Re: [PATCH] x86/PV: guest_get_eff_kern_l1e() may still need to switch page tables

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 14/12/2020 13:57, Jan Beulich wrote:
> While indeed unnecessary for pv_ro_page_fault(), pv_map_ldt_shadow_page()
> may run when guest user mode is active, and hence may need to switch to
> the kernel page tables in order to retrieve an LDT page mapping.
>
> Fixes: 9ff970564764 ("x86/mm: drop guest_get_eff_l1e()")
> Reported-by: Manuel Bouyer <bouyer@xxxxxxxxxxxxxxx>
> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
> Reviewed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> ---
> Manuel, could you test this again, just to be on the safe side
> before we throw it in (at which point we could then also again
> add a Tested-by)? Thanks.

I've got a repro of the issue (literally - just booting the
netinstaller), and this does fix it.

~Andrew