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[70.27.3.10]) by smtp.gmail.com with ESMTPSA id y6-20020a05620a25c600b006b59f02224asm2017524qko.60.2022.08.26.08.55.43 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 26 Aug 2022 08:55:44 -0700 (PDT) Date: Fri, 26 Aug 2022 11:55:42 -0400 From: Peter Xu To: David Hildenbrand Cc: Alistair Popple , linux-mm@kvack.org, akpm@linux-foundation.org, Nadav Amit , huang ying , LKML , "Sierra Guiza, Alejandro (Alex)" , Felix Kuehling , Jason Gunthorpe , John Hubbard , Ralph Campbell , Matthew Wilcox , Karol Herbst , Lyude Paul , Ben Skeggs , Logan Gunthorpe , paulus@ozlabs.org, linuxppc-dev@lists.ozlabs.org, stable@vger.kernel.org, Huang Ying Subject: Re: [PATCH v3 2/3] mm/migrate_device.c: Copy pte dirty bit to page Message-ID: References: <3b01af093515ce2960ac39bb16ff77473150d179.1661309831.git-series.apopple@nvidia.com> <8735dkeyyg.fsf@nvdebian.thelocal> <8735dj7qwb.fsf@nvdebian.thelocal> <72146725-3d70-0427-50d4-165283a5a85d@redhat.com> MIME-Version: 1.0 In-Reply-To: <72146725-3d70-0427-50d4-165283a5a85d@redhat.com> X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Disposition: inline ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1661529353; a=rsa-sha256; cv=none; b=ciA7dlNkzCdD4Gr/s4bWayhhREGiGGbI43fOowt2kqNyPUs79Db9uQQ4L5/NOgX/X2CBtt 382eAy5WwY9VFFjbHskPhLOhVFq+AGNgkARpzrNCqgLMq9ZWUdsJQ631Rd7+f0gSXH5O9X fN2RYUGHgH2OpKuaK9223XUJ9ZvWKEE= ARC-Authentication-Results: i=1; imf21.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b="R06HI/A4"; dmarc=pass (policy=none) header.from=redhat.com; spf=pass (imf21.hostedemail.com: domain of peterx@redhat.com designates 170.10.133.124 as permitted sender) smtp.mailfrom=peterx@redhat.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1661529353; 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-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=kxP+Dmq/9QrBSNE7t25KnXniHyhrvm0D5T7RzuSjQVM=; b=6PHPofyduinBwiBU/lMLu2u3nJfleeYIaUgJeX5w4zytsBG8cOXmF9fyy5ULAJ0glxLZ/O Rdgaxxrzfvmq/5l7fzsM6h0VHbaukOL5cXE4EHqMUj5lbT9jWwS8dCp1FPFqSQx9At4P8b 1YHBmx2j4e828k8yHypltzwS7eDk0+E= X-Rspamd-Queue-Id: ED2871C0013 Authentication-Results: imf21.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b="R06HI/A4"; dmarc=pass (policy=none) header.from=redhat.com; spf=pass (imf21.hostedemail.com: domain of peterx@redhat.com designates 170.10.133.124 as permitted sender) smtp.mailfrom=peterx@redhat.com X-Rspam-User: X-Rspamd-Server: rspam01 X-Stat-Signature: fpxxyyh7tonxukx7owq5p1y3pgrth5jt X-HE-Tag: 1661529352-255475 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: On Fri, Aug 26, 2022 at 04:47:22PM +0200, David Hildenbrand wrote: > > To me anon exclusive only shows this mm exclusively owns this page. I > > didn't quickly figure out why that requires different handling on tlb > > flushs. Did I perhaps miss something? > > GUP-fast is the magic bit, we have to make sure that we won't see new > GUP pins, thus the TLB flush. > > include/linux/mm.h:gup_must_unshare() contains documentation. Hmm.. Shouldn't ptep_get_and_clear() (e.g., xchg() on x86_64) already guarantees that no other process/thread will see this pte anymore afterwards? -- Peter Xu