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

[Peter Milesson <miles@xxxxxxxx>]

On 2016-09-14 16:17, George Dunlap wrote:
> On Wed, Sep 14, 2016 at 3:04 PM, Peter Milesson <miles@xxxxxxxx> wrote:
> > On 2016-09-14 14:50, Jan Beulich wrote:
> > > > > > On 14.09.16 at 13:34, <george.dunlap@xxxxxxxxxx> wrote:
> > > > >    On 2016-09-09 09:51, Peter Milesson wrote:
> > > > [snip]
> > > > > > I've been using Xen for 3 years, starting out with 4.2, and I've been
> > > > > > upgrading regularly, and installed 4.7.0 today.
> > > > > >
> > > > > > I'm using Windows 10, 64-bit with PCI pass through in a VM with
> > > > > > PV-drivers, using a AMD Radeon HD6450 card (AMD graphics cards don't
> > > > > > seem to
> > > > > > need graphics pass through)
> > > > > >
> > > > > > Previously (up till Xen 4.6.3), the graphics output has displayed some
> > > > > > shorter lines, a bit like thin coarse snow, when watching videos. The
> > > > > > distortions stayed within the movie, and was tolerable.
> > > > > >
> > > > > > After upgrade to Xen 4.7.0, the video performance is seriously ugly.
> > > > > > Just
> > > > > > for example, I open cnn.com and move the mouse pointer up and down over
> > > > > > the
> > > > > > photos, which creates a bunch of flickering lines over the display. The
> > > > > > same
> > > > > > with moving content in Youtube for example. Or opening a Cygwin
> > > > > > terminal
> > > > > > window and scrolling through a file. Terrible.
> > > > > >
> > > > > > Nothing else has changed, only the Xen version.
> > > > [snip]
> > > >
> > > > On Fri, Sep 9, 2016 at 10:35 AM, Peter Milesson <miles@xxxxxxxx> wrote:
> > > > > Hi again,
> > > > >
> > > > > I've been playing around a bit more.
> > > > >
> > > > > It seems one of the problems is that I passed a couple of PCI-devices
> > > > > (USB
> > > > > controllers) to the VM, beside the graphics card.
> > > > >
> > > > > When I pass the USB-devices individually in the VM configuration file
> > > > > (usbdevice=['tablet','host:1.4','host:1:9','host:x.y']), the display
> > > > > problems seem to be more or less gone.
> > > > Jan / Andy,
> > > >
> > > > 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?
> > >
> > > Jan
> > Hi Jan,
> >
> > 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.
> Well crashing twice a day isn't what most people would call "stable".
> :-)  In any case, I was trying to debug the issue you had with passing
> through both the video card and the usb controller -- that is
> obviously an important configuration, but if there's a bug in that
> configuration it probably affects a large number of wider
> configurations as well.
>
> > 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.
> Yeah, those definitely look important.  This is with just the video
> card passed through, or with both passed through?
>
>   -George
Hi George,

This is with both the USB controller, and the graphics card.

Best regards,

Peter


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