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[2003:d8:2f30:b00:cea9:dee:d607:41d]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-42ac679c5dcsm23727969f8f.44.2025.11.10.01.09.32 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 10 Nov 2025 01:09:32 -0800 (PST) Message-ID: <690ce196-58cb-4252-ab72-967e1e1574cf@gmail.com> Date: Mon, 10 Nov 2025 10:09:31 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm/huge_memory: restrict __GFP_ZEROTAGS to HW tagging architectures 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> From: "David Hildenbrand (Red Hat)" Content-Language: en-US In-Reply-To: <20251109003613.1461433-1-japo@linux.ibm.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: E7DE9A0006 X-Stat-Signature: 545kzt7hznr9et89zhpua86a16im1sid X-Rspam-User: X-HE-Tag: 1762766211-921772 X-HE-Meta: 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 DjB92hWo 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 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 09.11.25 01:36, Jan Polensky wrote: > The previous change added __GFP_ZEROTAGS when allocating the huge zero > folio to ensure tag initialization for arm64 with MTE enabled. However, > on s390 this flag is unnecessary and triggers a regression > (observed as a crash during repeated 'dnf makecache'). > > Restrict the use of __GFP_ZEROTAGS to architectures that support > hardware memory tagging (currently arm64 with MTE or KASAN HW tags). > This avoids unintended side effects on other platforms. > > Fixes: 1579227fe0f0 ("mm/huge_memory: initialise the tags of the huge zero folio") > Link: https://lore.kernel.org/r/20251031170133.280742-1-catalin.marinas@arm.com > Signed-off-by: Jan Polensky > --- > mm/huge_memory.c | 9 +++++---- > 1 file changed, 5 insertions(+), 4 deletions(-) > > diff --git a/mm/huge_memory.c b/mm/huge_memory.c > index aae283b00857..0c1794656d7a 100644 > --- a/mm/huge_memory.c > +++ b/mm/huge_memory.c > @@ -209,14 +209,15 @@ unsigned long __thp_vma_allowable_orders(struct vm_area_struct *vma, > > static bool get_huge_zero_folio(void) > { > + gfp_t gfp = (GFP_TRANSHUGE | __GFP_ZERO) & ~__GFP_MOVABLE; > struct folio *zero_folio; > retry: > if (likely(atomic_inc_not_zero(&huge_zero_refcount))) > return true; > - > - zero_folio = folio_alloc((GFP_TRANSHUGE | __GFP_ZERO | __GFP_ZEROTAGS) & > - ~__GFP_MOVABLE, > - HPAGE_PMD_ORDER); > +#if IS_ENABLED(CONFIG_KASAN_HW_TAGS) || IS_ENABLED(CONFIG_ARM64_MTE) > + gfp |= __GFP_ZEROTAGS; > +#endif That looks like the wrong approach. If an architecture does not support __GFP_ZEROTAGS it should not trigger anything. __GFP_ZEROTAGS should be ignored. I think the problem is that post_alloc_hook() does if (zero_tags) { /* Initialize both memory and memory tags. */ for (i = 0; i != 1 << order; ++i) tag_clear_highpage(page + i); /* Take note that memory was initialized by the loop above. */ init = false; } And tag_clear_highpage() is a NOP on other architectures. Gah. 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.