Commit 1ab9287a authored by Ilias Stamatis's avatar Ilias Stamatis Committed by Paolo Bonzini
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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: default avatarSean Christopherson <seanjc@google.com>
Signed-off-by: default avatarIlias Stamatis <ilstam@amazon.com>
Message-Id: <20210607105438.16541-1-ilstam@amazon.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent edcfe540

arch/x86/include/asm/kvm-x86-ops.h

+1 −0
Original line number Diff line number Diff line
@@ -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)

arch/x86/include/asm/kvm_host.h

+1 −0
Original line number Diff line number Diff line
@@ -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

arch/x86/kvm/svm/svm.c

+6 −0
Original line number Diff line number Diff line
@@ -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,

arch/x86/kvm/vmx/nested.c

+4 −5
Original line number Diff line number Diff line
@@ -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);

arch/x86/kvm/vmx/vmx.c

+6 −5
Original line number Diff line number Diff line
@@ -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,