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From: Tom Lendacky <thomas.lendacky@amd.com>
To: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, x86@kernel.org
Cc: Paolo Bonzini <pbonzini@redhat.com>,
	Jim Mattson <jmattson@google.com>, Joerg Roedel <joro@8bytes.org>,
	Sean Christopherson <sean.j.christopherson@intel.com>,
	Vitaly Kuznetsov <vkuznets@redhat.com>,
	Wanpeng Li <wanpengli@tencent.com>,
	Borislav Petkov <bp@alien8.de>, Ingo Molnar <mingo@redhat.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Brijesh Singh <brijesh.singh@amd.com>
Subject: [PATCH v3 26/34] KVM: SVM: Guest FPU state save/restore not needed for SEV-ES guest
Date: Mon,  9 Nov 2020 16:25:52 -0600	[thread overview]
Message-ID: <579db8e765d66dddb9546f11b5917880073ccdcf.1604960760.git.thomas.lendacky@amd.com> (raw)
In-Reply-To: <cover.1604960760.git.thomas.lendacky@amd.com>

From: Tom Lendacky <thomas.lendacky@amd.com>

The guest FPU state is automatically restored on VMRUN and saved on VMEXIT
by the hardware, so there is no reason to do this in KVM. 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 <thomas.lendacky@amd.com>
---
 arch/x86/include/asm/kvm_host.h |  2 ++
 arch/x86/kvm/svm/svm.c          |  8 +++++
 arch/x86/kvm/x86.c              | 56 +++++++++++++++++++++++++++------
 3 files changed, 56 insertions(+), 10 deletions(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 51343c7e69fb..3ef63ab71701 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -1473,6 +1473,8 @@ 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 b8167a889d8d..ecec3d872922 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -1317,6 +1317,14 @@ static int svm_create_vcpu(struct kvm_vcpu *vcpu)
 		vmsa_page = alloc_page(GFP_KERNEL_ACCOUNT | __GFP_ZERO);
 		if (!vmsa_page)
 			goto error_free_vmcb_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);
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index aecd931f46be..c0a33d5cdc00 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -4494,6 +4494,9 @@ 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);
@@ -4511,9 +4514,14 @@ 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)) {
 		/*
@@ -9238,9 +9246,14 @@ 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();
@@ -9253,7 +9266,12 @@ 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);
 
@@ -9769,6 +9787,9 @@ 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;
@@ -9789,6 +9810,9 @@ 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;
@@ -9847,6 +9871,9 @@ 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 =
@@ -9860,6 +9887,15 @@ 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)
@@ -9955,7 +9991,7 @@ 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:
@@ -10009,7 +10045,7 @@ 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);
@@ -10057,7 +10093,7 @@ 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;
 
 		/*
-- 
2.28.0


  parent reply	other threads:[~2020-11-09 22:29 UTC|newest]

Thread overview: 39+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-11-09 22:25 [PATCH v3 00/34] SEV-ES hypervisor support Tom Lendacky
2020-11-09 22:25 ` [PATCH v3 01/34] x86/cpu: Add VM page flush MSR availablility as a CPUID feature Tom Lendacky
2020-11-09 22:25 ` [PATCH v3 02/34] KVM: SVM: Remove the call to sev_platform_status() during setup Tom Lendacky
2020-11-09 22:25 ` [PATCH v3 03/34] KVM: SVM: Add support for SEV-ES capability in KVM Tom Lendacky
2020-11-09 22:25 ` [PATCH v3 04/34] KVM: SVM: Add GHCB accessor functions for retrieving fields Tom Lendacky
2020-11-09 22:25 ` [PATCH v3 05/34] KVM: SVM: Add support for the SEV-ES VMSA Tom Lendacky
2020-11-10  3:25   ` kernel test robot
2020-11-10  3:25     ` kernel test robot
2020-11-09 22:25 ` [PATCH v3 06/34] KVM: x86: Mark GPRs dirty when written Tom Lendacky
2020-11-09 22:25 ` [PATCH v3 07/34] KVM: SVM: Add required changes to support intercepts under SEV-ES Tom Lendacky
2020-11-09 22:25 ` [PATCH v3 08/34] KVM: SVM: Prevent debugging " Tom Lendacky
2020-11-09 22:25 ` [PATCH v3 09/34] KVM: SVM: Do not allow instruction emulation " Tom Lendacky
2020-11-09 22:25 ` [PATCH v3 10/34] KVM: SVM: Cannot re-initialize the VMCB after shutdown with SEV-ES Tom Lendacky
2020-11-09 22:25 ` [PATCH v3 11/34] KVM: SVM: Prepare for SEV-ES exit handling in the sev.c file Tom Lendacky
2020-11-09 22:25 ` [PATCH v3 12/34] KVM: SVM: Add initial support for a VMGEXIT VMEXIT Tom Lendacky
2020-11-09 22:25 ` [PATCH v3 13/34] KVM: SVM: Create trace events for VMGEXIT processing Tom Lendacky
2020-11-09 22:25 ` [PATCH v3 14/34] KVM: SVM: Add support for SEV-ES GHCB MSR protocol function 0x002 Tom Lendacky
2020-11-09 22:25 ` [PATCH v3 15/34] KVM: SVM: Add support for SEV-ES GHCB MSR protocol function 0x004 Tom Lendacky
2020-11-09 22:25 ` [PATCH v3 16/34] KVM: SVM: Add support for SEV-ES GHCB MSR protocol function 0x100 Tom Lendacky
2020-11-09 22:25 ` [PATCH v3 17/34] KVM: SVM: Create trace events for VMGEXIT MSR protocol processing Tom Lendacky
2020-11-09 22:25 ` [PATCH v3 18/34] KVM: SVM: Support MMIO for an SEV-ES guest Tom Lendacky
2020-11-09 22:25 ` [PATCH v3 19/34] KVM: SVM: Support string IO operations " Tom Lendacky
2020-11-10  3:56   ` kernel test robot
2020-11-10  3:56     ` kernel test robot
2020-11-09 22:25 ` [PATCH v3 20/34] KVM: SVM: Add support for EFER write traps " Tom Lendacky
2020-11-09 22:25 ` [PATCH v3 21/34] KVM: SVM: Add support for CR0 " Tom Lendacky
2020-11-09 22:25 ` [PATCH v3 22/34] KVM: SVM: Add support for CR4 " Tom Lendacky
2020-11-09 22:25 ` [PATCH v3 23/34] KVM: SVM: Add support for CR8 " Tom Lendacky
2020-11-09 22:25 ` [PATCH v3 24/34] KVM: x86: Update __get_sregs() / __set_sregs() to support SEV-ES Tom Lendacky
2020-11-09 22:25 ` [PATCH v3 25/34] KVM: SVM: Do not report support for SMM for an SEV-ES guest Tom Lendacky
2020-11-09 22:25 ` Tom Lendacky [this message]
2020-11-09 22:25 ` [PATCH v3 27/34] KVM: SVM: Add support for booting APs " Tom Lendacky
2020-11-09 22:25 ` [PATCH v3 28/34] KVM: SVM: Add NMI support " Tom Lendacky
2020-11-09 22:25 ` [PATCH v3 29/34] KVM: SVM: Set the encryption mask for the SVM host save area Tom Lendacky
2020-11-09 22:25 ` [PATCH v3 30/34] KVM: SVM: Update ASID allocation to support SEV-ES guests Tom Lendacky
2020-11-09 22:25 ` [PATCH v3 31/34] KVM: SVM: Provide support for SEV-ES vCPU creation/loading Tom Lendacky
2020-11-09 22:25 ` [PATCH v3 32/34] KVM: SVM: Provide support for SEV-ES vCPU loading Tom Lendacky
2020-11-09 22:25 ` [PATCH v3 33/34] KVM: SVM: Provide an updated VMRUN invocation for SEV-ES guests Tom Lendacky
2020-11-09 22:26 ` [PATCH v3 34/34] KVM: SVM: Provide support to launch and run an SEV-ES guest Tom Lendacky

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