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Peter Anvin" , kvm@vger.kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, Josh Hilke Content-Type: text/plain; charset="us-ascii" On Thu, Feb 05, 2026, Jim Mattson wrote: > Add KVM_X86_QUIRK_VMCS12_FREEZE_IN_SMM_CC to allow L1 to set FREEZE_IN_SMM > in vmcs12's GUEST_IA32_DEBUGCTL field, as permitted prior to > commit 6b1dd26544d0 ("KVM: VMX: Preserve host's DEBUGCTLMSR_FREEZE_IN_SMM > while running the guest"). The quirk is enabled by default for backwards > compatibility; 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: 095686e6fcb4 ("KVM: nVMX: Check vmcs12->guest_ia32_debugctl on nested VM-Enter") > Signed-off-by: Jim Mattson I'll tag for stable, but otherwise LGTM. It's too late for 6.19, but I'll get it queued up for 6.20 after giving others a chance to react. It'll miss the initial batch of pull requests, but I'll try to send a fixes for the second half of the merge window (I just realized I need to create+send the pull requests...)