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

[Peter Milesson <miles@xxxxxxxx>]

On 2016-09-14 15:23, Andrew Cooper wrote:
> On 14/09/16 13:50, 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?
> Furthermore, does "Nothing else has changed, only the Xen version." mean
> switching your distro packages between two versions of xen, or literally
> only switching the hypervisor itself.
>
> A substantial quantity of the complexity here is in qemu, rather than Xen.
>
> ~Andrew
Hi Andrew,

I previously compiled and run Xen 4.6.3 in the same environment. Without 
making any changes to anything else, then downloading, compiling and 
installing Xen 4.7.0.
But read my following 2 posts. I stopped passing the original USB 
controller (2 PCI devices), and switched to another USB controller. All 
the previous problems completely gone. Logically, it doesn't make sense, 
because passing those 2 PCI devices, or these 2, should be completely 
irrelevant.
Best regards,

Peter


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