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

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

Upstream your patch will be fine, but before kernel 5.9 it will
break running as 32-bit PV guest (see commit 36104cb9012a82e7).

So I will take your patch as is, but for kernels 5.8 and older I
recommend a different approach by directly setting the NX
capability after checking the cpuid bit instead of letting that
do get_cpu_cap().


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