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b=vKxzX0wr6ntIaxsK/A53hJWE8lLaVeIm69oxgve/EX5SRbhA+pZALO6oZirT/Ncwi jUAHgUFt6USdqjMZj9fX0ByuYJS9TgpZrbp1dalhANR68mARv7EpZCA7T0WH1PJ1Ql s96onujRGUeSVaDS57BbFqPQIkf68jPyOfckNz/F7YWI4ppD3ttAHnnTblSm67XLjT pol5Cl5oPHZO1FrLjEgRMsnDwtaPc0ktaq/LnFNnSlUNquxzwSPzCDjgAhEJFgeLAs gL80VUVermJRjuSoQ1suChEgy3U4XFDrDNGY9Up2R4zc8gDnU4jVyVobAoZ1wjVhx/ DQX5sdotI1TDA== Message-ID: <2093f05a-542f-4d4d-b8e9-22b14d0a7a4c@kernel.org> Date: Tue, 11 Nov 2025 13:28:40 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm/huge_memory: restrict __GFP_ZEROTAGS to HW tagging architectures From: "David Hildenbrand (Red Hat)" To: Jan Polensky , catalin.marinas@arm.com Cc: akpm@linux-foundation.org, linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org, will@kernel.org References: <20251031170133.280742-1-catalin.marinas@arm.com> <20251109003613.1461433-1-japo@linux.ibm.com> <690ce196-58cb-4252-ab72-967e1e1574cf@gmail.com> Content-Language: en-US In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: 2855C1C0007 X-Stat-Signature: iwum15p4uam1dnmj8it7wtmstpmf97nt X-Rspamd-Server: rspam02 X-Rspam-User: X-HE-Tag: 1762864125-608910 X-HE-Meta: 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 chp1glsi KA/n3nDe74LFYU/BE1Ycj2+RExBmgLhpG9pTlaSSBtSYw/1MKfrHCURVQ/9i/GIJiRmmzldE5+w2Sz/6cw0VkRNqcLy2NXzzpQZmr//jVWMuYKnEBHYkIEfck5c1kGhI19JTmne2iZdTFtF20tqZIC27rvw0BGukxM0jGx9WrlBBK0AIMlR65lKstM2FAwrvGpyGs1L5dWvxZed9PNph77UUA5VBIyNYEEv7zBkbivkDmi83ktYRF1akvVmzKSDLSduKD3dKOef18dusuDRMRaqmcJvPys3wgYL1EN3fF1e9dmNeAPaBaMBCRUqc4DMCg1DaCfd4jX4+b2bg8pjy6nHekY78vC34omhRY X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 11.11.25 13:27, David Hildenbrand (Red Hat) wrote: > On 11.11.25 11:44, Jan Polensky wrote: >> On Mon, Nov 10, 2025 at 10:53:33AM +0100, David Hildenbrand (Red Hat) wrote: >>> On 10.11.25 10:48, Jan Polensky wrote: >>>> On Mon, Nov 10, 2025 at 10:09:31AM +0100, David Hildenbrand (Red Hat) wrote: >>>>> On 09.11.25 01:36, Jan Polensky wrote: >> ---8<--- snip ---8<--- >>>>> I wonder if the following would work: >>>>> >>>>> >>>>> diff --git a/include/linux/gfp_types.h b/include/linux/gfp_types.h >>>>> index 65db9349f9053..56b82e116cb79 100644 >>>>> --- a/include/linux/gfp_types.h >>>>> +++ b/include/linux/gfp_types.h >>>>> @@ -47,7 +47,9 @@ enum { >>>>> ___GFP_HARDWALL_BIT, >>>>> ___GFP_THISNODE_BIT, >>>>> ___GFP_ACCOUNT_BIT, >>>>> +#ifdef __HAVE_ARCH_TAG_CLEAR_HIGHPAGE >>>>> ___GFP_ZEROTAGS_BIT, >>>>> +#endif >>>>> #ifdef CONFIG_KASAN_HW_TAGS >>>>> ___GFP_SKIP_ZERO_BIT, >>>>> ___GFP_SKIP_KASAN_BIT, >>>>> @@ -85,7 +87,11 @@ enum { >>>>> #define ___GFP_HARDWALL BIT(___GFP_HARDWALL_BIT) >>>>> #define ___GFP_THISNODE BIT(___GFP_THISNODE_BIT) >>>>> #define ___GFP_ACCOUNT BIT(___GFP_ACCOUNT_BIT) >>>>> +#ifdef __HAVE_ARCH_TAG_CLEAR_HIGHPAGE >>>>> #define ___GFP_ZEROTAGS BIT(___GFP_ZEROTAGS_BIT) >>>>> +#else >>>>> +#define ___GFP_ZEROTAGS 0 >>>>> +#endif >>>>> #ifdef CONFIG_KASAN_HW_TAGS >>>>> #define ___GFP_SKIP_ZERO BIT(___GFP_SKIP_ZERO_BIT) >>>>> #define ___GFP_SKIP_KASAN BIT(___GFP_SKIP_KASAN_BIT) >>>>> >>>>> >>>>> Likely we'd have to make __HAVE_ARCH_TAG_CLEAR_HIGHPAGE a proper >>>>> kconfig option. >>>>> >>>>> >>>>> Then we could turn the default implementation of >>>>> tag_clear_highpage() into a BUILD_BUG. >>>>> >>>> I'd like to suggest to keep the enum untouched and only use the second >>>> part of your suggestion. >>> >>> Why? We also do that for CONFIG_KASAN_HW_TAGS, CONFIG_LOCKDEP and >>> CONFIG_SLAB_OBJ_EXT. >> If we remove the enum entry, we’d also need to update mmflags.h because >> the trace macros reference it. >> Enums are compile-time only, so they don’t affect the generated binary. >> My thought was to keep the enum list as it is and just apply the second >> part of your suggestion. >> That way, the trace definitions stay consistent without extra changes. >> Just an idea, happy to go with whatever you prefer. > > I think we'd remove the enum value as well, because then there is no way > it could accidentally be reused. > > And yes, as you correctly state we'll have to update mmflags as well > like we did for CONFIG_KASAN_HW_TAGS etc. /me realizing that my mail client decided to use yet another mail alias, I hope I have it fixed now such that everything is sent from my kernel.org account ... -- Cheers David