Re: [PATCH 15/17] x86/shadow: drop SH_type_l2h_pae_shadow

[Jan Beulich <jbeulich@xxxxxxxx>]

On 22.01.2021 14:11, Tim Deegan wrote:
> At 16:10 +0100 on 14 Jan (1610640627), Jan Beulich wrote:
>> This is a remnant from 32-bit days, having no place anymore where a
>> shadow of this type would be created.
>>
>> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
>> ---
>> hash_{domain,vcpu}_foreach() have a use each of literal 15. It's not
>> clear to me what the proper replacement constant would be, as it
>> doesn't look as if SH_type_monitor_table was meant.
> 
> Good spot.  I think the '<= 15' should be replaced with '< SH_type_unused'.
> It originally matched the callback arrays all being coded as
> "static hash_callback_t callbacks[16]".

So are you saying this was off by one then prior to this patch
(when SH_type_unused was still 17), albeit in apparently a
benign way? And the comments in sh_remove_write_access(),
sh_remove_all_mappings(), sh_remove_shadows(), and
sh_reset_l3_up_pointers() are then wrong as well, and would
instead better be like in shadow_audit_tables()?

Because of this having been benign (due to none of the callback
tables specifying non-NULL entries there), wouldn't it make
sense to dimension the tables by SH_type_max_shadow + 1 only?
Or would you consider this too risky?

In any event I guess I'll make the patch addressing this (one
way or the other) a prereq to everything here.

Jan