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

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

On Thu, Aug 16, 2012 at 04:40:26PM -0400, Daniel De Graaf wrote:
> 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.

applied
> 
> ----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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