From nobody Mon Jun 15 03:52:56 2026 Received: from mail-pf1-f202.google.com (mail-pf1-f202.google.com [209.85.210.202]) (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 41DC43793BA for ; Tue, 7 Apr 2026 19:03:56 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.210.202 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1775588637; cv=none; b=ngn0eAAoPZ12Hfn7tbaldUhiGWELbWwBqI75yMGrGcLPoIWfPmpJtqmf3gwFPmy4fGF2bsbd6GM4xnV6Y/ubO3bfIp04hgUN7HobAmg+2e0hiZFr+RriSbsT+HeZpskiYaDmKaSC1HjgXKzRXczVdwM7WNxwcqMMMXwXz3R7aCU= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1775588637; c=relaxed/simple; bh=HE16aqvo2kSNiQCGfnKf8BZKOYvkGmEshj6tm2tsYAY=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=GzetOnycdk6M+XEJ5lXgYwGwosdIIOZrr7vGoswy10A/pYS5m0v82is4cIQ0J3bLA7nTgttpATF4TPgb9oF1XmyvsteNkjJWDwMP++EoVqWLE1nmjJD/OOdao2XKBI8bg1Ovlhwwot+D8tbfOJxdIERKozdFmiHQzDmUbP3gpWA= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--jmattson.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=pdCCV2D5; arc=none smtp.client-ip=209.85.210.202 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--jmattson.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="pdCCV2D5" Received: by mail-pf1-f202.google.com with SMTP id d2e1a72fcca58-82c9364612fso7810446b3a.2 for ; Tue, 07 Apr 2026 12:03:55 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20251104; t=1775588635; x=1776193435; 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=pqVeCtX1aVyum4q4mSfbZ8Tffgvj54dtcUsGbe5OM+k=; b=pdCCV2D5a99FyKHrD6HCpjSYrflQl2Z28LOqUM41pFT5X9kdmZtE8fW4KHic8RBqtB xn9cJ8yq9wMZaKRT6SOKyl3s7KVDPAGPxjkiFVh8tKSyRiAmdoZVyT3cITOW3NmUHo4S /DtxRky6eFRWrnJ9XRIDLbTjlAj5RXzz5ZXjzp6onupT9+AysTSQGNk2QcyWfxAMjt30 6jfMX+4hcyyrpywC7nFhiSnjie5XU0Jlkb2vFQ3Qd6BorUgtu7idpVpoVR8KlBIx6fdx kNbceG8EHiQefjE+c3ctNpX4OeF/rRKfdIaZzfUcSx8fxnxdL/2/b0WwgjneCbQ2i6ud QMfg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1775588635; x=1776193435; 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=pqVeCtX1aVyum4q4mSfbZ8Tffgvj54dtcUsGbe5OM+k=; b=NBC3zsNA7TszI8A0FTdMbvQ8nU4pedlzGVE5IDxTN50iqfPWu0y8zjUdwGY9vNSUqj 7cy24iqqDjf+dr6NwTnrExE+WqWqGFFO3+yBrJ4Vd8FqRZmNIU0bMAh2kJ1C2+6Rktcc 99r962vdhnu4vx8wk984giJfOdWhfOMkecY1e/exmM9ADjy1qtiVHUbghWxlPXl/lvC9 5tolOL0s49Fx/JK96w2FTFLxQmm0noJweVvojqz+Rz8G8yP/Bj6RMOfqM1pL/8gBM04G HHj2G3KkOgBFAJqofr/+WMBBPEtkPsDCrmI73D+/gMHTx8VZT9wJadNYIV6oHNWP8QlN L0JA== X-Forwarded-Encrypted: i=1; AJvYcCXZ3Pj9QxyyOMVUeTbVdL1P3TOyzKJU9MjVQd9DeYA2k6HR7fD0msHbLYyDEiB4qAgd8TAtDCmHr/QPe0Y=@vger.kernel.org X-Gm-Message-State: AOJu0YwJ4tjVyOGT7Aqt2SISo62ZnKvdmbYjQl2XCC9RTm9mlJkfnFe9 9/ujbWfedsSSI+hAQn+quiI6uoNjKVgzcXYXU3N68YI8EqxH3va+taaaiUBWfQyEkgiXbsbFHa9 WDbBlsshDxA8KQg== X-Received: from pfbcm16.prod.google.com ([2002:a05:6a00:3390:b0:824:c676:35a8]) (user=jmattson job=prod-delivery.src-stubby-dispatcher) by 2002:a05:6a00:1388:b0:82c:9c4f:da3 with SMTP id d2e1a72fcca58-82d0db5abefmr18297546b3a.31.1775588635172; Tue, 07 Apr 2026 12:03:55 -0700 (PDT) Date: Tue, 7 Apr 2026 12:03:28 -0700 In-Reply-To: <20260407190343.325299-1-jmattson@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20260407190343.325299-1-jmattson@google.com> X-Mailer: git-send-email 2.53.0.1213.gd9a14994de-goog Message-ID: <20260407190343.325299-6-jmattson@google.com> Subject: [PATCH] KVM: x86: nSVM: Redirect IA32_PAT accesses to either hPAT or gPAT From: Jim Mattson To: Paolo Bonzini , Jonathan Corbet , Shuah Khan , Sean Christopherson , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , kvm@vger.kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, Yosry Ahmed Cc: Jim Mattson Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" When KVM_X86_QUIRK_NESTED_SVM_SHARED_PAT is disabled and the vCPU is in guest mode with nested NPT enabled, guest accesses to IA32_PAT are redirected to the gPAT register, which is stored in VMCB02's g_pat field. Non-guest accesses (e.g. from userspace) to IA32_PAT are always redirected to hPAT, which is stored in vcpu->arch.pat. Directing host-initiated accesses to hPAT ensures that KVM_GET/SET_MSRS and KVM_GET/SET_NESTED_STATE are independent of each other and can be ordered arbitrarily during save and restore. gPAT is saved and restored separately via KVM_GET/SET_NESTED_STATE. Use WARN_ON_ONCE to flag any host-initiated accesses originating from KVM itself rather than userspace. Use pr_warn_once to flag any use of the common MSR-handling code (now shared by VMX and TDX) for IA32_PAT by a vCPU that is SVM-capable. Fixes: 15038e147247 ("KVM: SVM: obey guest PAT") Signed-off-by: Jim Mattson Co-developed-by: Sean Christopherson Signed-off-by: Sean Christopherson --- arch/x86/kvm/svm/nested.c | 9 --------- arch/x86/kvm/svm/svm.c | 36 +++++++++++++++++++++++++++++++++--- arch/x86/kvm/svm/svm.h | 1 - 3 files changed, 33 insertions(+), 13 deletions(-) diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c index 58574e803812..8c9dd685b616 100644 --- a/arch/x86/kvm/svm/nested.c +++ b/arch/x86/kvm/svm/nested.c @@ -703,15 +703,6 @@ static int nested_svm_load_cr3(struct kvm_vcpu *vcpu, = unsigned long cr3, return 0; } =20 -void nested_vmcb02_compute_g_pat(struct vcpu_svm *svm) -{ - if (!svm->nested.vmcb02.ptr) - return; - - /* FIXME: merge g_pat from vmcb01 and vmcb12. */ - vmcb_set_gpat(svm->nested.vmcb02.ptr, svm->vmcb01.ptr->save.g_pat); -} - static bool nested_vmcb12_has_lbrv(struct kvm_vcpu *vcpu) { return guest_cpu_cap_has(vcpu, X86_FEATURE_LBRV) && diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c index 56b6bd5dfdca..8d968ead6f45 100644 --- a/arch/x86/kvm/svm/svm.c +++ b/arch/x86/kvm/svm/svm.c @@ -2767,6 +2767,20 @@ static bool sev_es_prevent_msr_access(struct kvm_vcp= u *vcpu, !msr_write_intercepted(vcpu, msr_info->index); } =20 +static bool svm_pat_accesses_gpat(struct kvm_vcpu *vcpu, bool from_host) +{ + /* + * When KVM_X86_QUIRK_NESTED_SVM_SHARED_PAT is disabled and nested + * NPT is enabled, L2 has a separate PAT from L1. Guest accesses + * to IA32_PAT while running L2 target L2's gPAT; host-initiated + * accesses always target L1's hPAT so that KVM_GET/SET_MSRS and + * KVM_GET/SET_NESTED_STATE are independent of each other and can + * be ordered arbitrarily during save and restore. + */ + WARN_ON_ONCE(from_host && vcpu->wants_to_run); + return !from_host && is_guest_mode(vcpu) && l2_has_separate_pat(vcpu); +} + static int svm_get_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info) { struct vcpu_svm *svm =3D to_svm(vcpu); @@ -2883,6 +2897,12 @@ static int svm_get_msr(struct kvm_vcpu *vcpu, struct= msr_data *msr_info) case MSR_AMD64_DE_CFG: msr_info->data =3D svm->msr_decfg; break; + case MSR_IA32_CR_PAT: + if (svm_pat_accesses_gpat(vcpu, msr_info->host_initiated)) { + msr_info->data =3D svm->vmcb->save.g_pat; + break; + } + return kvm_get_msr_common(vcpu, msr_info); default: return kvm_get_msr_common(vcpu, msr_info); } @@ -2966,13 +2986,23 @@ static int svm_set_msr(struct kvm_vcpu *vcpu, struc= t msr_data *msr) =20 break; case MSR_IA32_CR_PAT: + if (svm_pat_accesses_gpat(vcpu, msr->host_initiated)) { + if (!kvm_pat_valid(data)) + return 1; + + vmcb_set_gpat(svm->vmcb, data); + break; + } + ret =3D kvm_set_msr_common(vcpu, msr); if (ret) break; =20 - vmcb_set_gpat(svm->vmcb01.ptr, data); - if (is_guest_mode(vcpu)) - nested_vmcb02_compute_g_pat(svm); + if (npt_enabled) { + vmcb_set_gpat(svm->vmcb01.ptr, data); + if (is_guest_mode(vcpu) && !l2_has_separate_pat(vcpu)) + vmcb_set_gpat(svm->vmcb, data); + } break; case MSR_IA32_SPEC_CTRL: if (!msr->host_initiated && diff --git a/arch/x86/kvm/svm/svm.h b/arch/x86/kvm/svm/svm.h index fdd6286d965e..677e899bda33 100644 --- a/arch/x86/kvm/svm/svm.h +++ b/arch/x86/kvm/svm/svm.h @@ -881,7 +881,6 @@ void nested_copy_vmcb_control_to_cache(struct vcpu_svm = *svm, void nested_copy_vmcb_save_to_cache(struct vcpu_svm *svm, struct vmcb_save_area *save); void nested_sync_control_from_vmcb02(struct vcpu_svm *svm); -void nested_vmcb02_compute_g_pat(struct vcpu_svm *svm); void svm_switch_vmcb(struct vcpu_svm *svm, struct kvm_vmcb_info *target_vm= cb); =20 extern struct kvm_x86_nested_ops svm_nested_ops; --=20 2.53.0.1213.gd9a14994de-goog