From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pj1-f74.google.com (mail-pj1-f74.google.com [209.85.216.74]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 225DC255F2C for ; Wed, 4 Mar 2026 00:44:20 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.216.74 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772585062; cv=none; b=MpBL1wp16ddJyAwar0M9YN3jYzzyLE//m4Sws5qujK9vE03gDxFkPv8ClMTHlxUCakbzlYmYWoRmZHW76gsUDoL6OiBeQOlsqaoRIXcJwCJXvvZYyi+vNXUIZCtd1+hyBd/km2ld8lhi8DboTIrWcfJMj5y7LCGDGfivGZ8xdpc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772585062; c=relaxed/simple; bh=8EUfImJqXCjwEv07osmggtN7dOfogWe0w9ZDpEIMa58=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=HWMsS0AcMzHiD/E69twighU36ZXh0ItOXFIs/MfTyMeT4qhRdoKZ4jLtOIlvCxAwa3VLuTMcD8EJjApSllBkbypXn196oZm5oKhB8eJRqlKMvcxZEsxvoJsJkoFEweP06raLB0FdfzR3iZ3e7Sqz5RARkxqYIEh1yfv+6weWw5g= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--seanjc.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=t8cOi5ey; arc=none smtp.client-ip=209.85.216.74 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--seanjc.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="t8cOi5ey" Received: by mail-pj1-f74.google.com with SMTP id 98e67ed59e1d1-35641c14663so6440666a91.2 for ; Tue, 03 Mar 2026 16:44:20 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1772585060; x=1773189860; darn=vger.kernel.org; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=2TShG9/ZQ57MX/DikZ+o/2CGuAlBGVqbkJk365Mxb28=; b=t8cOi5eyGUfddZApwlSXf16xFCFV2yhoeqxi73ZzjREe9QCD3FlSIgsMG8UgIbdjpC 884Pbwmt7J8eW1+b69A/MfJsRxaJ6hLURkTXZFRa+hxYaZCSo+CqoU06jamEiyUFrl0i ufgbTuCL1BVbLj/Wivfk2oochP3rt0gHXc9vDcZYIwCh+jYB3yz9a8DRS6Rsx0ZObCm4 4nNuF29IKv7jYOg6snvJeBTkbfscwxId0RB6ndVAYFQbhe9deL5Sf8lRWK84Nc4O437e 7fEfqJVBCoYffgQKg6u2kZBRGWVjd+XceqwCY4A6UYXOczMV2Dr3nicv0S6zUgF0DFTY dX9g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1772585060; x=1773189860; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=2TShG9/ZQ57MX/DikZ+o/2CGuAlBGVqbkJk365Mxb28=; b=Rkc4+9GQOQ1fty3IvbrpAMnic/cuN7W+IAYWi3rqV5Ywi+DqUhunfh8CEXqZH/w7T+ 2Mfsvhn5BeNmk5H8XBsUTzV6buRJ5pkaU0rP1Oje/41UZ+80Yr1Hg9E11eHnku5bFl0b ruXf2gcvTtk9CQNtfWYq7eJuQiVivlnw7A8HyRYDv51PL7NAmCNRJxB8CGZ578g3vhsP /BUSrN6bmkJNXjk3oCruzW+N7rvEpydzVvAa4VlDDDBe6RQNNLsR/6CLr8O0YaElCI48 Cd6Sk/imfCtgdGXHXaTX2Jq5PgpWd7OR27osQa94FD4ZeLZ0NMrCaX/BoFbaMtAc/ATs SyGw== X-Forwarded-Encrypted: i=1; AJvYcCXLQyNJvePlBrAdyejJHWhYsJnvqPXAkr5zHoYEQJlqklDRqQgIquMn8/taqGHcQHMV1iJHnJM=@vger.kernel.org X-Gm-Message-State: AOJu0Yz0G4hwTCMerbBq8ClZPUR1UzI3d5MBhcYT4RqlQmeRjHQKfYW+ NFAFfukZPm9yQqpVLalZFP1jPLlb2GZ22xklbINRttT1hlT2Fpg0WzXkrTW++TuFc/lnnge69BN 2jIZE/g== X-Received: from pgbfq7.prod.google.com ([2002:a05:6a02:2987:b0:c6e:18ac:7af8]) (user=seanjc job=prod-delivery.src-stubby-dispatcher) by 2002:a05:6a20:d794:b0:393:e25b:7d77 with SMTP id adf61e73a8af0-3982dd55feemr145106637.13.1772585060135; Tue, 03 Mar 2026 16:44:20 -0800 (PST) Date: Tue, 3 Mar 2026 16:44:18 -0800 In-Reply-To: Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20260303003421.2185681-1-yosry@kernel.org> <20260303003421.2185681-4-yosry@kernel.org> Message-ID: Subject: Re: [PATCH v7 03/26] KVM: SVM: Add missing save/restore handling of LBR MSRs From: Sean Christopherson To: Yosry Ahmed Cc: Paolo Bonzini , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org, Jim Mattson Content-Type: text/plain; charset="us-ascii" On Tue, Mar 03, 2026, Yosry Ahmed wrote: > > > diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c > > So all in all (not yet tested), this? If this is the only issue in the series, > > or at least in the stable@ part of the series, no need for a v8 (I've obviously > > already done the fixup). > > Looks good with a minor nit below (could be a followup). > > > @@ -3075,6 +3075,38 @@ static int svm_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr) > > vmcb_mark_dirty(svm->vmcb, VMCB_LBR); > > svm_update_lbrv(vcpu); > > break; > > + case MSR_IA32_LASTBRANCHFROMIP: > > + if (!lbrv) > > + return KVM_MSR_RET_UNSUPPORTED; > > + if (!msr->host_initiated) > > + return 1; > > + svm->vmcb->save.br_from = data; > > + vmcb_mark_dirty(svm->vmcb, VMCB_LBR); > > + break; > > + case MSR_IA32_LASTBRANCHTOIP: > > + if (!lbrv) > > + return KVM_MSR_RET_UNSUPPORTED; > > + if (!msr->host_initiated) > > + return 1; > > + svm->vmcb->save.br_to = data; > > + vmcb_mark_dirty(svm->vmcb, VMCB_LBR); > > + break; > > + case MSR_IA32_LASTINTFROMIP: > > + if (!lbrv) > > + return KVM_MSR_RET_UNSUPPORTED; > > + if (!msr->host_initiated) > > + return 1; > > + svm->vmcb->save.last_excp_from = data; > > + vmcb_mark_dirty(svm->vmcb, VMCB_LBR); > > + break; > > + case MSR_IA32_LASTINTTOIP: > > + if (!lbrv) > > + return KVM_MSR_RET_UNSUPPORTED; > > + if (!msr->host_initiated) > > + return 1; > > + svm->vmcb->save.last_excp_to = data; > > + vmcb_mark_dirty(svm->vmcb, VMCB_LBR); > > + break; > > There's so much repeated code here. Ya :-( > We can use gotos to share code, but I am not sure if that's a strict > improvement. We can also use a helper, perhaps? Where's your sense of adventure? case MSR_IA32_LASTBRANCHFROMIP: case MSR_IA32_LASTBRANCHTOIP: case MSR_IA32_LASTINTFROMIP: case MSR_IA32_LASTINTTOIP: if (!lbrv) return KVM_MSR_RET_UNSUPPORTED; if (!msr->host_initiated) return 1; *(&svm->vmcb->save.br_from + (ecx - MSR_IA32_LASTBRANCHFROMIP)) = data; vmcb_mark_dirty(svm->vmcb, VMCB_LBR); break; Jokes aside, maybe this, to dedup get() at the same time? diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c index 68b747a94294..f1811105e89f 100644 --- a/arch/x86/kvm/svm/svm.c +++ b/arch/x86/kvm/svm/svm.c @@ -2720,6 +2720,23 @@ static int svm_get_feature_msr(u32 msr, u64 *data) return 0; } +static __always_inline u64 *svm_vmcb_lbr(struct vcpu_svm *svm, u32 msr) +{ + switch (msr) { + case MSR_IA32_LASTBRANCHFROMIP: + return &svm->vmcb->save.br_from; + case MSR_IA32_LASTBRANCHTOIP: + return &svm->vmcb->save.br_to; + case MSR_IA32_LASTINTFROMIP: + return &svm->vmcb->save.last_excp_from; + case MSR_IA32_LASTINTTOIP: + return &svm->vmcb->save.last_excp_to; + default: + break; + } + BUILD_BUG(); +} + static bool sev_es_prevent_msr_access(struct kvm_vcpu *vcpu, struct msr_data *msr_info) { @@ -2838,16 +2855,10 @@ static int svm_get_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info) msr_info->data = lbrv ? svm->vmcb->save.dbgctl : 0; break; case MSR_IA32_LASTBRANCHFROMIP: - msr_info->data = lbrv ? svm->vmcb->save.br_from : 0; - break; case MSR_IA32_LASTBRANCHTOIP: - msr_info->data = lbrv ? svm->vmcb->save.br_to : 0; - break; case MSR_IA32_LASTINTFROMIP: - msr_info->data = lbrv ? svm->vmcb->save.last_excp_from : 0; - break; case MSR_IA32_LASTINTTOIP: - msr_info->data = lbrv ? svm->vmcb->save.last_excp_to : 0; + msr_info->data = lbrv ? *svm_vmcb_lbr(svm, msr_info->index) : 0; break; case MSR_VM_HSAVE_PA: msr_info->data = svm->nested.hsave_msr; @@ -3122,35 +3133,14 @@ static int svm_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr) svm_update_lbrv(vcpu); break; case MSR_IA32_LASTBRANCHFROMIP: - if (!lbrv) - return KVM_MSR_RET_UNSUPPORTED; - if (!msr->host_initiated) - return 1; - svm->vmcb->save.br_from = data; - vmcb_mark_dirty(svm->vmcb, VMCB_LBR); - break; case MSR_IA32_LASTBRANCHTOIP: - if (!lbrv) - return KVM_MSR_RET_UNSUPPORTED; - if (!msr->host_initiated) - return 1; - svm->vmcb->save.br_to = data; - vmcb_mark_dirty(svm->vmcb, VMCB_LBR); - break; case MSR_IA32_LASTINTFROMIP: - if (!lbrv) - return KVM_MSR_RET_UNSUPPORTED; - if (!msr->host_initiated) - return 1; - svm->vmcb->save.last_excp_from = data; - vmcb_mark_dirty(svm->vmcb, VMCB_LBR); - break; case MSR_IA32_LASTINTTOIP: if (!lbrv) return KVM_MSR_RET_UNSUPPORTED; if (!msr->host_initiated) return 1; - svm->vmcb->save.last_excp_to = data; + *svm_vmcb_lbr(svm, ecx) = data; vmcb_mark_dirty(svm->vmcb, VMCB_LBR); break; case MSR_VM_HSAVE_PA: