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linux/Documentation/virt
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Jim Mattson e2ffe85b6d KVM: x86: Introduce KVM_X86_QUIRK_VMCS12_ALLOW_FREEZE_IN_SMM 
Add KVM_X86_QUIRK_VMCS12_ALLOW_FREEZE_IN_SMM to allow L1 to set
FREEZE_IN_SMM in vmcs12's GUEST_IA32_DEBUGCTL field, as permitted
prior to commit 6b1dd26544 ("KVM: VMX: Preserve host's
DEBUGCTLMSR_FREEZE_IN_SMM while running the guest").  Enable the quirk
by default for backwards compatibility (like all quirks); userspace
can disable it via KVM_CAP_DISABLE_QUIRKS2 for consistency with the
constraints on WRMSR(IA32_DEBUGCTL).

Note that the quirk only bypasses the consistency check.  The vmcs02 bit is
still owned by the host, and PMCs are not frozen during virtualized SMM.
In particular, if a host administrator decides that PMCs should not be
frozen during physical SMM, then L1 has no say in the matter.

Fixes: 095686e6fc ("KVM: nVMX: Check vmcs12->guest_ia32_debugctl on nested VM-Enter")
Cc: stable@vger.kernel.org
Signed-off-by: Jim Mattson <jmattson@google.com>
Link: https://patch.msgid.link/20260205231537.1278753-1-jmattson@google.com
[sean: tag for stable@, clean-up and fix goofs in the comment and docs]
Signed-off-by: Sean Christopherson <seanjc@google.com>
[Rename quirk. - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
History 2026-03-11 18:41:11 +01:00
..
acrn docs: acrn: Introduce ACRN 2021-02-09 10:58:18 +01:00
coco ARM: 2024-07-20 12:41:03 -07:00
hyperv Documentation: hyperv: Confidential VMBus 2025-11-15 06:18:14 +00:00
kvm KVM: x86: Introduce KVM_X86_QUIRK_VMCS12_ALLOW_FREEZE_IN_SMM 2026-03-11 18:41:11 +01:00
uml um: Remove legacy network transport infrastructure 2025-05-05 10:26:59 +02:00
guest-halt-polling.rst Documentation: virt: correct location of haltpoll module params 2023-06-16 08:17:21 -06:00
index.rst Documentation: use a source-read extension for the index link boilerplate 2026-01-23 11:59:34 -07:00
ne_overview.rst nitro_enclaves: Update documentation for Arm64 support 2021-09-14 11:11:20 +02:00
paravirt_ops.rst Documentation: virt: Clean up paravirt_ops doc 2023-06-19 12:09:54 +02:00