From 1ab9287add5e265352d18517551abf6d01d004fd Mon Sep 17 00:00:00 2001 From: Ilias Stamatis Date: Mon, 7 Jun 2021 11:54:38 +0100 Subject: [PATCH] KVM: X86: Add vendor callbacks for writing the TSC multiplier Currently vmx_vcpu_load_vmcs() writes the TSC_MULTIPLIER field of the VMCS every time the VMCS is loaded. Instead of doing this, set this field from common code on initialization and whenever the scaling ratio changes. Additionally remove vmx->current_tsc_ratio. This field is redundant as vcpu->arch.tsc_scaling_ratio already tracks the current TSC scaling ratio. The vmx->current_tsc_ratio field is only used for avoiding unnecessary writes but it is no longer needed after removing the code from the VMCS load path. Suggested-by: Sean Christopherson Signed-off-by: Ilias Stamatis Message-Id: <20210607105438.16541-1-ilstam@amazon.com> Signed-off-by: Paolo Bonzini --- arch/x86/include/asm/kvm-x86-ops.h | 1 + arch/x86/include/asm/kvm_host.h | 1 + arch/x86/kvm/svm/svm.c | 6 ++++++ arch/x86/kvm/vmx/nested.c | 9 ++++----- arch/x86/kvm/vmx/vmx.c | 11 ++++++----- arch/x86/kvm/vmx/vmx.h | 8 -------- arch/x86/kvm/x86.c | 30 +++++++++++++++++++++++------- 7 files changed, 41 insertions(+), 25 deletions(-) diff --git a/arch/x86/include/asm/kvm-x86-ops.h b/arch/x86/include/asm/kvm-x86-ops.h index 026ca50..aeb5f11 100644 --- a/arch/x86/include/asm/kvm-x86-ops.h +++ b/arch/x86/include/asm/kvm-x86-ops.h @@ -90,6 +90,7 @@ KVM_X86_OP_NULL(has_wbinvd_exit) KVM_X86_OP(get_l2_tsc_offset) KVM_X86_OP(get_l2_tsc_multiplier) KVM_X86_OP(write_tsc_offset) +KVM_X86_OP(write_tsc_multiplier) KVM_X86_OP(get_exit_info) KVM_X86_OP(check_intercept) KVM_X86_OP(handle_exit_irqoff) diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h index 0877398..ca3b192 100644 --- a/arch/x86/include/asm/kvm_host.h +++ b/arch/x86/include/asm/kvm_host.h @@ -1314,6 +1314,7 @@ struct kvm_x86_ops { u64 (*get_l2_tsc_offset)(struct kvm_vcpu *vcpu); u64 (*get_l2_tsc_multiplier)(struct kvm_vcpu *vcpu); void (*write_tsc_offset)(struct kvm_vcpu *vcpu, u64 offset); + void (*write_tsc_multiplier)(struct kvm_vcpu *vcpu, u64 multiplier); /* * Retrieve somewhat arbitrary exit information. Intended to be used diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c index 623f3c4..a4d29ee 100644 --- a/arch/x86/kvm/svm/svm.c +++ b/arch/x86/kvm/svm/svm.c @@ -1101,6 +1101,11 @@ static void svm_write_tsc_offset(struct kvm_vcpu *vcpu, u64 offset) vmcb_mark_dirty(svm->vmcb, VMCB_INTERCEPTS); } +static void svm_write_tsc_multiplier(struct kvm_vcpu *vcpu, u64 multiplier) +{ + wrmsrl(MSR_AMD64_TSC_RATIO, multiplier); +} + /* Evaluate instruction intercepts that depend on guest CPUID features. */ static void svm_recalc_instruction_intercepts(struct kvm_vcpu *vcpu, struct vcpu_svm *svm) @@ -4526,6 +4531,7 @@ static struct kvm_x86_ops svm_x86_ops __initdata = { .get_l2_tsc_offset = svm_get_l2_tsc_offset, .get_l2_tsc_multiplier = svm_get_l2_tsc_multiplier, .write_tsc_offset = svm_write_tsc_offset, + .write_tsc_multiplier = svm_write_tsc_multiplier, .load_mmu_pgd = svm_load_mmu_pgd, diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c index 6058a65..239154d 100644 --- a/arch/x86/kvm/vmx/nested.c +++ b/arch/x86/kvm/vmx/nested.c @@ -2533,9 +2533,8 @@ static int prepare_vmcs02(struct kvm_vcpu *vcpu, struct vmcs12 *vmcs12, } vmcs_write64(TSC_OFFSET, vcpu->arch.tsc_offset); - if (kvm_has_tsc_control) - decache_tsc_multiplier(vmx); + vmcs_write64(TSC_MULTIPLIER, vcpu->arch.tsc_scaling_ratio); nested_vmx_transition_tlb_flush(vcpu, vmcs12, true); @@ -4501,12 +4500,12 @@ void nested_vmx_vmexit(struct kvm_vcpu *vcpu, u32 vm_exit_reason, vmcs_write32(VM_EXIT_MSR_LOAD_COUNT, vmx->msr_autoload.host.nr); vmcs_write32(VM_ENTRY_MSR_LOAD_COUNT, vmx->msr_autoload.guest.nr); vmcs_write64(TSC_OFFSET, vcpu->arch.tsc_offset); + if (kvm_has_tsc_control) + vmcs_write64(TSC_MULTIPLIER, vcpu->arch.tsc_scaling_ratio); + if (vmx->nested.l1_tpr_threshold != -1) vmcs_write32(TPR_THRESHOLD, vmx->nested.l1_tpr_threshold); - if (kvm_has_tsc_control) - decache_tsc_multiplier(vmx); - if (vmx->nested.change_vmcs01_virtual_apic_mode) { vmx->nested.change_vmcs01_virtual_apic_mode = false; vmx_set_virtual_apic_mode(vcpu); diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c index 54d08be..092a045 100644 --- a/arch/x86/kvm/vmx/vmx.c +++ b/arch/x86/kvm/vmx/vmx.c @@ -1390,11 +1390,6 @@ void vmx_vcpu_load_vmcs(struct kvm_vcpu *vcpu, int cpu, vmx->loaded_vmcs->cpu = cpu; } - - /* Setup TSC multiplier */ - if (kvm_has_tsc_control && - vmx->current_tsc_ratio != vcpu->arch.tsc_scaling_ratio) - decache_tsc_multiplier(vmx); } /* @@ -1813,6 +1808,11 @@ static void vmx_write_tsc_offset(struct kvm_vcpu *vcpu, u64 offset) vmcs_write64(TSC_OFFSET, offset); } +static void vmx_write_tsc_multiplier(struct kvm_vcpu *vcpu, u64 multiplier) +{ + vmcs_write64(TSC_MULTIPLIER, multiplier); +} + /* * nested_vmx_allowed() checks whether a guest should be allowed to use VMX * instructions and MSRs (i.e., nested VMX). Nested VMX is disabled for @@ -7707,6 +7707,7 @@ static struct kvm_x86_ops vmx_x86_ops __initdata = { .get_l2_tsc_offset = vmx_get_l2_tsc_offset, .get_l2_tsc_multiplier = vmx_get_l2_tsc_multiplier, .write_tsc_offset = vmx_write_tsc_offset, + .write_tsc_multiplier = vmx_write_tsc_multiplier, .load_mmu_pgd = vmx_load_mmu_pgd, diff --git a/arch/x86/kvm/vmx/vmx.h b/arch/x86/kvm/vmx/vmx.h index aa97c82..3eaa86a 100644 --- a/arch/x86/kvm/vmx/vmx.h +++ b/arch/x86/kvm/vmx/vmx.h @@ -322,8 +322,6 @@ struct vcpu_vmx { /* apic deadline value in host tsc */ u64 hv_deadline_tsc; - u64 current_tsc_ratio; - unsigned long host_debugctlmsr; /* @@ -532,12 +530,6 @@ static inline struct vmcs *alloc_vmcs(bool shadow) GFP_KERNEL_ACCOUNT); } -static inline void decache_tsc_multiplier(struct vcpu_vmx *vmx) -{ - vmx->current_tsc_ratio = vmx->vcpu.arch.tsc_scaling_ratio; - vmcs_write64(TSC_MULTIPLIER, vmx->current_tsc_ratio); -} - static inline bool vmx_has_waitpkg(struct vcpu_vmx *vmx) { return vmx->secondary_exec_control & diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index b42f6c8..85b40e9 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -2179,14 +2179,15 @@ static u32 adjust_tsc_khz(u32 khz, s32 ppm) return v; } +static void kvm_vcpu_write_tsc_multiplier(struct kvm_vcpu *vcpu, u64 l1_multiplier); + static int set_tsc_khz(struct kvm_vcpu *vcpu, u32 user_tsc_khz, bool scale) { u64 ratio; /* Guest TSC same frequency as host TSC? */ if (!scale) { - vcpu->arch.l1_tsc_scaling_ratio = kvm_default_tsc_scaling_ratio; - vcpu->arch.tsc_scaling_ratio = kvm_default_tsc_scaling_ratio; + kvm_vcpu_write_tsc_multiplier(vcpu, kvm_default_tsc_scaling_ratio); return 0; } @@ -2212,7 +2213,7 @@ static int set_tsc_khz(struct kvm_vcpu *vcpu, u32 user_tsc_khz, bool scale) return -1; } - vcpu->arch.l1_tsc_scaling_ratio = vcpu->arch.tsc_scaling_ratio = ratio; + kvm_vcpu_write_tsc_multiplier(vcpu, ratio); return 0; } @@ -2224,8 +2225,7 @@ static int kvm_set_tsc_khz(struct kvm_vcpu *vcpu, u32 user_tsc_khz) /* tsc_khz can be zero if TSC calibration fails */ if (user_tsc_khz == 0) { /* set tsc_scaling_ratio to a safe value */ - vcpu->arch.l1_tsc_scaling_ratio = kvm_default_tsc_scaling_ratio; - vcpu->arch.tsc_scaling_ratio = kvm_default_tsc_scaling_ratio; + kvm_vcpu_write_tsc_multiplier(vcpu, kvm_default_tsc_scaling_ratio); return -1; } @@ -2383,6 +2383,23 @@ static void kvm_vcpu_write_tsc_offset(struct kvm_vcpu *vcpu, u64 l1_offset) static_call(kvm_x86_write_tsc_offset)(vcpu, vcpu->arch.tsc_offset); } +static void kvm_vcpu_write_tsc_multiplier(struct kvm_vcpu *vcpu, u64 l1_multiplier) +{ + vcpu->arch.l1_tsc_scaling_ratio = l1_multiplier; + + /* Userspace is changing the multiplier while L2 is active */ + if (is_guest_mode(vcpu)) + vcpu->arch.tsc_scaling_ratio = kvm_calc_nested_tsc_multiplier( + l1_multiplier, + static_call(kvm_x86_get_l2_tsc_multiplier)(vcpu)); + else + vcpu->arch.tsc_scaling_ratio = l1_multiplier; + + if (kvm_has_tsc_control) + static_call(kvm_x86_write_tsc_multiplier)( + vcpu, vcpu->arch.tsc_scaling_ratio); +} + static inline bool kvm_check_tsc_unstable(void) { #ifdef CONFIG_X86_64 @@ -10364,8 +10381,6 @@ int kvm_arch_vcpu_create(struct kvm_vcpu *vcpu) else vcpu->arch.mp_state = KVM_MP_STATE_UNINITIALIZED; - kvm_set_tsc_khz(vcpu, max_tsc_khz); - r = kvm_mmu_create(vcpu); if (r < 0) return r; @@ -10433,6 +10448,7 @@ int kvm_arch_vcpu_create(struct kvm_vcpu *vcpu) vcpu->arch.msr_platform_info = MSR_PLATFORM_INFO_CPUID_FAULT; kvm_vcpu_mtrr_init(vcpu); vcpu_load(vcpu); + kvm_set_tsc_khz(vcpu, max_tsc_khz); kvm_vcpu_reset(vcpu, false); kvm_init_mmu(vcpu, false); vcpu_put(vcpu); -- 2.7.4