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KVM: nVMX: Selectively use TLB_FLUSH_CURRENT for nested VM-Enter/VM-Exit

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Flush only the current context, as opposed to all contexts, when
requesting a TLB flush to handle the scenario where a L1 does not expect
a TLB flush, but one is required because L1 and L2 shared an ASID.  This
occurs if EPT is disabled (no per-EPTP tag), VPID is enabled (hardware
doesn't flush unconditionally) and vmcs02 does not have its own VPID due
to exhaustion of available VPIDs.

Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Message-Id: <20200320212833.3507-27-sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Sean Christopherson 2020-03-20 14:28:22 -07:00 committed by Paolo Bonzini
parent 8c8560b833
commit c51e1ffee5
1 changed files with 5 additions and 3 deletions
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8
arch/x86/kvm/vmx/nested.c
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@ -1152,8 +1152,8 @@ static void nested_vmx_transition_tlb_flush(struct kvm_vcpu *vcpu,
*
* If VPID is enabled and used by vmc12, but L2 does not have a unique
* TLB tag (ASID), i.e. EPT is disabled and KVM was unable to allocate
* a VPID for L2, flush the TLB as the effective ASID is common to both
* L1 and L2.
* a VPID for L2, flush the current context as the effective ASID is
* common to both L1 and L2.
*
* Defer the flush so that it runs after vmcs02.EPTP has been set by
* KVM_REQ_LOAD_MMU_PGD (if nested EPT is enabled) and to avoid
@ -1165,8 +1165,10 @@ static void nested_vmx_transition_tlb_flush(struct kvm_vcpu *vcpu,
* mapping between vpid02 and vpid12, vpid02 is per-vCPU and reused for
* all nested vCPUs.
*/
if (!nested_cpu_has_vpid(vmcs12) || !nested_has_guest_tlb_tag(vcpu)) {
if (!nested_cpu_has_vpid(vmcs12)) {
kvm_make_request(KVM_REQ_TLB_FLUSH, vcpu);
} else if (!nested_has_guest_tlb_tag(vcpu)) {
kvm_make_request(KVM_REQ_TLB_FLUSH_CURRENT, vcpu);
} else if (is_vmenter &&
vmcs12->virtual_processor_id != vmx->nested.last_vpid) {
vmx->nested.last_vpid = vmcs12->virtual_processor_id;