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| author |   Liran Alon <liran.alon@oracle.com> | 2019-11-12 20:33:00 +0200 |
|---|---|---|
| committer |   Paolo Bonzini <pbonzini@redhat.com> | 2019-11-15 11:44:11 +0100 |
| commit | 1924242b2abadfb1144c3c22083fd6f71caadd64 (patch) | |
| tree | a474c30bbbf7fe88ad627d66d7179737605cbc7e | |
| parent | KVM: x86/vPMU: Add lazy mechanism to release perf_event per vPMC (diff) | |
| download | linux-dev-1924242b2abadfb1144c3c22083fd6f71caadd64.tar.xz linux-dev-1924242b2abadfb1144c3c22083fd6f71caadd64.zip | |
KVM: x86: Optimization: Requst TLB flush in fast_cr3_switch() instead of do it directly
When KVM emulates a nested VMEntry (L1->L2 VMEntry), it switches mmu root
page. If nEPT is used, this will happen from
kvm_init_shadow_ept_mmu()->__kvm_mmu_new_cr3() and otherwise it will
happpen from nested_vmx_load_cr3()->kvm_mmu_new_cr3(). Either case,
__kvm_mmu_new_cr3() will use fast_cr3_switch() in attempt to switch to a
previously cached root page.
In case fast_cr3_switch() finds a matching cached root page, it will
set it in mmu->root_hpa and request KVM_REQ_LOAD_CR3 such that on
next entry to guest, KVM will set root HPA in appropriate hardware
fields (e.g. vmcs->eptp). In addition, fast_cr3_switch() calls
kvm_x86_ops->tlb_flush() in order to flush TLB as MMU root page
was replaced.
This works as mmu->root_hpa, which vmx_flush_tlb() use, was
already replaced in cached_root_available(). However, this may
result in unnecessary INVEPT execution because a KVM_REQ_TLB_FLUSH
may have already been requested. For example, by prepare_vmcs02()
in case L1 don't use VPID.
Therefore, change fast_cr3_switch() to just request TLB flush on
next entry to guest.
Reviewed-by: Bhavesh Davda <bhavesh.davda@oracle.com>
Signed-off-by: Liran Alon <liran.alon@oracle.com>
Reviewed-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Reviewed-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
| -rw-r--r-- | arch/x86/kvm/mmu.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c index 24c23c66b226..150d982ec1d2 100644 --- a/arch/x86/kvm/mmu.c +++ b/arch/x86/kvm/mmu.c @@ -4295,7 +4295,7 @@ static bool fast_cr3_switch(struct kvm_vcpu *vcpu, gpa_t new_cr3, kvm_make_request(KVM_REQ_LOAD_CR3, vcpu); if (!skip_tlb_flush) { kvm_make_request(KVM_REQ_MMU_SYNC, vcpu); - kvm_x86_ops->tlb_flush(vcpu, true); + kvm_make_request(KVM_REQ_TLB_FLUSH, vcpu); } /* |