FAILED: patch "[PATCH] KVM: SVM: Mark VMCB_LBR dirty when MSR_IA32_DEBUGCTLMSR is" failed to apply to 6.1-stable tree
Subsystems (3)
[email protected]
maintainerThe patch below does not apply to the 6.1-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 <[email protected]>.
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-6.1.y
git checkout FETCH_HEAD
git cherry-pick -x dc55b3c3f61246e483e50c85d8d5366f9567e188
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2025112036-abdominal-envelope-7ca0@gregkh' --subject-prefix 'PATCH 6.1.y' HEAD^..
Possible dependencies:
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From dc55b3c3f61246e483e50c85d8d5366f9567e188 Mon Sep 17 00:00:00 2001
From: Yosry Ahmed <[email protected]>
Date: Sat, 8 Nov 2025 00:45:19 +0000
Subject: [PATCH] KVM: SVM: Mark VMCB_LBR dirty when MSR_IA32_DEBUGCTLMSR is
updated
The APM lists the DbgCtlMsr field as being tracked by the VMCB_LBR clean bit. Always clear the bit when MSR_IA32_DEBUGCTLMSR is updated.
The history is complicated, it was correctly cleared for L1 before commit 1d5a1b5860ed ("KVM: x86: nSVM: correctly virtualize LBR msrs when L2 is running"). At that point svm_set_msr() started to rely on svm_update_lbrv() to clear the bit, but when nested virtualization is enabled the latter does not always clear it even if MSR_IA32_DEBUGCTLMSR changed. Go back to clearing it directly in svm_set_msr().
arch/x86/kvm/svm/svm.c +4 -0
@@ -3004,7 +3004,11 @@ static int svm_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr)if (data &DEBUGCTL_RESERVED_BITS )return 1 ; +if (svm_get_lbr_vmcb (svm)->save.dbgctl == data) +break ; +svm_get_lbr_vmcb (svm)->save.dbgctl = data; +vmcb_mark_dirty (svm->vmcb,VMCB_LBR );svm_update_lbrv (vcpu);break ;case MSR_VM_HSAVE_PA :
Sasha Levin
maintainerPATCH 1/1 KVM: SVM: Mark VMCB_LBR dirty when MSR_IA32_DEBUGCTLMSR is updated
From: Yosry Ahmed <[email protected]>
[ Upstream commit dc55b3c3f61246e483e50c85d8d5366f9567e188 ]
The APM lists the DbgCtlMsr field as being tracked by the VMCB_LBR clean bit. Always clear the bit when MSR_IA32_DEBUGCTLMSR is updated.
The history is complicated, it was correctly cleared for L1 before commit 1d5a1b5860ed ("KVM: x86: nSVM: correctly virtualize LBR msrs when L2 is running"). At that point svm_set_msr() started to rely on svm_update_lbrv() to clear the bit, but when nested virtualization is enabled the latter does not always clear it even if MSR_IA32_DEBUGCTLMSR changed. Go back to clearing it directly in svm_set_msr().
--- arch/x86/kvm/svm/svm.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-)
arch/x86/kvm/svm/svm.c +8 -2
@@ -3053,11 +3053,17 @@ static int svm_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr)if (data &DEBUGCTL_RESERVED_BITS )return 1 ; -if (svm->vmcb->control.virt_ext &LBR_CTL_ENABLE_MASK ) +if (svm->vmcb->control.virt_ext &LBR_CTL_ENABLE_MASK ) { +if (svm->vmcb->save.dbgctl == data) +break ; svm->vmcb->save.dbgctl = data; -else + }else { +if (svm->vmcb01.ptr->save.dbgctl == data) +break ; svm->vmcb01.ptr->save.dbgctl = data; + } +vmcb_mark_dirty (svm->vmcb,VMCB_LBR );svm_update_lbrv (vcpu);break ;
Signature · 1 line
2.51.0
Re: [PATCH 6.1.y] KVM: SVM: Mark VMCB_LBR dirty when MSR_IA32_DEBUGCTLMSR is updated
Quoted 40 lines · Sasha Levin
From: Yosry Ahmed <[email protected]>
[ Upstream commit
dc55b3c3f61246e483e50c85d8d5366f9567e188]The APM lists the DbgCtlMsr field as being tracked by the
VMCB_LBRclean bit. Always clear the bit whenMSR_IA32_DEBUGCTLMSRis updated.The history is complicated, it was correctly cleared for L1 before commit
1d5a1b5860ed("KVM: x86: nSVM: correctly virtualize LBR msrs when L2 is running"). At that pointsvm_set_msr()started to rely onsvm_update_lbrv()to clear the bit, but when nested virtualization is enabled the latter does not always clear it even ifMSR_IA32_DEBUGCTLMSRchanged. Go back to clearing it directly insvm_set_msr().Fixes 1d5a1b5860ed ("KVM: x86: nSVM: correctly virtualize LBR msrs when L2 is running")Reported-by Matteo Rizzo <[email protected]>Reported-by [email protected]Co-developed-by Jim Mattson <[email protected]>Signed-off-by Jim Mattson <[email protected]>Signed-off-by Yosry Ahmed <[email protected]>Signed-off-by Paolo Bonzini <[email protected]>[ Open coded svm_get_lbr_vmcb() call ]Signed-off-by Sasha Levin <[email protected]>--- arch/x86/kvm/svm/svm.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-)arch/x86/kvm/svm/svm.c +2
-1@@ -3053,11 +3053,17 @@ static int svm_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr)if (data &DEBUGCTL_RESERVED_BITS )return 1 ; -if (svm->vmcb->control.virt_ext &LBR_CTL_ENABLE_MASK ) +if (svm->vmcb->control.virt_ext &LBR_CTL_ENABLE_MASK ) { +if (svm->vmcb->save.dbgctl == data)
arch/x86/kvm/svm/svm.c static int svm_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr) · line 3066
Quoted 10 lines
arch/x86/kvm/svm/svm.c +6
-1+break ; svm->vmcb->save.dbgctl = data; - else + }else { +if (svm->vmcb01.ptr->save.dbgctl == data) +break ; svm->vmcb01.ptr->save.dbgctl = data; + } +vmcb_mark_dirty (svm->vmcb,VMCB_LBR );
The patch LGTM, thanks. FWIW, the call to vmcb_mark_dirty() is the real fix, the above changes are just a microoptimization, so we can just drop it if we want to keep it simple.
Quoted 6 lines
arch/x86/kvm/svm/svm.c +0
-0svm_update_lbrv (vcpu);break ;Signature · 1 line
2.51.0