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KVM: nVMX: Don't reread VMCS-agnostic state when switching VMCS

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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>
This commit is contained in:
Sean Christopherson 2019-05-07 09:06:32 -07:00 committed by Paolo Bonzini
parent 13b964a29d
commit 8ef863e67a
3 changed files with 15 additions and 6 deletions
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2
arch/x86/kvm/vmx/nested.c
View File

@ -279,7 +279,7 @@ static void vmx_switch_vmcs(struct kvm_vcpu *vcpu, struct loaded_vmcs *vmcs)
cpu = get_cpu();
prev = vmx->loaded_vmcs;
vmx->loaded_vmcs = vmcs;
vmx_vcpu_load(vcpu, cpu);
vmx_vcpu_load_vmcs(vcpu, cpu);
vmx_sync_vmcs_host_state(vmx, prev);
put_cpu();

18
arch/x86/kvm/vmx/vmx.c
View File

@ -1234,11 +1234,7 @@ static void vmx_vcpu_pi_load(struct kvm_vcpu *vcpu, int cpu)
pi_set_on(pi_desc);
}
/*
* 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)
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;
@ -1299,8 +1295,20 @@ void vmx_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
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();
vmx->host_debugctlmsr = get_debugctlmsr();
}

1
arch/x86/kvm/vmx/vmx.h
View File

@ -302,6 +302,7 @@ struct kvm_vmx {
};
bool nested_vmx_allowed(struct kvm_vcpu *vcpu);
void vmx_vcpu_load_vmcs(struct kvm_vcpu *vcpu, int cpu);
void vmx_vcpu_load(struct kvm_vcpu *vcpu, int cpu);
int allocate_vpid(void);
void free_vpid(int vpid);