linux-kernel - [PATCH v3 09/12] KVM: VMX: Remove vmx->current_tsc_ratio and decache_tsc

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Message-ID: <20210521102449.21505-10-ilstam@amazon.com>
Date:   Fri, 21 May 2021 11:24:46 +0100
From:   Ilias Stamatis <ilstam@...zon.com>
To:     <kvm@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <pbonzini@...hat.com>
CC:     <mlevitsk@...hat.com>, <seanjc@...gle.com>, <vkuznets@...hat.com>,
        <wanpengli@...cent.com>, <jmattson@...gle.com>, <joro@...tes.org>,
        <zamsden@...il.com>, <mtosatti@...hat.com>, <dwmw@...zon.co.uk>,
        <ilstam@...zon.com>
Subject: [PATCH v3 09/12] KVM: VMX: Remove vmx->current_tsc_ratio and decache_tsc_multiplier()

The vmx->current_tsc_ratio field is redundant as
vcpu->arch.tsc_scaling_ratio already tracks the current TSC scaling
ratio. Removing this field makes decache_tsc_multiplier() an one-liner
so remove that too and do a vmcs_write64() directly in order to be more
consistent with surrounding code.

Signed-off-by: Ilias Stamatis <ilstam@...zon.com>
---
 arch/x86/kvm/vmx/nested.c | 9 ++++-----
 arch/x86/kvm/vmx/vmx.c    | 5 ++---
 arch/x86/kvm/vmx/vmx.h    | 8 --------
 3 files changed, 6 insertions(+), 16 deletions(-)

diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index 6058a65a6ede..239154d3e4e7 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 4b70431c2edd..7c52c697cfe3 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -1392,9 +1392,8 @@ void vmx_vcpu_load_vmcs(struct kvm_vcpu *vcpu, int cpu,
 	}
 
 	/* Setup TSC multiplier */
-	if (kvm_has_tsc_control &&
-	    vmx->current_tsc_ratio != vcpu->arch.tsc_scaling_ratio)
-		decache_tsc_multiplier(vmx);
+	if (kvm_has_tsc_control)
+		vmcs_write64(TSC_MULTIPLIER, vcpu->arch.tsc_scaling_ratio);
 }
 
 /*
diff --git a/arch/x86/kvm/vmx/vmx.h b/arch/x86/kvm/vmx/vmx.h
index aa97c82e3451..3eaa86a0ba3e 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 &
-- 
2.17.1