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

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> 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


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