On 19.02.2020 06:35, Jürgen Groß wrote:

On 18.02.20 22:03, Thomas Gleixner wrote:

quoted

Juergen Gross [off-list ref] writes:

quoted

Commit 111e7b15cf10f6 ("x86/ioperm: Extend IOPL config to control
ioperm() as well") reworked the iopl syscall to use I/O bitmaps.

Unfortunately this broke Xen PV domains using that syscall as there
is currently no I/O bitmap support in PV domains.

Add I/O bitmap support via a new paravirt function update_io_bitmap
which Xen PV domains can use to update their I/O bitmaps via a
hypercall.

Fixes: 111e7b15cf10f6 ("x86/ioperm: Extend IOPL config to control ioperm() as well")
Reported-by: Jan Beulich <redacted>
Cc: <redacted> # 5.5
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Jan Beulich <redacted>
Tested-by: Jan Beulich <redacted>

Duh, sorry about that and thanks for fixing it.

BTW, why isn't stuff like this not catched during next or at least
before the final release? Is nothing running CI on upstream with all
that XEN muck active?

This problem showed up by not being able to start the X server (probably
not the freshest one) in dom0 on a moderate aged AMD system.

Not the freshest one, yes, but also on a system where KMS would not
be available (my success rate with KMS is rather low overall, and
with newer Linux I see rather more systems to stop working than ones
to become working, but I simply don't have the time to investigate).

Jan