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 v6 05/12] KVM: x86: Set guest's fixed-1 DR6 bits when delivering #DB payload
Date: Wed, 30 Sep 2026 12:36:27 -0700 [thread overview]
Message-ID: <20260930193634.3415089-6-seanjc@google.com> (raw)
In-Reply-To: <20260930193634.3415089-1-seanjc@google.com>
When delivering a #DB payload, set all DR6 bits that are fixed-1 from the
guest's perspective, not just the host's perspective. Don't WARN on a
"bad" payload (or existing DR6) even though KVM itself shouldn't set DR6
or synthesize a payload without the fixed-1 bits set, as userspace can
provide a completely arbitrary payload via KVM_SET_VCPU_EVENTS (and
"hardening" that flow is not worth the effort as there's no benefit in
practice).
Signed-off-by: Sean Christopherson <seanjc@google.com>
---
arch/x86/kvm/x86.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 99518e3265b4..816c6df8dcea 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -440,7 +440,7 @@ void kvm_deliver_exception_payload(struct kvm_vcpu *vcpu,
* breakpoint), it is reserved and must be zero in DR6.
*/
vcpu->arch.dr6 &= ~BIT(12);
- vcpu->arch.dr6 |= DR6_FIXED_1;
+ vcpu->arch.dr6 |= kvm_get_dr6_fixed_1(vcpu);
break;
case PF_VECTOR:
vcpu->arch.cr2 = ex->payload;
--
2.56.0.rc1.315.gc6ed9934b7-goog
next prev parent reply other threads:[~2026-09-30 19:36 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-09-30 19:36 [PATCH v6 00/12] KVM: x86: Bus Lock Detect fixes and SVM support Sean Christopherson
2026-09-30 19:36 ` [PATCH v6 01/12] KVM: x86: Preserve DR6.BLD (Bus Lock Detect) when delivering #DB payload Sean Christopherson
2026-09-30 23:46 ` Shivansh Dhiman
2026-09-30 19:36 ` [PATCH v6 02/12] KVM: x86: Rename kvm_dr6_fixed() => kvm_get_dr6_fixed_1() Sean Christopherson
2026-09-30 19:36 ` [PATCH v6 03/12] KVM: Return an "unsigned long", not "u64" for the fixed-1 DR6 bits Sean Christopherson
2026-09-30 19:36 ` [PATCH v6 04/12] KVM: x86: Force fixed-1 bits in DR6 after synchronizing with hardware Sean Christopherson
2026-09-30 19:36 ` Sean Christopherson [this message]
2026-09-30 19:36 ` [PATCH v6 06/12] KVM: x86: Kill off DR6_FIXED_1 to prevent future misuse Sean Christopherson
2026-09-30 19:36 ` [PATCH v6 07/12] KVM: SVM: Add helper to query if LBR virtualization needs to be enabled Sean Christopherson
2026-09-30 19:36 ` [PATCH v6 08/12] KVM: nSVM: Disable LBRV in nested control cache when unsupported Sean Christopherson
2026-09-30 19:36 ` [PATCH v6 09/12] KVM: nSVM: Open code check on LBR virtualization being enabled in vmcb12 Sean Christopherson
2026-09-30 19:36 ` [PATCH v6 10/12] KVM: nSVM: Don't assume all active-low bits DR6 are fixed-1 Sean Christopherson
2026-09-30 19:36 ` [PATCH v6 11/12] KVM: SVM: Add a vCPU-aware helper to get supported DEBUGCTL bits Sean Christopherson
2026-09-30 19:36 ` [PATCH v6 12/12] KVM: SVM: Add support for virtualizating Bus Lock Detect Sean Christopherson
2026-10-02 21:07 ` [PATCH v6 00/12] KVM: x86: Bus Lock Detect fixes and SVM support Sean Christopherson
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