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 70E11C3DA7F for ; Thu, 15 Aug 2024 10:31:58 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id D44116B00C1; Thu, 15 Aug 2024 06:31:57 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id CCD616B00C2; Thu, 15 Aug 2024 06:31:57 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id B6DEC6B00C3; Thu, 15 Aug 2024 06:31:57 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0011.hostedemail.com [216.40.44.11]) by kanga.kvack.org (Postfix) with ESMTP id 94E496B00C1 for ; Thu, 15 Aug 2024 06:31:57 -0400 (EDT) Received: from smtpin26.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay06.hostedemail.com (Postfix) with ESMTP id 06C92A8747 for ; 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s=arc-20220608; d=hostedemail.com; t=1723717834; a=rsa-sha256; cv=none; b=24TB1ACcRmgJMbybrO6+PQecehGaOGSge6ZP3UGNu4wxQtEBO6YR4SuoTjMIMt85zc5m1P Z4toh3+831C79gSuAFFl37USdopHqvcLhGa0KzCUpgozFpXhb20wT1PmdBsY6n6AUfNjBv ZP0WL8gRv2C+VntM63mQA2X4jyWyh2Y= ARC-Authentication-Results: i=1; imf09.hostedemail.com; dkim=none; dmarc=fail reason="SPF not aligned (relaxed), No valid DKIM" header.from=arm.com (policy=none); spf=pass (imf09.hostedemail.com: domain of cmarinas@kernel.org designates 139.178.84.217 as permitted sender) smtp.mailfrom=cmarinas@kernel.org Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by dfw.source.kernel.org (Postfix) with ESMTP id 269F761D51; Thu, 15 Aug 2024 10:31:54 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7EDC5C32786; Thu, 15 Aug 2024 10:31:52 +0000 (UTC) Date: Thu, 15 Aug 2024 11:31:50 +0100 From: Catalin Marinas To: Yang Shi Cc: muchun.song@linux.dev, will@kernel.org, akpm@linux-foundation.org, linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] hugetlbfs: add MTE support Message-ID: References: <20240625233717.2769975-1-yang@os.amperecomputing.com> <7a4a60af-e471-484b-a4a3-ed31daaca30b@os.amperecomputing.com> <546bf8d4-3680-4af3-8d4d-af2d7c192d04@os.amperecomputing.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 4A06A140009 X-Stat-Signature: osgzyympqw3qaprhc1z54y34fwetab1p X-Rspam-User: X-HE-Tag: 1723717915-378998 X-HE-Meta: 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 Ktk5UQsh yWsZ6X3lGdodqVZmgfDzWu97ybyOVNQQSiuvT90JlFJ1nzJTVPyL5VPY6nUocTzxyB46dDlvzbGcdJI1wjL08WC54OIjXlHoO2ZF3kg1Rz7Gnem8iAb5hAibXG1A36bp0gfuRmBGHcGdvr3nfq87/l7Tr1axlFOzOR1fW8Z9Dg3LyqEQokqXft92EfOtE+99yFC3yrGDoNe53D2U7jjmzk9lpZG8RI3mJ/aGrjc16Oe+xCm5BUskLISrARvNFx7kCkWFq8PATRx/6YUXY9dtLX1vULDmiHf6kcmIYzuma1hf57n7ha18m6/3sseclbSMdyScstqsODob04DR79Biqtbu0tU8qH5FI8rOefmHEyAtaApvapaJXIb6z2w== 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: Sorry for the delay (holidays etc.) On Tue, Jul 09, 2024 at 10:42:58AM -0700, Yang Shi wrote: > On 7/4/24 6:44 AM, Catalin Marinas wrote: > > It might be better to convert those page flag checks to only happen on > > the head page. My stashed changes from over a year ago (before we had > > more folio conversions) below. However, as I mentioned, I got stuck on > > folio_copy() which also does a cond_resched() between copy_highpage(). > > We can have the page flags set for head only for hugetlb page. For > copy_highpage(), we should be able to do something like the below: > > if  page_is_head && page_is_hugetlb && page_has_mte_tagged >     set page_mte_tagged flags >     copy tags for all sub pages > else // <-- tail page or non-hugetlb page >     current copy_highpage implementation Ah, so you want in the first copy_highpage() for the head page to populate the tags for the tail pages. I guess this would work. > The hugetlb folio can't go away under us since migration path should pin it > so the status of folio is stable. The preemption caused by cond_resched() > should be fine too due to the pin and the page table entry keeps being > migration entry until migration is done, so every one should just see > migration entry and wait for migration is done. Yeah, I don't see those pages going away, otherwise folio_copy() would corrupt data. > The other concerned user of copy_highpage() is uprobe, but it also pins the > page then doing copy and it is called with holding write mmap_lock. > > IIUC, it should work if I don't miss something. This also should have no > impact on HVO. The overhead for other users of copy_highpage() should be > also acceptable. I also think so. We also have the copy_user_highpage() on arm64 that calls copy_highpage() but I think that's also safe. -- Catalin