From d225157bc6a442b1214882635fbf287d7d0e8133 Mon Sep 17 00:00:00 2001 From: Avi Kivity Date: Wed, 6 Jan 2010 10:55:27 +0200 Subject: [PATCH] KVM: SVM: Selective cr0 intercept If two conditions apply: - no bits outside TS and EM differ between the host and guest cr0 - the fpu is active then we can activate the selective cr0 write intercept and drop the unconditional cr0 read and write intercept, and allow the guest to run with the host fpu state. This reduces cr0 exits due to guest fpu management while the guest fpu is loaded. Acked-by: Joerg Roedel Signed-off-by: Avi Kivity --- arch/x86/kvm/svm.c | 32 ++++++++++++++++++++++++++------ 1 file changed, 26 insertions(+), 6 deletions(-) diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c index 27273ed..83c7ab1 100644 --- a/arch/x86/kvm/svm.c +++ b/arch/x86/kvm/svm.c @@ -571,6 +571,7 @@ static void init_vmcb(struct vcpu_svm *svm) control->intercept = (1ULL << INTERCEPT_INTR) | (1ULL << INTERCEPT_NMI) | (1ULL << INTERCEPT_SMI) | + (1ULL << INTERCEPT_SELECTIVE_CR0) | (1ULL << INTERCEPT_CPUID) | (1ULL << INTERCEPT_INVD) | (1ULL << INTERCEPT_HLT) | @@ -963,6 +964,27 @@ static void svm_decache_cr4_guest_bits(struct kvm_vcpu *vcpu) { } +static void update_cr0_intercept(struct vcpu_svm *svm) +{ + ulong gcr0 = svm->vcpu.arch.cr0; + u64 *hcr0 = &svm->vmcb->save.cr0; + + if (!svm->vcpu.fpu_active) + *hcr0 |= SVM_CR0_SELECTIVE_MASK; + else + *hcr0 = (*hcr0 & ~SVM_CR0_SELECTIVE_MASK) + | (gcr0 & SVM_CR0_SELECTIVE_MASK); + + + if (gcr0 == *hcr0 && svm->vcpu.fpu_active) { + svm->vmcb->control.intercept_cr_read &= ~INTERCEPT_CR0_MASK; + svm->vmcb->control.intercept_cr_write &= ~INTERCEPT_CR0_MASK; + } else { + svm->vmcb->control.intercept_cr_read |= INTERCEPT_CR0_MASK; + svm->vmcb->control.intercept_cr_write |= INTERCEPT_CR0_MASK; + } +} + static void svm_set_cr0(struct kvm_vcpu *vcpu, unsigned long cr0) { struct vcpu_svm *svm = to_svm(vcpu); @@ -994,6 +1016,7 @@ static void svm_set_cr0(struct kvm_vcpu *vcpu, unsigned long cr0) */ cr0 &= ~(X86_CR0_CD | X86_CR0_NW); svm->vmcb->save.cr0 = cr0; + update_cr0_intercept(svm); } static void svm_set_cr4(struct kvm_vcpu *vcpu, unsigned long cr4) @@ -1239,11 +1262,8 @@ static int ud_interception(struct vcpu_svm *svm) static int nm_interception(struct vcpu_svm *svm) { svm->vmcb->control.intercept_exceptions &= ~(1 << NM_VECTOR); - if (!kvm_read_cr0_bits(&svm->vcpu, X86_CR0_TS)) - svm->vmcb->save.cr0 &= ~X86_CR0_TS; - else - svm->vmcb->save.cr0 |= X86_CR0_TS; svm->vcpu.fpu_active = 1; + update_cr0_intercept(svm); return 1; } @@ -2296,7 +2316,7 @@ static int (*svm_exit_handlers[])(struct vcpu_svm *svm) = { [SVM_EXIT_READ_CR3] = emulate_on_interception, [SVM_EXIT_READ_CR4] = emulate_on_interception, [SVM_EXIT_READ_CR8] = emulate_on_interception, - /* for now: */ + [SVM_EXIT_CR0_SEL_WRITE] = emulate_on_interception, [SVM_EXIT_WRITE_CR0] = emulate_on_interception, [SVM_EXIT_WRITE_CR3] = emulate_on_interception, [SVM_EXIT_WRITE_CR4] = emulate_on_interception, @@ -2914,8 +2934,8 @@ static void svm_fpu_deactivate(struct kvm_vcpu *vcpu) return; } + update_cr0_intercept(svm); svm->vmcb->control.intercept_exceptions |= 1 << NM_VECTOR; - svm->vmcb->save.cr0 |= X86_CR0_TS; } static struct kvm_x86_ops svm_x86_ops = { -- 2.7.4