From mboxrd@z Thu Jan  1 00:00:00 1970
From: Andrew Cooper <andrew.cooper3@citrix.com>
Subject: Re: [PATCH 3/4] docs: Document xenstore paths for
 domain hotplug features
Date: Fri, 6 Nov 2015 18:08:25 +0000
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To: Paul Durrant <paul.durrant@citrix.com>, xen-devel@lists.xenproject.org
Cc: Ian Jackson <ian.jackson@eu.citrix.com>, Tim Deegan <tim@xen.org>, Keir Fraser <keir@xen.org>, Ian Campbell <ian.campbell@citrix.com>, Jan Beulich <jbeulich@suse.com>
List-Id: xen-devel@lists.xenproject.org

On 06/11/15 17:21, Paul Durrant wrote:
> Without some indication from an HVM domain it is not possible for a
> toolstack to know whether instantiation of a new vbd or vif should
> result in a new PV device of the appropriate type being instantiated
> in a guest. (In other words whether PV drivers are present and
> functioning).
>
> This patch document two paths which vif and vbd frontend drivers can
> use to advertise their ability to respond to new vif or vbd
> instantiations.
>
> Signed-off-by: Paul Durrant <paul.durrant@citrix.com>
> Cc: Ian Campbell <ian.campbell@citrix.com>
> Cc: Ian Jackson <ian.jackson@eu.citrix.com>
> Cc: Jan Beulich <jbeulich@suse.com>
> Cc: Keir Fraser <keir@xen.org>
> Cc: Tim Deegan <tim@xen.org>
> ---
>  docs/misc/xenstore-paths.markdown | 12 ++++++++++++
>  1 file changed, 12 insertions(+)
>
> diff --git a/docs/misc/xenstore-paths.markdown b/docs/misc/xenstore-paths.markdown
> index 7701632..9e98d6f 100644
> --- a/docs/misc/xenstore-paths.markdown
> +++ b/docs/misc/xenstore-paths.markdown
> @@ -387,6 +387,18 @@ A domain writable path. Available for arbitrary domain use.
>  A domain may write version information for PV driver $NAME using
>  this path.
>  
> +#### ~/feature/hotplug/vif = ("0"|"1") [w,HVM]
> +
> +An HVM domain can indicate to a toolstack that it is capable
> +of responding to instantiation of a new vif by bringing online a
> +new PV network device without the need for a reboot.
> +
> +#### ~/feature/hotplug/vbd = ("0"|"1") [w,HVM]
> +
> +An HVM domain can indicate to a toolstack that it is capable
> +of responding to instantiation of a new vbd by bringing online a
> +new PV block device without the need for a reboot.

These flags are not inherently restricted to HVM guests.  Therefore, I
would avoid specifying them as such.  (It is quite possible for a PV
guest not to be able to hotplug a vbd for example.)

~Andrew