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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id E5EF9C5AD49 for ; Fri, 30 May 2025 14:05:18 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 87D106B012B; Fri, 30 May 2025 10:05:18 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 854A06B012C; Fri, 30 May 2025 10:05:18 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 76A4A6B012D; Fri, 30 May 2025 10:05:18 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0016.hostedemail.com [216.40.44.16]) by kanga.kvack.org (Postfix) with ESMTP id 5EA226B012B for ; Fri, 30 May 2025 10:05:18 -0400 (EDT) Received: from smtpin18.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay08.hostedemail.com (Postfix) with ESMTP id 153C91409C8 for ; Fri, 30 May 2025 14:05:18 +0000 (UTC) X-FDA: 83499746316.18.CE214BE Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by imf17.hostedemail.com (Postfix) with ESMTP id 765404000C for ; Fri, 30 May 2025 14:05:16 +0000 (UTC) Authentication-Results: imf17.hostedemail.com; dkim=none; dmarc=pass (policy=none) header.from=arm.com; spf=pass (imf17.hostedemail.com: domain of ryan.roberts@arm.com designates 217.140.110.172 as permitted sender) smtp.mailfrom=ryan.roberts@arm.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1748613916; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=VxJ879xfWVw2euMHLsyZ78IytOrwh9H1JRyt75VdXa0=; b=JV/cZUNSCuBDQeYFXYpxzx9KMBbrpUnEN2bixHUoQh2hGzQ0lOa2qLwn5G6gn+0Sqd9Hlf F75lw/5ycWd4fcMLicp5q24K9nUtkDkMcGW7DtNWDLCD38w5+3pXmHt4zCTqZXpkc2tbn4 y+/HY1OLOEGaSjPuufQQcCuS8qkwBTE= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1748613916; a=rsa-sha256; cv=none; b=H0pxn1O8w60tM3bw19qCD9nNDsqE4PgiL4dkImscY05i2V7rhlt0JeoN6cZAqZ64BU/7/Y 0aPTdVI75dc+tYNqSIB0sbIL+OZqM49ylHh7WgugnSVVGh3eQL05QMs1/cF9j5Z8n87dG4 pn0Yxofo6wuBOLPbQJR9rg25eIQFQdU= ARC-Authentication-Results: i=1; imf17.hostedemail.com; dkim=none; dmarc=pass (policy=none) header.from=arm.com; spf=pass (imf17.hostedemail.com: domain of ryan.roberts@arm.com designates 217.140.110.172 as permitted sender) smtp.mailfrom=ryan.roberts@arm.com 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 23F3F2247; Fri, 30 May 2025 07:04:59 -0700 (PDT) Received: from e125769.cambridge.arm.com (e125769.cambridge.arm.com [10.1.196.27]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 8DD213F673; Fri, 30 May 2025 07:05:10 -0700 (PDT) From: Ryan Roberts To: Catalin Marinas , Will Deacon , Madhavan Srinivasan , Michael Ellerman , Nicholas Piggin , Christophe Leroy , "David S. Miller" , Andreas Larsson , Juergen Gross , Ajay Kaher , Alexey Makhalov , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , "H. Peter Anvin" , Boris Ostrovsky , "Aneesh Kumar K.V" , Andrew Morton , Peter Zijlstra , Arnd Bergmann , David Hildenbrand , Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Alexei Starovoitov , Andrey Ryabinin Cc: Ryan Roberts , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, sparclinux@vger.kernel.org, virtualization@lists.linux.dev, xen-devel@lists.xenproject.org, linux-mm@kvack.org Subject: [RFC PATCH v1 2/6] mm: Fix pte update and tlb maintenance ordering in migrate_vma_collect_pmd() Date: Fri, 30 May 2025 15:04:40 +0100 Message-ID: <20250530140446.2387131-3-ryan.roberts@arm.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20250530140446.2387131-1-ryan.roberts@arm.com> References: <20250530140446.2387131-1-ryan.roberts@arm.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 765404000C X-Stat-Signature: nhhehmyu19swkiedtgzyibnxbniyc1eo X-Rspam-User: X-HE-Tag: 1748613916-190965 X-HE-Meta: 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 nag2YuZD nj2IxaX/qq+wExa0Ypi+5sFsBf+Eu/g3enmJ6PPe7KzNmYCoAZiwpfjNJLxU/tP/uJOgwHLSH/NXlTPpDgOevQcLWX4BglhUE4ySIQ0MJmHy96LnSLA9MiOWI9h25hGPpPbxWnF9Fj8bNCBAqiybgfy5smZyjx8+HFeZU5qYZkKKsCSPHEPuxJ1bLXA/zOBFAfJK+lKt1u2cLs5h6AMxAFH6ttgnq4WQwwC4rb7DRrty5QEW1qH003B6+JGeF4tepOoApEz/lyBsm0zTVEUpA0iT+kA== 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: migrate_vma_collect_pmd() was previously modifying ptes while in lazy mmu mode, then performing tlb maintenance for the modified ptes, then leaving lazy mmu mode. But any pte modifications during lazy mmu mode may be deferred until arch_leave_lazy_mmu_mode(), inverting the required ordering between pte modificaiton and tlb maintenance. Let's fix that by leaving mmu mode (forcing all the pte updates to be actioned) before doing the tlb maintenance. This is a theorectical bug discovered during code review. Fixes: 60bae7370896 ("mm/migrate_device.c: flush TLB while holding PTL") Signed-off-by: Ryan Roberts --- mm/migrate_device.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/mm/migrate_device.c b/mm/migrate_device.c index 3158afe7eb23..fc73a940c112 100644 --- a/mm/migrate_device.c +++ b/mm/migrate_device.c @@ -283,11 +283,12 @@ static int migrate_vma_collect_pmd(pmd_t *pmdp, migrate->src[migrate->npages++] = mpfn; } + arch_leave_lazy_mmu_mode(); + /* Only flush the TLB if we actually modified any entries */ if (unmapped) flush_tlb_range(walk->vma, start, end); - arch_leave_lazy_mmu_mode(); pte_unmap_unlock(ptep - 1, ptl); return 0; -- 2.43.0