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Thu, 26 Mar 2026 11:18:17 -0700 (PDT) X-Received: by 2002:a05:600c:34c1:b0:485:3c66:e21d with SMTP id 5b1f17b1804b1-48715fd47a5mr121812375e9.2.1774549096577; Thu, 26 Mar 2026 11:18:16 -0700 (PDT) Received: from [192.168.10.48] ([151.49.85.67]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-48725d38f52sm10686885e9.0.2026.03.26.11.18.14 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 26 Mar 2026 11:18:14 -0700 (PDT) From: Paolo Bonzini To: linux-kernel@vger.kernel.org, kvm@vger.kernel.org Cc: Jon Kohler , Nikunj A Dadhania , Amit Shah , Sean Christopherson , Marcelo Tosatti Subject: [PATCH 19/24] KVM: x86/mmu: introduce cpu_role bit for availability of PFEC.I/D Date: Thu, 26 Mar 2026 19:17:17 +0100 Message-ID: <20260326181723.218115-20-pbonzini@redhat.com> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260326181723.218115-1-pbonzini@redhat.com> References: <20260326181723.218115-1-pbonzini@redhat.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" While GMET looks a lot like SMEP, it has several annoying differences. The main one is that the availability of the I/D bit in the page fault error code still depends on the host CR4.SMEP and EFER.NXE bits. If the base.cr4_smep bit of the cpu_role is (ab)used to enable GMET, there needs to be another place where the host CR4.SMEP is read from; just merge it with EFER.NXE into a new cpu_role bit that tells paging_tmpl.h whether to set the I/D bit at all. Signed-off-by: Paolo Bonzini --- arch/x86/include/asm/kvm_host.h | 7 +++++++ arch/x86/kvm/mmu/mmu.c | 8 ++++++++ arch/x86/kvm/mmu/paging_tmpl.h | 2 +- 3 files changed, 16 insertions(+), 1 deletion(-) diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_hos= t.h index 50a941ff61d1..df46ee605b9b 100644 --- a/arch/x86/include/asm/kvm_host.h +++ b/arch/x86/include/asm/kvm_host.h @@ -413,6 +413,13 @@ union kvm_mmu_extended_role { unsigned int cr4_smap:1; unsigned int cr4_la57:1; unsigned int efer_lma:1; + + /* + * True if either CR4.SMEP or EFER.NXE are set. For AMD NPT + * this is the "real" host CR4.SMEP whereas cr4_smep is + * actually GMET. + */ + unsigned int has_pferr_fetch:1; }; }; =20 diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c index 834ba9c0c809..94d7e39a9417 100644 --- a/arch/x86/kvm/mmu/mmu.c +++ b/arch/x86/kvm/mmu/mmu.c @@ -234,6 +234,11 @@ BUILD_MMU_ROLE_ACCESSOR(ext, cr4, la57); BUILD_MMU_ROLE_ACCESSOR(base, efer, nx); BUILD_MMU_ROLE_ACCESSOR(ext, efer, lma); =20 +static inline bool has_pferr_fetch(struct kvm_mmu *mmu) +{ + return mmu->cpu_role.ext.has_pferr_fetch; +} + static inline bool is_cr0_pg(struct kvm_mmu *mmu) { return mmu->cpu_role.base.level > 0; @@ -5774,6 +5779,8 @@ static union kvm_cpu_role kvm_calc_cpu_role(struct kv= m_vcpu *vcpu, role.ext.cr4_pke =3D ____is_efer_lma(regs) && ____is_cr4_pke(regs); role.ext.cr4_la57 =3D ____is_efer_lma(regs) && ____is_cr4_la57(regs); role.ext.efer_lma =3D ____is_efer_lma(regs); + + role.ext.has_pferr_fetch =3D role.base.efer_nx | role.base.cr4_smep; return role; } =20 @@ -5927,6 +5934,7 @@ void kvm_init_shadow_npt_mmu(struct kvm_vcpu *vcpu, u= nsigned long cr0, =20 /* NPT requires CR0.PG=3D1. */ WARN_ON_ONCE(cpu_role.base.direct || !cpu_role.base.guest_mode); + cpu_role.base.cr4_smep =3D false; =20 root_role =3D cpu_role.base; root_role.level =3D kvm_mmu_get_tdp_level(vcpu); diff --git a/arch/x86/kvm/mmu/paging_tmpl.h b/arch/x86/kvm/mmu/paging_tmpl.h index 31331fe10723..8ea248e1918b 100644 --- a/arch/x86/kvm/mmu/paging_tmpl.h +++ b/arch/x86/kvm/mmu/paging_tmpl.h @@ -486,7 +486,7 @@ static int FNAME(walk_addr_generic)(struct guest_walker= *walker, =20 error: errcode |=3D write_fault | user_fault; - if (fetch_fault && (is_efer_nx(mmu) || is_cr4_smep(mmu))) + if (fetch_fault && has_pferr_fetch(mmu)) errcode |=3D PFERR_FETCH_MASK; =20 walker->fault.vector =3D PF_VECTOR; --=20 2.53.0