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Fri, 2 Oct 2020 17:06:42 +0000 From: Tom Lendacky To: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, x86@kernel.org Cc: Paolo Bonzini , Jim Mattson , Joerg Roedel , Sean Christopherson , Vitaly Kuznetsov , Wanpeng Li , Borislav Petkov , Ingo Molnar , Thomas Gleixner , Brijesh Singh Subject: [RFC PATCH v2 25/33] KVM: SVM: Guest FPU state save/restore not needed for SEV-ES guest Date: Fri, 2 Oct 2020 12:02:49 -0500 Message-Id: <7f5959a865807fac16f377100fbc141e1155eaf0.1601658176.git.thomas.lendacky@amd.com> X-Mailer: git-send-email 2.28.0 In-Reply-To: References: X-Originating-IP: [165.204.77.1] X-ClientProxiedBy: SN1PR12CA0072.namprd12.prod.outlook.com (2603:10b6:802:20::43) To DM5PR12MB1355.namprd12.prod.outlook.com (2603:10b6:3:6e::7) MIME-Version: 1.0 X-MS-Exchange-MessageSentRepresentingType: 1 Received: from tlendack-t1.amd.com (165.204.77.1) by SN1PR12CA0072.namprd12.prod.outlook.com (2603:10b6:802:20::43) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.3433.37 via Frontend Transport; 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Eliminate the allocation of the guest_fpu save area and key off that to skip operations related to the guest FPU state. Signed-off-by: Tom Lendacky --- arch/x86/include/asm/kvm_host.h | 2 ++ arch/x86/kvm/svm/svm.c | 10 ++++++ arch/x86/kvm/x86.c | 56 +++++++++++++++++++++++++++------ 3 files changed, 58 insertions(+), 10 deletions(-) diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h index 30f1300a05c0..d5ca8c6b0d5e 100644 --- a/arch/x86/include/asm/kvm_host.h +++ b/arch/x86/include/asm/kvm_host.h @@ -1444,6 +1444,8 @@ void kvm_vcpu_deliver_sipi_vector(struct kvm_vcpu *vcpu, u8 vector); int kvm_task_switch(struct kvm_vcpu *vcpu, u16 tss_selector, int idt_index, int reason, bool has_error_code, u32 error_code); +void kvm_free_guest_fpu(struct kvm_vcpu *vcpu); + int __kvm_set_cr0(struct kvm_vcpu *vcpu, unsigned long old_cr0, unsigned long cr0); int kvm_set_cr0(struct kvm_vcpu *vcpu, unsigned long cr0); int kvm_set_cr3(struct kvm_vcpu *vcpu, unsigned long cr3); diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c index de44f7f2b7a8..13560b90b81a 100644 --- a/arch/x86/kvm/svm/svm.c +++ b/arch/x86/kvm/svm/svm.c @@ -1301,6 +1301,14 @@ static int svm_create_vcpu(struct kvm_vcpu *vcpu) vmsa_page = alloc_page(GFP_KERNEL_ACCOUNT | __GFP_ZERO); if (!vmsa_page) goto error_free_hsave_page; + + /* + * SEV-ES guests maintain an encrypted version of their FPU + * state which is restored and saved on VMRUN and VMEXIT. + * Free the fpu structure to prevent KVM from attempting to + * access the FPU state. + */ + kvm_free_guest_fpu(vcpu); } err = avic_init_vcpu(svm); @@ -3792,6 +3800,7 @@ static __no_kcsan fastpath_t svm_vcpu_run(struct kvm_vcpu *vcpu) svm_set_dr6(svm, DR6_FIXED_1 | DR6_RTM); clgi(); + kvm_load_guest_xsave_state(vcpu); kvm_wait_lapic_expire(vcpu); @@ -3837,6 +3846,7 @@ static __no_kcsan fastpath_t svm_vcpu_run(struct kvm_vcpu *vcpu) kvm_before_interrupt(&svm->vcpu); kvm_load_host_xsave_state(vcpu); + stgi(); /* Any pending NMI will happen here */ diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 20fabf578ab7..931a17ba5cbd 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -4407,6 +4407,9 @@ static void load_xsave(struct kvm_vcpu *vcpu, u8 *src) static void kvm_vcpu_ioctl_x86_get_xsave(struct kvm_vcpu *vcpu, struct kvm_xsave *guest_xsave) { + if (!vcpu->arch.guest_fpu) + return; + if (boot_cpu_has(X86_FEATURE_XSAVE)) { memset(guest_xsave, 0, sizeof(struct kvm_xsave)); fill_xsave((u8 *) guest_xsave->region, vcpu); @@ -4424,9 +4427,14 @@ static void kvm_vcpu_ioctl_x86_get_xsave(struct kvm_vcpu *vcpu, static int kvm_vcpu_ioctl_x86_set_xsave(struct kvm_vcpu *vcpu, struct kvm_xsave *guest_xsave) { - u64 xstate_bv = - *(u64 *)&guest_xsave->region[XSAVE_HDR_OFFSET / sizeof(u32)]; - u32 mxcsr = *(u32 *)&guest_xsave->region[XSAVE_MXCSR_OFFSET / sizeof(u32)]; + u64 xstate_bv; + u32 mxcsr; + + if (!vcpu->arch.guest_fpu) + return 0; + + xstate_bv = *(u64 *)&guest_xsave->region[XSAVE_HDR_OFFSET / sizeof(u32)]; + mxcsr = *(u32 *)&guest_xsave->region[XSAVE_MXCSR_OFFSET / sizeof(u32)]; if (boot_cpu_has(X86_FEATURE_XSAVE)) { /* @@ -9126,9 +9134,14 @@ static void kvm_load_guest_fpu(struct kvm_vcpu *vcpu) kvm_save_current_fpu(vcpu->arch.user_fpu); - /* PKRU is separately restored in kvm_x86_ops.run. */ - __copy_kernel_to_fpregs(&vcpu->arch.guest_fpu->state, - ~XFEATURE_MASK_PKRU); + /* + * Guests with protected state can't have it set by the hypervisor, + * so skip trying to set it. + */ + if (vcpu->arch.guest_fpu) + /* PKRU is separately restored in kvm_x86_ops.run. */ + __copy_kernel_to_fpregs(&vcpu->arch.guest_fpu->state, + ~XFEATURE_MASK_PKRU); fpregs_mark_activate(); fpregs_unlock(); @@ -9141,7 +9154,12 @@ static void kvm_put_guest_fpu(struct kvm_vcpu *vcpu) { fpregs_lock(); - kvm_save_current_fpu(vcpu->arch.guest_fpu); + /* + * Guests with protected state can't have it read by the hypervisor, + * so skip trying to save it. + */ + if (vcpu->arch.guest_fpu) + kvm_save_current_fpu(vcpu->arch.guest_fpu); copy_kernel_to_fpregs(&vcpu->arch.user_fpu->state); @@ -9657,6 +9675,9 @@ int kvm_arch_vcpu_ioctl_get_fpu(struct kvm_vcpu *vcpu, struct kvm_fpu *fpu) { struct fxregs_state *fxsave; + if (!vcpu->arch.guest_fpu) + return 0; + vcpu_load(vcpu); fxsave = &vcpu->arch.guest_fpu->state.fxsave; @@ -9677,6 +9698,9 @@ int kvm_arch_vcpu_ioctl_set_fpu(struct kvm_vcpu *vcpu, struct kvm_fpu *fpu) { struct fxregs_state *fxsave; + if (!vcpu->arch.guest_fpu) + return 0; + vcpu_load(vcpu); fxsave = &vcpu->arch.guest_fpu->state.fxsave; @@ -9735,6 +9759,9 @@ static int sync_regs(struct kvm_vcpu *vcpu) static void fx_init(struct kvm_vcpu *vcpu) { + if (!vcpu->arch.guest_fpu) + return; + fpstate_init(&vcpu->arch.guest_fpu->state); if (boot_cpu_has(X86_FEATURE_XSAVES)) vcpu->arch.guest_fpu->state.xsave.header.xcomp_bv = @@ -9748,6 +9775,15 @@ static void fx_init(struct kvm_vcpu *vcpu) vcpu->arch.cr0 |= X86_CR0_ET; } +void kvm_free_guest_fpu(struct kvm_vcpu *vcpu) +{ + if (vcpu->arch.guest_fpu) { + kmem_cache_free(x86_fpu_cache, vcpu->arch.guest_fpu); + vcpu->arch.guest_fpu = NULL; + } +} +EXPORT_SYMBOL_GPL(kvm_free_guest_fpu); + int kvm_arch_vcpu_precreate(struct kvm *kvm, unsigned int id) { if (kvm_check_tsc_unstable() && atomic_read(&kvm->online_vcpus) != 0) @@ -9843,7 +9879,7 @@ int kvm_arch_vcpu_create(struct kvm_vcpu *vcpu) return 0; free_guest_fpu: - kmem_cache_free(x86_fpu_cache, vcpu->arch.guest_fpu); + kvm_free_guest_fpu(vcpu); free_user_fpu: kmem_cache_free(x86_fpu_cache, vcpu->arch.user_fpu); free_emulate_ctxt: @@ -9897,7 +9933,7 @@ void kvm_arch_vcpu_destroy(struct kvm_vcpu *vcpu) kmem_cache_free(x86_emulator_cache, vcpu->arch.emulate_ctxt); free_cpumask_var(vcpu->arch.wbinvd_dirty_mask); kmem_cache_free(x86_fpu_cache, vcpu->arch.user_fpu); - kmem_cache_free(x86_fpu_cache, vcpu->arch.guest_fpu); + kvm_free_guest_fpu(vcpu); kvm_hv_vcpu_uninit(vcpu); kvm_pmu_destroy(vcpu); @@ -9944,7 +9980,7 @@ void kvm_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event) kvm_async_pf_hash_reset(vcpu); vcpu->arch.apf.halted = false; - if (kvm_mpx_supported()) { + if (vcpu->arch.guest_fpu && kvm_mpx_supported()) { void *mpx_state_buffer; /*