Remove the completely pointess global INVEPT, i.e. EPT TLB flush, from
KVM's VMX enablement path. KVM always does a targeted TLB flush when
using a "new" EPT root, in quotes because "new" simply means a root that
isn't currently being used by the vCPU.
KVM also _deliberately_ runs with stale TLB entries for defunct roots,
i.e. doesn't do a TLB flush when vCPUs stop using roots, precisely because
KVM does the flush on first use. As called out by the comment in
kvm_mmu_load(), the reason KVM flushes on first use is because KVM can't
guarantee the correctness of past hypervisors.
Jumping back to the global INVEPT, when the painfully terse commit
1439442c7b25 ("KVM: VMX: Enable EPT feature for KVM") was added, the
effective TLB flush being performed was:
static void vmx_flush_tlb(struct kvm_vcpu *vcpu)
{
vpid_sync_vcpu_all(to_vmx(vcpu));
}
I.e. KVM was not flushing EPT TLB entries when allocating a "new" root,
which very strongly suggests that the global INVEPT during hardware
enabling was a misguided hack that addressed the most obvious symptom,
but failed to fix the underlying bug.
Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
---
arch/x86/kvm/vmx/vmx.c | 3 ---
1 file changed, 3 deletions(-)
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 0e3aaf520db2..21dbe20f50ba 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -2832,9 +2832,6 @@ int vmx_hardware_enable(void)
return r;
}
- if (enable_ept)
- ept_sync_global();
-
return 0;
}
base-commit: af0903ab52ee6d6f0f63af67fa73d5eb00f79b9a
--
2.45.2.505.gda0bf45e8d-goog
