From: Sean Christopherson <sean.j.christopherson@intel.com>
Date: Tue, 7 May 2019 09:06:32 -0700
Subject: KVM: nVMX: Don't reread VMCS-agnostic state when switching VMCS
Git-commit: 8ef863e67a89c72b5af893a1214f6c35a5f456f8
Patch-mainline: v5.3-rc1
References: bsc#1114279

When switching between vmcs01 and vmcs02, there is no need to update
state tracking for values that aren't tied to any particular VMCS as
the per-vCPU values are already up-to-date (vmx_switch_vmcs() can only
be called when the vCPU is loaded).

Avoiding the update eliminates a RDMSR, and potentially a RDPKRU and
posted-interrupt update (cmpxchg64() and more).

Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Acked-by: Borislav Petkov <bp@suse.de>
---
 arch/x86/kvm/vmx.c |   20 ++++++++++++++------
 1 file changed, 14 insertions(+), 6 deletions(-)

--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -2483,11 +2483,7 @@ static void decache_tsc_multiplier(struc
 	vmcs_write64(TSC_MULTIPLIER, vmx->current_tsc_ratio);
 }
 
-/*
- * Switches to specified vcpu, until a matching vcpu_put(), but assumes
- * vcpu mutex is already taken.
- */
-static void vmx_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
+void vmx_vcpu_load_vmcs(struct kvm_vcpu *vcpu, int cpu)
 {
 	struct vcpu_vmx *vmx = to_vmx(vcpu);
 	bool already_loaded = vmx->loaded_vmcs->cpu == cpu;
@@ -2548,8 +2544,20 @@ static void vmx_vcpu_load(struct kvm_vcp
 	if (kvm_has_tsc_control &&
 	    vmx->current_tsc_ratio != vcpu->arch.tsc_scaling_ratio)
 		decache_tsc_multiplier(vmx);
+}
+
+/*
+ * Switches to specified vcpu, until a matching vcpu_put(), but assumes
+ * vcpu mutex is already taken.
+ */
+void vmx_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
+{
+	struct vcpu_vmx *vmx = to_vmx(vcpu);
+
+	vmx_vcpu_load_vmcs(vcpu, cpu);
 
 	vmx_vcpu_pi_load(vcpu, cpu);
+
 	vmx->host_pkru = read_pkru();
 }
 
@@ -9956,7 +9964,7 @@ static void vmx_switch_vmcs(struct kvm_v
 	cpu = get_cpu();
 	vmx_vcpu_put(vcpu);
 	vmx->loaded_vmcs = vmcs;
-	vmx_vcpu_load(vcpu, cpu);
+	vmx_vcpu_load_vmcs(vcpu, cpu);
 	put_cpu();
 
 	vm_entry_controls_reset_shadow(vmx);