From patchwork Tue Feb 9 01:07:17 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Alistair Popple X-Patchwork-Id: 12076961 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-19.3 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 475E5C433DB for ; Tue, 9 Feb 2021 01:09:37 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 0347564E6C for ; Tue, 9 Feb 2021 01:09:36 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 0347564E6C Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=nvidia.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 9245D8D0003; Mon, 8 Feb 2021 20:09:36 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 8D2D46B0070; Mon, 8 Feb 2021 20:09:36 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 7C15C8D0003; Mon, 8 Feb 2021 20:09:36 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0009.hostedemail.com [216.40.44.9]) by kanga.kvack.org (Postfix) with ESMTP id 652376B006E for ; Mon, 8 Feb 2021 20:09:36 -0500 (EST) Received: from smtpin27.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id 33310181D2FE9 for ; Tue, 9 Feb 2021 01:09:36 +0000 (UTC) X-FDA: 77796946752.27.cake40_290848427603 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin27.hostedemail.com (Postfix) with ESMTP id 143A43D663 for ; Tue, 9 Feb 2021 01:09:36 +0000 (UTC) X-HE-Tag: cake40_290848427603 X-Filterd-Recvd-Size: 5074 Received: from hqnvemgate26.nvidia.com (hqnvemgate26.nvidia.com [216.228.121.65]) by imf15.hostedemail.com (Postfix) with ESMTP for ; Tue, 9 Feb 2021 01:09:35 +0000 (UTC) Received: from hqmail.nvidia.com (Not Verified[216.228.121.13]) by hqnvemgate26.nvidia.com (using TLS: TLSv1.2, AES256-SHA) id ; Mon, 08 Feb 2021 17:09:34 -0800 Received: from DRHQMAIL107.nvidia.com (10.27.9.16) by HQMAIL101.nvidia.com (172.20.187.10) with Microsoft SMTP Server (TLS) id 15.0.1473.3; Tue, 9 Feb 2021 01:09:34 +0000 Received: from localhost (172.20.145.6) by DRHQMAIL107.nvidia.com (10.27.9.16) with Microsoft SMTP Server (TLS) id 15.0.1473.3; Tue, 9 Feb 2021 01:09:33 +0000 From: Alistair Popple To: , , , CC: , , , , , , , "Alistair Popple" Subject: [PATCH 4/9] Documentation: Add unmap and pin to HMM Date: Tue, 9 Feb 2021 12:07:17 +1100 Message-ID: <20210209010722.13839-5-apopple@nvidia.com> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20210209010722.13839-1-apopple@nvidia.com> References: <20210209010722.13839-1-apopple@nvidia.com> MIME-Version: 1.0 X-Originating-IP: [172.20.145.6] X-ClientProxiedBy: HQMAIL101.nvidia.com (172.20.187.10) To DRHQMAIL107.nvidia.com (10.27.9.16) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=nvidia.com; s=n1; t=1612832974; bh=pyZp6/9XNMC0mK0WRRvgfyWXvzV3+8u2/OO5kZH2+Vg=; h=From:To:CC:Subject:Date:Message-ID:X-Mailer:In-Reply-To: References:MIME-Version:Content-Transfer-Encoding:Content-Type: X-Originating-IP:X-ClientProxiedBy; b=jeZjl3nfuSeq3FgFlgTJUt58XPL3emJVARijzZ4vq7ltCLgRVsr0bJW0RX7cLsy4+ 6i2ssucV5jShnIDv0z47fip74hEH6p2G7xEJGuH3szVMZf9TbumLk+9q9cM2uqpJqF zp0STD/loZHiqwCk48WN2CUfYhM/po5OgnEr3p85w9nntk+tBlaEU/GEolQNOEp1iF zEl1WiliIccRiu3A/3Ps6CBlVCYypWGxVgimQYvt7/3b0HLJ79gnhK9hGtXogpZXon 2dFsEzwULBU/1bCkZF5FIg7ycfCM4V4o6iEhQSzOB1i8QXdnME+lFPKBFz1v+szxGz jVlzmZBk+PGQA== 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: Update the HMM documentation to include information on the unmap and pin operation. Signed-off-by: Alistair Popple --- Documentation/vm/hmm.rst | 22 +++++++++++++++++++--- 1 file changed, 19 insertions(+), 3 deletions(-) diff --git a/Documentation/vm/hmm.rst b/Documentation/vm/hmm.rst index 09e28507f5b2..83234984f656 100644 --- a/Documentation/vm/hmm.rst +++ b/Documentation/vm/hmm.rst @@ -346,7 +346,15 @@ between device driver specific code and shared common code: from the LRU (if system memory since device private pages are not on the LRU), unmapped from the process, and a special migration PTE is inserted in place of the original PTE. - migrate_vma_setup() also clears the ``args->dst`` array. + + A device driver may also initialise ``src`` entries with the + ``MIGRATE_PFN_PIN`` flag. This allows the device driver to unmap and pin + the existing system page in place whilst migrating page metadata to a + device private page. This leaves the page isolated from the LRU and gives + the device exclusive access to the page data without the need to migrate + data as any CPU access will trigger a fault. The device driver needs to + keep track of the ``src`` page as it effectively becomes the owner of + the page and needs to pass it in when remapping and unpinning the page. 3. The device driver allocates destination pages and copies source pages to destination pages. @@ -357,8 +365,8 @@ between device driver specific code and shared common code: array for that page. The driver then allocates either a device private struct page or a - system memory page, locks the page with ``lock_page()``, and fills in the - ``dst`` array entry with:: + system memory page, locks the page with ``lock_page()``, and fills in + the ``dst`` array entry with:: dst[i] = migrate_pfn(page_to_pfn(dpage)) | MIGRATE_PFN_LOCKED; @@ -373,6 +381,14 @@ between device driver specific code and shared common code: destination or clear the destination device private memory if the pointer is ``NULL`` meaning the source page was not populated in system memory. + Alternatively a driver that is remapping and unpinning a source page + obtained from a ``MIGRATE_PFN_PIN`` operation should lock the original + source page and pass it in along with the ``MIGRATE_PFN_UNPIN`` flag + without any need to copy data:: + + dst[i] = migrate_pfn(page_to_pfn(spage)) | MIGRATE_PFN_LOCKED + | MIGRATE_PFN_UNPIN; + 4. ``migrate_vma_pages()`` This step is where the migration is actually "committed".