On 21.05.21 09:26, Jan Beulich wrote:
> On 21.05.2021 09:18, Juergen Gross wrote:
>> On 20.05.21 14:08, Jan Beulich wrote:
>>> On 20.05.2021 13:57, Juergen Gross wrote:
>>>> On 20.05.21 13:42, Jan Beulich wrote:
>>>>> xen_setup_gdt(), via xen_load_gdt_boot(), wants to adjust page tables.
>>>>> For this to work when NX is not available, x86_configure_nx() needs 
to
>>>>> be called first.
>>>>>
>>>>> Reported-by: Olaf Hering <olaf@aepfle.de>
>>>>> Signed-off-by: Jan Beulich <jbeulich@suse.com>
>>>>
>>>> Reviewed-by: Juergen Gross <jgross@suse.com>
>>>
>>> Thanks. I guess I forgot
>>>
>>> Cc: stable@vger.kernel.org
>>>
>>> If you agree, can you please add this before pushing to Linus?
>>
>> Uh, just had a look why x86_configure_nx() was called after
>> xen_setup_gdt().
>>
>> Upstream your patch will be fine, but before kernel 5.9 it will
>> break running as 32-bit PV guest (see commit 36104cb9012a82e7).
> 
> Oh, indeed. That commit then actually introduced the issue here,
> and hence a Fixes: tag may be warranted.

Added it already. :-)

And I've limited the backport to happen not for 5.8 and older, of
course.


Juergen