Re: [Xen-devel] [Xen-users] Xen 4.7.0 graphics pass through problems (Win10, AMD Radeon)

[Peter Milesson <miles@xxxxxxxx>]

On 2016-09-14 16:49, Jan Beulich wrote:
> > > > On 14.09.16 at 16:04, <miles@xxxxxxxx> wrote:
> > On 2016-09-14 14:50, Jan Beulich wrote:
> > > > > > On 14.09.16 at 13:34, <george.dunlap@xxxxxxxxxx> wrote:
> > > > Can you think of anything that's changed between 4.6 and 4.7 that
> > > > would cause the performance problems he's describing when both a video
> > > > card and a usb controller are passed through, but not when only the
> > > > video card is passed through?
> > > Not really, no. Peter - are there any indications of problems in
> > > one or more of the logs (Xen, xl, qemu)? Did you try running a
> > > debug build of all Xen components?
> > No, I did not try a debug build. However, the system seems fairly stable
> > now, only the display driver crashing once, or twice a day. That did
> > occur with Xen 4.6.3 also, but maybe once a week. Looking at the log
> > files, I cannot see anything particular that stands out, except for the
> > domU log.
> >
> > The domU log file qemu-dm-<Name>.log started to contain the following
> > lines after upgrading to 4.7:
> >
> > [00:06.0] xen_pt_bar_read: Error: Should not read BAR through QEMU.
> > @0x0000000000000004
> > [00:06.0] xen_pt_bar_write: Error: Should not write BAR through QEMU.
> > @0x0000000000000000
> >
> > There are only a couple of lines with write, the rest with read. I don't
> > know what significance it's got, but there are around 350 lines every day.
> Looks wrong in any case, but I have no clue whether it's indicative
> of the problem you're having. In any event in the qemu tree in
> hw/xen/xen_pt.h there's an "#ifdef XEN_PT_LOGGING_ENABLED"
> conditional close to the top. Could you make this "#if 1" instead
> (or simply #define XEN_PT_LOGGING_ENABLED in the line above)
> and re-build at least qemu? The log of a subsequent guest run
> should then be quite a bit more helpful in possibly spotting what's
> going wrong to cause those messages.
>
> And then it's of course rather relevant to know what device 00:06.0
> actually is (iirc these are guest BDF values), considering that you're
> passing through more than one.
>
> Jan
Hi Jan,

I had a look at the guest devices, and Windows says "Standard Enhanced 
PCI to USB Host Controller". Having a look at the Properties, in the 
Device status field is the following message:
---
This device cannot start. (Code 10)

{Operation Failed}
The requested operation was unsuccessful.
---

This USB device wasn't there with Xen 4.6.3. Has it got something to do 
with the new USB passthrough? However, I have tried USB passthrough (xl 
usbctrl-attach), which doesn't work. But that is possibly another problem.
No problem to recompile Xen with the logging flag, if it would be required.

Best regards,

Peter

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