[PATCH 5/7] KVM: nVMX: Reset eVMCS clean fields data from prepare_vmcs02()

Vitaly Kuznetsov
2021-05-11T11:20:32Z

When nested state migration happens during L1's execution, it
is incorrect to modify eVMCS as it is L1 who 'owns' it at the moment.
At lease genuine Hyper-v seems to not be very happy when 'clean fields'
data changes underneath it.

'Clean fields' data is used in KVM twice: by copy_enlightened_to_vmcs12()
and prepare_vmcs02_rare() so we can reset it from prepare_vmcs02() instead.

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
---
arch/x86/kvm/vmx/nested.c | 9 ++++++---
1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index 3257a2291693..1661e2e19560 100644
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -2090,9 +2090,6 @@ void nested_sync_vmcs12_to_shadow(struct kvm_vcpu *vcpu)

if (vmx->nested.hv_evmcs) {
copy_vmcs12_to_enlightened(vmx);
- /* All fields are clean */
- vmx->nested.hv_evmcs->hv_clean_fields |=
- HV_VMX_ENLIGHTENED_CLEAN_FIELD_ALL;
} else {
copy_vmcs12_to_shadow(vmx);
}
@@ -2636,6 +2633,12 @@ static int prepare_vmcs02(struct kvm_vcpu *vcpu, struct vmcs12 *vmcs12,

kvm_rsp_write(vcpu, vmcs12->guest_rsp);
kvm_rip_write(vcpu, vmcs12->guest_rip);
+
+ /* Mark all fields as clean so L1 hypervisor can set what's dirty */
+ if (hv_evmcs)
+ vmx->nested.hv_evmcs->hv_clean_fields |=
+ HV_VMX_ENLIGHTENED_CLEAN_FIELD_ALL;
+
return 0;
}

--
2.30.2