Re: [PATCH RESEND qemu-xen-traditional] xen/pt: allow QEMU to request MSI unmasking at bind time

["Paraschiv, Andra-Irina" <andraprs@amazon.com>]

On Sun, Nov 4, 2018 at 10:49:02PM +0200, Pasi Kärkkäinen wrote:
>
> Hello Ian,
>
> On Mon, Oct 29, 2018 at 08:55:09PM +0000, Paraschiv, Andra-Irina wrote:
> >
> >
> > On Mon, Oct 29, 2018 at 04:58:22PM +0200, Pasi Kärkkäinen wrote:
> > > Hi,
> > >
> > > On Wed, Oct 24, 2018 at 04:20:35PM +0100, Ian Jackson wrote:
> > > > Andra Paraschiv writes ("[PATCH RESEND qemu-xen-traditional] xen/pt: allow QEMU to request MSI unmasking at bind time"):
> > > > > When a MSI interrupt is bound to a guest using
> > > > > xc_domain_update_msi_irq (XEN_DOMCTL_bind_pt_irq) the interrupt is
> > > > > left masked by default.
> > > >
> > > > Applied, and pushed the corresponding update to QEMU_TAG in
> > > > qemu-xen-unstable.
> > > >
> > > > Does this patch need to be backported to earlier Xen releases ?  It
> > > > wasn't clear to me whether there is new Xen code in this area without
> > > > which the problem (which the patch solves) does not arise; or whether,
> > > > conversely, simply running a new guest is sufficient.
> > > >
> > >
> > > Good question. In the earlier thread about this patch it was mentioned
> > > the bug happens with latest stable version of Xen, which sounds like
> > > this patch should be backported to stable Xen versions. Is that correct?
> >
> > Replied later than expected, but I'm back now.
> >
> > Ian, Pasi,
> >
> > Right. We have this mail thread where the issue was originally reported:
> > https://lists.xenproject.org/archives/html/xen-devel/2017-07/msg00915.html
> >
> > And the follow-up with the patches for Xen and QEMU (not traditional):
> > https://lists.xenproject.org/archives/html/xen-devel/2018-05/msg01238.html
> >
> > "Hm, I think I might have fixed this issue, see:
> >
> > https://git.qemu.org/?p=qemu.git;a=commit;h=a8036336609d2e184fc3543a4c439c0ba7d7f3a2
> >
> > And the Xen side:
> >
> > http://xenbits.xen.org/gitweb/?p=xen.git;a=commit;h=69d99d1b223fc5082400374698ddd7486e5ea953"
> >
> > The Xen patch above is present in the tree from 4.10.0-rc1 tag forward.
> >
> 
> This sounds like an important fix to have for PCI passthrough users, and it seems the back port
> of this patch needs to go to Xen qemu-traditional to both 4.10 and 4.11 branches,
because the Xen hypervisor side patch is already in those branches.

As a follow-up, tested and the fix applied cleanly
over the patch [0] that corresponds to xen-4.10.0 and
xen-4.11.0 tags.

Thanks, Ian, Pasi.

Andra

[0] https://xenbits.xen.org/gitweb/?p=qemu-xen-traditional.git;a=commit;h=c8ea0457495342c417c3dc033bba25148b279f60

> 
> 
> Thanks,
> 
> -- Pasi
> 
> > Thanks for feedback. Anything I can help further, we can discuss about it.
> >
> > Andra
> >
> > > Thanks,
> > >
> > > -- Pasi
> > >
> > > > Regards,
> > > > Ian.
> > > >
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