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Sun, 2 May 2021 23:32:50 +0000 Received: from [10.2.50.162] (172.20.145.6) by HQMAIL107.nvidia.com (172.20.187.13) with Microsoft SMTP Server (TLS) id 15.0.1497.2; Sun, 2 May 2021 23:32:50 +0000 Subject: Re: [PATCH 09/16] dma-direct: Support PCI P2PDMA pages in dma-direct map_sg From: John Hubbard To: Logan Gunthorpe , , , , , , CC: Stephen Bates , Christoph Hellwig , Dan Williams , Jason Gunthorpe , =?UTF-8?Q?Christian_K=c3=b6nig?= , Don Dutile , Matthew Wilcox , Daniel Vetter , Jakowski Andrzej , Minturn Dave B , Jason Ekstrand , Dave Hansen , Xiong Jianxin , Bjorn Helgaas , Ira Weiny , Robin Murphy References: <20210408170123.8788-1-logang@deltatee.com> <20210408170123.8788-10-logang@deltatee.com> <37fa46c7-2c24-1808-16e9-e543f4601279@nvidia.com> Message-ID: Date: Sun, 2 May 2021 16:32:50 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.10.0 MIME-Version: 1.0 In-Reply-To: <37fa46c7-2c24-1808-16e9-e543f4601279@nvidia.com> Content-Type: text/plain; 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X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 02 May 2021 23:32:50.9216 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: ccf9cb84-36f7-42fc-2b50-08d90dc29a1f X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=43083d15-7273-40c1-b7db-39efd9ccc17a;Ip=[216.228.112.34];Helo=[mail.nvidia.com] X-MS-Exchange-CrossTenant-AuthSource: CO1NAM11FT042.eop-nam11.prod.protection.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: MW2PR12MB2425 Authentication-Results: imf05.hostedemail.com; dkim=pass header.d=Nvidia.com header.s=selector2 header.b=MO49TZfx; dmarc=pass (policy=none) header.from=nvidia.com; spf=none (imf05.hostedemail.com: domain of jhubbard@nvidia.com has no SPF policy when checking 40.107.220.71) smtp.mailfrom=jhubbard@nvidia.com X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: DF601E00011D X-Stat-Signature: ipshf9magxijj6ywfcj8hz3kkm7m4879 Received-SPF: none (nvidia.com>: No applicable sender policy available) receiver=imf05; identity=mailfrom; envelope-from=""; helo=NAM11-CO1-obe.outbound.protection.outlook.com; client-ip=40.107.220.71 X-HE-DKIM-Result: pass/pass X-HE-Tag: 1619998369-649168 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 5/2/21 4:28 PM, John Hubbard wrote: > On 4/8/21 10:01 AM, Logan Gunthorpe wrote: ... >> @@ -387,19 +388,37 @@ void dma_direct_unmap_sg(struct device *dev, struct scatterlist *sgl, > > This routine now deserves a little bit of commenting, now that it is > doing less obvious things. How about something like this: > > /* > * Unmaps pages, except for PCI_P2PDMA pages, which were never mapped in the > * first place. Instead of unmapping PCI_P2PDMA entries, simply remove the > * SG_PCI_P2PDMA mark > */ I got that kind of wrong. They *were* mapped, but need to be left mostly alone...maybe you can word it better. Here's my second draft: /* * Unmaps pages, except for PCI_P2PDMA pages, which should not be unmapped at * this point. Instead of unmapping PCI_P2PDMA entries, simply remove the * SG_PCI_P2PDMA mark. */ ...am I getting close? :) thanks, -- John Hubbard NVIDIA