From: Sean Christopherson <seanjc@google.com>
To: Sean Christopherson <seanjc@google.com>,
Paolo Bonzini <pbonzini@redhat.com>
Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
Yosry Ahmed <yosry@kernel.org>,
Shivansh Dhiman <shivansh.dhiman@amd.com>,
Nikunj A Dadhania <nikunj@amd.com>,
Ravi Bangoria <ravi.bangoria@amd.com>,
Tom Lendacky <thomas.lendacky@amd.com>
Subject: [PATCH v5 08/12] KVM: nSVM: Disable LBRV in nested control cache when unsupported
Date: Tue, 29 Sep 2026 18:13:09 -0700 [thread overview]
Message-ID: <20260930011313.3197688-9-seanjc@google.com> (raw)
In-Reply-To: <20260930011313.3197688-1-seanjc@google.com>
From: Shivansh Dhiman <shivansh.dhiman@amd.com>
Clear SVM_MISC2_ENABLE_V_LBR in __nested_copy_vmcb_control_to_cache() when
the vCPU does not support LBR Virtualization. This lets the cached value be
consumed directly instead of re-checking X86_FEATURE_LBRV on every access.
Suggested-by: Yosry Ahmed <yosry@kernel.org>
Signed-off-by: Shivansh Dhiman <shivansh.dhiman@amd.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
---
arch/x86/kvm/svm/nested.c | 8 +++++---
arch/x86/kvm/svm/svm.c | 2 +-
2 files changed, 6 insertions(+), 4 deletions(-)
diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c
index b61149814acc..aca2bbc66f47 100644
--- a/arch/x86/kvm/svm/nested.c
+++ b/arch/x86/kvm/svm/nested.c
@@ -527,12 +527,16 @@ void __nested_copy_vmcb_control_to_cache(struct kvm_vcpu *vcpu,
/* Always clear misc_ctl bits that the guest cannot use */
to->misc_ctl = from->misc_ctl;
+ to->misc_ctl2 = from->misc_ctl2;
if (!guest_cpu_cap_has(vcpu, X86_FEATURE_NPT))
to->misc_ctl &= ~SVM_MISC_ENABLE_NP;
if (!gmet_enabled || !guest_cpu_cap_has(vcpu, X86_FEATURE_GMET))
to->misc_ctl &= ~SVM_MISC_ENABLE_GMET;
+ if (!guest_cpu_cap_has(vcpu, X86_FEATURE_LBRV))
+ to->misc_ctl2 &= ~SVM_MISC2_ENABLE_V_LBR;
+
to->iopm_base_pa = from->iopm_base_pa & PAGE_MASK;
to->msrpm_base_pa = from->msrpm_base_pa & PAGE_MASK;
to->tsc_offset = from->tsc_offset;
@@ -550,7 +554,6 @@ void __nested_copy_vmcb_control_to_cache(struct kvm_vcpu *vcpu,
to->event_inj_err = from->event_inj_err;
to->next_rip = from->next_rip;
to->nested_cr3 = from->nested_cr3;
- to->misc_ctl2 = from->misc_ctl2;
to->pause_filter_count = from->pause_filter_count;
to->pause_filter_thresh = from->pause_filter_thresh;
@@ -737,8 +740,7 @@ static int nested_svm_load_cr3(struct kvm_vcpu *vcpu, unsigned long cr3,
static bool nested_vmcb12_has_lbrv(struct kvm_vcpu *vcpu)
{
- return guest_cpu_cap_has(vcpu, X86_FEATURE_LBRV) &&
- (to_svm(vcpu)->nested.ctl.misc_ctl2 & SVM_MISC2_ENABLE_V_LBR);
+ return to_svm(vcpu)->nested.ctl.misc_ctl2 & SVM_MISC2_ENABLE_V_LBR;
}
static void nested_vmcb02_prepare_save(struct vcpu_svm *svm)
diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index 775eccfb7b24..5253c0143666 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -882,7 +882,7 @@ static bool svm_need_lbr_virtualization(struct kvm_vcpu *vcpu)
if (svm->vmcb->save.dbgctl & DEBUGCTLMSR_LBR)
return true;
- return is_guest_mode(vcpu) && guest_cpu_cap_has(vcpu, X86_FEATURE_LBRV) &&
+ return is_guest_mode(vcpu) &&
(svm->nested.ctl.misc_ctl2 & SVM_MISC2_ENABLE_V_LBR);
}
--
2.56.0.rc1.315.gc6ed9934b7-goog
next prev parent reply other threads:[~2026-09-30 1:13 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-09-30 1:13 [PATCH v5 00/12] KVM: x86: Bus Lock Detect fixes and SVM support Sean Christopherson
2026-09-30 1:13 ` [PATCH v5 01/12] KVM: x86: Preserve DR6.BLD (Bus Lock Detect) when delivering #DB payload Sean Christopherson
2026-09-30 1:13 ` [PATCH v5 02/12] KVM: x86: Rename kvm_dr6_fixed() => kvm_get_dr6_fixed_1() Sean Christopherson
2026-09-30 1:13 ` [PATCH v5 03/12] KVM: Return an "unsigned long", not "u64" for the fixed-1 DR6 bits Sean Christopherson
2026-09-30 1:13 ` [PATCH v5 04/12] KVM: x86: Force fixed-1 bits in DR6 after synchronizing with hardware Sean Christopherson
2026-09-30 1:13 ` [PATCH v5 05/12] KVM: x86: WARN if fixed-1 DR6 bits aren't already set when delivering payload Sean Christopherson
2026-09-30 1:13 ` [PATCH v5 06/12] KVM: x86: Kill off DR6_FIXED_1 to prevent future misuse Sean Christopherson
2026-09-30 1:13 ` [PATCH v5 07/12] KVM: SVM: Add helper to query if LBR virtualization needs to be enabled Sean Christopherson
2026-09-30 1:13 ` Sean Christopherson [this message]
2026-09-30 1:13 ` [PATCH v5 09/12] KVM: nSVM: Open code check on LBR virtualization being enabled in vmcb12 Sean Christopherson
2026-09-30 1:13 ` [PATCH v5 10/12] KVM: nSVM: Don't assume all active-low bits DR6 are fixed-1 Sean Christopherson
2026-09-30 1:13 ` [PATCH v5 11/12] KVM: SVM: Add a vCPU-aware helper to get supported DEBUGCTL bits Sean Christopherson
2026-09-30 1:13 ` [PATCH v5 12/12] KVM: SVM: Add support for virtualizating Bus Lock Detect Sean Christopherson
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