svm_vmexit(), continue cleaning up the
vCPU state (e.g. switch back to vmcb01), to handle the failure as
gracefully as possible.

Fixes: cf74a78b22 ("KVM: SVM: Add VMEXIT handler and intercepts")
CC: stable@vger.kernel.org
Co-developed-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Yosry Ahmed <yosry@kernel.org>
Link: https://patch.msgid.link/20260303003421.2185681-9-yosry@kernel.org
Signed-off-by: Sean Christopherson <seanjc@google.com>
2026-03-04 16:08:48 -08:00
Yosry Ahmed
dcf3648ab7 KVM: nSVM: Refactor writing vmcb12 on nested #VMEXIT as a helper
Move mapping vmcb12 and updating it out of nested_svm_vmexit() into a
helper, no functional change intended.

CC: stable@vger.kernel.org
Co-developed-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Yosry Ahmed <yosry@kernel.org>
Link: https://patch.msgid.link/20260303003421.2185681-8-yosry@kernel.org
Signed-off-by: Sean Christopherson <seanjc@google.com>
2026-03-04 16:08:47 -08:00
Yosry Ahmed
290c8d8202 KVM: nSVM: Refactor checking LBRV enablement in vmcb12 into a helper
Refactor the vCPU cap and vmcb12 flag checks into a helper. The
unlikely() annotation is dropped, it's unlikely (huh) to make a
difference and the CPU will probably predict it better on its own.

CC: stable@vger.kernel.org
Co-developed-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Yosry Ahmed <yosry@kernel.org>
Link: https://patch.msgid.link/20260303003421.2185681-7-yosry@kernel.org
Signed-off-by: Sean Christopherson <seanjc@google.com>
2026-03-04 16:08:46 -08:00
Yosry Ahmed
01ddcdc55e KVM: nSVM: Always inject a #GP if mapping VMCB12 fails on nested VMRUN
nested_svm_vmrun() currently only injects a #GP if kvm_vcpu_map() fails
with -EINVAL. But it could also fail with -EFAULT if creating a host
mapping failed. Inject a #GP in all cases, no reason to treat failure
modes differently.

Fixes: 8c5fbf1a72 ("KVM/nSVM: Use the new mapping API for mapping guest memory")
CC: stable@vger.kernel.org
Co-developed-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Yosry Ahmed <yosry@kernel.org>
Link: https://patch.msgid.link/20260303003421.2185681-6-yosry@kernel.org
Signed-off-by: Sean Christopherson <seanjc@google.com>
2026-03-04 16:08:46 -08:00
Yosry Ahmed
ac17892e51 KVM: selftests: Add a test for LBR save/restore (ft. nested)
Add a selftest exercising save/restore with usage of LBRs in both L1 and
L2, and making sure all LBRs remain intact.

Signed-off-by: Yosry Ahmed <yosry@kernel.org>
Link: https://patch.msgid.link/20260303003421.2185681-5-yosry@kernel.org
Signed-off-by: Sean Christopherson <seanjc@google.com>
2026-03-04 16:08:45 -08:00
Yosry Ahmed
3700f0788d KVM: SVM: Add missing save/restore handling of LBR MSRs
MSR_IA32_DEBUGCTLMSR and LBR MSRs are currently not enumerated by
KVM_GET_MSR_INDEX_LIST, and LBR MSRs cannot be set with KVM_SET_MSRS. So
save/restore is completely broken.

Fix it by adding the MSRs to msrs_to_save_base, and allowing writes to
LBR MSRs from userspace only (as they are read-only MSRs) if LBR
virtualization is enabled.  Additionally, to correctly restore L1's LBRs
while L2 is running, make sure the LBRs are copied from the captured
VMCB01 save area in svm_copy_vmrun_state().

Note, for VMX, this also fixes a flaw where MSR_IA32_DEBUGCTLMSR isn't
reported as an MSR to save/restore.

Note #2, over-reporting MSR_IA32_LASTxxx on Intel is ok, as KVM already
handles unsupported reads and writes thanks to commit b5e2fec0eb ("KVM:
Ignore DEBUGCTL MSRs with no effect") (kvm_do_msr_access() will morph the
unsupported userspace write into a nop).

Fixes: 24e09cbf48 ("KVM: SVM: enable LBR virtualization")
Cc: stable@vger.kernel.org
Reported-by: Jim Mattson <jmattson@google.com>
Signed-off-by: Yosry Ahmed <yosry@kernel.org>
Link: https://patch.msgid.link/20260303003421.2185681-4-yosry@kernel.org
[sean: guard with lbrv checks, massage changelog]
Signed-off-by: Sean Christopherson <seanjc@google.com>
2026-03-04 16:08:44 -08:00
Yosry Ahmed
361dbe8173 KVM: SVM: Switch svm_copy_lbrs() to a macro
In preparation for using svm_copy_lbrs() with 'struct vmcb_save_area'
without a containing 'struct vmcb', and later even 'struct
vmcb_save_area_cached', make it a macro.

Macros are generally not preferred compared to functions, mainly due to
type-safety. However, in this case it seems like having a simple macro
copying a few fields is better than copy-pasting the same 5 lines of
code in different places.

Cc: stable@vger.kernel.org
Signed-off-by: Yosry Ahmed <yosry@kernel.org>
Link: https://patch.msgid.link/20260303003421.2185681-3-yosry@kernel.org
Signed-off-by: Sean Christopherson <seanjc@google.com>
2026-03-04 16:08:44 -08:00
Yosry Ahmed
b53ab5167a KVM: nSVM: Avoid clearing VMCB_LBR in vmcb12
svm_copy_lbrs() always marks VMCB_LBR dirty in the destination VMCB.
However, nested_svm_vmexit() uses it to copy LBRs to vmcb12, and
clearing clean bits in vmcb12 is not architecturally defined.

Move vmcb_mark_dirty() to callers and drop it for vmcb12.

This also facilitates incoming refactoring that does not pass the entire
VMCB to svm_copy_lbrs().

Fixes: d20c796ca3 ("KVM: x86: nSVM: implement nested LBR virtualization")
Cc: stable@vger.kernel.org
Signed-off-by: Yosry Ahmed <yosry@kernel.org>
Link: https://patch.msgid.link/20260303003421.2185681-2-yosry@kernel.org
Signed-off-by: Sean Christopherson <seanjc@google.com>
2026-03-04 16:08:43 -08:00
Kevin Cheng
d99df02ff4 KVM: SVM: Inject #UD for INVLPGA if EFER.SVME=0
INVLPGA should cause a #UD when EFER.SVME is not set. Add a check to
properly inject #UD when EFER.SVME=0.

Fixes: ff092385e8 ("KVM: SVM: Implement INVLPGA")
Cc: stable@vger.kernel.org
Signed-off-by: Kevin Cheng <chengkev@google.com>
Reviewed-by: Yosry Ahmed <yosry.ahmed@linux.dev>
Link: https://patch.msgid.link/20260228033328.2285047-3-chengkev@google.com
[sean: tag for stable@]
Signed-off-by: Sean Christopherson <seanjc@google.com>
2026-03-04 16:08:42 -08:00
Sean Christopherson
c64bc6ed17 KVM: nSVM: Delay setting soft IRQ RIP tracking fields until vCPU run
In the save+restore path, when restoring nested state, the values of RIP
and CS base passed into nested_vmcb02_prepare_control() are mostly
incorrect.  They are both pulled from the vmcb02. For CS base, the value
is only correct if system regs are restored before nested state. The
value of RIP is whatever the vCPU had in vmcb02 before restoring nested
state (zero on a freshly created vCPU).

Instead, take a similar approach to NextRIP, and delay initializing the
RIP tracking fields until shortly before the vCPU is run, to make sure
the most up-to-date values of RIP and CS base are used regardless of
KVM_SET_SREGS, KVM_SET_REGS, and KVM_SET_NESTED_STATE's relative
ordering.

Fixes: cc440cdad5 ("KVM: nSVM: implement KVM_GET_NESTED_STATE and KVM_SET_NESTED_STATE")
CC: stable@vger.kernel.org
Suggested-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Yosry Ahmed <yosry@kernel.org>
Link: https://patch.msgid.link/20260225005950.3739782-8-yosry@kernel.org
[sean: deal with the svm_cancel_injection() madness]
Signed-off-by: Sean Christopherson <seanjc@google.com>
2026-03-04 16:06:56 -08:00
Yosry Ahmed
a0592461f3 KVM: nSVM: Delay stuffing L2's current RIP into NextRIP until vCPU run
For guests with NRIPS disabled, L1 does not provide NextRIP when running
an L2 with an injected soft interrupt, instead it advances L2's RIP
before running it. KVM uses L2's current RIP as the NextRIP in vmcb02 to
emulate a CPU without NRIPS.

However, in svm_set_nested_state(), the value used for L2's current RIP
comes from vmcb02, which is just whatever the vCPU had in vmcb02 before
restoring nested state (zero on a freshly created vCPU). Passing the
cached RIP value instead (i.e. kvm_rip_read()) would only fix the issue
if registers are restored before nested state.

Instead, split the logic of setting NextRIP in vmcb02. Handle the
'normal' case of initializing vmcb02's NextRIP using NextRIP from vmcb12
(or KVM_GET_NESTED_STATE's payload) in nested_vmcb02_prepare_control().
Delay the special case of stuffing L2's current RIP into vmcb02's
NextRIP until shortly before the vCPU is run, to make sure the most
up-to-date value of RIP is used regardless of KVM_SET_REGS and
KVM_SET_NESTED_STATE's relative ordering.

Fixes: cc440cdad5 ("KVM: nSVM: implement KVM_GET_NESTED_STATE and KVM_SET_NESTED_STATE")
CC: stable@vger.kernel.org
Suggested-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Yosry Ahmed <yosry@kernel.org>
Link: https://patch.msgid.link/20260225005950.3739782-7-yosry@kernel.org
[sean: use new helper, svm_fixup_nested_rips()]
Signed-off-by: Sean Christopherson <seanjc@google.com>
2026-03-04 16:05:43 -08:00
Yosry Ahmed
8d397582f6 KVM: nSVM: Always use NextRIP as vmcb02's NextRIP after first L2 VMRUN
For guests with NRIPS disabled, L1 does not provide NextRIP when running
an L2 with an injected soft interrupt, instead it advances the current RIP
before running it. KVM uses the current RIP as the NextRIP in vmcb02 to
emulate a CPU without NRIPS.

However, after L2 runs the first time, NextRIP will be updated by the CPU
and/or KVM, and the current RIP is no longer the correct value to use in
vmcb02.  Hence, after save/restore, use the current RIP if and only if a
nested run is pending, otherwise use NextRIP.  Give soft_int_next_rip the
same treatment, as it's the same logic, just for a narrower use case.

Fixes: cc440cdad5 ("KVM: nSVM: implement KVM_GET_NESTED_STATE and KVM_SET_NESTED_STATE")
CC: stable@vger.kernel.org
Signed-off-by: Yosry Ahmed <yosry@kernel.org>
Link: https://patch.msgid.link/20260225005950.3739782-6-yosry@kernel.org
[sean: give soft_int_next_rip the same treatment]
Signed-off-by: Sean Christopherson <seanjc@google.com>
2026-03-04 10:38:38 -08:00
Yosry Ahmed
e5cdd34b5f KVM: selftests: Extend state_test to check next_rip
Similar to vGIF, extend state_test to make sure that next_rip is saved
correctly in nested state. GUEST_SYNC() in L2 causes IO emulation by
KVM, which advances the RIP to the value of next_rip. Hence, if next_rip
is saved correctly, its value should match the saved RIP value.

Signed-off-by: Yosry Ahmed <yosry@kernel.org>
Link: https://patch.msgid.link/20260225005950.3739782-5-yosry@kernel.org
Signed-off-by: Sean Christopherson <seanjc@google.com>
2026-03-02 15:58:23 -08:00
Yosry Ahmed
2303ca26fb KVM: selftests: Extend state_test to check vGIF
V_GIF_MASK is one of the fields written by the CPU after VMRUN, and
sync'd by KVM from vmcb02 to cached vmcb12 after running L2. Part of the
reason is to make sure V_GIF_MASK is saved/restored correctly, as the
cached vmcb12 is the payload of nested state.

Verify that V_GIF_MASK is saved/restored correctly in state_test by
enabling vGIF in vmcb12, toggling GIF in L2 at different GUEST_SYNC()
points, and verifying that V_GIF_MASK is correctly propagated to the
nested state.

Signed-off-by: Yosry Ahmed <yosry@kernel.org>
Link: https://patch.msgid.link/20260225005950.3739782-4-yosry@kernel.org
Signed-off-by: Sean Christopherson <seanjc@google.com>
2026-03-02 15:58:22 -08:00
Yosry Ahmed
03bee264f8 KVM: nSVM: Sync interrupt shadow to cached vmcb12 after VMRUN of L2
After VMRUN in guest mode, nested_sync_control_from_vmcb02() syncs
fields written by the CPU from vmcb02 to the cached vmcb12. This is
because the cached vmcb12 is used as the authoritative copy of some of
the controls, and is the payload when saving/restoring nested state.

int_state is also written by the CPU, specifically bit 0 (i.e.
SVM_INTERRUPT_SHADOW_MASK) for nested VMs, but it is not sync'd to
cached vmcb12. This does not cause a problem if KVM_SET_NESTED_STATE
preceeds KVM_SET_VCPU_EVENTS in the restore path, as an interrupt shadow
would be correctly restored to vmcb02 (KVM_SET_VCPU_EVENTS overwrites
what KVM_SET_NESTED_STATE restored in int_state).

However, if KVM_SET_VCPU_EVENTS preceeds KVM_SET_NESTED_STATE, an
interrupt shadow would be restored into vmcb01 instead of vmcb02. This
would mostly be benign for L1 (delays an interrupt), but not for L2. For
L2, the vCPU could hang (e.g. if a wakeup interrupt is delivered before
a HLT that should have been in an interrupt shadow).

Sync int_state to the cached vmcb12 in nested_sync_control_from_vmcb02()
to avoid this problem. With that, KVM_SET_NESTED_STATE restores the
correct interrupt shadow state, and if KVM_SET_VCPU_EVENTS follows it
would overwrite it with the same value.

Fixes: cc440cdad5 ("KVM: nSVM: implement KVM_GET_NESTED_STATE and KVM_SET_NESTED_STATE")
CC: stable@vger.kernel.org
Signed-off-by: Yosry Ahmed <yosry@kernel.org>
Link: https://patch.msgid.link/20260225005950.3739782-3-yosry@kernel.org
Signed-off-by: Sean Christopherson <seanjc@google.com>
2026-03-02 15:58:22 -08:00
Yosry Ahmed
778d8c1b2a KVM: nSVM: Sync NextRIP to cached vmcb12 after VMRUN of L2
After VMRUN in guest mode, nested_sync_control_from_vmcb02() syncs
fields written by the CPU from vmcb02 to the cached vmcb12. This is
because the cached vmcb12 is used as the authoritative copy of some of
the controls, and is the payload when saving/restoring nested state.

NextRIP is also written by the CPU (in some cases) after VMRUN, but is
not sync'd to the cached vmcb12. As a result, it is corrupted after
save/restore (replaced by the original value written by L1 on nested
VMRUN). This could cause problems for both KVM (e.g. when injecting a
soft IRQ) or L1 (e.g. when using NextRIP to advance RIP after emulating
an instruction).

Fix this by sync'ing NextRIP to the cache after VMRUN of L2, but only
after completing interrupts (not in nested_sync_control_from_vmcb02()),
as KVM may update NextRIP (e.g. when re-injecting a soft IRQ).

Fixes: cc440cdad5 ("KVM: nSVM: implement KVM_GET_NESTED_STATE and KVM_SET_NESTED_STATE")
CC: stable@vger.kernel.org
Co-developed-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Yosry Ahmed <yosry@kernel.org>
Link: https://patch.msgid.link/20260225005950.3739782-2-yosry@kernel.org
Signed-off-by: Sean Christopherson <seanjc@google.com>
2026-03-02 15:58:21 -08:00
Yosry Ahmed
24f7d36b82 KVM: nSVM: Ensure AVIC is inhibited when restoring a vCPU to guest mode
On nested VMRUN, KVM ensures AVIC is inhibited by requesting
KVM_REQ_APICV_UPDATE, triggering a check of inhibit reasons, finding
APICV_INHIBIT_REASON_NESTED, and disabling AVIC.

However, when KVM_SET_NESTED_STATE is performed on a vCPU not in guest
mode with AVIC enabled, KVM_REQ_APICV_UPDATE is not requested, and AVIC
is not inhibited.

Request KVM_REQ_APICV_UPDATE in the KVM_SET_NESTED_STATE path if AVIC is
active, similar to the nested VMRUN path.

Fixes: f44509f849 ("KVM: x86: SVM: allow AVIC to co-exist with a nested guest running")
Cc: stable@vger.kernel.org
Signed-off-by: Yosry Ahmed <yosry@kernel.org>
Link: https://patch.msgid.link/20260224225017.3303870-1-yosry@kernel.org
Signed-off-by: Sean Christopherson <seanjc@google.com>
2026-03-02 15:58:19 -08:00
Yosry Ahmed
e63fb1379f KVM: nSVM: Mark all of vmcb02 dirty when restoring nested state
When restoring a vCPU in guest mode, any state restored before
KVM_SET_NESTED_STATE (e.g. KVM_SET_SREGS) will mark the corresponding
dirty bits in vmcb01, as it is the active VMCB before switching to
vmcb02 in svm_set_nested_state().

Hence, mark all fields in vmcb02 dirty in svm_set_nested_state() to
capture any previously restored fields.

Fixes: cc440cdad5 ("KVM: nSVM: implement KVM_GET_NESTED_STATE and KVM_SET_NESTED_STATE")
CC: stable@vger.kernel.org
Signed-off-by: Yosry Ahmed <yosry.ahmed@linux.dev>
Link: https://patch.msgid.link/20260210010806.3204289-1-yosry.ahmed@linux.dev
Signed-off-by: Sean Christopherson <seanjc@google.com>
2026-03-02 14:46:40 -08:00
Sean Christopherson
d0ad1b05bb KVM: x86: Defer non-architectural deliver of exception payload to userspace read
When attempting to play nice with userspace that hasn't enabled
KVM_CAP_EXCEPTION_PAYLOAD, defer KVM's non-architectural delivery of the
payload until userspace actually reads relevant vCPU state, and more
importantly, force delivery of the payload in *all* paths where userspace
saves relevant vCPU state, not just KVM_GET_VCPU_EVENTS.

Ignoring userspace save/restore for the moment, delivering the payload
before the exception is injected is wrong regardless of whether L1 or L2
is running.  To make matters even more confusing, the flaw *currently*
being papered over by the !is_guest_mode() check isn't even the same bug
that commit da998b46d2 ("kvm: x86: Defer setting of CR2 until #PF
delivery") was trying to avoid.

At the time of commit da998b46d2, KVM didn't correctly handle exception
intercepts, as KVM would wait until VM-Entry into L2 was imminent to check
if the queued exception should morph to a nested VM-Exit.  I.e. KVM would
deliver the payload to L2 and then synthesize a VM-Exit into L1.  But the
payload was only the most blatant issue, e.g. waiting to check exception
intercepts would also lead to KVM incorrectly escalating a
should-be-intercepted #PF into a #DF.

That underlying bug was eventually fixed by commit 7709aba8f7 ("KVM: x86:
Morph pending exceptions to pending VM-Exits at queue time"), but in the
interim, commit a06230b62b ("KVM: x86: Deliver exception payload on
KVM_GET_VCPU_EVENTS") came along and subtly added another dependency on
the !is_guest_mode() check.

While not recorded in the changelog, the motivation for deferring the
!exception_payload_enabled delivery was to fix a flaw where a synthesized
MTF (Monitor Trap Flag) VM-Exit would drop a pending #DB and clobber DR6.
On a VM-Exit, VMX CPUs save pending #DB information into the VMCS, which
is emulated by KVM in nested_vmx_update_pending_dbg() by grabbing the
payload from the queue/pending exception.  I.e. prematurely delivering the
payload would cause the pending #DB to not be recorded in the VMCS, and of
course, clobber L2's DR6 as seen by L1.

Jumping back to save+restore, the quirked behavior of forcing delivery of
the payload only works if userspace does KVM_GET_VCPU_EVENTS *before*
CR2 or DR6 is saved, i.e. before KVM_GET_SREGS{,2} and KVM_GET_DEBUGREGS.
E.g. if userspace does KVM_GET_SREGS before KVM_GET_VCPU_EVENTS, then the
CR2 saved by userspace won't contain the payload for the exception save by
KVM_GET_VCPU_EVENTS.

Deliberately deliver the payload in the store_regs() path, as it's the
least awful option even though userspace may not be doing save+restore.
Because if userspace _is_ doing save restore, it could elide KVM_GET_SREGS
knowing that SREGS were already saved when the vCPU exited.

Link: https://lore.kernel.org/all/20200207103608.110305-1-oupton@google.com
Cc: Yosry Ahmed <yosry.ahmed@linux.dev>
Cc: stable@vger.kernel.org
Reviewed-by: Yosry Ahmed <yosry.ahmed@linux.dev>
Tested-by: Yosry Ahmed <yosry.ahmed@linux.dev>
Link: https://patch.msgid.link/20260218005438.2619063-1-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
2026-03-02 09:53:50 -08:00
Yosry Ahmed
5c247d08bc KVM: nSVM: Use vcpu->arch.cr2 when updating vmcb12 on nested #VMEXIT
KVM currently uses the value of CR2 from vmcb02 to update vmcb12 on
nested #VMEXIT. This value is incorrect in some cases, causing L1 to run
L2 with a corrupted CR2. This could lead to segfaults or data corruption
if L2 is in the middle of handling a #PF and reads a corrupted CR2. Use
the correct value in vcpu->arch.cr2 instead.

The value in vcpu->arch.cr2 is sync'd to vmcb02 shortly before a VMRUN
of L2, and sync'd back to vcpu->arch.cr2 shortly after. The value are
only out-of-sync in two cases: after save+restore, and after a #PF is
injected into L2. In either case, if a #VMEXIT to L1 is synthesized
before L2 runs, using the value in vmcb02 would be incorrect.

After save+restore, the value of CR2 is restored by KVM_SET_SREGS into
vcpu->arch.cr2. It is not reflect in vmcb02 until a VMRUN of L2. Before
that, it holds whatever was in vmcb02 before restore, which would be
zero on a new vCPU that never ran nested. If a #VMEXIT to L1 is
synthesized before L2 ever runs, using vcpu->arch.cr2 to update vmcb12
is the right thing to do.

The #PF injection case is more nuanced.  Although the APM is a bit
unclear about when CR2 is written during a #PF, the SDM is more clear:

	Processors update CR2 whenever a page fault is detected. If a
	second page fault occurs while an earlier page fault is being
	delivered, the faulting linear address of the second fault will
	overwrite the contents of CR2 (replacing the previous address).
	These updates to CR2 occur even if the page fault results in a
	double fault or occurs during the delivery of a double fault.

KVM injecting the exception surely counts as the #PF being "detected".
More importantly, when an exception is injected into L2 at the time of a
synthesized #VMEXIT, KVM updates exit_int_info in vmcb12 accordingly,
such that an L1 hypervisor can re-inject the exception. If CR2 is not
written at that point, the L1 hypervisor have no way of correctly
re-injecting the #PF. Hence, if a #VMEXIT to L1 is synthesized after
the #PF is injected into L2 but before it actually runs, using
vcpu->arch.cr2 to update vmcb12 is also the right thing to do.

Note that KVM does _not_ update vcpu->arch.cr2 when a #PF is pending for
L2, only when it is injected. The distinction is important, because only
injected (but not intercepted) exceptions are propagated to L1 through
exit_int_info. It would be incorrect to update CR2 in vmcb12 for a
pending #PF, as L1 would perceive an updated CR2 value with no #PF.

Cc: stable@vger.kernel.org
Signed-off-by: Yosry Ahmed <yosry.ahmed@linux.dev>
Link: https://patch.msgid.link/20260203201010.1871056-1-yosry.ahmed@linux.dev
Signed-off-by: Sean Christopherson <seanjc@google.com>
2026-03-02 09:52:29 -08:00
Linus Torvalds
11439c4635 Linux 7.0-rc2 v7.0-rc2 2026-03-01 15:39:31 -08:00
Linus Torvalds
949d0a46ad Arm:
* Make sure we don't leak any S1POE state from guest to guest when
   the feature is supported on the HW, but not enabled on the host
 
 * Propagate the ID registers from the host into non-protected VMs
   managed by pKVM, ensuring that the guest sees the intended feature set
 
 * Drop double kern_hyp_va() from unpin_host_sve_state(), which could
   bite us if we were to change kern_hyp_va() to not being idempotent
 
 * Don't leak stage-2 mappings in protected mode
 
 * Correctly align the faulting address when dealing with single page
   stage-2 mappings for PAGE_SIZE > 4kB
 
 * Fix detection of virtualisation-capable GICv5 IRS, due to the
   maintainer being obviously fat fingered... [his words, not mine]
 
 * Remove duplication of code retrieving the ASID for the purpose of
   S1 PT handling
 
 * Fix slightly abusive const-ification in vgic_set_kvm_info()
 
 Generic:
 
 * Remove internal Kconfigs that are now set on all architectures.
 
 * Remove per-architecture code to enable KVM_CAP_SYNC_MMU, all
   architectures finally enable it in Linux 7.0.
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Merge tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm

Pull kvm fixes from Paolo Bonzini:
 "Arm:

   - Make sure we don't leak any S1POE state from guest to guest when
     the feature is supported on the HW, but not enabled on the host

   - Propagate the ID registers from the host into non-protected VMs
     managed by pKVM, ensuring that the guest sees the intended feature
     set

   - Drop double kern_hyp_va() from unpin_host_sve_state(), which could
     bite us if we were to change kern_hyp_va() to not being idempotent

   - Don't leak stage-2 mappings in protected mode

   - Correctly align the faulting address when dealing with single page
     stage-2 mappings for PAGE_SIZE > 4kB

   - Fix detection of virtualisation-capable GICv5 IRS, due to the
     maintainer being obviously fat fingered... [his words, not mine]

   - Remove duplication of code retrieving the ASID for the purpose of
     S1 PT handling

   - Fix slightly abusive const-ification in vgic_set_kvm_info()

  Generic:

   - Remove internal Kconfigs that are now set on all architectures

   - Remove per-architecture code to enable KVM_CAP_SYNC_MMU, all
     architectures finally enable it in Linux 7.0"

* tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm:
  KVM: always define KVM_CAP_SYNC_MMU
  KVM: remove CONFIG_KVM_GENERIC_MMU_NOTIFIER
  KVM: arm64: Deduplicate ASID retrieval code
  irqchip/gic-v5: Fix inversion of IRS_IDR0.virt flag
  KVM: arm64: Revert accidental drop of kvm_uninit_stage2_mmu() for non-NV VMs
  KVM: arm64: Fix protected mode handling of pages larger than 4kB
  KVM: arm64: vgic: Handle const qualifier from gic_kvm_info allocation type
  KVM: arm64: Remove redundant kern_hyp_va() in unpin_host_sve_state()
  KVM: arm64: Fix ID register initialization for non-protected pKVM guests
  KVM: arm64: Optimise away S1POE handling when not supported by host
  KVM: arm64: Hide S1POE from guests when not supported by the host
2026-03-01 15:34:47 -08:00
Linus Torvalds
e2bd1b1369 A single fix for debugobjects.
The deferred page initialization prevents debug objects from allocating
 slab pages until the initialization is complete. That causes depletion of
 the pool and disabling of debugobjects.
 
 The reason is that debugobjects uses __GFP_HIGH for allocations as it might
 be invoked from arbitrary contexts. When PREEMPT_COUNT is disabled there is
 no way to know whether the context is safe to set __GFP_KSWAPD_RECLAIM.
 
 This worked until v6.18. Since then allocations w/o a reclaim flag cause
 new_slab() to end up in alloc_frozen_pages_nolock_noprof(), which returns
 early when deferred page initialization has not yet completed.
 
 Work around that when PREEMPT_COUNT is enabled as the preempt counter
 allows debugobjects to add __GFP_KSWAPD_RECLAIM to the GFP flags when the
 context is preemtible. When PREEMPT_COUNT is disabled the context is
 unknown and the reclaim bit can't be set because the caller might hold
 locks which might deadlock in the allocator.
 
 That makes debugobjects depend on PREEMPT_COUNT || !DEFERRED_STRUCT_PAGE_INIT,
 which limits the coverage slightly, but keeps it functional for most cases.
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Merge tag 'core-debugobjects-2026-03-01' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull debugobjects fix from Thomas Gleixner:
 "A single fix for debugobjects.

  The deferred page initialization prevents debug objects from
  allocating slab pages until the initialization is complete. That
  causes depletion of the pool and disabling of debugobjects.

  The reason is that debugobjects uses __GFP_HIGH for allocations as it
  might be invoked from arbitrary contexts. When PREEMPT_COUNT is
  disabled there is no way to know whether the context is safe to set
  __GFP_KSWAPD_RECLAIM.

  This worked until v6.18. Since then allocations w/o a reclaim flag
  cause new_slab() to end up in alloc_frozen_pages_nolock_noprof(),
  which returns early when deferred page initialization has not yet
  completed.

  Work around that when PREEMPT_COUNT is enabled as the preempt counter
  allows debugobjects to add __GFP_KSWAPD_RECLAIM to the GFP flags when
  the context is preemtible. When PREEMPT_COUNT is disabled the context
  is unknown and the reclaim bit can't be set because the caller might
  hold locks which might deadlock in the allocator.

  That makes debugobjects depend on PREEMPT_COUNT ||
  !DEFERRED_STRUCT_PAGE_INIT, which limits the coverage slightly, but
  keeps it functional for most cases"

* tag 'core-debugobjects-2026-03-01' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  debugobject: Make it work with deferred page initialization - again
2026-03-01 13:32:32 -08:00
Linus Torvalds
5920da4455 Miscellaneous x86 fixes:
- Fix speculative safety in fred_extint()
 
  - Fix __WARN_printf() trap in early_fixup_exception()
 
  - Fix clang-build boot bug for unusual alignments,
    triggered by CONFIG_DEBUG_FORCE_FUNCTION_ALIGN_64B=y
 
  - Replace the final few __ASSEMBLY__ stragglers that snuck
    in lately into non-UAPI x86 headers and use __ASSEMBLER__
    consistently (again).
 
 Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Merge tag 'x86-urgent-2026-03-01' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull x86 fixes from Ingo Molnar:

 - Fix speculative safety in fred_extint()

 - Fix __WARN_printf() trap in early_fixup_exception()

 - Fix clang-build boot bug for unusual alignments, triggered by
   CONFIG_DEBUG_FORCE_FUNCTION_ALIGN_64B=y

 - Replace the final few __ASSEMBLY__ stragglers that snuck in lately
   into non-UAPI x86 headers and use __ASSEMBLER__ consistently (again)

* tag 'x86-urgent-2026-03-01' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/headers: Replace __ASSEMBLY__ stragglers with __ASSEMBLER__
  x86/cfi: Fix CFI rewrite for odd alignments
  x86/bug: Handle __WARN_printf() trap in early_fixup_exception()
  x86/fred: Correct speculative safety in fred_extint()
2026-03-01 13:16:35 -08:00
Linus Torvalds
f6542af922 Improve the inlining of jiffies_to_msecs() and jiffies_to_usecs(),
for the common HZ=100, 250 or 1000 cases, only inlining them
 for odd HZ values like HZ=300.
 
 The inlining overhead showed up in performance tests of the TCP code.
 
 (Marked as an RFC pull request, as it's not a regression.)
 
 Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Merge tag 'timers-urgent-2026-03-01' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull timer fix from Ingo Molnar:
 "Improve the inlining of jiffies_to_msecs() and jiffies_to_usecs(), for
  the common HZ=100, 250 or 1000 cases. Only use a function call for odd
  HZ values like HZ=300 that generate more code.

  The function call overhead showed up in performance tests of the TCP
  code"

* tag 'timers-urgent-2026-03-01' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  time/jiffies: Inline jiffies_to_msecs() and jiffies_to_usecs()
2026-03-01 12:15:58 -08:00
Linus Torvalds
6170625149 Miscellaneous fixes:
- Fix zero_vruntime tracking when there's a single task running
 
  - Fix slice protection logic
 
  - Fix the ->vprot logic for reniced tasks
 
  - Fix lag clamping in mixed slice workloads
 
  - Fix objtool uaccess warning (and bug) in the
    !CONFIG_RSEQ_SLICE_EXTENSION case caused by unexpected
    un-inlining, which triggers with older compilers
 
  - Fix a comment in the rseq registration rseq_size bound check code
 
  - Fix a legacy RSEQ ABI quirk that handled 32-byte area sizes
    differently, which special size we now reached naturally and
    want to avoid. The visible ugliness of the new reserved field
    will be avoided the next time the RSEQ area is extended.
 
 Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Merge tag 'sched-urgent-2026-03-01' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull scheduler fixes from Ingo Molnar:

 - Fix zero_vruntime tracking when there's a single task running

 - Fix slice protection logic

 - Fix the ->vprot logic for reniced tasks

 - Fix lag clamping in mixed slice workloads

 - Fix objtool uaccess warning (and bug) in the
   !CONFIG_RSEQ_SLICE_EXTENSION case caused by unexpected un-inlining,
   which triggers with older compilers

 - Fix a comment in the rseq registration rseq_size bound check code

 - Fix a legacy RSEQ ABI quirk that handled 32-byte area sizes
   differently, which special size we now reached naturally and want to
   avoid. The visible ugliness of the new reserved field will be avoided
   the next time the RSEQ area is extended.

* tag 'sched-urgent-2026-03-01' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  rseq: slice ext: Ensure rseq feature size differs from original rseq size
  rseq: Clarify rseq registration rseq_size bound check comment
  sched/core: Fix wakeup_preempt's next_class tracking
  rseq: Mark rseq_arm_slice_extension_timer() __always_inline
  sched/fair: Fix lag clamp
  sched/eevdf: Update se->vprot in reweight_entity()
  sched/fair: Only set slice protection at pick time
  sched/fair: Fix zero_vruntime tracking
2026-03-01 11:09:24 -08:00
Linus Torvalds
cb36eabcaf Miscellaneous fixes:
- Fix lock ordering bug found by lockdep in perf_event_wakeup()
  - Fix uncore counter enumeration on Granite Rapids and Sierra Forest
  - Fix perf_mmap() refcount bug found by Syzkaller
  - Fix __perf_event_overflow() vs. perf_remove_from_context() race
 
 Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Merge tag 'perf-urgent-2026-03-01' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull perf events fixes from Ingo Molnar:

 - Fix lock ordering bug found by lockdep in perf_event_wakeup()

 - Fix uncore counter enumeration on Granite Rapids and Sierra Forest

 - Fix perf_mmap() refcount bug found by Syzkaller

 - Fix __perf_event_overflow() vs perf_remove_from_context() race

* tag 'perf-urgent-2026-03-01' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  perf: Fix __perf_event_overflow() vs perf_remove_from_context() race
  perf/core: Fix refcount bug and potential UAF in perf_mmap
  perf/x86/intel/uncore: Add per-scheduler IMC CAS count events
  perf/core: Fix invalid wait context in ctx_sched_in()
2026-03-01 11:07:20 -08:00
Linus Torvalds
b410220870 Now that LLVM 22 has been released officially, require a release
version to use the new CONFIG_WARN_CONTEXT_ANALYSIS feature.
 
 In particular this avoids the widely used Android clang 22.0.1
 pre-release build which is known to be broken for this usecase.
 
 Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Merge tag 'locking-urgent-2026-03-01' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull locking fix from Ingo Molnar:
 "Now that LLVM 22 has been released officially, require a release
  version to use the new CONFIG_WARN_CONTEXT_ANALYSIS feature.

  In particular this avoids the widely used Android clang 22.0.1
  pre-release build which is known to be broken for this usecase"

* tag 'locking-urgent-2026-03-01' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  lib/Kconfig.debug: Require a release version of LLVM 22 for context analysis
2026-03-01 11:00:43 -08:00
Linus Torvalds
afa844360b Miscellaneous irqchip driver fixes:
- Fix frozen interrupt bug in the sifive-plic driver
 
  - Limit per-device MSI interrupts on uncommon gic-v3-its
    hardware variants
 
  - Address Sparse warning by constifying a variable in
    the MMP driver
 
  - Revert broken commit and also fix an error check
    in the ls-extirq driver
 
 Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Merge tag 'irq-urgent-2026-03-01' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull irqchip driver fixes from Ingo Molnar:

 - Fix frozen interrupt bug in the sifive-plic driver

 - Limit per-device MSI interrupts on uncommon gic-v3-its hardware
   variants

 - Address Sparse warning by constifying a variable in the MMP driver

 - Revert broken commit and also fix an error check in the ls-extirq
   driver

* tag 'irq-urgent-2026-03-01' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  irqchip/ls-extirq: Fix devm_of_iomap() error check
  Revert "irqchip/ls-extirq: Use for_each_of_imap_item iterator"
  irqchip/mmp: Make icu_irq_chip variable static const
  irqchip/gic-v3-its: Limit number of per-device MSIs to the range the ITS supports
  irqchip/sifive-plic: Fix frozen interrupt due to affinity setting
2026-03-01 10:58:16 -08:00
Linus Torvalds
39c6332614 SCSI fixes on 20260228
All changes in drivers (well technically ses is enclosure services,
 but its change is minor).  The biggest is the write combining change
 in lpfc followed by the additional NULL checks in mpi3mr.
 
 Signed-off-by: James E.J. Bottomley <James.Bottomley@HansenPartnership.com>
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Merge tag 'scsi-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/jejb/scsi

Pull SCSI fixes from James Bottomley:
 "All changes in drivers (well technically SES is enclosure services,
  but its change is minor). The biggest is the write combining change in
  lpfc followed by the additional NULL checks in mpi3mr"

* tag 'scsi-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/jejb/scsi:
  scsi: ufs: core: Fix shift out of bounds when MAXQ=32
  scsi: ufs: core: Move link recovery for hibern8 exit failure to wl_resume
  scsi: ufs: core: Fix possible NULL pointer dereference in ufshcd_add_command_trace()
  scsi: snic: MAINTAINERS: Update snic maintainers
  scsi: snic: Remove unused linkstatus
  scsi: pm8001: Fix use-after-free in pm8001_queue_command()
  scsi: mpi3mr: Add NULL checks when resetting request and reply queues
  scsi: ufs: core: Reset urgent_bkops_lvl to allow runtime PM power mode
  scsi: ses: Fix devices attaching to different hosts
  scsi: ufs: core: Fix RPMB region size detection for UFS 2.2
  scsi: storvsc: Fix scheduling while atomic on PREEMPT_RT
  scsi: lpfc: Properly set WC for DPP mapping
2026-03-01 09:59:29 -08:00
Linus Torvalds
eb71ab2bf7 bpf-fixes
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Merge tag 'bpf-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf

Pull bpf fixes from Alexei Starovoitov:

 - Fix alignment of arm64 JIT buffer to prevent atomic tearing (Fuad
   Tabba)

 - Fix invariant violation for single value tnums in the verifier
   (Harishankar Vishwanathan, Paul Chaignon)

 - Fix a bunch of issues found by ASAN in selftests/bpf (Ihor Solodrai)

 - Fix race in devmpa and cpumap on PREEMPT_RT (Jiayuan Chen)

 - Fix show_fdinfo of kprobe_multi when cookies are not present (Jiri
   Olsa)

 - Fix race in freeing special fields in BPF maps to prevent memory
   leaks (Kumar Kartikeya Dwivedi)

 - Fix OOB read in dmabuf_collector (T.J. Mercier)

* tag 'bpf-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf: (36 commits)
  selftests/bpf: Avoid simplification of crafted bounds test
  selftests/bpf: Test refinement of single-value tnum
  bpf: Improve bounds when tnum has a single possible value
  bpf: Introduce tnum_step to step through tnum's members
  bpf: Fix race in devmap on PREEMPT_RT
  bpf: Fix race in cpumap on PREEMPT_RT
  selftests/bpf: Add tests for special fields races
  bpf: Retire rcu_trace_implies_rcu_gp() from local storage
  bpf: Delay freeing fields in local storage
  bpf: Lose const-ness of map in map_check_btf()
  bpf: Register dtor for freeing special fields
  selftests/bpf: Fix OOB read in dmabuf_collector
  selftests/bpf: Fix a memory leak in xdp_flowtable test
  bpf: Fix stack-out-of-bounds write in devmap
  bpf: Fix kprobe_multi cookies access in show_fdinfo callback
  bpf, arm64: Force 8-byte alignment for JIT buffer to prevent atomic tearing
  selftests/bpf: Don't override SIGSEGV handler with ASAN
  selftests/bpf: Check BPFTOOL env var in detect_bpftool_path()
  selftests/bpf: Fix out-of-bounds array access bugs reported by ASAN
  selftests/bpf: Fix array bounds warning in jit_disasm_helpers
  ...
2026-02-28 19:54:28 -08:00
Linus Torvalds
63a43faf6a Driver core fixes for 7.0-rc2
- Do not register imx_clk_scu_driver in imx8qxp_clk_probe(); besides
   fixing two other issues, this avoids a deadlock in combination with
   commit dc23806a7c ("driver core: enforce device_lock for
   driver_match_device()").
 
 - Move secondary node lookup from device_get_next_child_node() to
   fwnode_get_next_child_node(); this avoids issues when users switch
   from the device API to the fwnode API.
 
 - Export io_define_{read,write}!() to avoid unused import warnings when
   CONFIG_PCI=n.
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Merge tag 'driver-core-7.0-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/driver-core/driver-core

Pull driver core fixes from Danilo Krummrich:

 - Do not register imx_clk_scu_driver in imx8qxp_clk_probe(); besides
   fixing two other issues, this avoids a deadlock in combination with
   commit dc23806a7c ("driver core: enforce device_lock for
   driver_match_device()")

 - Move secondary node lookup from device_get_next_child_node() to
   fwnode_get_next_child_node(); this avoids issues when users switch
   from the device API to the fwnode API

 - Export io_define_{read,write}!() to avoid unused import warnings when
   CONFIG_PCI=n

* tag 'driver-core-7.0-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/driver-core/driver-core:
  clk: scu/imx8qxp: do not register driver in probe()
  rust: io: macro_export io_define_read!() and io_define_write!()
  device property: Allow secondary lookup in fwnode_get_next_child_node()
2026-02-28 19:35:30 -08:00
Linus Torvalds
42eb017830 five client changesets
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Merge tag 'v7.0rc1-smb3-client-fixes' of git://git.samba.org/sfrench/cifs-2.6

Pull smb client fixes from Steve French:

 - Two multichannel fixes

 - Locking fix for superblock flags

 - Fix to remove debug message that could log password

 - Cleanup fix for setting credentials

* tag 'v7.0rc1-smb3-client-fixes' of git://git.samba.org/sfrench/cifs-2.6:
  smb: client: Use snprintf in cifs_set_cifscreds
  smb: client: Don't log plaintext credentials in cifs_set_cifscreds
  smb: client: fix broken multichannel with krb5+signing
  smb: client: use atomic_t for mnt_cifs_flags
  smb: client: fix cifs_pick_channel when channels are equally loaded
2026-02-28 10:45:56 -08:00
Takashi Sakamoto
9197e5949a firewire: ohci: initialize page array to use alloc_pages_bulk() correctly
The call of alloc_pages_bulk() skips to fill entries of page array when
the entries already have values. While, 1394 OHCI PCI driver passes the
page array without initializing. It could cause invalid state at PFN
validation in vmap().

Fixes: f2ae92780a ("firewire: ohci: split page allocation from dma mapping")
Reported-by: John Ogness <john.ogness@linutronix.de>
Reported-and-tested-by: Harald Arnesen <linux@skogtun.org>
Reported-and-tested-by: David Gow <david@davidgow.net>
Closes: https://lore.kernel.org/lkml/87tsv1vig5.fsf@jogness.linutronix.de/
Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2026-02-28 10:09:24 -08:00
Linus Torvalds
2f9339c052 spi: Fixes for v7.0
One fix for the stm32 driver which got broken for DMA chaining cases,
 plus a removal of some straggling bindings for the Bikal SoC which has
 been pulled out of the kernel.
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Merge tag 'spi-fix-v7.0-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/broonie/spi

Pull spi fixes from Mark Brown:
 "One fix for the stm32 driver which got broken for DMA chaining cases,
  plus a removal of some straggling bindings for the Bikal SoC which has
  been pulled out of the kernel"

* tag 'spi-fix-v7.0-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/broonie/spi:
  spi: stm32: fix missing pointer assignment in case of dma chaining
  spi: dt-bindings: snps,dw-abp-ssi: Remove unused bindings
2026-02-28 09:21:18 -08:00
Linus Torvalds
463e133751 regulator: Fixes for v7.0
A small pile of fixes, none of which are super major - the code fixes
 are improved error handling and fixing a leak of a device node.  We also
 have a typo fix and an improvement to make the binding example for
 mt6359 more directly usable.
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Merge tag 'regulator-fix-v7.0-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/broonie/regulator

Pull regulator fixes from Mark Brown:
 "A small pile of fixes, none of which are super major - the code fixes
  are improved error handling and fixing a leak of a device node.

  We also have a typo fix and an improvement to make the binding example
  for mt6359 more directly usable"

* tag 'regulator-fix-v7.0-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/broonie/regulator:
  regulator: Kconfig: fix a typo
  regulator: bq257xx: Fix device node reference leak in bq257xx_reg_dt_parse_gpio()
  regulator: fp9931: Fix PM runtime reference leak in fp9931_hwmon_read()
  regulator: tps65185: check devm_kzalloc() result in probe
  regulator: dt-bindings: mt6359: make regulator names unique
2026-02-28 09:18:02 -08:00
Linus Torvalds
201795a1b7 s390 updates for 7.0-rc2
- Fix guest pfault init to pass a physical address to DIAG 0x258,
   restoring pfault interrupts and avoiding vCPU stalls during host page-in
 
 - Fix kexec/kdump hangs with stack protector by marking
   s390_reset_system() __no_stack_protector; set_prefix(0) switches
   lowcore and the canary no longer matches
 
 - Fix idle/vtime cputime accounting (idle-exit ordering, vtimer
   double-forwarding) and small cleanups
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Merge tag 's390-7.0-3' of git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux

Pull s390 fixes from Vasily Gorbik:

 - Fix guest pfault init to pass a physical address to DIAG 0x258,
   restoring pfault interrupts and avoiding vCPU stalls during host
   page-in

 - Fix kexec/kdump hangs with stack protector by marking
   s390_reset_system() __no_stack_protector; set_prefix(0) switches
   lowcore and the canary no longer matches

 - Fix idle/vtime cputime accounting (idle-exit ordering, vtimer
   double-forwarding) and small cleanups

* tag 's390-7.0-3' of git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux:
  s390/pfault: Fix virtual vs physical address confusion
  s390/kexec: Disable stack protector in s390_reset_system()
  s390/idle: Remove psw_idle() prototype
  s390/vtime: Use lockdep_assert_irqs_disabled() instead of BUG_ON()
  s390/vtime: Use __this_cpu_read() / get rid of READ_ONCE()
  s390/irq/idle: Remove psw bits early
  s390/idle: Inline update_timer_idle()
  s390/idle: Slightly optimize idle time accounting
  s390/idle: Add comment for non obvious code
  s390/vtime: Fix virtual timer forwarding
  s390/idle: Fix cpu idle exit cpu time accounting
2026-02-28 09:01:33 -08:00
Paolo Bonzini
55365ab85a KVM/arm64 fixes for 7.0, take #1
- Make sure we don't leak any S1POE state from guest to guest when
   the feature is supported on the HW, but not enabled on the host
 
 - Propagate the ID registers from the host into non-protected VMs
   managed by pKVM, ensuring that the guest sees the intended feature set
 
 - Drop double kern_hyp_va() from unpin_host_sve_state(), which could
   bite us if we were to change kern_hyp_va() to not being idempotent
 
 - Don't leak stage-2 mappings in protected mode
 
 - Correctly align the faulting address when dealing with single page
   stage-2 mappings for PAGE_SIZE > 4kB
 
 - Fix detection of virtualisation-capable GICv5 IRS, due to the
   maintainer being obviously fat fingered...
 
 - Remove duplication of code retrieving the ASID for the purpose of
   S1 PT handling
 
 - Fix slightly abusive const-ification in vgic_set_kvm_info()
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Merge tag 'kvmarm-fixes-7.0-1' of git://git.kernel.org/pub/scm/linux/kernel/git/kvmarm/kvmarm into HEAD

KVM/arm64 fixes for 7.0, take #1

- Make sure we don't leak any S1POE state from guest to guest when
  the feature is supported on the HW, but not enabled on the host

- Propagate the ID registers from the host into non-protected VMs
  managed by pKVM, ensuring that the guest sees the intended feature set

- Drop double kern_hyp_va() from unpin_host_sve_state(), which could
  bite us if we were to change kern_hyp_va() to not being idempotent

- Don't leak stage-2 mappings in protected mode

- Correctly align the faulting address when dealing with single page
  stage-2 mappings for PAGE_SIZE > 4kB

- Fix detection of virtualisation-capable GICv5 IRS, due to the
  maintainer being obviously fat fingered...

- Remove duplication of code retrieving the ASID for the purpose of
  S1 PT handling

- Fix slightly abusive const-ification in vgic_set_kvm_info()
2026-02-28 15:33:34 +01:00
Paolo Bonzini
70295a479d KVM: always define KVM_CAP_SYNC_MMU
KVM_CAP_SYNC_MMU is provided by KVM's MMU notifiers, which are now always
available.  Move the definition from individual architectures to common
code.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2026-02-28 15:31:35 +01:00
Paolo Bonzini
407fd8b8d8 KVM: remove CONFIG_KVM_GENERIC_MMU_NOTIFIER
All architectures now use MMU notifier for KVM page table management.
Remove the Kconfig symbol and the code that is used when it is
disabled.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2026-02-28 15:31:35 +01:00
Alexei Starovoitov
b9c0a5c483 Merge branch 'fix-invariant-violation-for-single-value-tnums'
Paul Chaignon says:

====================
Fix invariant violation for single-value tnums

We're hitting an invariant violation in Cilium that sometimes leads to
BPF programs being rejected and Cilium failing to start [1]. As far as
I know this is the first case of invariant violation found in a real
program (i.e., not by a fuzzer). The following extract from verifier
logs shows what's happening:

  from 201 to 236: R1=0 R6=ctx() R7=1 R9=scalar(smin=umin=smin32=umin32=3584,smax=umax=smax32=umax32=3840,var_off=(0xe00; 0x100)) R10=fp0
  236: R1=0 R6=ctx() R7=1 R9=scalar(smin=umin=smin32=umin32=3584,smax=umax=smax32=umax32=3840,var_off=(0xe00; 0x100)) R10=fp0
  ; if (magic == MARK_MAGIC_HOST || magic == MARK_MAGIC_OVERLAY || magic == MARK_MAGIC_ENCRYPT) @ bpf_host.c:1337
  236: (16) if w9 == 0xe00 goto pc+45   ; R9=scalar(smin=umin=smin32=umin32=3585,smax=umax=smax32=umax32=3840,var_off=(0xe00; 0x100))
  237: (16) if w9 == 0xf00 goto pc+1
  verifier bug: REG INVARIANTS VIOLATION (false_reg1): range bounds violation u64=[0xe01, 0xe00] s64=[0xe01, 0xe00] u32=[0xe01, 0xe00] s32=[0xe01, 0xe00] var_off=(0xe00, 0x0)

More details are given in the second patch, but in short, the verifier
should be able to detect that the false branch of instruction 237 is
never true. After instruction 236, the u64 range and the tnum overlap
in a single value, 0xf00.

The long-term solution to invariant violation is likely to rely on the
refinement + invariant violation check to detect dead branches, as
started by Eduard. To fix the current issue, we need something with
less refactoring that we can backport to affected kernels.

The solution implemented in the second patch is to improve the bounds
refinement to avoid this case. It relies on a new tnum helper,
tnum_step, first sent as an RFC in [2]. The last two patches extend and
update the selftests.

Link: https://github.com/cilium/cilium/issues/44216 [1]
Link: https://lore.kernel.org/bpf/20251107192328.2190680-2-harishankar.vishwanathan@gmail.com/ [2]

Changes in v3:
  - Fix commit description error spotted by AI bot.
  - Simplify constants in first two tests (Eduard).
  - Rework comment on third test (Eduard).
  - Add two new negative test cases (Eduard).
  - Rebased.
Changes in v2:
  - Add guard suggested by Hari in tnum_step, to avoid undefined
    behavior spotted by AI code review.
  - Add explanation diagrams in code as suggested by Eduard.
  - Rework conditions for readability as suggested by Eduard.
  - Updated reference to SMT formula.
  - Rebased.
====================

Link: https://patch.msgid.link/cover.1772225741.git.paul.chaignon@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
2026-02-27 16:11:50 -08:00
Paul Chaignon
024cea2d64 selftests/bpf: Avoid simplification of crafted bounds test
The reg_bounds_crafted tests validate the verifier's range analysis
logic. They focus on the actual ranges and thus ignore the tnum. As a
consequence, they carry the assumption that the tested cases can be
reproduced in userspace without using the tnum information.

Unfortunately, the previous change the refinement logic breaks that
assumption for one test case:

  (u64)2147483648 (u32)<op> [4294967294; 0x100000000]

The tested bytecode is shown below. Without our previous improvement, on
the false branch of the condition, R7 is only known to have u64 range
[0xfffffffe; 0x100000000]. With our improvement, and using the tnum
information, we can deduce that R7 equals 0x100000000.

  19: (bc) w0 = w6                ; R6=0x80000000
  20: (bc) w0 = w7                ; R7=scalar(smin=umin=0xfffffffe,smax=umax=0x100000000,smin32=-2,smax32=0,var_off=(0x0; 0x1ffffffff))
  21: (be) if w6 <= w7 goto pc+3  ; R6=0x80000000 R7=0x100000000

R7's tnum is (0; 0x1ffffffff). On the false branch, regs_refine_cond_op
refines R7's u32 range to [0; 0x7fffffff]. Then, __reg32_deduce_bounds
refines the s32 range to 0 using u32 and finally also sets u32=0.
From this, __reg_bound_offset improves the tnum to (0; 0x100000000).
Finally, our previous patch uses this new tnum to deduce that it only
intersect with u64=[0xfffffffe; 0x100000000] in a single value:
0x100000000.

Because the verifier uses the tnum to reach this constant value, the
selftest is unable to reproduce it by only simulating ranges. The
solution implemented in this patch is to change the test case such that
there is more than one overlap value between u64 and the tnum. The max.
u64 value is thus changed from 0x100000000 to 0x300000000.

Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Signed-off-by: Paul Chaignon <paul.chaignon@gmail.com>
Link: https://lore.kernel.org/r/50641c6a7ef39520595dcafa605692427c1006ec.1772225741.git.paul.chaignon@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
2026-02-27 16:11:50 -08:00
Paul Chaignon
e6ad477d1b selftests/bpf: Test refinement of single-value tnum
This patch introduces selftests to cover the new bounds refinement
logic introduced in the previous patch. Without the previous patch,
the first two tests fail because of the invariant violation they
trigger. The last test fails because the R10 access is not detected as
dead code. In addition, all three tests fail because of R0 having a
non-constant value in the verifier logs.

In addition, the last two cases are covering the negative cases: when we
shouldn't refine the bounds because the u64 and tnum overlap in at least
two values.

Signed-off-by: Paul Chaignon <paul.chaignon@gmail.com>
Link: https://lore.kernel.org/r/90d880c8cf587b9f7dc715d8961cd1b8111d01a8.1772225741.git.paul.chaignon@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
2026-02-27 16:11:50 -08:00
Paul Chaignon
efc11a6678 bpf: Improve bounds when tnum has a single possible value
We're hitting an invariant violation in Cilium that sometimes leads to
BPF programs being rejected and Cilium failing to start [1]. The
following extract from verifier logs shows what's happening:

  from 201 to 236: R1=0 R6=ctx() R7=1 R9=scalar(smin=umin=smin32=umin32=3584,smax=umax=smax32=umax32=3840,var_off=(0xe00; 0x100)) R10=fp0
  236: R1=0 R6=ctx() R7=1 R9=scalar(smin=umin=smin32=umin32=3584,smax=umax=smax32=umax32=3840,var_off=(0xe00; 0x100)) R10=fp0
  ; if (magic == MARK_MAGIC_HOST || magic == MARK_MAGIC_OVERLAY || magic == MARK_MAGIC_ENCRYPT) @ bpf_host.c:1337
  236: (16) if w9 == 0xe00 goto pc+45   ; R9=scalar(smin=umin=smin32=umin32=3585,smax=umax=smax32=umax32=3840,var_off=(0xe00; 0x100))
  237: (16) if w9 == 0xf00 goto pc+1
  verifier bug: REG INVARIANTS VIOLATION (false_reg1): range bounds violation u64=[0xe01, 0xe00] s64=[0xe01, 0xe00] u32=[0xe01, 0xe00] s32=[0xe01, 0xe00] var_off=(0xe00, 0x0)

We reach instruction 236 with two possible values for R9, 0xe00 and
0xf00. This is perfectly reflected in the tnum, but of course the ranges
are less accurate and cover [0xe00; 0xf00]. Taking the fallthrough path
at instruction 236 allows the verifier to reduce the range to
[0xe01; 0xf00]. The tnum is however not updated.

With these ranges, at instruction 237, the verifier is not able to
deduce that R9 is always equal to 0xf00. Hence the fallthrough pass is
explored first, the verifier refines the bounds using the assumption
that R9 != 0xf00, and ends up with an invariant violation.

This pattern of impossible branch + bounds refinement is common to all
invariant violations seen so far. The long-term solution is likely to
rely on the refinement + invariant violation check to detect dead
branches, as started by Eduard. To fix the current issue, we need
something with less refactoring that we can backport.

This patch uses the tnum_step helper introduced in the previous patch to
detect the above situation. In particular, three cases are now detected
in the bounds refinement:

1. The u64 range and the tnum only overlap in umin.
   u64:  ---[xxxxxx]-----
   tnum: --xx----------x-

2. The u64 range and the tnum only overlap in the maximum value
   represented by the tnum, called tmax.
   u64:  ---[xxxxxx]-----
   tnum: xx-----x--------

3. The u64 range and the tnum only overlap in between umin (excluded)
   and umax.
   u64:  ---[xxxxxx]-----
   tnum: xx----x-------x-

To detect these three cases, we call tnum_step(tnum, umin), which
returns the smallest member of the tnum greater than umin, called
tnum_next here. We're in case (1) if umin is part of the tnum and
tnum_next is greater than umax. We're in case (2) if umin is not part of
the tnum and tnum_next is equal to tmax. Finally, we're in case (3) if
umin is not part of the tnum, tnum_next is inferior or equal to umax,
and calling tnum_step a second time gives us a value past umax.

This change implements these three cases. With it, the above bytecode
looks as follows:

  0: (85) call bpf_get_prandom_u32#7    ; R0=scalar()
  1: (47) r0 |= 3584                    ; R0=scalar(smin=0x8000000000000e00,umin=umin32=3584,smin32=0x80000e00,var_off=(0xe00; 0xfffffffffffff1ff))
  2: (57) r0 &= 3840                    ; R0=scalar(smin=umin=smin32=umin32=3584,smax=umax=smax32=umax32=3840,var_off=(0xe00; 0x100))
  3: (15) if r0 == 0xe00 goto pc+2      ; R0=3840
  4: (15) if r0 == 0xf00 goto pc+1
  4: R0=3840
  6: (95) exit

In addition to the new selftests, this change was also verified with
Agni [3]. For the record, the raw SMT is available at [4]. The property
it verifies is that: If a concrete value x is contained in all input
abstract values, after __update_reg_bounds, it will continue to be
contained in all output abstract values.

Link: https://github.com/cilium/cilium/issues/44216 [1]
Link: https://pchaigno.github.io/test-verifier-complexity.html [2]
Link: https://github.com/bpfverif/agni [3]
Link: https://pastebin.com/raw/naCfaqNx [4]
Fixes: 0df1a55afa ("bpf: Warn on internal verifier errors")
Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Tested-by: Marco Schirrmeister <mschirrmeister@gmail.com>
Co-developed-by: Harishankar Vishwanathan <harishankar.vishwanathan@gmail.com>
Signed-off-by: Harishankar Vishwanathan <harishankar.vishwanathan@gmail.com>
Signed-off-by: Paul Chaignon <paul.chaignon@gmail.com>
Link: https://lore.kernel.org/r/ef254c4f68be19bd393d450188946821c588565d.1772225741.git.paul.chaignon@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
2026-02-27 16:11:50 -08:00
Harishankar Vishwanathan
76e954155b bpf: Introduce tnum_step to step through tnum's members
This commit introduces tnum_step(), a function that, when given t, and a
number z returns the smallest member of t larger than z. The number z
must be greater or equal to the smallest member of t and less than the
largest member of t.

The first step is to compute j, a number that keeps all of t's known
bits, and matches all unknown bits to z's bits. Since j is a member of
the t, it is already a candidate for result. However, we want our result
to be (minimally) greater than z.

There are only two possible cases:

(1) Case j <= z. In this case, we want to increase the value of j and
make it > z.
(2) Case j > z. In this case, we want to decrease the value of j while
keeping it > z.

(Case 1) j <= z

t = xx11x0x0
z = 10111101 (189)
j = 10111000 (184)
         ^
         k

(Case 1.1) Let's first consider the case where j < z. We will address j
== z later.

Since z > j, there had to be a bit position that was 1 in z and a 0 in
j, beyond which all positions of higher significance are equal in j and
z. Further, this position could not have been unknown in a, because the
unknown positions of a match z. This position had to be a 1 in z and
known 0 in t.

Let k be position of the most significant 1-to-0 flip. In our example, k
= 3 (starting the count at 1 at the least significant bit).  Setting (to
1) the unknown bits of t in positions of significance smaller than
k will not produce a result > z. Hence, we must set/unset the unknown
bits at positions of significance higher than k. Specifically, we look
for the next larger combination of 1s and 0s to place in those
positions, relative to the combination that exists in z. We can achieve
this by concatenating bits at unknown positions of t into an integer,
adding 1, and writing the bits of that result back into the
corresponding bit positions previously extracted from z.

>From our example, considering only positions of significance greater
than k:

t =  xx..x
z =  10..1
    +    1
     -----
     11..0

This is the exact combination 1s and 0s we need at the unknown bits of t
in positions of significance greater than k. Further, our result must
only increase the value minimally above z. Hence, unknown bits in
positions of significance smaller than k should remain 0. We finally
have,

result = 11110000 (240)

(Case 1.2) Now consider the case when j = z, for example

t = 1x1x0xxx
z = 10110100 (180)
j = 10110100 (180)

Matching the unknown bits of the t to the bits of z yielded exactly z.
To produce a number greater than z, we must set/unset the unknown bits
in t, and *all* the unknown bits of t candidates for being set/unset. We
can do this similar to Case 1.1, by adding 1 to the bits extracted from
the masked bit positions of z. Essentially, this case is equivalent to
Case 1.1, with k = 0.

t =  1x1x0xxx
z =  .0.1.100
    +       1
    ---------
     .0.1.101

This is the exact combination of bits needed in the unknown positions of
t. After recalling the known positions of t, we get

result = 10110101 (181)

(Case 2) j > z

t = x00010x1
z = 10000010 (130)
j = 10001011 (139)
	^
	k

Since j > z, there had to be a bit position which was 0 in z, and a 1 in
j, beyond which all positions of higher significance are equal in j and
z. This position had to be a 0 in z and known 1 in t. Let k be the
position of the most significant 0-to-1 flip. In our example, k = 4.

Because of the 0-to-1 flip at position k, a member of t can become
greater than z if the bits in positions greater than k are themselves >=
to z. To make that member *minimally* greater than z, the bits in
positions greater than k must be exactly = z. Hence, we simply match all
of t's unknown bits in positions more significant than k to z's bits. In
positions less significant than k, we set all t's unknown bits to 0
to retain minimality.

In our example, in positions of greater significance than k (=4),
t=x000. These positions are matched with z (1000) to produce 1000. In
positions of lower significance than k, t=10x1. All unknown bits are set
to 0 to produce 1001. The final result is:

result = 10001001 (137)

This concludes the computation for a result > z that is a member of t.

The procedure for tnum_step() in this commit implements the idea
described above. As a proof of correctness, we verified the algorithm
against a logical specification of tnum_step. The specification asserts
the following about the inputs t, z and output res that:

1. res is a member of t, and
2. res is strictly greater than z, and
3. there does not exist another value res2 such that
	3a. res2 is also a member of t, and
	3b. res2 is greater than z
	3c. res2 is smaller than res

We checked the implementation against this logical specification using
an SMT solver. The verification formula in SMTLIB format is available
at [1]. The verification returned an "unsat": indicating that no input
assignment exists for which the implementation and the specification
produce different outputs.

In addition, we also automatically generated the logical encoding of the
C implementation using Agni [2] and verified it against the same
specification. This verification also returned an "unsat", confirming
that the implementation is equivalent to the specification. The formula
for this check is also available at [3].

Link: https://pastebin.com/raw/2eRWbiit [1]
Link: https://github.com/bpfverif/agni [2]
Link: https://pastebin.com/raw/EztVbBJ2 [3]
Co-developed-by: Srinivas Narayana <srinivas.narayana@rutgers.edu>
Signed-off-by: Srinivas Narayana <srinivas.narayana@rutgers.edu>
Co-developed-by: Santosh Nagarakatte <santosh.nagarakatte@rutgers.edu>
Signed-off-by: Santosh Nagarakatte <santosh.nagarakatte@rutgers.edu>
Signed-off-by: Harishankar Vishwanathan <harishankar.vishwanathan@gmail.com>
Link: https://lore.kernel.org/r/93fdf71910411c0f19e282ba6d03b4c65f9c5d73.1772225741.git.paul.chaignon@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
2026-02-27 16:11:50 -08:00