[Xen-devel] [PATCH v2] xen/sysfs: Use XENVER_guest_handle to query UUID

[Daniel De Graaf <dgdegra@xxxxxxxxxxxxx>]

On 08/16/2012 04:22 PM, Matt Wilson wrote:
> 
> Hi Daniel,
> 
> What do you think about retaining a fallback of looking in xenstore if
> the hypercall fails?
> 
> Matt
> 

That sounds good; there's little cost to leaving the fallback in.

----8<-----------------------------------------------------

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@xxxxxxxxxxxxx>
---
 drivers/xen/sys-hypervisor.c    | 13 ++++++++++++-
 include/xen/interface/version.h |  3 +++
 2 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/drivers/xen/sys-hypervisor.c b/drivers/xen/sys-hypervisor.c
index 4c7db7d..284df8a 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)
diff --git a/include/xen/interface/version.h b/include/xen/interface/version.h
index e8b6519..dd58cf5 100644
--- a/include/xen/interface/version.h
+++ b/include/xen/interface/version.h
@@ -60,4 +60,7 @@ struct xen_feature_info {
 /* arg == NULL; returns host memory page size. */
 #define XENVER_pagesize 7
 
+/* arg == xen_domain_handle_t. */
+#define XENVER_guest_handle 8
+
 #endif /* __XEN_PUBLIC_VERSION_H__ */
-- 
1.7.11.2

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