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KVM: nVMX: Reload APIC access page on nested VM-Exit only if necessary

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Defer reloading L1's APIC page by logging the need for a reload and
processing it during nested VM-Exit instead of unconditionally reloading
the APIC page on nested VM-Exit.  This eliminates a TLB flush on the
majority of VM-Exits as the APIC page rarely needs to be reloaded.

Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Message-Id: <20200320212833.3507-28-sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Sean Christopherson 2020-03-20 14:28:23 -07:00 committed by Paolo Bonzini
parent c51e1ffee5
commit 1196cb970b
3 changed files with 12 additions and 8 deletions
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9
arch/x86/kvm/vmx/nested.c
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@ -4346,11 +4346,10 @@ void nested_vmx_vmexit(struct kvm_vcpu *vcpu, u32 exit_reason,
kvm_vcpu_unmap(vcpu, &vmx->nested.pi_desc_map, true);
vmx->nested.pi_desc = NULL;
/*
* We are now running in L2, mmu_notifier will force to reload the
* page's hpa for L2 vmcs. Need to reload it for L1 before entering L1.
*/
kvm_make_request(KVM_REQ_APIC_PAGE_RELOAD, vcpu);
if (vmx->nested.reload_vmcs01_apic_access_page) {
vmx->nested.reload_vmcs01_apic_access_page = false;
kvm_make_request(KVM_REQ_APIC_PAGE_RELOAD, vcpu);
}
if ((exit_reason != -1) && (enable_shadow_vmcs || vmx->nested.hv_evmcs))
vmx->nested.need_vmcs12_to_shadow_sync = true;

10
arch/x86/kvm/vmx/vmx.c
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@ -6142,10 +6142,14 @@ void vmx_set_virtual_apic_mode(struct kvm_vcpu *vcpu)
static void vmx_set_apic_access_page_addr(struct kvm_vcpu *vcpu, hpa_t hpa)
{
if (!is_guest_mode(vcpu)) {
vmcs_write64(APIC_ACCESS_ADDR, hpa);
vmx_flush_tlb_current(vcpu);
/* Defer reload until vmcs01 is the current VMCS. */
if (is_guest_mode(vcpu)) {
to_vmx(vcpu)->nested.reload_vmcs01_apic_access_page = true;
return;
}
vmcs_write64(APIC_ACCESS_ADDR, hpa);
vmx_flush_tlb_current(vcpu);
}
static void vmx_hwapic_isr_update(struct kvm_vcpu *vcpu, int max_isr)

1
arch/x86/kvm/vmx/vmx.h
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@ -136,6 +136,7 @@ struct nested_vmx {
bool vmcs02_initialized;
bool change_vmcs01_virtual_apic_mode;
bool reload_vmcs01_apic_access_page;
/*
* Enlightened VMCS has been enabled. It does not mean that L1 has to