[PATCH 1/2] KVM: x86/xen: Fix return code when clearing vcpu_info and vcpu_time_info

[David Woodhouse <dwmw2@xxxxxxxxxxxxx>]

From: David Woodhouse <dwmw@xxxxxxxxxxxx>

When clearing the per-vCPU shared regions, set the return value to zero
to indicate success. This was causing spurious errors to be returned to
userspace on soft reset.

Also add a paranoid BUILD_BUG_ON() for compat structure compatibility.

Fixes: 0c165b3c01fe ("KVM: x86/xen: Allow reset of Xen attributes")
Signed-off-by: David Woodhouse <dwmw@xxxxxxxxxxxx>
---
 arch/x86/kvm/xen.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/arch/x86/kvm/xen.c b/arch/x86/kvm/xen.c
index af8f6562fce4..77b20ff09078 100644
--- a/arch/x86/kvm/xen.c
+++ b/arch/x86/kvm/xen.c
@@ -187,9 +187,12 @@ int kvm_xen_vcpu_set_attr(struct kvm_vcpu *vcpu, struct kvm_xen_vcpu_attr *data)
 		/* No compat necessary here. */
 		BUILD_BUG_ON(sizeof(struct vcpu_info) !=
 			     sizeof(struct compat_vcpu_info));
+		BUILD_BUG_ON(offsetof(struct vcpu_info, time) !=
+			     offsetof(struct compat_vcpu_info, time));
 
 		if (data->u.gpa == GPA_INVALID) {
 			vcpu->arch.xen.vcpu_info_set = false;
+			r = 0;
 			break;
 		}
 
@@ -206,6 +209,7 @@ int kvm_xen_vcpu_set_attr(struct kvm_vcpu *vcpu, struct kvm_xen_vcpu_attr *data)
 	case KVM_XEN_VCPU_ATTR_TYPE_VCPU_TIME_INFO:
 		if (data->u.gpa == GPA_INVALID) {
 			vcpu->arch.xen.vcpu_time_info_set = false;
+			r = 0;
 			break;
 		}
 
-- 
2.29.2