From: Paul Durrant <Paul.Durrant@citrix.com>
To: Paul Durrant <Paul.Durrant@citrix.com>,
Paolo Bonzini <pbonzini@redhat.com>,
Martin Cerveny <M.Cerveny@computer.org>
Cc: "xen-devel@lists.xensource.com" <xen-devel@lists.xensource.com>,
George Dunlap <George.Dunlap@citrix.com>
Subject: Re: Overlaped PIO with multiple ioreq_server (Xen4.6.1)
Date: Mon, 9 May 2016 16:02:16 +0000 [thread overview]
Message-ID: <95a929eb370a4761b2a3ef504e79f0cb@AMSPEX02CL03.citrite.net> (raw)
In-Reply-To: <abd0f2cfba4e4f0fa3ed50741bb2984b@AMSPEX02CL03.citrite.net>
> -----Original Message-----
> From: Xen-devel [mailto:xen-devel-bounces@lists.xen.org] On Behalf Of
> Paul Durrant
> Sent: 09 May 2016 14:00
> To: Paolo Bonzini; Martin Cerveny
> Cc: xen-devel@lists.xensource.com; George Dunlap
> Subject: Re: [Xen-devel] Overlaped PIO with multiple ioreq_server
> (Xen4.6.1)
>
> > -----Original Message-----
> > From: Paolo Bonzini [mailto:pbonzini@redhat.com]
> > Sent: 09 May 2016 13:56
> > To: Paul Durrant; Martin Cerveny
> > Cc: George Dunlap; xen-devel@lists.xensource.com
> > Subject: Re: [Xen-devel] Overlaped PIO with multiple ioreq_server
> > (Xen4.6.1)
> >
> >
> >
> > On 28/04/2016 13:25, Paul Durrant wrote:
> > >> Maybe you are lucky, qemu is registered before your own demu
> > >> emulator.
> > >
> > > I guess I was lucky.
> >
> > Yeah, QEMU has been doing that since 2013 (commit 3bb28b7, "memory:
> > Provide separate handling of unassigned io ports accesses", 2013-09-05).
> >
> > >> I used for testing your "demu" 2 years ago, now extending Citrix
> > >> "vgpu", all was fine up to xen 4.5.2 (with qemu 2.0.2) but
> > >> problem begin when I switched to 4.6.1 (with qemu 2.2.1), but it
> > >> maybe lucky timing in registration.
> > >
> > > I think Xen should really be spotting range overlaps like this, but
> > > the QEMU<->Xen interface will clearly need to be fixed to avoid the
> > > over-claiming of I/O ports like this.
> >
> > If the handling of unassigned I/O ports is sane in Xen (in QEMU they
> > return all ones and discard writes),
>
> Yes, it does exactly that.
>
> > it would be okay to make the
> > background 0-65535 range conditional on !xen_enabled(). See
> > memory_map_init() in QEMU's exec.c file.
> >
>
> Cool. Thanks for the tip. Will have a look at that now.
>
Looks like creation of the background range is required. (Well, when I simply #if 0-ed out creating it QEMU crashed on invocation). So, I guess I need to be able to spot, from the memory listener callback in Xen, when a background range is being added so it can be ignored. Same actually goes for memory as well as I/O, since Xen will handle access to unimplemented MMIO ranges in a similar fashion.
Paul
> Cheers,
>
> Paul
>
> > Paolo
>
> _______________________________________________
> Xen-devel mailing list
> Xen-devel@lists.xen.org
> http://lists.xen.org/xen-devel
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next prev parent reply other threads:[~2016-05-09 16:02 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-04-27 19:38 Overlaped PIO with multiple ioreq_server (Xen4.6.1) Martin Cerveny
2016-04-28 8:50 ` George Dunlap
2016-04-28 9:46 ` Paul Durrant
2016-04-28 11:16 ` Martin Cerveny
2016-04-28 11:25 ` Paul Durrant
2016-05-09 12:55 ` Paolo Bonzini
2016-05-09 12:59 ` Paul Durrant
2016-05-09 16:02 ` Paul Durrant [this message]
2016-05-09 16:14 ` Paul Durrant
2016-05-09 16:18 ` Paolo Bonzini
2016-05-09 16:19 ` Paul Durrant
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