Re: [PATCH] x86/Xen: swap NX determination and GDT setup on BSP

[Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>]

On 5/21/21 3:45 AM, Juergen Gross wrote:
> 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@xxxxxxxxx>
>>>>>> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
>>>>>
>>>>> Reviewed-by: Juergen Gross <jgross@xxxxxxxx>
>>>>
>>>> Thanks. I guess I forgot
>>>>
>>>> Cc: stable@xxxxxxxxxxxxxxx
>>>>
>>>> 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.


Did something changed recently that this became a problem? That commit has been 
there for 3 years.


Didn't Olaf report this to be a problem only on SLES kernels?



-boris