Re: IGD pass-through failures since 4.10.

From: "Roger Pau Monné" <roger.pau@citrix.com>
To: "Dr. Greg" <greg@enjellic.com>
Cc: <xen-devel@lists.xen.org>
Subject: Re: IGD pass-through failures since 4.10.
Date: Mon, 14 Feb 2022 10:21:01 +0100	[thread overview]
Message-ID: <Ygoe/e+UzAtHe3Ac@Air-de-Roger> (raw)
In-Reply-To: <20220214060011.GA24404@wind.enjellic.com>

On Mon, Feb 14, 2022 at 12:00:11AM -0600, Dr. Greg wrote:
> Good morning, I hope the week is starting well for everyone.
> 
> We've made extensive use of PCI based graphics pass through for many
> years, since around Xen 4.2.  In fact, we maintained a set of patches
> for ATI cards against qemu-traditional that have seen a lot of
> downloads from our FTP site.
> 
> We ended up switching to IGD based graphics a couple of years ago and
> built a stack on top of Xen 4.10 using qemu-traditional.  That
> coincided with our transition from Windows 7 to Windows 10.
> 
> We've never enjoyed anywhere near the stability with IGD/Windows-10
> that we had with the ATI/Windows-7 desktops, ie. we see fairly
> frequent crashes, lockups, reduced performance etc.  The ATI/Windows-y
> desktops were almost astonishingly reliable, ie. hundreds of
> consecutive Windows VM boot/passthrough cycles.
> 
> In order to try and address this issue we set out to upgrade our
> workstation infrastructure.  Unfortunately we haven't found anything
> that has worked post 4.10.
> 
> To be precise, 4.11 with qemu-traditional works, but upon exit from
> the virtual machine, to which the graphics adapter and USB controller
> are passed through to, both the USB controller and the graphics
> controller cannot be re-initialized and re-attached to the Dom0
> instance.
> 
> It appears to be a problem with mapping interrupts back to dom0 given
> that we see the following:
> 
> Feb 10 08:16:05 hostname kernel: xhci_hcd 0000:00:14.0: xen map irq failed -19 for 32752 domain
> 
> Feb 10 08:16:05 hostname kernel: i915 0000:00:02.0: xen map irq failed -19 for 32752 domain
> 
> Feb 10 08:16:12 hostname kernel: xhci_hcd 0000:00:14.0: Error while assigning device slot ID

Are you testing with an hypervisor with debug enabled? If not, please
build one and see if there are any messages in Xen dmesg also as a
result of the error (uisng `xl dmesg` if you don't have a serial
attached to the box). Posting full Linux and Xen dmesgs (Xen build
with debug=y) could also help.

PHYSDEVOP_map_pirq is failing but without further information it's
impossible to limit the scope of the issue (and whether the issue is
with PHYSDEVOP_map_pirq or some previous operation).

Thanks, Roger.