[PATCH v2 2/7] KVM: nVMX: Release enlightened VMCS on VMCLEAR

Vitaly Kuznetsov
2021-05-17T13:51:16Z

Unlike VMREAD/VMWRITE/VMPTRLD, VMCLEAR is a valid instruction when
enlightened VMCS is in use. TLFS has the following brief description:
"The L1 hypervisor can execute a VMCLEAR instruction to transition an
enlightened VMCS from the active to the non-active state". Normally,
this change can be ignored as unmapping active eVMCS can be postponed
until the next VMLAUNCH instruction but in case nested state is migrated
with KVM_GET_NESTED_STATE/KVM_SET_NESTED_STATE, keeping eVMCS mapped
may result in its synchronization with VMCS12 and this is incorrect:
L1 hypervisor is free to reuse inactive eVMCS memory for something else.

Inactive eVMCS after VMCLEAR can just be unmapped.

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
---
arch/x86/kvm/vmx/nested.c | 2 ++
1 file changed, 2 insertions(+)

diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index 3080e00c8f90..ea2869d8b823 100644
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -5008,6 +5008,8 @@ static int handle_vmclear(struct kvm_vcpu *vcpu)
vmptr + offsetof(struct vmcs12,
launch_state),
&zero, sizeof(zero));
+ } else if (vmx->nested.hv_evmcs && vmptr == vmx->nested.hv_evmcs_vmptr) {
+ nested_release_evmcs(vcpu);
}

return nested_vmx_succeed(vcpu);
--
2.31.1