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

[Juergen Gross <jgross@xxxxxxxx>]

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.


Juergen

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