From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:41888) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1a8RWl-0007ro-Sw for qemu-devel@nongnu.org; Mon, 14 Dec 2015 06:42:53 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1a8RWg-0002KK-VL for qemu-devel@nongnu.org; Mon, 14 Dec 2015 06:42:51 -0500 Received: from smtp02.citrix.com ([66.165.176.63]:17958) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1a8RWg-0002Iz-Qy for qemu-devel@nongnu.org; Mon, 14 Dec 2015 06:42:46 -0500 Message-ID: <1450093294.16856.46.camel@citrix.com> From: Ian Campbell Date: Mon, 14 Dec 2015 11:41:34 +0000 In-Reply-To: References: <56548BD202000078000B881F@prv-mh.provo.novell.com> <56548D8402000078000B8840@prv-mh.provo.novell.com> <5665921202000078000BCA2A@prv-mh.provo.novell.com> <5665B56E02000078000BCB52@prv-mh.provo.novell.com> <566AF76502000078000BEB76@prv-mh.provo.novell.com> <1449852961.30975.71.camel@citrix.com> Content-Type: text/plain; charset="UTF-8" MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Subject: Re: [Qemu-devel] [Xen-devel] [PATCH RFC v2 4/4] xen/MSI: re-expose masking capability List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Stefano Stabellini Cc: xen-devel , qemu-devel@nongnu.org, Jan Beulich On Mon, 2015-12-14 at 11:19 +0000, Stefano Stabellini wrote: > On Fri, 11 Dec 2015, Ian Campbell wrote: > > On Fri, 2015-12-11 at 16:44 +0000, Stefano Stabellini wrote: > > > =C2=A0 > > > It is not possible to do this at runtime. I think we should do this > > > at > > > compile time because in any case it is not supported to run a QEMU > > > built > > > for a given Xen version on a different Xen version. > >=20 > > I am currently working pretty hard to make this possible in the future, > > it > > would be a shame to add another reason it wasn't possible at this > > stage. > >=20 > > I proposed (in <1445442435.9563.184.camel@citrix.com>) that as well as > > the > > various stable libraries extracted from libxenctrl we will probably > > also > > want to have a libxendevicemodel.so at some point, to provide a stable > > way > > to interface with all the stuff which being a DM involves. >=20 > I understand the direction we are heading toward, but unfortunately we > are still pretty far from it. I don't think we want to block this patch > until we have a stable libxendevicemodel ABI? No, but I would appreciate if such things were explicitly considered on a case by case by case basis rather than just bundled under a generic "it's not possible yet", since there may be cases where we want to hold off, or more likely where doing something a particular way now will ease things for the transition in the future. > Also this particular > change regards PCI passthrough, which is not convered by the proposed > ABI yet. >=20 >=20 > > Maybe that library could contain a way to get this information? (In > > which > > case it could be hardcoded at compile time now and I'll see what I can > > do > > when I get to producing the library). >=20 > Given the choice, I would rather have only compile time or only run time > Xen version checks in QEMU and not both to avoid complexity. Especially > as long as the underlying libraries don't make any stability guarantees. "that library" obviously will make such guarantees as a matter of design. Ian.