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

[George Dunlap <george.dunlap@xxxxxxxxxx>]

> 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?

Details on hardware / config / guest OS below.

 -George

>> *Hardware*
>> CPU: AMD FX-6100 (6-core)
>> Chipset: AMD 970A (has got a working IOMMU)
>> RAM: 16GB DDR3-1600MHz
>> Video: AMD Radeon HD6450
>>
>> *OS*
>> Linux Slackware 14.2 (latest)
>> Kernel: 4.4.19 long term stable
>>
>> *Xen*
>> Version: 4.7.0 (configure same as 4.6.3 and previous versions)
>>  ./configure --prefix=/usr --localstatedir=/var --sysconfdir=/etc
>> --libdir=/usr/lib64 --with-xenstored=oxenstored --disable-qemu-traditional
>> --disable-rombios --disable-stubdom
>> Xen dom0 boot entry (grub2):
>> menuentry "Xen 4.7.0 / Slackware 14.2 (kernel 4.4.19-dom0)" {
>>        set root=(hd0,1)
>>        multiboot /boot/xen-4.7.0.gz iommu=1 dom0_mem=2048M
>> dom0_max_vcpus=2 dom0_vcpus_pin console=vga cpufreq=xen:performance noreboot
>>        module /boot/vmlinuz-4.4.19-dom0 console=vga earlyprintk=xen
>> root=/dev/sda1 ro clocksource=xen xencons=off
>> }
>>
>> *Guest OS*
>> Windows 10 Pro 64-bit (2VCPUs)
>> Latest PV Drivers (8.2 series)
>> Graphics driver: Latest WHQL driver 15.201.1151.1008

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