xen/sysfs: Use XENVER_guest_handle to query UUID

This hypercall has been present since Xen 3.1, and is the preferred
method for a domain to obtain its UUID. Fall back to the xenstore method
if using an older version of Xen (which returns -ENOSYS).

Signed-off-by: Daniel De Graaf <dgdegra@tycho.nsa.gov>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

1 files changed, 12 insertions, 1 deletions

diff --git a/drivers/xen/sys-hypervisor.c b/drivers/xen/sys-hypervisor.c
index fdb6d229c9bb..5e5ad7e28858 100644
--- a/drivers/xen/sys-hypervisor.c
+++ b/drivers/xen/sys-hypervisor.c
@@ -114,7 +114,7 @@ static void xen_sysfs_version_destroy(void)
 
 /* UUID */
 
-static ssize_t uuid_show(struct hyp_sysfs_attr *attr, char *buffer)
+static ssize_t uuid_show_fallback(struct hyp_sysfs_attr *attr, char *buffer)
 {
         char *vm, *val;
         int ret;
@@ -135,6 +135,17 @@ static ssize_t uuid_show(struct hyp_sysfs_attr *attr, char *buffer)
         return ret;
 }
 
+static ssize_t uuid_show(struct hyp_sysfs_attr *attr, char *buffer)
+{
+        xen_domain_handle_t uuid;
+        int ret;
+        ret = HYPERVISOR_xen_version(XENVER_guest_handle, uuid);
+        if (ret)
+                return uuid_show_fallback(attr, buffer);
+        ret = sprintf(buffer, "%pU\n", uuid);
+        return ret;
+}
+
 HYPERVISOR_ATTR_RO(uuid);
 
 static int __init xen_sysfs_uuid_init(void)