AW: [BUG] Passed through PCI devices lost after Windows HVM DomU reboot

[Paul Leiber <paul@xxxxxxxxxxxxxxxx>]

> Von: Jan Beulich <jbeulich@xxxxxxxx>
> Gesendet: Dienstag, 8. Juni 2021 08:24
> 
> On 08.06.2021 01:44, Paul Leiber wrote:
> > After more testing, I have come to the following conclusion: It seems that
> every time I do a _reboot_ from within a Windows DomU, the PCI device
> does not get attached to the DomU. After DomU reboot, it is immediately
> available for attachment in the Dom0 when I check for it with "xl pci-
> assignable-list", and I can reattach it to the DomU with "xl pci-attach" 
> without
> any major problems beside some annoying side effects (e. g. need to reapply
> settings).
> 
> A well-known problem on ...
> 
> > xl info:
> >
> > host                   : xxx
> > release                : 4.19.0-14-amd64
> > version                : #1 SMP Debian 4.19.171-2 (2021-01-30)
> > machine                : x86_64
> > nr_cpus                : 4
> > max_cpu_id             : 3
> > nr_nodes               : 1
> > cores_per_socket       : 4
> > threads_per_core       : 1
> > cpu_mhz                : 1992.100
> > hw_caps                :
> bfebfbff:77faf3ff:2c100800:00000121:0000000f:009c6fbf:00000000:00000100
> > virt_caps              : hvm hvm_directio
> > total_memory           : 32542
> > free_memory            : 20836
> > sharing_freed_memory   : 0
> > sharing_used_memory    : 0
> > outstanding_claims     : 0
> > free_cpus              : 0
> > xen_major              : 4
> > xen_minor              : 11
> > xen_extra              : .4
> > xen_version            : 4.11.4
> 
> ... this old Xen version, I believe. I don't recall when exactly it was
> fixed (and I don't know at all whether the fix was backported), but
> trying a recent version of Xen should get you past this. If a fully
> maintained version is still affected, a backport could be requested.

I switched to xen_version 4.14.2-pre (the standard package from Debian 
bullseye), result: the issue is gone. The PCI device is attached reliably to 
the DomU, even after reboot.

I had searched for information on this issue on the web or in Xen mailing 
lists, but I only found one superold bug report, therefore I didn't try out a 
more recent Xen version myself. It now turns out I should have...

Anyway, thank you for your superfast help!

Paul