From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 17FC0C47DDB for ; Thu, 1 Feb 2024 08:12:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:From:References:Cc:To: Subject:MIME-Version:Date:Message-ID:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=t81ISp5JjsWkINtaO5GAJhca6LLdAyoGx838BV9Txag=; b=B5CpE8vafOJzAY x6XOSLUWn328Lz3oQedxFPD4S+5IANAl78Y2QnZ747zk+09iuHGpgAimOhRREKv09qMMmQTIWJVUl kBx1jBlQrVsOFjvCbMczSCw9U36rCfdDIjsPKNrUmCFO2B58JZd+xQcG+txQBxODYfNT52LXl1Dxj reAYLmFcbzqyQ8IN0/cNE2bIrnogU43oJJ3GFAIocBWjdzP6518GjKDT2spSwHfIgsL6kpVegX/O4 KSOSEntVXARuzz8Vuwyrpo/NLwSVRTSx94+B5tnaffNpABe4dhN0S8yb3lmR4teuvIt/Tg4zdHuj+ gqhfV2xYRp544LnRlRow==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.97.1 #2 (Red Hat Linux)) id 1rVSBU-000000070wq-3dau; Thu, 01 Feb 2024 08:12:32 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.97.1 #2 (Red Hat Linux)) id 1rVSBR-000000070vP-1Hgh for linux-arm-kernel@lists.infradead.org; Thu, 01 Feb 2024 08:12:31 +0000 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> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20240201_001229_464782_D5F58238 X-CRM114-Status: GOOD ( 19.73 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org 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. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel