On 09.02.2023 18:26, Andrew Cooper wrote:
> On 08/02/2023 2:38 pm, Jan Beulich wrote:
>> First of all move the almost loop-invariant condition out of the loop;
>> transform it into an altered loop boundary, noting that the updating of
>> _gl2p is relevant only at one use site, and then also only inside the
>> _code blob it provides. Then drop the shadow_mode_external() part of the
>> condition as being redundant with the is_pv_32bit_domain() check.
>> Further, since the new local variable wants to be "unsigned int",
>> convert the loop induction variable accordingly. Finally also adjust
>> formatting as most code needs touching anyway.
>>
>> Signed-off-by: Jan Beulich <jbeul...@suse.com>
>
> Acked-by: Andrew Cooper <andrew.coop...@citrix.com>
Thanks.
>> --- a/xen/arch/x86/mm/shadow/multi.c
>> +++ b/xen/arch/x86/mm/shadow/multi.c
>> @@ -861,23 +861,22 @@ do {
>> /* 64-bit l2: touch all entries except for PAE compat guests. */
>> #define SHADOW_FOREACH_L2E(_sl2mfn, _sl2e, _gl2p, _done, _dom, _code)
>> \
>> do {
>> \
>> - int _i;
>> \
>> - int _xen = !shadow_mode_external(_dom);
>> \
>> + unsigned int _i, _end = SHADOW_L2_PAGETABLE_ENTRIES;
>> \
>> shadow_l2e_t *_sp = map_domain_page((_sl2mfn));
>> \
>> ASSERT_VALID_L2(mfn_to_page(_sl2mfn)->u.sh.type);
>> \
>> - for ( _i = 0; _i < SHADOW_L2_PAGETABLE_ENTRIES; _i++ )
>> \
>> + if ( is_pv_32bit_domain(_dom) /* implies !shadow_mode_external(_dom) */
>> && \
>
> As this is a comment, I think can reasonably be
>
> /* implies !shadow_mode_external */
>
> which shortens it enough to maintain the RHS justification.
I would certainly have done it without pushing out the escape, but both
alternative variants look worse to me: In
/* Implies !shadow_mode_external(_dom) */ \
if ( is_pv_32bit_domain(_dom) && \
mfn_to_page(_sl2mfn)->u.sh.type != SH_type_l2_64_shadow ) \
_end = COMPAT_L2_PAGETABLE_FIRST_XEN_SLOT(_dom); \
it isn't clear that the comment applies to only the first part of the
conditions, whereas
if ( /* Implies !shadow_mode_external(_dom): */ \
is_pv_32bit_domain(_dom) && \
mfn_to_page(_sl2mfn)->u.sh.type != SH_type_l2_64_shadow ) \
_end = COMPAT_L2_PAGETABLE_FIRST_XEN_SLOT(_dom); \
looks more clumsy to me. I'm not very likely to accept a suggestion to
for the former route; if you think the latter variant is strictly
better than the original, I might make the change while committing.
Hmm, or maybe
if ( mfn_to_page(_sl2mfn)->u.sh.type != SH_type_l2_64_shadow ) \
/* Implies !shadow_mode_external(_dom): */ \
is_pv_32bit_domain(_dom) && \
_end = COMPAT_L2_PAGETABLE_FIRST_XEN_SLOT(_dom); \
?
Jan
