From: "Yosry Ahmed" <yosry.ahmed@linux.dev>
To: "Sean Christopherson" <seanjc@google.com>
Cc: "Paolo Bonzini" <pbonzini@redhat.com>,
"Jim Mattson" <jmattson@google.com>,
"Maxim Levitsky" <mlevitsk@redhat.com>,
kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
stable@vger.kernel.org
Subject: Re: [PATCH 5/6] KVM: SVM: Add missing save/restore handling of LBR MSRs
Date: Sat, 08 Nov 2025 09:08:58 +0000 [thread overview]
Message-ID: <3759161383b53759888f64d9a03983c05026ab1c@linux.dev> (raw)
In-Reply-To: <20251108004524.1600006-6-yosry.ahmed@linux.dev>
November 7, 2025 at 4:45 PM, "Yosry Ahmed" <yosry.ahmed@linux.dev mailto:yosry.ahmed@linux.dev?to=%22Yosry%20Ahmed%22%20%3Cyosry.ahmed%40linux.dev%3E > wrote:
>
> MSR_IA32_DEBUGCTLMSR and LBR MSRs are currently not enumerated by
> KVM_GET_MSR_INDEX_LIST, and LBR MSRs cannot be set with KVM_SET_MSRS. So
> save/restore is completely broken.
>
> Fix it by adding the MSRs to msrs_to_save_base, and allowing writes to
> LBR MSRs from userspace only (as they are read-only MSRs). Additionally,
> to correctly restore L1's LBRs while L2 is running, make sure the LBRs
> are copied from the captured VMCB01 save area in svm_copy_vmrun_state().
>
> Fixes: 24e09cbf480a ("KVM: SVM: enable LBR virtualization")
> Cc: stable@vger.kernel.org
>
Reported-by: Jim Mattson <jmattson@google.com>
> Signed-off-by: Yosry Ahmed <yosry.ahmed@linux.dev>
[..]
next prev parent reply other threads:[~2025-11-08 9:09 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-11-08 0:45 [PATCH 0/6] KVM: SVM: LBR virtualization fixes Yosry Ahmed
2025-11-08 0:45 ` [PATCH 1/6] KVM: SVM: Mark VMCB_LBR dirty when MSR_IA32_DEBUGCTLMSR is updated Yosry Ahmed
2025-11-09 7:42 ` Paolo Bonzini
2025-11-08 0:45 ` [PATCH 2/6] KVM: nSVM: Always recalculate LBR MSR intercepts in svm_update_lbrv() Yosry Ahmed
2025-11-11 3:11 ` Yosry Ahmed
2025-11-11 18:55 ` Yosry Ahmed
2025-11-11 22:30 ` Sean Christopherson
2025-11-08 0:45 ` [PATCH 3/6] KVM: nSVM: Fix and simplify LBR virtualization handling with nested Yosry Ahmed
2025-11-08 0:45 ` [PATCH 4/6] KVM: SVM: Switch svm_copy_lbrs() to a macro Yosry Ahmed
2025-11-09 7:59 ` Paolo Bonzini
2025-11-10 19:23 ` Yosry Ahmed
2025-11-10 19:41 ` Sean Christopherson
2025-11-08 0:45 ` [PATCH 5/6] KVM: SVM: Add missing save/restore handling of LBR MSRs Yosry Ahmed
2025-11-08 9:08 ` Yosry Ahmed [this message]
2025-11-08 0:45 ` [PATCH 6/6] KVM: selftests: Add a test for LBR save/restore (ft. nested) Yosry Ahmed
2025-11-09 7:57 ` [PATCH 0/6] KVM: SVM: LBR virtualization fixes Paolo Bonzini
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