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imf20.hostedemail.com; dkim=none; spf=pass (imf20.hostedemail.com: domain of anshuman.khandual@arm.com designates 217.140.110.172 as permitted sender) smtp.mailfrom=anshuman.khandual@arm.com; dmarc=pass (policy=none) header.from=arm.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1706775144; a=rsa-sha256; cv=none; b=hXIW3pvynNb1bktXKKwITMPJPevouxag29TJ5OzcL+Gw73XHEyMpYPC9vQT5DLhHZJWhlt puSLb2XU1CThijiDiEoyR8IhjLLdfy1cOMJfopiBV8rNNHyhnMnSd3d7fEej8bhYVbQSeX b0zsIVvLGVewOoClcBNB6+YNGn13y7c= Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 2F301DA7; Thu, 1 Feb 2024 00:13:05 -0800 (PST) Received: from [10.162.42.11] (a077893.blr.arm.com [10.162.42.11]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 8267D3F738; Thu, 1 Feb 2024 00:12:11 -0800 (PST) Message-ID: <599769c3-0aef-4c5b-ac98-f109649862f7@arm.com> Date: Thu, 1 Feb 2024 13:42:08 +0530 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH RFC v3 31/35] khugepaged: arm64: Don't collapse MTE enabled VMAs Content-Language: en-US To: Alexandru Elisei , catalin.marinas@arm.com, will@kernel.org, oliver.upton@linux.dev, maz@kernel.org, james.morse@arm.com, suzuki.poulose@arm.com, yuzenghui@huawei.com, arnd@arndb.de, akpm@linux-foundation.org, mingo@redhat.com, peterz@infradead.org, juri.lelli@redhat.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, bristot@redhat.com, vschneid@redhat.com, mhiramat@kernel.org, rppt@kernel.org, hughd@google.com Cc: pcc@google.com, steven.price@arm.com, vincenzo.frascino@arm.com, david@redhat.com, eugenis@google.com, kcc@google.com, hyesoo.yu@samsung.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, kvmarm@lists.linux.dev, linux-fsdevel@vger.kernel.org, linux-arch@vger.kernel.org, linux-mm@kvack.org, linux-trace-kernel@vger.kernel.org References: <20240125164256.4147-1-alexandru.elisei@arm.com> <20240125164256.4147-32-alexandru.elisei@arm.com> From: Anshuman Khandual In-Reply-To: <20240125164256.4147-32-alexandru.elisei@arm.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: B60BD1C0023 X-Rspam-User: X-Stat-Signature: txpxbw73snbg38npfh8z54qy3ejb58rg X-Rspamd-Server: rspam01 X-HE-Tag: 1706775143-169136 X-HE-Meta: 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 Eot4vR6T ZFrfZvZLEGs6ls71BiI2Fg9SBkd4zSZBAaCh3G6+0J2UDH2+yZXdgzUf7X9nva3Qetdt0mjQrpbquguavCsAjhJwKfl4+VuFUr+lWzt7obLdaL5xZoCdSOo9eIh7NgyOz9m2j4IWWBfQow2bZYrTKJC16VCCtIuDTQXRR+yNFhQ+xgW3Ne/idjqHPJHdv/8XmItGXafps4OmIX6ciQXLMXOxXAQ9HNb4P6T8W28kq5QsFYxB3gzVzOryMQw== 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 1/25/24 22:12, Alexandru Elisei wrote: > copy_user_highpage() will do memory allocation if there are saved tags for > the destination page, and the page is missing tag storage. > > After commit a349d72fd9ef ("mm/pgtable: add rcu_read_lock() and > rcu_read_unlock()s"), collapse_huge_page() calls > __collapse_huge_page_copy() -> .. -> copy_user_highpage() with the RCU lock > held, which means that copy_user_highpage() can only allocate memory using > GFP_ATOMIC or equivalent. > > Get around this by refusing to collapse pages into a transparent huge page > if the VMA is MTE-enabled. Makes sense when copy_user_highpage() will allocate memory for tag storage. > > Signed-off-by: Alexandru Elisei > --- > > Changes since rfc v2: > > * New patch. I think an agreement on whether copy*_user_highpage() should be > always allowed to sleep, or should not be allowed, would be useful. This is a good question ! Even after preventing the collapse of MTE VMA here, there still might be more paths where a sleeping (i.e memory allocating) copy*_user_highpage() becomes problematic ? > > arch/arm64/include/asm/pgtable.h | 3 +++ > arch/arm64/kernel/mte_tag_storage.c | 5 +++++ > include/linux/khugepaged.h | 5 +++++ > mm/khugepaged.c | 4 ++++ > 4 files changed, 17 insertions(+) > > diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h > index 87ae59436162..d0473538c926 100644 > --- a/arch/arm64/include/asm/pgtable.h > +++ b/arch/arm64/include/asm/pgtable.h > @@ -1120,6 +1120,9 @@ static inline bool arch_alloc_cma(gfp_t gfp_mask) > return true; > } > > +bool arch_hugepage_vma_revalidate(struct vm_area_struct *vma, unsigned long address); > +#define arch_hugepage_vma_revalidate arch_hugepage_vma_revalidate > + > #endif /* CONFIG_ARM64_MTE_TAG_STORAGE */ > #endif /* CONFIG_ARM64_MTE */ > > diff --git a/arch/arm64/kernel/mte_tag_storage.c b/arch/arm64/kernel/mte_tag_storage.c > index ac7b9c9c585c..a99959b70573 100644 > --- a/arch/arm64/kernel/mte_tag_storage.c > +++ b/arch/arm64/kernel/mte_tag_storage.c > @@ -636,3 +636,8 @@ void arch_alloc_page(struct page *page, int order, gfp_t gfp) > if (tag_storage_enabled() && alloc_requires_tag_storage(gfp)) > reserve_tag_storage(page, order, gfp); > } > + > +bool arch_hugepage_vma_revalidate(struct vm_area_struct *vma, unsigned long address) > +{ > + return !(vma->vm_flags & VM_MTE); > +} > diff --git a/include/linux/khugepaged.h b/include/linux/khugepaged.h > index f68865e19b0b..461e4322dff2 100644 > --- a/include/linux/khugepaged.h > +++ b/include/linux/khugepaged.h > @@ -38,6 +38,11 @@ static inline void khugepaged_exit(struct mm_struct *mm) > if (test_bit(MMF_VM_HUGEPAGE, &mm->flags)) > __khugepaged_exit(mm); > } > + > +#ifndef arch_hugepage_vma_revalidate > +#define arch_hugepage_vma_revalidate(vma, address) 1 Please replace s/1/true as arch_hugepage_vma_revalidate() returns bool ? > +#endif Right, above construct is much better than __HAVE_ARCH_XXXX based one. > + > #else /* CONFIG_TRANSPARENT_HUGEPAGE */ > static inline void khugepaged_fork(struct mm_struct *mm, struct mm_struct *oldmm) > { > diff --git a/mm/khugepaged.c b/mm/khugepaged.c > index 2b219acb528e..cb9a9ddb4d86 100644 > --- a/mm/khugepaged.c > +++ b/mm/khugepaged.c > @@ -935,6 +935,10 @@ static int hugepage_vma_revalidate(struct mm_struct *mm, unsigned long address, > */ > if (expect_anon && (!(*vmap)->anon_vma || !vma_is_anonymous(*vmap))) > return SCAN_PAGE_ANON; > + > + if (!arch_hugepage_vma_revalidate(vma, address)) > + return SCAN_VMA_CHECK; > + > return SCAN_SUCCEED; > } > Otherwise this LGTM.