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 12/12] KVM: SVM: Add support for virtualizating Bus Lock Detect
Date: Tue, 29 Sep 2026 18:13:13 -0700 [thread overview]
Message-ID: <20260930011313.3197688-13-seanjc@google.com> (raw)
In-Reply-To: <20260930011313.3197688-1-seanjc@google.com>
From: Ravi Bangoria <ravi.bangoria@amd.com>
Advertise support for virtualizing Bus Lock Detect and allow the guest to
enable BUS_LOCK_DETECT if LBR Virtualization is enabled (Bus Lock Detect is
enabled through MSR_IA32_DEBUGCTLMSR, which context-switched if and only if
LBR Virtualization is enabled).
Signed-off-by: Ravi Bangoria <ravi.bangoria@amd.com>
Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
Co-developed-by: Shivansh Dhiman <shivansh.dhiman@amd.com>
Signed-off-by: Shivansh Dhiman <shivansh.dhiman@amd.com>
[sean: massage changelog]
Signed-off-by: Sean Christopherson <seanjc@google.com>
---
arch/x86/kvm/svm/svm.c | 12 ++++++++++--
arch/x86/kvm/svm/svm.h | 7 ++++++-
2 files changed, 16 insertions(+), 3 deletions(-)
diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index 1e58ad8691e9..e7c296c52591 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -879,7 +879,7 @@ static bool svm_need_lbr_virtualization(struct kvm_vcpu *vcpu)
{
struct vcpu_svm *svm = to_svm(vcpu);
- if (svm->vmcb->save.dbgctl & DEBUGCTLMSR_LBR)
+ if (svm->vmcb->save.dbgctl & (DEBUGCTLMSR_LBR | DEBUGCTLMSR_BUS_LOCK_DETECT))
return true;
return is_guest_mode(vcpu) &&
@@ -5712,9 +5712,17 @@ static __init void svm_set_cpu_caps(void)
* Clear capabilities that are automatically configured by common code,
* but that require explicit SVM support (that isn't yet implemented).
*/
- kvm_cpu_cap_clear(X86_FEATURE_BUS_LOCK_DETECT);
kvm_cpu_cap_clear(X86_FEATURE_MSR_IMM);
+ /*
+ * LBR Virtualization must be enabled to support BusLockTrap inside the
+ * guest, since BusLockTrap is enabled through MSR_IA32_DEBUGCTLMSR and
+ * MSR_IA32_DEBUGCTLMSR is virtualized only if LBR Virtualization is
+ * enabled.
+ */
+ if (!lbrv)
+ kvm_cpu_cap_clear(X86_FEATURE_BUS_LOCK_DETECT);
+
kvm_setup_xss_caps();
kvm_finalize_cpu_caps();
}
diff --git a/arch/x86/kvm/svm/svm.h b/arch/x86/kvm/svm/svm.h
index c3380d865b75..6d0242966dc8 100644
--- a/arch/x86/kvm/svm/svm.h
+++ b/arch/x86/kvm/svm/svm.h
@@ -789,7 +789,12 @@ BUILD_SVM_MSR_BITMAP_HELPERS(void, set, __set)
static inline u64 svm_get_supported_debugctl(struct kvm_vcpu *vcpu)
{
- return DEBUGCTLMSR_LBR;
+ u64 debugctl = DEBUGCTLMSR_LBR;
+
+ if (guest_cpu_cap_has(vcpu, X86_FEATURE_BUS_LOCK_DETECT))
+ debugctl |= DEBUGCTLMSR_BUS_LOCK_DETECT;
+
+ return debugctl;
}
/* svm.c */
--
2.56.0.rc1.315.gc6ed9934b7-goog
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 ` [PATCH v5 08/12] KVM: nSVM: Disable LBRV in nested control cache when unsupported Sean Christopherson
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 ` Sean Christopherson [this message]
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