From mboxrd@z Thu Jan 1 00:00:00 1970 From: Anthony PERARD Subject: Re: Processed: Re: [HVM} xen_platform_pci=0 doesn't prevent platform device creation and disk and nic take over by PV drivers. Date: Fri, 11 Oct 2013 18:31:36 +0100 Message-ID: <20131011173136.GC3195@perard.uk.xensource.com> References: <1571692646.20131009000945@eikelenboom.it> <1381320002.7600.10.camel@kazak.uk.xensource.com> <1381503844.24708.46.camel@kazak.uk.xensource.com> <1493710998.20131011172247@eikelenboom.it> <20131011165332.GB3195@perard.uk.xensource.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline In-Reply-To: List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: George Dunlap Cc: Sander Eikelenboom , xen-devel , Ian Campbell , Stefano Stabellini List-Id: xen-devel@lists.xenproject.org On Fri, Oct 11, 2013 at 06:10:32PM +0100, George Dunlap wrote: > On Fri, Oct 11, 2013 at 5:53 PM, Anthony PERARD > wrote: > > On Fri, Oct 11, 2013 at 05:22:47PM +0200, Sander Eikelenboom wrote: > >> > The original message was simply: > >> >> While trying to get to the bottom of my passthrough problem with the rom bar, > >> >> i noticed that specifiying "xen_platform_pci=0" in the config file does not prevent > >> >> the platform device to appear in my HVM guest and consequently the disk and nic are taken over. > >> >> > >> >> Running latest xen-unstable, together with upstream qemu and upstream seabios. > > > > I've start looking at this, and the fix would be easy: removing the > > creation of the xen-platform from QEMU, and let xl ask QEMU to create > > it. > > > > But if one uses an older version of one project (qemu/xl) and a newer > > version of the other, then we can end-up with no xen-platform or two > > xen-platform ... > > So what's the plan for compatibility here -- full forward and backward > compatibily on both sides? (i.e., newer qemu works with older Xen, > newer Xen works with older qemu)? > > > So should we try to be clever about this, or just backport patchs for > > both qemu and xl? > > > > "Clever" option: There is a recent patch for xl that make use of > > the -nodefault QEMU's command line option. So if it's present, we could > > ask QEMU to not add xen-platform, and xl can decide. > > I wouldn't mind doing something like this; but would it make more > sense to have some kind of a "capability" or "version" interface, like > we have between Xen and Linux, rather than relying on other quirks > like the presence of "-nodefault"? Well, we can always check if the xen-platform-pci is already there after having started QEMU (through QMP) and react by adding it, display a warning or do nothing more, depending the result and the config of the vm. -- Anthony PERARD