From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pg1-f201.google.com (mail-pg1-f201.google.com [209.85.215.201]) (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 1780117A31C for ; Wed, 4 Mar 2026 00:44:20 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.215.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772585063; cv=none; b=ZKxZjOw7TPArThInYevIQSO36ynVnh4AHzHJNPeYiCXRgaHM81qepb7+6SsT+nnV9PYU5Mdq+vLxhernas/Z+NyeMRG1aJauQlyZWPUoPBI8Lw49WJ9XL9sxAAONDX5NGYLyzDnhu4aOgtOiHmYXiCwK8i5ZibS/Fb6AxilPHJI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772585063; c=relaxed/simple; bh=8EUfImJqXCjwEv07osmggtN7dOfogWe0w9ZDpEIMa58=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=gR5bZ90wfXKqKJCrzH58CaSgAOfMo7SyqQSD99qqgLDSrMJtEL4gPAsDD4biJwBnPyjjSyjV1R5q1awcNMWEWCYYZxgxc6uVr7+KhC59S4chu7+v7GvBLwoTCi/pQ45KPPQ8tdHMNBKaxGjkQAEKHP7txSfARZguSP+ETEFwS2I= 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=209.85.215.201 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-pg1-f201.google.com with SMTP id 41be03b00d2f7-c737b6686ddso30537a12.3 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=dL2WihuNrX2odnddhXlURUJR5xS3C/Nt0rVq8kye65V4zfFpcey4NL6JN1cbWm9LuB qd5we3EavPPui702hEfqkjsUAI6U6pVaWV/ZhQ6fiCZl/BnCarK4Kq/QdpxrCJG2vowx zwoFs/6UibjuXe+EFNnOjOJPDfF3bwM6bMlPZCfwWU5XmnAuSqu45j8+r5pcZHrKgGpp EiW+k8BdulqrEunTOiOO3Q8W7R2AYIBvpMoDQR61vkI39KDrzmQz2zFrraTJGr6Hk+Pv bqDmQSIJY2lhrFYodhb+YebFGurfN3vBhUguvu2+qj1BAdvbCGWe3NIsaxIejnv+L2UK KKoA== X-Forwarded-Encrypted: i=1; AJvYcCU0KLOb4BfFxl3oi6iRAMTFASgw6hD2WyJzgTxjhG9RP2vT5fJidiZ5IETrl67HUMC9IDPlPxfgVjDkrEo=@vger.kernel.org X-Gm-Message-State: AOJu0Yyl8/cFgRfSZbEx7n8bBkygm2jYij+2bRZzz3a133OmDe28vHdm 1OEWi4V2DvT+SDUzxQar1a9BX+CnLmvWAQ0fOrZdsItDCln3aaJrXawN4VrwJ9tpjGfBM/UExyB qz39gbg== 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: linux-kernel@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: