[PATCH v6 09/13] x86/kvm/nVMX: allow bare VMXON state migration

[Vitaly Kuznetsov]

It is perfectly valid for a guest to do VMXON and not do VMPTRLD. This
state needs to be preserved on migration.

Signed-off-by: Vitaly Kuznetsov <vkuzn...@redhat.com>
---
 arch/x86/kvm/vmx.c | 15 ++++++++-------
 1 file changed, 8 insertions(+), 7 deletions(-)

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 0b665c74fadc..5df47291ad4d 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -14827,13 +14827,6 @@ static int vmx_set_nested_state(struct kvm_vcpu *vcpu,
        if (!page_address_valid(vcpu, kvm_state->vmx.vmxon_pa))
                return -EINVAL;
 
-       if (kvm_state->size < sizeof(kvm_state) + sizeof(*vmcs12))
-               return -EINVAL;
-
-       if (kvm_state->vmx.vmcs_pa == kvm_state->vmx.vmxon_pa ||
-           !page_address_valid(vcpu, kvm_state->vmx.vmcs_pa))
-               return -EINVAL;
-
        if ((kvm_state->vmx.smm.flags & KVM_STATE_NESTED_SMM_GUEST_MODE) &&
            (kvm_state->flags & KVM_STATE_NESTED_GUEST_MODE))
                return -EINVAL;
@@ -14863,6 +14856,14 @@ static int vmx_set_nested_state(struct kvm_vcpu *vcpu,
        if (ret)
                return ret;
 
+       /* Empty 'VMXON' state is permitted */
+       if (kvm_state->size < sizeof(kvm_state) + sizeof(*vmcs12))
+               return 0;
+
+       if (kvm_state->vmx.vmcs_pa == kvm_state->vmx.vmxon_pa ||
+           !page_address_valid(vcpu, kvm_state->vmx.vmcs_pa))
+               return -EINVAL;
+
        set_current_vmptr(vmx, kvm_state->vmx.vmcs_pa);
 
        if (kvm_state->vmx.smm.flags & KVM_STATE_NESTED_SMM_VMXON) {
-- 
2.17.1