The patch below does not apply to the 6.6-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.6.y git checkout FETCH_HEAD git cherry-pick -x 189ecdb3e112da703ac0699f4ec76aa78122f911 # <resolve conflicts, build, test, etc.> git commit -s git send-email --to 'stable@vger.kernel.org' --in-reply-to '2025031002-campsite-railroad-4d13@gregkh' --subject-prefix 'PATCH 6.6.y' HEAD^..

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 189ecdb3e112da703ac0699f4ec76aa78122f911 Mon Sep 17 00:00:00 2001 From: Sean Christopherson seanjc@google.com Date: Thu, 27 Feb 2025 14:24:10 -0800 Subject: [PATCH] KVM: x86: Snapshot the host's DEBUGCTL after disabling IRQs

Snapshot the host's DEBUGCTL after disabling IRQs, as perf can toggle debugctl bits from IRQ context, e.g. when enabling/disabling events via smp_call_function_single(). Taking the snapshot (long) before IRQs are disabled could result in KVM effectively clobbering DEBUGCTL due to using a stale snapshot.

Cc: stable@vger.kernel.org Reviewed-and-tested-by: Ravi Bangoria ravi.bangoria@amd.com Link: https://lore.kernel.org/r/20250227222411.3490595-6-seanjc@google.com Signed-off-by: Sean Christopherson seanjc@google.com

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 5c6fd0edc41f..12d5f47c1bbe 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -4968,7 +4968,6 @@ void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu)

/* Save host pkru register if supported */ vcpu->arch.host_pkru = read_pkru(); - vcpu->arch.host_debugctl = get_debugctlmsr();

/* Apply any externally detected TSC adjustments (due to suspend) */ if (unlikely(vcpu->arch.tsc_offset_adjustment)) { @@ -10969,6 +10968,8 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu) set_debugreg(0, 7); }

+ vcpu->arch.host_debugctl = get_debugctlmsr(); + guest_timing_enter_irqoff();

for (;;) {