linux-kernel - [PATCH 5.4 19/61] KVM: nVMX: Sync unsyncd vmcs02 state to vmcs12 on migration

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Date:   Tue,  2 Feb 2021 14:37:57 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Sean Christopherson <seanjc@...gle.com>,
        Maxim Levitsky <mlevitsk@...hat.com>,
        Paolo Bonzini <pbonzini@...hat.com>
Subject: [PATCH 5.4 19/61] KVM: nVMX: Sync unsyncd vmcs02 state to vmcs12 on migration

From: Maxim Levitsky <mlevitsk@...hat.com>

commit d51e1d3f6b4236e0352407d8a63f5c5f71ce193d upstream.

Even when we are outside the nested guest, some vmcs02 fields
may not be in sync vs vmcs12.  This is intentional, even across
nested VM-exit, because the sync can be delayed until the nested
hypervisor performs a VMCLEAR or a VMREAD/VMWRITE that affects those
rarely accessed fields.

However, during KVM_GET_NESTED_STATE, the vmcs12 has to be up to date to
be able to restore it.  To fix that, call copy_vmcs02_to_vmcs12_rare()
before the vmcs12 contents are copied to userspace.

Fixes: 7952d769c29ca ("KVM: nVMX: Sync rarely accessed guest fields only when needed")
Reviewed-by: Sean Christopherson <seanjc@...gle.com>
Signed-off-by: Maxim Levitsky <mlevitsk@...hat.com>
Message-Id: <20210114205449.8715-2-mlevitsk@...hat.com>
Cc: stable@...r.kernel.org
Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 arch/x86/kvm/vmx/nested.c |   13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -5579,11 +5579,14 @@ static int vmx_get_nested_state(struct k
 	if (is_guest_mode(vcpu)) {
 		sync_vmcs02_to_vmcs12(vcpu, vmcs12);
 		sync_vmcs02_to_vmcs12_rare(vcpu, vmcs12);
-	} else if (!vmx->nested.need_vmcs12_to_shadow_sync) {
-		if (vmx->nested.hv_evmcs)
-			copy_enlightened_to_vmcs12(vmx);
-		else if (enable_shadow_vmcs)
-			copy_shadow_to_vmcs12(vmx);
+	} else  {
+		copy_vmcs02_to_vmcs12_rare(vcpu, get_vmcs12(vcpu));
+		if (!vmx->nested.need_vmcs12_to_shadow_sync) {
+			if (vmx->nested.hv_evmcs)
+				copy_enlightened_to_vmcs12(vmx);
+			else if (enable_shadow_vmcs)
+				copy_shadow_to_vmcs12(vmx);
+		}
 	}
 
 	BUILD_BUG_ON(sizeof(user_vmx_nested_state->vmcs12) < VMCS12_SIZE);