linux-kernel - [PATCH 2/7] KVM: nVMX: Release enlightened VMCS on VMCLEAR

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Date:   Tue, 11 May 2021 13:19:51 +0200
From:   Vitaly Kuznetsov <vkuznets@...hat.com>
To:     kvm@...r.kernel.org, Paolo Bonzini <pbonzini@...hat.com>
Cc:     linux-kernel@...r.kernel.org,
        Sean Christopherson <seanjc@...gle.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Maxim Levitsky <mlevitsk@...hat.com>
Subject: [PATCH 2/7] KVM: nVMX: Release enlightened VMCS on VMCLEAR

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@...hat.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);
-- 
2.30.2