- Make the clearcpuid= boot parameter less prominent
and warn about its dangers & caveats (Borislav Petkov)
- Do not access the (new) PLATFORM_ID MSR when running as a guest
(Borislav Petkov)
- x86 ftrace: Relocate %rip-relative percpu refs in dynamic
trampolines, to fix crash when using such trampolines
(Alexis Lothoré)
- Fix x86-64 CFI build error (Peter Zijlstra)
- Revert FPU signal return magic number check optimization, because
it broke CRIU and gVisor in certain FPU configurations
(Andrei Vagin)
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Merge tag 'x86-urgent-2026-05-31' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull x86 fixes from Ingo Molnar:
- Make the clearcpuid= boot parameter less prominent
and warn about its dangers & caveats (Borislav Petkov)
- Do not access the (new) PLATFORM_ID MSR when running
as a guest (Borislav Petkov)
- x86 ftrace: Relocate %rip-relative percpu refs in dynamic
trampolines, to fix crash when using such trampolines
(Alexis Lothoré)
- Fix x86-64 CFI build error (Peter Zijlstra)
- Revert FPU signal return magic number check optimization,
because it broke CRIU and gVisor in certain FPU configurations
(Andrei Vagin)
* tag 'x86-urgent-2026-05-31' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
Revert "x86/fpu: Refine and simplify the magic number check during signal return"
x86/kvm/vmx: Fix x86_64 CFI build
x86/ftrace: Relocate %rip-relative percpu refs in dynamic trampolines
x86/microcode: Do not access MSR_IA32_PLATFORM_ID when running as a guest
Documentation/arch/x86: Hide clearcpuid=
This reverts
dc8aa31a7a ("x86/fpu: Refine and simplify the magic number check during signal return").
The aforementioned commit broke applications that construct signal frames in
userspace (such as CRIU and gVisor) if the frame's xstate size is smaller than
the kernel's fpstate->user_size.
Furthermore, this introduces a critical issue for checkpoint/restore tools
like CRIU. If a process is checkpointed while inside a signal handler, its
stack contains a signal frame formatted according to the source host's xstate
capabilities.
If that process is later restored on a destination host with larger xstate
capabilities (e.g., a newer CPU with more features enabled, resulting in
a larger fpstate->user_size), the kernel will look for FP_XSTATE_MAGIC2 at the
destination host's larger user_size offset instead of the offset encoded in
the frame's fx_sw->xstate_size.
This causes the magic2 check to fail, forcing sigreturn to silently fall back
to "FX-only" mode. Upon return from the signal handler, the process's extended
state is reset to initial values instead of being restored, leading to silent
data corruption.
The aforementioned commit cited
d877550eaf ("x86/fpu: Stop relying on userspace for info to fault in xsave buffer")
as justification to stop relying on userspace for the magic number check.
However, these two changes are fundamentally different. The last one only
changed how much memory the kernel ensures is paged-in before running XRSTOR
to prevent an infinite loop. It did not change the signal frame format or how
the layout is validated.
Reverting this change restores the use of fx_sw->xstate_size for
locating magic2 and restores the necessary sanity checks, ensuring that
the signal frame remains self-describing and portable.
[ bp: Massage commit message. ]
Fixes: dc8aa31a7a ("x86/fpu: Refine and simplify the magic number check during signal return")
Signed-off-by: Andrei Vagin <avagin@google.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Acked-by: Chang S. Bae <chang.seok.bae@intel.com>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/all/20260429000623.3356606-1-avagin@google.com
Use READ_ONCE() when reading entries/indices from the guest-accessible
Page State Change buffer to defend against TOCTOU bugs.
Don't bother with READ_ONCE()/WRITE_ONCE() for cases where KVM is writing
(and not consuming the result!), as the guest isn't supposed to touch the
buffer while it's being processed. I.e. using READ_ONCE() is all about
protecting against misbehaving guests.
Fixes: 9b54e248d2 ("KVM: SEV: Add support to handle Page State Change VMGEXIT")
Cc: stable@vger.kernel.org
Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-ID: <20260501202250.2115252-11-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
When processing Page State Change (PSC) requests, validate the PSC buffer
against the effective size of the scratch area, which could be less than
the maximum size if the guest provided a pointer that isn't exactly at the
start of the GHCB shared buffer.
Fixes: 9b54e248d2 ("KVM: SEV: Add support to handle Page State Change VMGEXIT")
Cc: stable@vger.kernel.org
Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
Reviewed-by: Michael Roth <michael.roth@amd.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-ID: <20260501202250.2115252-10-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Stop explicitly passing the PSC buffer to snp_begin_psc(): it *must*
be the scratch area. This will allow fixing a variety of bugs without
further complicating the code.
No functional change intended.
Cc: stable@vger.kernel.org
Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
Reviewed-by: Michael Roth <michael.roth@amd.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-ID: <20260501202250.2115252-9-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Now that all paths in KVM properly validate the length needed for the
scratch area, and are guaranteed to pass in a non-zero length, WARN if KVM
attempts to configured the scratch area with min_len==0 to guard against
future bugs.
Cc: stable@vger.kernel.org
Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
Reviewed-by: Michael Roth <michael.roth@amd.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-ID: <20260501202250.2115252-8-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
When setting the length of the GHCB scratch area, and the area is in the
GHCB shared buffer, set the effective length of the scratch area to the max
possible size given the start of the guest-provided pointer, and the end of
the shared buffer.
The code was "fine" when first introduced, as KVM doesn't consult the
length of the buffer when emulating MMIO, because the passed in @len always
specifies the *max* size required. But for PSC requests, the incoming @len
is just the minimum length (to process the header), and KVM needs to know
the full size of the scratch area to avoid buffer overflows (spoiler alert).
Opportunistically rename @len => @min_len to better reflect its role.
Fixes: 9b54e248d2 ("KVM: SEV: Add support to handle Page State Change VMGEXIT")
Cc: stable@vger.kernel.org
Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
Reviewed-by: Michael Roth <michael.roth@amd.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-ID: <20260501202250.2115252-7-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
When handling a Page State Change (PSC) #VMGEXIT use the size of the PSC
header as the minimum size for the scratch area. Per the GHCB spec, PSC
requests do NOT provide the length, i.e. using control->exit_info_2 for the
length is completely made up behavior. The existing code "works", e.g.
even though Linux-as-a-guest always passes '0', because KVM doesn't do
anything with the length when the request is in the GHCB's shared buffer.
Use the header as the min length. Once the header is retrieved, KVM can
use the specified indices to compute the full size of the request.
Fixes: 9b54e248d2 ("KVM: SEV: Add support to handle Page State Change VMGEXIT")
Cc: stable@vger.kernel.org
Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
Reviewed-by: Michael Roth <michael.roth@amd.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-ID: <20260501202250.2115252-6-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Explicitly ignore Port I/O requests of length '0' (or count '0'), so that
setting up the software scratch area (and other code) doesn't have to
worry about underflowing the length, and to allow for WARNing on trying
to configure the scratch area with len==0.
Fixes: 291bd20d5d ("KVM: SVM: Add initial support for a VMGEXIT VMEXIT")
Cc: stable@vger.kernel.org
Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-ID: <20260501202250.2115252-5-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
When using GHCB v2+, reject MMIO requests that are larger than 8 bytes.
Per the GHCB spec:
SW_EXITINFO2 must be less than or equal to 0x7fffffff for version 1 and
less than or equal to 0x8 for all other versions.
Fixes: 4af663c2f6 ("KVM: SEV: Allow per-guest configuration of GHCB protocol version")
Cc: stable@vger.kernel.org
Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-ID: <20260501202250.2115252-4-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Explicitly ignore MMIO requests of length '0', so that setting up the
software scratch area (and other code) doesn't have to worry about
underflowing the length, and to allow for special casing '0' in the
future.
Fixes: 8f423a80d2 ("KVM: SVM: Support MMIO for an SEV-ES guest")
Cc: stable@vger.kernel.org
Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-ID: <20260501202250.2115252-3-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
As per the GHCB spec, when using GHCB v2+ require the software scratch area
to reside in the GHCB's shared buffer. Note, things like Page State Change
(PSC) requests _rely_ on this behavior, as the guest can't provide a length
when making the request, i.e. the size of the guest payload is bounded by
the size of the shared buffer.
Failure to force usage of the GHCB, and a slew of other flaws, lets a
malicious SNP guest corrupt host kernel heap memory, and leak host heap
layout information.
setup_vmgexit_scratch() allocates a buffer via kvzalloc(exit_info_2),
where exit_info_2 is guest-controlled. With exit_info_2=24, this yields
a 24-byte allocation in kmalloc-cg-32 (32-byte slab objects). The buffer
holds an 8-byte psc_hdr followed by 8-byte psc_entry structs, so only
entries[0] and entries[1] are in-bounds.
snp_begin_psc() validates end_entry against VMGEXIT_PSC_MAX_COUNT (253)
but NOT against the actual buffer size:
idx_end = hdr->end_entry;
if (idx_end >= VMGEXIT_PSC_MAX_COUNT) { // checks 253, not buffer
snp_complete_psc(svm, ...);
return 1;
}
for (idx = idx_start; idx <= idx_end; idx++) {
entry_start = entries[idx]; // OOB when idx >= 2
The guest sets end_entry=10+, causing the host to iterate entries[2+]
which are OOB into adjacent slab objects. For each OOB entry:
- The host reads 8 bytes (OOB READ / info leak oracle)
- If the data passes PSC validation, __snp_complete_one_psc() writes
cur_page = 1 or 512 into the entry (OOB WRITE, sev.c:3806)
- If validation fails, the error response reveals whether adjacent
memory is zero vs non-zero (information disclosure to guest)
The guest controls allocation size (exit_info_2), entry range
(cur_entry/end_entry), and can fire unlimited VMGEXITs to repeatedly
hit different slab positions.
By exploiting the variety of bugs, a malicious SEV-SNP guest can:
- OOB read adjacent kmalloc-cg-32 objects (heap layout disclosure)
- OOB write cur_page bits into adjacent objects (heap corruption)
- Trigger use-after-free conditions across VMGEXITs
E.g. with KASAN enabled, a single insmod of the PoC guest module
produces 73 KASAN reports:
BUG: KASAN: slab-out-of-bounds in snp_begin_psc+0x126/0x890
Read of size 8 at addr ffff888219ffb5e0 by task qemu-system-x86/2199
BUG: KASAN: slab-out-of-bounds in snp_begin_psc+0x468/0x890
Write of size 8 at addr ffff888351566648 by task qemu-system-x86/2199
The buggy address belongs to the object at ffff888XXXXXXXXX
which belongs to the cache kmalloc-cg-32 of size 32
The buggy address is located N bytes to the right of
allocated 32-byte region [ffff888XXXXXXXXX, ffff888XXXXXXXXX)
Breakdown:
62 slab-out-of-bounds (reads + writes past allocation)
7 slab-use-after-free
4 use-after-free
All credit to Stan for the wonderful description and reproducer!
Reported-by: Stan Shaw <shawstan96@gmail.com>
Cc: Michael Roth <michael.roth@amd.com>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Cc: Peter Gonda <pgonda@google.com>
Cc: Jacky Li <jackyli@google.com>
Fixes: 4af663c2f6 ("KVM: SEV: Allow per-guest configuration of GHCB protocol version")
Cc: stable@vger.kernel.org
Signed-off-by: Michael Roth <michael.roth@amd.com>
[sean: write changelog]
Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-ID: <20260501202250.2115252-2-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
- Include the kernel's linux/mman.h in KVM selftests to ensure MADV_COLLAPSE
is defined, as older libc versions may not provide it.
- Include execinfo.h if and only if KVM selftests are building against glibc,
and provide a test_dump_stack() for non-glibc builds.
- Fudge around an RCU splat in the emegerncy reboot code that is technically
a legitimate flaw, but in practice is a non-issue and fixing the flaw, e.g.
by adding locking, would incur meaningful risk, i.e. do more harm than good.
- Rate-limit global clock updates once again (but without delayed work), as
KVM was subtly relying on the old rate-limiting for NPT correction to guard
against "update storms" when running without a master clock on systems with
overcommitted CPUs.
- Fix a brown paper bag goof where KVM checked if ERAPS is "dirty" instead of
marking it dirty when emulating INVPCID.
- Flush the TLB when transitioning from xAVIC => x2AVIC to ensure the CPU TLB
doesn't contain AVIC-tagged entries for the APIC base GPA.
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Merge tag 'kvm-x86-fixes-7.1-rc6' of https://github.com/kvm-x86/linux into HEAD
KVM x86 fixes for 7.1-rcN
- Include the kernel's linux/mman.h in KVM selftests to ensure MADV_COLLAPSE
is defined, as older libc versions may not provide it.
- Include execinfo.h if and only if KVM selftests are building against glibc,
and provide a test_dump_stack() for non-glibc builds.
- Fudge around an RCU splat in the emegerncy reboot code that is technically
a legitimate flaw, but in practice is a non-issue and fixing the flaw, e.g.
by adding locking, would incur meaningful risk, i.e. do more harm than good.
- Rate-limit global clock updates once again (but without delayed work), as
KVM was subtly relying on the old rate-limiting for NPT correction to guard
against "update storms" when running without a master clock on systems with
overcommitted CPUs.
- Fix a brown paper bag goof where KVM checked if ERAPS is "dirty" instead of
marking it dirty when emulating INVPCID.
- Flush the TLB when transitioning from xAVIC => x2AVIC to ensure the CPU TLB
doesn't contain AVIC-tagged entries for the APIC base GPA.
It was missed that idt_do_interrupt_irqoff() gets compiled on x84_64;
this is a problem for CFI builds because it includes an unadorned
indirect call. It is however completely dead code.
Rework things to not emit this function at all.
Fixes: 0701c9e17b ("x86/kvm/vmx: Move IRQ/NMI dispatch from KVM into x86 core")
Reported-by: Nathan Chancellor <nathan@kernel.org>
Reported-by: Calvin Owens <calvin@wbinvd.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: Nathan Chancellor <nathan@kernel.org>
Link: https://patch.msgid.link/20260526090631.GA4149641@noisy.programming.kicks-ass.net
With CONFIG_CALL_DEPTH_TRACKING enabled on an x86 retbleed-affected platform
(eg: Skylake), with retbleed=stuff, registering a dynamic ftrace trampoline
crashes on the first call into the traced function:
BUG: unable to handle page fault for address: ffff88817ae18880
#PF: supervisor write access in kernel mode
#PF: error_code(0x0002) - not-present page
PGD 4b53067 P4D 4b53067 PUD 0
Oops: Oops: 0002 [#1] SMP PTI
CPU: 3 UID: 0 PID: 187 Comm: usleep Not tainted 7.0.10 #243 PREEMPT(full)
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Arch Linux 1.17.0-2-2 04/01/2014
Code: 24 78 00 00 00 00 48 89 ea 48 89 54 24 20 48 8b b4 24 b8 00 00 00 48 8b bc 24 b0 00 00 00 48 89 bc 24 80 00 00 00 48 83 ef 05 <65> 48 c1 3d 1f a8 b6 02 05 48 8b 15 f6 00 00 00 4c 89 3c 24 4c 89
Call Trace:
<TASK>
? find_held_lock
? exc_page_fault
? lock_release
? __x64_sys_clock_nanosleep
? lockdep_hardirqs_on_prepare
? trace_hardirqs_on
__x64_sys_clock_nanosleep
do_syscall_64
? exc_page_fault
? call_depth_return_thunk
entry_SYSCALL_64_after_hwframe
...
Kernel panic - not syncing: Fatal exception
This small reproducer allows to easily trigger the crash:
# echo 'p __x64_sys_clock_nanosleep' > /sys/kernel/tracing/kprobe_events
# echo 1 > /sys/kernel/tracing/events/kprobes/p___x64_sys_clock_nanosleep_0/enable
# usleep 1
Monitoring the crash under GDB points to the exact instruction in charge of
incrementing the call depth:
sarq $5, %gs:__x86_call_depth(%rip)
This instruction matches the one inserted by the ftrace_regs_caller from
ftrace_64.S. This emitted code was likely working fine until the introduction
of
59bec00ace ("x86/percpu: Introduce %rip-relative addressing to PER_CPU_VAR()"):
it has made the call depth accounting addressing relative to $rip, instead of
being based on an absolute address.
As this code exact location depends on where the trampoline lives in memory,
the corresponding displacement needs to be adjusted at runtime to actually
correctly find the per-cpu __x86_call_depth value, otherwise the targeted
address is wrong, leading to the page fault seen above.
Fix the %rip-relative displacement of the copied CALL_DEPTH_ACCOUNT
instruction (from ftrace_regs_caller) by calling text_poke_apply_relocation(),
as it is done for example by the x86 BPF JIT compiler through
x86_call_depth_emit_accounting(). This corrects both CALL_DEPTH_ACCOUNT slots,
in ftrace_caller and ftrace_regs_caller.
[ bp: Massage. ]
Fixes: 59bec00ace ("x86/percpu: Introduce %rip-relative addressing to PER_CPU_VAR()")
Signed-off-by: Alexis Lothoré (eBPF Foundation) <alexis.lothore@bootlin.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
Cc: <stable@kernel.org>
Link: https://patch.msgid.link/20260527-fix_call_depth_in_trampoline-v1-1-1c1abc8ae310@bootlin.com
Patch in Fixes: causes the usual:
unchecked MSR access error: RDMSR from 0x17 at ... (intel_get_platform_id)
Call Trace:
early_init_intel
early_cpu_init
setup_arch
_printk
start_kernel
x86_64_start_reservations
x86_64_start_kernel
common_startup_64
because the kernel is booted in a guest.
In order to avoid it, this MSR access needs to be prevented when running
virtualized. That is usually done by checking X86_FEATURE_HYPERVISOR but
for this particular case it is too early yet.
The platform ID needs to be read as early as when microcode is loaded on
the BSP:
load_ucode_bsp ... -> get_microcode_blob ... -> intel_find_matching_signature
and by that time, CPUID leafs haven't been parsed yet.
The microcode loader already has logic to check early whether the kernel
is running virtualized so make that globally available to arch/x86/. The
query whether running virtualized is getting more and more prominent in
recent times so might as well make it an arch-global var which the rest
of the code can use.
Fixes: d8630b67ca ("x86/cpu: Add platform ID to CPU info structure")
Reported-by: Vishal Verma <vishal.l.verma@intel.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Binbin Wu <binbin.wu@linux.intel.com>
Reviewed-by: Xiaoyao Li <xiaoyao.li@intel.com>
Tested-by: Binbin Wu <binbin.wu@linux.intel.com>
Link: https://lore.kernel.org/all/20260430020953.1405535-1-binbin.wu@linux.intel.com
- Fix ITS EventID sanitisation when restoring an interrupt translation
table.
- Fix PPI memory leak when failing to initialise a vcpu.
- Correctly return an error when the validation of a hypervisor trace
descriptor fails, and limit this validation to protected mode only.
RISC-V:
- Fix invalid HVA warning in steal-time recording
- Return SBI_ERR_FAILURE to guest upon OOM in pmu_event_info()
and pmu_snapshot_set_shmem()
- Fix NULL pointer dereference in SBI v0.1 SEND_IPI handler
- Fix sign extension of value for MMIO loads
s390:
- Fix bugs in vSIE (nested virtualization) and UCONTROL, caused by the page
table rewrite.
x86:
- Apply erratum #1235 workaround (disable AVIC IPI virtualization) on Hygon
Family 18h, just like on AMD Family 17h.
- When KVM_CAP_X86_APIC_BUS_CYCLES_NS is queried on a specific VM, return
the VM's configured APIC bus frequency instead of the default. This
is less confusing (read: not wrong) and makes it easier to fill in CPUID
information that communicates the APIC bus frequency to the guest.
Selftests:
- Do not include glibc-internal <bits/endian.h>; it worked by chance and
broke building KVM selftests with musl.
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Merge tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm
Pull kvm fixes from Paolo Bonzini:
"arm64:
- Fix ITS EventID sanitisation when restoring an interrupt
translation table.
- Fix PPI memory leak when failing to initialise a vcpu.
- Correctly return an error when the validation of a hypervisor trace
descriptor fails, and limit this validation to protected mode only.
RISC-V:
- Fix invalid HVA warning in steal-time recording
- Return SBI_ERR_FAILURE to guest upon OOM in pmu_event_info() and
pmu_snapshot_set_shmem()
- Fix NULL pointer dereference in SBI v0.1 SEND_IPI handler
- Fix sign extension of value for MMIO loads
s390:
- Fix bugs in vSIE (nested virtualization) and UCONTROL, caused by
the page table rewrite.
x86:
- Apply erratum #1235 workaround (disable AVIC IPI virtualization) on
Hygon Family 18h, just like on AMD Family 17h.
- When KVM_CAP_X86_APIC_BUS_CYCLES_NS is queried on a specific VM,
return the VM's configured APIC bus frequency instead of the
default. This is less confusing (read: not wrong) and makes it
easier to fill in CPUID information that communicates the APIC bus
frequency to the guest.
Selftests:
- Do not include glibc-internal <bits/endian.h>; it worked by chance
and broke building KVM selftests with musl"
* tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm:
KVM: SVM: Disable AVIC IPI virtualization on Hygon Family 18h (erratum #1235)
KVM: selftests: Verify that KVM returns the configured APIC cycle length
KVM: x86: Return the VM's configured APIC bus frequency when queried
KVM: selftests: elf: Include <endian.h> instead of <bits/endian.h>
KVM: s390: Properly reset zero bit in PGSTE
KVM: s390: vsie: Fix redundant rmap entries
KVM: s390: vsie: Fix unshadowing logic
KVM: s390: Fix leaking kvm_s390_mmu_cache in case of errors
KVM: s390: vsie: Fix memory leak when unshadowing
KVM: arm64: Fix nVHE/pKVM hyp tracing error on invalid desc
KVM: arm64: vgic: Free private_irqs when init fails after allocation
KVM: arm64: vgic-its: Reject restored DTE with out-of-range num_eventid_bits
RISC-V: KVM: Fix sign extension for MMIO loads
RISC-V: KVM: Fix NULL pointer dereference in SBI v0.1 SEND_IPI handler
riscv: kvm: return SBI_ERR_FAILURE for pmu_event_info() when OOM
riscv: kvm: return SBI_ERR_FAILURE for pmu_snapshot_set_shmem() when OOM
RISC-V: KVM: Fix invalid HVA warning in steal-time recording
- On SEV guests, handle set_memory_{encrypted,decrypted}()
failures more conservatively by assuming that all affected
pages are unencrypted (Carlos López)
- Disable broadcast TLB flush when PCID is disabled
(Tom Lendacky)
- Fix VMX vs. hrtimer_rearm_deferred() regression
(Peter Zijlstra)
- Move IRQ/NMI dispatch code from KVM into x86 core, to
prepare for a KVM x2apic fix (Peter Zijlstra)
- Fix incorrect munmap() size on map_vdso() failure
(Guilherme Giacomo Simoes)
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Merge tag 'x86-urgent-2026-05-24' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull x86 fixes from Ingo Molnar:
- On SEV guests, handle set_memory_{encrypted,decrypted}() failures
more conservatively by assuming that all affected pages are
unencrypted (Carlos López)
- Disable broadcast TLB flush when PCID is disabled (Tom Lendacky)
- Fix VMX vs. hrtimer_rearm_deferred() regression (Peter Zijlstra)
- Move IRQ/NMI dispatch code from KVM into x86 core, to prepare for a
KVM x2apic fix (Peter Zijlstra)
- Fix incorrect munmap() size on map_vdso() failure (Guilherme Giacomo
Simoes)
* tag 'x86-urgent-2026-05-24' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
virt: sev-guest: Explicitly leak pages in unknown state
x86/mm: Disable broadcast TLB flush when PCID is disabled
x86/kvm/vmx: Fix VMX vs hrtimer_rearm_deferred()
x86/kvm/vmx: Move IRQ/NMI dispatch from KVM into x86 core
x86/vdso: Fix incorrect size in munmap() on map_vdso() failure
Hygon Family 18h CPUs are derived from AMD Family 17h (Zen1) silicon and
share the same erratum #1235: hardware may read a stale IsRunning=1 bit
during ICR write emulation and silently fail to generate an
AVIC_IPI_FAILURE_TARGET_NOT_RUNNING VM-Exit on the sending vCPU.
The absence of the VM-Exit causes KVM to miss the required wakeup of
blocking target vCPUs, leading to hung vCPUs and unbounded delays in
guest execution.
Extend the existing AMD Family 17h erratum #1235 workaround to also cover
Hygon Family 18h. With IPI virtualization disabled, KVM never sets
IsRunning=1 in the Physical ID table, so every non-self IPI generates a
VM-Exit and is correctly emulated.
Fixes: 8de4a1c816 ("KVM: SVM: Disable (x2)AVIC IPI virtualization if CPU has erratum #1235")
Cc: <stable@vger.kernel.org>
Signed-off-by: Tina Zhang <zhang_wei@open-hieco.net>
Message-ID: <20260522040014.3380201-1-zhang_wei@open-hieco.net>
When KVM_CAP_X86_APIC_BUS_CYCLES_NS is queried on a specific VM, return the
VM's configured APIC bus frequency, not KVM's default. Aside from the fact
that returning the default frequency is blatantly wrong if userspace has
changed the frequency, returning the configured frequency means userspace
can blindly trust the result, e.g. when filling PV CPUID information that
communicates the APIC bus frequency to the guest.
Fixes: 6fef518594 ("KVM: x86: Add a capability to configure bus frequency for APIC timer")
Reported-by: David Woodhouse <dwmw2@infradead.org>
Closes: https://lore.kernel.org/all/ab84153e33fbe7c25667f595c56b310d4d5a93ef.camel@infradead.org
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-ID: <20260522173526.3539407-2-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Flush the current TLB when xAVIC *or* x2AVIC is activated, as KVM is
(apparently) responsible for purging TLB entries when transitioning from
xAVIC to x2AVIC. The APM says a whole lot of nothing about TLB flushing
with respect to (x2)AVIC, but empirical data strongly suggests hardware
also does a whole lot of nothing.
Failure to flush the TLB when enabling x2AVIC can lead to guest accesses
to the APIC base address getting incorrectly redirected to the virtual
APIC page. The flaw most visibly manifests as failures in KVM-Unit-Test's
verify_disabled_apic_mmio() testcase when x2APIC is enabled (though for
reasons unknown, the test only reliably fails with EFI builds).
Fixes: 0ccf3e7cb9 ("KVM: SVM: Flush the "current" TLB when activating AVIC")
Fixes: 4d1d7942e3 ("KVM: SVM: Introduce logic to (de)activate x2AVIC mode")
Cc: stable@vger.kernel.org
Cc: Naveen N Rao (AMD) <naveen@kernel.org>
Link: https://patch.msgid.link/20260515171536.1841645-1-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
Use kvm_register_mark_dirty() instead of kvm_register_is_dirty() to
actually mark VCPU_EXREG_ERAPS as dirty when emulating
INVPCID_TYPE_SINGLE_CTXT. kvm_register_is_dirty() is a read-only
predicate whose return value is discarded, making the call a no-op.
Without this fix, a single-context INVPCID will not trigger a RAP clear
on the next VMRUN, breaking the ERAPS security guarantee.
Fixes: db5e824964 ("KVM: SVM: Virtualize and advertise support for ERAPS")
Signed-off-by: Emily Ehlert <ehemily@amazon.de>
Link: https://patch.msgid.link/20260518135956.82569-1-ehemily@amazon.de
Signed-off-by: Sean Christopherson <seanjc@google.com>
On real hardware, panic and machine reboot may not flush hardware cache
to memory. This means the persistent ring buffer, which relies on a
coherent state of memory, may not have its events written to the buffer
and they may be lost. Moreover, there may be inconsistency with the
counters which are used for validation of the integrity of the
persistent ring buffer which may cause all data to be discarded.
To avoid this issue, stop recording of the ring buffer on panic and
flush the cache of the ring buffer's memory.
Fixes: e645535a95 ("tracing: Add option to use memmapped memory for trace boot instance")
Cc: stable@vger.kernel.org
Cc: Will Deacon <will@kernel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Ian Rogers <irogers@google.com>
Link: https://patch.msgid.link/177751969602.2136606.12031934362587643488.stgit@mhiramat.tok.corp.google.com
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Booting with "nopcid" clears X86_FEATURE_PCID and keeps CR4.PCIDE from being
set to one. On AMD CPUs that support INVLPGB, broadcast TLB flushing remains
enabled.
There are two checks that decide whether the global ASID code runs,
mm_global_asid() and consider_global_asid(), that key off of the
X86_FEATURE_INVLPGB feature. Once an mm becomes active on more than three
CPUs, consider_global_asid() assigns it a global ASID, after which
flush_tlb_mm_range() takes the broadcast_tlb_flush() path using a non-zero
PCID. Issuing an INVLPGB with a non-zero PCID while CR4.PCIDE is not set
results in a #GP:
Oops: general protection fault, kernel NULL pointer dereference 0x1: 0000 [#1] SMP NOPTI
CPU: 158 UID: 0 PID: 3119 Comm: snap Not tainted 7.1.0-rc3 #1 PREEMPT(full)
Hardware name: ...
RIP: 0010:broadcast_tlb_flush
Code: ... 89 da 48 83 c8 07 <0f> 01 fe eb 08 cc cc cc ...
Call Trace:
<TASK>
flush_tlb_mm_range
ptep_clear_flush
wp_page_copy
? _raw_spin_unlock
__handle_mm_fault
handle_mm_fault
do_user_addr_fault
exc_page_fault
asm_exc_page_fault
All processors that support broadcast TLB invalidation also have PCID support,
so it is only the "nopcid" scenario that is of concern. In this situation just
disable the broadcast TLB support using the CPUID dependency support by making
X86_FEATURE_INVLPGB dependent on X86_FEATURE_PCID.
[ bp: Massage commit message. ]
Fixes: 4afeb0ed17 ("x86/mm: Enable broadcast TLB invalidation for multi-threaded processes")
Suggested-by: Dave Hansen <dave.hansen@intel.com>
Assisted-by: Claude:claude-opus-4.7
Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Acked-by: Rik van Riel <riel@surriel.com>
Cc: <stable@kernel.org>
Link: https://patch.msgid.link/b915acfd63e8b2a094fdeb8dc608738072518764.1779296450.git.thomas.lendacky@amd.com
Vishal reported that KVM unit test 'x2apic' started failing after commit
0e98eb1481 ("entry: Prepare for deferred hrtimer rearming").
The reason is that KVM/VMX is injecting interrupts while it has interrupts
disabled, for a context that will enable interrupts, this means that
regs->flags.X86_EFLAGS_IF == 0 and irqentry_exit() will not do the right
thing.
Notably, irqentry_exit() must not call hrtimer_rearm_deferred() when the return
context does not have IF set, because this will cause problems vs NMIs.
Therefore, fix up the state after the injection.
Fixes: 0e98eb1481 ("entry: Prepare for deferred hrtimer rearming")
Reported-by: "Verma, Vishal L" <vishal.l.verma@intel.com>
Suggested-by: Thomas Gleixner <tglx@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Tested-by: "Verma, Vishal L" <vishal.l.verma@intel.com>
Tested-by: David Woodhouse <dwmw@amazon.co.uk>
Tested-by: Zhao Liu <zhao1.liu@intel.com>
Tested-by: Sean Christopherson <seanjc@google.com>
Reviewed-by: Binbin Wu <binbin.wu@linux.intel.com>
Link: https://patch.msgid.link/20260423155936.957351833@infradead.org
Closes: https://lore.kernel.org/r/70cd3e97fbb796e2eb2ff8cd4b7614ada05a5f24.camel%40intel.com
Move the VMX interrupt dispatch magic into the x86 core code. This
isolates KVM from the FRED/IDT decisions and reduces the amount of
EXPORT_SYMBOL_FOR_KVM().
Suggested-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Tested-by: "Verma, Vishal L" <vishal.l.verma@intel.com>
Tested-by: Zhao Liu <zhao1.liu@intel.com>
Tested-by: Zhao Liu <zhao1.liu@intel.com>
Tested-by: Sean Christopherson <seanjc@google.com>
Reviewed-by: Binbin Wu <binbin.wu@linxu.intel.com>
Acked-by: Sean Christopherson <seanjc@google.com>
Link: https://patch.msgid.link/20260508091829.GO3126523@noisy.programming.kicks-ass.net
In map_vdso(), if a failure occurs during the installation of the VVAR
mappings, the error path attempts to clean up previously allocated mappings
using do_munmap(). However, the cleanup for the VVAR mapping is incorrectly
using image->size (the size of the vDSO text) instead of the actual size
allocated for the VVAR area.
Replace the incorrect do_munmap() image->size parameter with the constant
VDSO_NR_PAGES * PAGE_SIZE. Ensure the unmap size exactly matches the size
used during the vdso_install_vvar_mapping() phase to provide a symmetrical
and complete teardown of the memory region.
Fixes: e93d2521b2 ("x86/vdso: Split virtual clock pages into dedicated mapping")
Signed-off-by: Guilherme Giacomo Simoes <trintaeoitogc@gmail.com>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Reviewed-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Link: https://patch.msgid.link/20260503191609.551817-1-trintaeoitogc@gmail.com
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Merge tag 'for-linus-7.1b-rc4-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip
Pull xen fixes from Juergen Gross:
- one simple cleanup
- a fix for a corner case when running as Xen PV dom0
- a fix of a regression for Xen PV guests, introduced in 7.0
* tag 'for-linus-7.1b-rc4-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip:
x86/xen: Tolerate nested XEN_LAZY_MMU entering/leaving
x86/xen: Fix xen_e820_swap_entry_with_ram()
xen/arm: Replace __ASSEMBLY__ with __ASSEMBLER__ in interface.h
- Check ACPI_COMPANION() against NULL during probe in several core
ACPI device drivers (Rafael Wysocki)
- Restore log level of messages in amd_set_max_freq_ratio() (Mario
Limonciello)
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Merge tag 'acpi-7.1-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm
Pull ACPI support fixes from Rafael Wysocki:
"These fix several platform drivers that use the ACPI companion of the
given platform device without checking its presence, which may lead to
a NULL pointer dereference or other kind of malfunction if the driver
is forced to match a device without an ACPI companion via driver
override, and restore debug log level for some messages in the ACPI
CPPC library:
- Check ACPI_COMPANION() against NULL during probe in several core
ACPI device drivers (Rafael Wysocki)
- Restore log level of messages in amd_set_max_freq_ratio() (Mario
Limonciello)"
* tag 'acpi-7.1-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm:
ACPI: PAD: xen: Check ACPI_COMPANION() against NULL
ACPI: driver: Check ACPI_COMPANION() against NULL during probe
Revert "ACPI: CPPC: Adjust debug messages in amd_set_max_freq_ratio() to warn"
Merge a revert of an ACPI CPPC commit that increased the log level of
some debug messages which turned out to be a bad idea:
- Restore log level of messages in amd_set_max_freq_ratio() (Mario
Limonciello)
* acpi-cppc:
Revert "ACPI: CPPC: Adjust debug messages in amd_set_max_freq_ratio() to warn"
With the support of nested lazy mmu sections it can happen that
arch_enter_lazy_mmu_mode() is being called twice without a call of
arch_leave_lazy_mmu_mode() in between, as the lazy_mmu_*() helpers
are not disabling preemption when checking for nested lazy mmu
sections.
This is a problem when running as a Xen PV guest, as
xen_enter_lazy_mmu() and xen_leave_lazy_mmu() don't tolerate this
case.
Fix that in xen_enter_lazy_mmu() and xen_leave_lazy_mmu() in order
not to hurt all other lazy mmu mode users.
Fixes: 291b3abed6 ("x86/xen: use lazy_mmu_state when context-switching")
Tested-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
Message-ID: <20260508143933.493013-1-jgross@suse.com>
When swapping a not page-aligned E820 map entry with RAM, the start
address of the modified entry is calculated wrong (the offset into the
page is subtracted instead of being added to the page address).
Fixes: be35d91c88 ("xen: tolerate ACPI NVS memory overlapping with Xen allocated memory")
Reported-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
Message-ID: <20260505102417.208138-1-jgross@suse.com>
* Add the pKVM side of the workaround for ARM's erratum 4193714, provided
that the EL3 firmware does its part of the job. KVM will refuse to
initialise otherwise.
- Correctly handle 52bit VAs for guest EL2 stage-1 translations when
running under NV with E2H==0.
* Correctly deal with permission faults in guest_memfd memslots.
* Fix the steal-time selftest after the infrastructure was reworked.
* Make sure the host cannot pass a non-sensical clock update to the
EL2 tracing infrastructure.
* Appoint Steffen Eiden as a reviewer in anticipation of the KVM/s390
ability to run arm64 guests, which will inevitably lead to arm64
code being directly used on s390.
* Make sure that EL2 is configured with both exception entry and exit
being Context Synchronization Events.
* Handle the current vcpu being NULL on EL2 panic.
* Fix the selftest_vcpu memcache being empty at the point of donation or
sharing.
* Check that the memcache has enough capacity before engaging on the
share/donate path.
* Fix __deactivate_fgt() to use its parameter rather than a variable
in the macro context.
s390:
* Fix array overrun with large amounts of PCI devices.
x86:
* Never use L0's PAUSE loop exiting while L2 is running, since it's
unlikely that a nested guest will help solving the hypervisor's
spinlock contention
* Fix emulation of MOVNTDQA.
* Fix typo in Xen hypercall tracepoint
* Add back an optimization that was left behind when recently
fixing a bug.
* Add module parameter to disable CET, whose implementation seems
to have issues. For now it remains enabled by default.
Generic:
* Reject offset causing an unsigned overflow in kvm_reset_dirty_gfn()
Documentation:
* Update stale links
Selftests:
* Fix guest_memfd_test with host page size > guest page size.
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Merge tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm
Pull kvm fixes from Paolo Bonzini:
"arm64:
- Add the pKVM side of the workaround for ARM's erratum 4193714,
provided that the EL3 firmware does its part of the job. KVM will
refuse to initialise otherwise
- Correctly handle 52bit VAs for guest EL2 stage-1 translations when
running under NV with E2H==0
- Correctly deal with permission faults in guest_memfd memslots
- Fix the steal-time selftest after the infrastructure was reworked
- Make sure the host cannot pass a non-sensical clock update to the
EL2 tracing infrastructure
- Appoint Steffen Eiden as a reviewer in anticipation of the KVM/s390
ability to run arm64 guests, which will inevitably lead to arm64
code being directly used on s390
- Make sure that EL2 is configured with both exception entry and exit
being Context Synchronization Events
- Handle the current vcpu being NULL on EL2 panic
- Fix the selftest_vcpu memcache being empty at the point of donation
or sharing
- Check that the memcache has enough capacity before engaging on the
share/donate path
- Fix __deactivate_fgt() to use its parameter rather than a variable
in the macro context
s390:
- Fix array overrun with large amounts of PCI devices
x86:
- Never use L0's PAUSE loop exiting while L2 is running, since it's
unlikely that a nested guest will help solving the hypervisor's
spinlock contention
- Fix emulation of MOVNTDQA
- Fix typo in Xen hypercall tracepoint
- Add back an optimization that was left behind when recently fixing
a bug
- Add module parameter to disable CET, whose implementation seems to
have issues. For now it remains enabled by default
Generic:
- Reject offset causing an unsigned overflow in kvm_reset_dirty_gfn()
Documentation:
- Update stale links
Selftests:
- Fix guest_memfd_test with host page size > guest page size"
* tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm: (22 commits)
KVM: VMX: introduce module parameter to disable CET
KVM: x86: Swap the dst and src operand for MOVNTDQA
KVM: x86: use again the flush argument of __link_shadow_page()
KVM: selftests: Ensure gmem file sizes are multiple of host page size
Documentation: kvm: update links in the references section of AMD Memory Encryption
KVM: nSVM: Never use L0's PAUSE loop exiting while L2 is running
KVM: x86: Fix Xen hypercall tracepoint argument assignment
KVM: Reject wrapped offset in kvm_reset_dirty_gfn()
KVM: arm64: Pre-check vcpu memcache for host->guest donate
KVM: arm64: Pre-check vcpu memcache for host->guest share
KVM: arm64: Seed pkvm_ownership_selftest vcpu memcache
KVM: arm64: Fix __deactivate_fgt macro parameter typo
KVM: arm64: Guard against NULL vcpu on VHE hyp panic path
KVM: arm64: Make EL2 exception entry and exit context-synchronization events
MAINTAINERS: Add Steffen as reviewer for KVM/arm64
KVM: arm64: Remove potential UB on nvhe tracing clock update
KVM: selftests: arm64: Fix steal_time test after UAPI refactoring
KVM: arm64: Handle permission faults with guest_memfd
KVM: arm64: nv: Consider the DS bit when translating TCR_EL2
KVM: arm64: Work around C1-Pro erratum 4193714 for protected guests
...
commit 446fcce2a5 ("Revert "x86: kvm: rate-limit global clock updates"")
dropped the rate limiting for KVM_REQ_GLOBAL_CLOCK_UPDATE.
As a result, kvm_arch_vcpu_load() can queue global clock update requests
every time a vCPU is scheduled when the master clock is disabled or when
the vCPU is loaded for the first time.
Restore the throttling with a per-VM ratelimit state and gate
KVM_REQ_GLOBAL_CLOCK_UPDATE through __ratelimit(), so frequent vCPU
scheduling does not generate a steady stream of redundant clock update
requests.
Fixes: 446fcce2a5 ("Revert "x86: kvm: rate-limit global clock updates"")
Signed-off-by: Lei Chen <lei.chen@smartx.com>
Reported-by: Jaroslav Pulchart <jaroslav.pulchart@gooddata.com>
Closes: https://lore.kernel.org/all/CAK8fFZ5gY8_Mw2A=iZVFNVKQNrXQzVsn-HTd+Me9K6ZfmdgA+Q@mail.gmail.com/
Link: https://patch.msgid.link/20260409142226.2581-1-lei.chen@smartx.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
x86_virt_invoke_kvm_emergency_callback() reaches rcu_dereference()
through machine_crash_shutdown() with IRQs disabled but with RCU not
necessarily watching the crashing CPU, which triggers a suspicious
RCU usage splat on debug kernels (CONFIG_PROVE_RCU=y) during
panic/kdump:
WARNING: suspicious RCU usage
arch/x86/virt/hw.c:52 suspicious rcu_dereference_check() usage!
rcu_scheduler_active = 2, debug_locks = 1
1 lock held by tee/11119:
#0: ffff8881fa32c440 (sb_writers#3){.+.+}-{0:0}, at: ksys_write
Call Trace:
<TASK>
dump_stack_lvl+0x84/0xd0
lockdep_rcu_suspicious.cold+0x37/0x8f
x86_virt_invoke_kvm_emergency_callback+0x5f/0x70
x86_svm_emergency_disable_virtualization_cpu+0x2a/0x30
x86_virt_emergency_disable_virtualization_cpu+0x6b/0x90
native_machine_crash_shutdown+0x72/0x170
__crash_kexec+0x137/0x280
panic+0xce/0xd0
sysrq_handle_crash+0x1f/0x20
__handle_sysrq.cold+0x192/0x335
write_sysrq_trigger+0x8c/0xc0
proc_reg_write+0x1c3/0x3c0
vfs_write+0x1d0/0xf80
ksys_write+0x116/0x250
do_syscall_64+0x11c/0x1480
entry_SYSCALL_64_after_hwframe+0x76/0x7e
</TASK>
A truly correct fix is non-trivial: the RCU usage genuinely is wrong in
panic context (RCU may ignore the crashing CPU during synchronization),
and a concurrent KVM module unload could in principle race with the
callback read; see commit 2baa33a8dd ("KVM: x86: Leave user-return
notifier registered on reboot/shutdown") which notes that nothing
prevents module unload during panic/reboot.
However, the alternatives are worse:
- smp_store_release()/smp_load_acquire() handles ordering but not
liveness; the kernel still needs to keep the module text alive
while the callback is in flight.
- Taking a lock in the panic path is risky — any lock could be held
by a CPU that has already been NMI'd to a halt.
Use rcu_dereference_raw() to silence the splat and accept the
vanishingly small remaining race. Panic context inherently cannot
guarantee complete correctness; the goal here is to keep debug builds
quiet on the kdump path so the splat doesn't obscure the actual
kernel state being captured.
Reproducible on a debug kernel (CONFIG_PROVE_LOCKING=y, CONFIG_PROVE_RCU=y)
with kvm_amd or kvm_intel loaded by triggering kdump:
echo c > /proc/sysrq-trigger
Suggested-by: Sean Christopherson <seanjc@google.com>
Fixes: 428afac5a8 ("KVM: x86: Move bulk of emergency virtualizaton logic to virt subsystem")
Signed-off-by: Mikhail Gavrilov <mikhail.v.gavrilov@gmail.com>
Acked-by: Sean Christopherson <seanjc@google.com>
Link: https://patch.msgid.link/20260504235435.90957-1-mikhail.v.gavrilov@gmail.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
RongQing reported that the MCA polling interval doesn't halve when an
error gets logged. It was traced down to the commit in Fixes:, because:
mce_timer_fn()
|-> mce_poll_banks()
|-> machine_check_poll()
|-> mce_log()
which will queue the work and return.
Now, back in mce_timer_fn():
/*
* Alert userspace if needed. If we logged an MCE, reduce the polling
* interval, otherwise increase the polling interval.
*/
if (mce_notify_irq())
<--- here we haven't ran the notifier chain yet so mce_need_notify is
not set yet so this won't hit and we won't halve the interval iv.
Now the notifier chain runs. mce_early_notifier() sets the bit, does
mce_notify_irq(), that clears the bit and then the notifier chain
a little later logs the error.
So this is a silly timing issue.
But, that's all unnecessary.
All it needs to happen here is, the "should we notify of a logged MCE"
mce_notify_irq() asks, should be simply a question to the mce gen pool:
"Are you empty?"
And that then turns into a simple yes or no answer and it all
JustWorks(tm).
So do that and also distribute the functionality where it belongs:
- Print that MCE events have been logged in mce_log()
- Trigger the mcelog tool specific work in the first notifier
As a result, mce_notify_irq() can go now.
Fixes: 011d826111 ("RAS: Add a Corrected Errors Collector")
Reported-by: Li RongQing <lirongqing@baidu.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Qiuxu Zhuo <qiuxu.zhuo@intel.com>
Tested-by: Qiuxu Zhuo <qiuxu.zhuo@intel.com>
Link: https://lore.kernel.org/r/20260112082747.2842-1-lirongqing@baidu.com
There have been reports of host hangs caused by CET virtualization.
Until these are analyzed further, introduce a module parameter that
makes it possible to easily disable it.
Link: https://lore.kernel.org/all/85548beb-1486-40f9-beb4-632c78e3360b@proxmox.com/
Cc: David Riley <d.riley@proxmox.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Swap the MOVNTDQA operands, as MOVNTDQA does NOT in fact have "the same
characteristics as 0F E7 (MOVNTDQ)"; MOVNTDQA loads from memory and stores
to registers, while MOVNTDQ loads from registers and stores to memory.
Per the SDM:
MOVNTDQ - Move packed integer values in xmm1 to m128 using non-temporal
hint.
MOVNTDQA - Move double quadword from m128 to xmm1 using non-temporal hint
if WC memory type.
Reported-by: Josh Eads <josheads@google.com>
Fixes: c57d9bafbd ("KVM: x86: Add support for emulating MOVNTDQA")
Cc: stable@vger.kernel.org
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-ID: <20260506213514.2781948-1-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Except in the case of parentless nested-TDP pages, mmu_page_zap_pte()
clears the SPTE but leaves the invalid_list empty. In this case, using
kvm_flush_remote_tlbs() as kvm_mmu_remote_flush_or_zap() does is overkill.
Avoid flushing the entirety of the remote TLBs unless the invalid_list
was populated: instead, use a more efficient gfn-targeting flush (if
available) and skip it altogether if the caller guarantees that a TLB
flush is not necessary.
Based-on: <20260503201029.106481-1-pbonzini@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-ID: <20260503210917.121840-1-pbonzini@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Never use L0's (KVM's) PAUSE loop exiting controls while L2 is running,
and instead always configure vmcb02 according to L1's exact capabilities
and desires.
The purpose of intercepting PAUSE after N attempts is to detect when the
vCPU may be stuck waiting on a lock, so that KVM can schedule in a
different vCPU that may be holding said lock. Barring a very interesting
setup, L1 and L2 do not share locks, and it's extremely unlikely that an
L1 vCPU would hold a spinlock while running L2. I.e. having a vCPU
executing in L1 yield to a vCPU running in L2 will not allow the L1 vCPU
to make forward progress, and vice versa.
While teaching KVM's "on spin" logic to only yield to other vCPUs in L2 is
doable, in all likelihood it would do more harm than good for most setups.
KVM has limited visibility into which L2 "vCPUs" belong to the same VM,
and thus share a locking domain. And even if L2 vCPUs are in the same
VM, KVM has no visilibity into L2 vCPU's that are scheduled out by the
L1 hypervisor.
Furthermore, KVM doesn't actually steal PAUSE exits from L1. If L1 is
intercepting PAUSE, KVM will route PAUSE exits to L1, not L0, as
nested_svm_intercept() gives priority to the vmcb12 intercept. As such,
overriding the count/threshold fields in vmcb02 with vmcb01's values is
nonsensical, as doing so clobbers all the training/learning that has been
done in L1.
Even worse, if L1 is not intercepting PAUSE, i.e. KVM is handling PAUSE
exits, then KVM will adjust the PLE knobs based on L2 behavior, which could
very well be detrimental to L1, e.g. due to essentially poisoning L1 PLE
training with bad data.
And copying the count from vmcb02 to vmcb01 on a nested VM-Exit makes even
less sense, because again, the purpose of PLE is to detect spinning vCPUs.
Whether or not a vCPU is spinning in L2 at the time of a nested VM-Exit
has no relevance as to the behavior of the vCPU when it executes in L1.
The only scenarios where any of this actually works is if at least one
of KVM or L1 is NOT intercepting PAUSE for the guest. Per the original
changelog, those were the only scenarios considered to be supported.
Disabling KVM's use of PLE makes it so the VM is always in a "supported"
mode.
Last, but certainly not least, using KVM's count/threshold instead of the
values provided by L1 is a blatant violation of the SVM architecture.
Fixes: 74fd41ed16 ("KVM: x86: nSVM: support PAUSE filtering when L0 doesn't intercept PAUSE")
Cc: Maxim Levitsky <mlevitsk@redhat.com>
Tested-by: David Kaplan <david.kaplan@amd.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Link: https://patch.msgid.link/20260508213321.373309-1-seanjc@google.com/
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
TRACE_EVENT(kvm_xen_hypercall) stores a5 in __entry->a4 instead of
__entry->a5.
That overwrites the recorded a4 argument and leaves a5 unset in the
trace entry. Fix the typo so both arguments are captured correctly.
Signed-off-by: Qiang Ma <maqianga@uniontech.com>
Link: https://patch.msgid.link/20260512015313.1685784-1-maqianga@uniontech.com/
Cc: stable@vger.kernel.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Make sure resources are not improperly shared in the op cache and
cause instruction corruption this way.
Signed-off-by: Prathyushi Nangia <prathyushi.nangia@amd.com>
Co-developed-by: Borislav Petkov (AMD) <bp@alien8.de>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Cc: stable@vger.kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Some older systems don't support CPPC in the firmware and this just makes
noise for them when booting. Drop back to debug.
This reverts commit 21fb59ab4b.
Fixes: 21fb59ab4b ("ACPI: CPPC: Adjust debug messages in amd_set_max_freq_ratio() to warn")
Suggested-by: Kim Phillips <kim.phillips@amd.com>
Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
Tested-by: Kim Phillips <kim.phillips@amd.com>
Cc: All applicable <stable@vger.kernel.org>
Link: https://patch.msgid.link/20260504230141.484743-2-mario.limonciello@amd.com
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
The version of purgatory code shipped by kexec-tools attempts to look above
the top of its stack to find a return address for a kjump, even in a non-kjump
kexec.
After the commit in Fixes: the word above the stack might not be there,
leading to a fault (which is at least now caught by my exception-handling code
in kexec).
That commit fixed things for the actual kjump path, but no longer
"gratuitously" pushes the unused return address to the stack in the non-kjump
path. Put that *back* in the non-kjump path, to prevent purgatory from
crashing when trying to access it.
Fixes: 2cacf7f23a ("x86/kexec: Fix stack and handling of re-entry point for ::preserve_context")
Reported-by: Rohan Kakulawaram <rohanka@google.com>
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Acked-by: Dave Hansen <dave.hansen@linux.intel.com>
Tested-by: Rohan Kakulawaram <rohanka@google.com>
Cc: <stable@kernel.org>
Link: https://patch.msgid.link/32d627134143ffd957891cb697138e839c623211.camel@infradead.org
In commit:
157266edcc ("x86/boot/e820: Simplify append_e820_table() and remove restriction on single-entry tables")
the check on the number of entries in the e820 table was removed. The intention
was to support single-entry maps, but by removing the check entirely, we also
skip the fallback (to, e.g., the BIOS 88h function).
This means that if no E820 map is passed in from the bootloader (which is the
case on some bootloaders, like linld), we end up with an empty memory map, and
the kernel fails to boot (either by deadlocking on OOM, or by failing to
allocate the real mode trampoline, or similar).
Re-instate the check in append_e820_table(), but only check that nr_entries is
non-zero. This allows e820__memory_setup_default() to fall back to other memory
size sources, and doesn't affect e820__memory_setup_extended(), as the latter
ignores the return value from append_e820_table().
In doing so, we also update the return values to be proper error codes, with
-ENOENT for this case (there are no entries), and -EINVAL for the case where an
entry appears invalid. Given none of the callers check the actual value -- just
whether it's nonzero -- this is largely aesthetic in practice.
Tested against linld, and the kernel boots again fine.
[ mingo: Readability edits to the comment and the changelog. ]
Fixes: 157266edcc ("x86/boot/e820: Simplify append_e820_table() and remove restriction on single-entry tables")
Signed-off-by: David Gow <david@davidgow.net>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@intel.com>
Cc: stable@vger.kernel.org
Cc: Arnd Bergmann <arnd@kernel.org>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Link: https://patch.msgid.link/20260416065746.1896647-1-david@davidgow.net
