Re: [Xen-devel] Overlaped PIO with multiple ioreq_server (Xen4.6.1)

[Paul Durrant <Paul.Durrant@xxxxxxxxxx>]

> -----Original Message-----
> From: Paolo Bonzini [mailto:pbonzini@xxxxxxxxxx]
> Sent: 09 May 2016 13:56
> To: Paul Durrant; Martin Cerveny
> Cc: George Dunlap; xen-devel@xxxxxxxxxxxxxxxxxxx
> 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.

Cheers,

  Paul

> Paolo

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel