KVM: Advertise the bug in memory region destruction as fixed

Userspace might need to act differently.

Signed-off-by: Avi Kivity <avi@redhat.com>

include/linux/kvm.h

@@ -395,6 +395,8 @@ struct kvm_trace_rec {
 #if defined(CONFIG_X86)
 #define KVM_CAP_DEVICE_MSI 20
 #endif
+/* Bug in KVM_SET_USER_MEMORY_REGION fixed: */
+#define KVM_CAP_DESTROY_MEMORY_REGION_WORKS 21
 
 /*
  * ioctls for VM fds

virt/kvm/kvm_main.c

@@ -1905,6 +1905,17 @@ static int kvm_dev_ioctl_create_vm(void)
 	return fd;
 }
 
+static long kvm_dev_ioctl_check_extension_generic(long arg)
+{
+	switch (arg) {
+	case KVM_CAP_DESTROY_MEMORY_REGION_WORKS:
+		return 1;
+	default:
+		break;
+	}
+	return kvm_dev_ioctl_check_extension(arg);
+}
+
 static long kvm_dev_ioctl(struct file *filp,
 			  unsigned int ioctl, unsigned long arg)
 {
@@ -1924,7 +1935,7 @@ static long kvm_dev_ioctl(struct file *filp,
 		r = kvm_dev_ioctl_create_vm();
 		break;
 	case KVM_CHECK_EXTENSION:
-		r = kvm_dev_ioctl_check_extension(arg);
+		r = kvm_dev_ioctl_check_extension_generic(arg);
 		break;
 	case KVM_GET_VCPU_MMAP_SIZE:
 		r = -EINVAL;