[PATCH v2 5/7] KVM: nVMX: Reset eVMCS clean fields data from prepare_vmcs02()

Vitaly Kuznetsov
2021-05-17T13:51:25Z

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 | 14 ++++++++------
1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index eb2d25a93356..3bfbf991bf45 100644
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -2081,14 +2081,10 @@ void nested_sync_vmcs12_to_shadow(struct kvm_vcpu *vcpu)
{
struct vcpu_vmx *vmx = to_vmx(vcpu);

- if (vmx->nested.hv_evmcs) {
+ 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 {
+ else
copy_vmcs12_to_shadow(vmx);
- }

vmx->nested.need_vmcs12_to_shadow_sync = false;
}
@@ -2629,6 +2625,12 @@ 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;
}

--
2.31.1