linux-kernel - Re: [RFC 04/10] drivers: i915 selftest: use pgtable_has_pmd

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <81d3d168-fc0a-4519-ad7f-c6ab71294792@redhat.com>
Date: Wed, 3 Dec 2025 08:19:35 -0500
From: Luiz Capitulino <luizcap@...hat.com>
To: "David Hildenbrand (Red Hat)" <david@...nel.org>,
 linux-kernel@...r.kernel.org, linux-mm@...ck.org
Cc: ryan.roberts@....com, akpm@...ux-foundation.org,
 lorenzo.stoakes@...cle.com
Subject: Re: [RFC 04/10] drivers: i915 selftest: use pgtable_has_pmd_leaves()

On 2025-12-02 05:51, David Hildenbrand (Red Hat) wrote:
> On 11/17/25 19:55, Luiz Capitulino wrote:
>> On 2025-11-17 12:30, David Hildenbrand (Red Hat) wrote:
>>> On 06.11.25 22:28, Luiz Capitulino wrote:
>>>> igt_can_allocate_thp() uses has_transparente_hugepage() to check if
>>>> PMD-sized pages are supported, use pgtable_has_pmd_leaves() instead.
>>>>
>>>> Signed-off-by: Luiz Capitulino <luizcap@...hat.com>
>>>> ---
>>>>    drivers/gpu/drm/i915/gem/selftests/huge_pages.c | 2 +-
>>>>    1 file changed, 1 insertion(+), 1 deletion(-)
>>>>
>>>> diff --git a/drivers/gpu/drm/i915/gem/selftests/huge_pages.c b/drivers/gpu/drm/i915/gem/selftests/huge_pages.c
>>>> index bd08605a1611..c76aafa36d2b 100644
>>>> --- a/drivers/gpu/drm/i915/gem/selftests/huge_pages.c
>>>> +++ b/drivers/gpu/drm/i915/gem/selftests/huge_pages.c
>>>> @@ -1316,7 +1316,7 @@ typedef struct drm_i915_gem_object *
>>>>    static inline bool igt_can_allocate_thp(struct drm_i915_private *i915)
>>>>    {
>>>> -    return i915->mm.gemfs && has_transparent_hugepage();
>>>> +    return i915->mm.gemfs && pgtable_has_pmd_leaves();
>>>
>>> On second thought, is it problematic that we might be losing the CONFIG_TRANSPARENT_HUGEPAGE check? Should we check for that separately?
>>
>> That's a good point.
>>
>> In this RFC, pgtable_has_pmd_leaves() should be functionally equivalent
>> to has_transparent_hugepage() so I think we're good. That beind said, I
>> also think that we should disentangle pgtable_has_pmd_leaves() from THP
>> now or in the future. When we do this the breakage you're spotting will
>> happen.
>>
>> What about adding thp_has_pmd_support() which does:
>>
>>     return IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) && pgtable_has_pmd_leaves();
>>
>> Then I can convert all the cases you spotted to thp_has_pmd_support().
> 
> I hope we can avoid such a wrapper for the time being. Maybe we can just keep pgtable_has_pmd_leaves() glued to CONFIG_TRANSPARENT_HUGEPAGE for now, and leave untangling that for the next cleanup?

OK, I can do that in the v1 posting.