Re: [PATCH] x86/ioperm: add new paravirt function update_io_bitmap

[Jan Beulich <jbeulich@suse.com>]

On 19.02.2020 06:35, Jürgen Groß wrote:
> On 18.02.20 22:03, Thomas Gleixner wrote:
>> Juergen Gross <jgross@suse.com> writes:
>>> 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 <jbeulich@suse.com>
>>> Cc: <stable@vger.kernel.org> # 5.5
>>> Signed-off-by: Juergen Gross <jgross@suse.com>
>>> Reviewed-by: Jan Beulich <jbeulich@suse.com>
>>> Tested-by: Jan Beulich <jbeulich@suse.com>
>>
>> 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