Paul Durrant
2013-Jun-19 08:37 UTC
Re: [Qemu-devel] [PATCH] Remove hardcoded xen-platform device initialization
> -----Original Message----- > From: Ian Campbell > Sent: 19 June 2013 09:29 > To: Andreas Färber > Cc: Stefano Stabellini; Paolo Bonzini; Paul Durrant; xen-devel@lists.xen.org; > qemu-devel@nongnu.org > Subject: Re: [Qemu-devel] [Xen-devel] [PATCH] Remove hardcoded xen- > platform device initialization > > On Tue, 2013-06-18 at 23:38 +0200, Andreas Färber wrote: > > Am 18.06.2013 21:35, schrieb Stefano Stabellini: > > > On Tue, 18 Jun 2013, Paolo Bonzini wrote: > > >> Il 18/06/2013 20:56, Stefano Stabellini ha scritto: > > >>> xenfv-2.0 is a bad idea, like Paolo wrote, it should be possible to just > > >>> use -M pc for HVM guests and retain -M xenpv for pv guests. > > >>> > > >>> However it seems to me that we also need a way in libxl to find out > > >>> whether QEMU is new enough for us to be able to use -M pc. > > >>> We can't just assume that users will be able to figure out the magic > > >>> rune they need to write in the VM config file to solve their VM crash at > > >>> boot problem. > > >>> > > >>> We could spawn an instance of QEMU just to figure out the QEMU > version > > >>> but we certainly cannot do that every time we start a new VM. > > >>> Once we figure out the QEMU version the first time we could write it > to > > >>> xenstore so that the next time we don't have to go through the same > > >>> process again. > > >> > > >> Can you just assume that 4.4 requires QEMU 1.6 or newer? > > > > > > I would rather not make that assumption because we cannot control > what > > > distro are going to package. I wouldn't want a distro to ship with Xen > > > HVM guests broken because they choose the wrong QEMU version. Of > course > > > we could put that in the release notes, but there are lots of distros > > > out there and I am pretty sure that at least one of them is not going to > > > read them. > > > > You could check for existence of the pc-i440fx-1.6 machine and infer > > that it is at least v1.6 (might break in some distant future of course > > and for current git commits until your changes get merged). > > Actually, this raises an interesting point. AIUI "pc" is simply and > alias for the most recent "pc-X.Y" and "pc-X.Y" is present to allow for > qemu "upgrading" the set of emulated hardware, as in it represents > changing the set of emulated peripherals, not just fixing bugs in the > emulation etc, is that right? > > I think it would be preferable for us to request a specific platform > (pc-i440fx-1.6 if that's the one) and a conscious decision to support > newer platforms (and can test it etc). >If that is the case then the xenfv code is also incorrect, since it does not call through to a specific version of 'pc'. Paul _______________________________________________ Xen-devel mailing list Xen-devel@lists.xen.org http://lists.xen.org/xen-devel