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Tsirkin" , Miguel Ojeda , Robin Murphy , rust-for-linux@vger.kernel.org, Sagi Grimberg , Stefano Stabellini , Steven Rostedt , virtualization@lists.linux.dev, Will Deacon , xen-devel@lists.xenproject.org Subject: Re: [PATCH v4 00/16] dma-mapping: migrate to physical address-based API Message-ID: <20250908124526.GW616306@nvidia.com> References: <20250905174324.GI616306@nvidia.com> <20250907142509.GA507575@workstation.local> Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250907142509.GA507575@workstation.local> X-ClientProxiedBy: YT4PR01CA0305.CANPRD01.PROD.OUTLOOK.COM (2603:10b6:b01:10e::13) To PH7PR12MB5757.namprd12.prod.outlook.com (2603:10b6:510:1d0::13) Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: PH7PR12MB5757:EE_|BN7PPF915F74166:EE_ X-MS-Office365-Filtering-Correlation-Id: a297ed27-88a7-4d5b-a32b-08ddeed59743 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|376014|7416014|1800799024|366016|921020; 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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?VaRDYGzlyPZ446X9cUFcoyBn4ZNwDpZl+Wn1SszX+e8axirqjy+8nBXqF20N?= =?us-ascii?Q?9aKtqeEbs0Jq8B7NCS/khSfonEox/eWnFHb6kOf966QYkVg/ET8FoUvKKqBs?= =?us-ascii?Q?V3SUQYRMwHo9y8uXX3e/RdmPF/pmvKhvdm0Spa61mTHuGNXRojfrkkKuaOSU?= =?us-ascii?Q?h8XBNpQ8CHYvnI0fJHnJc2RyhrnvyE/7KZ1ah9zOSyDw2D6SqGFiMN5S454N?= =?us-ascii?Q?9CUDie0XpqHCbhArrhnYqWk5yEPecvZDL/ADhpHbKH+XYubEnKJZraeW4uor?= =?us-ascii?Q?8lEdL7JGpHDvrxXJ2JFAXFwbTCLSVPFx+xVqa1N1ByLX1AIjkCTQXU9th90X?= =?us-ascii?Q?Z2YrgDTc9Lq2tLjCMN6A6a08AckBGfEaFnPnABhrWuGD6Dx/DUECxnxL4Smm?= =?us-ascii?Q?j180nsWWH0EKFvhP/fwJuixzWKoj1gQL4jWDtJBormM/nSEDvS2OKF+4SVZ9?= =?us-ascii?Q?zxK2/RCBGAAdzl8uV0xrBNNFkpkRAnlez7v2PCxpTEzfAuollRpheC1xqfht?= =?us-ascii?Q?3HjN8M0xDa4a0wr8CW65uMdG1gwwRt9qrU5jnaWgT2n5gicGXcRSAdrRhx2a?= =?us-ascii?Q?/XmGx/189f0TGjStS02vZHAtQ3L5vtToX4bGwAKFAUq479985fhUESmNttMA?= =?us-ascii?Q?6Q2vmD6vLFaWZGjjpAY3kTV5LVzOtcFf7w16oM+Hddu70x29LoG42kbaNSGm?= =?us-ascii?Q?1lJm3SXmb2ykDFOcSeYoT/GONUv2ewDZqf7gh4rs8oA1HHXhs5UqzY2r3QJQ?= =?us-ascii?Q?/VOjHqme64F4KM8eT/nGkZeryj3tBQZ00Om5sH++YOs4GxP4TthE7mjG9o1/?= =?us-ascii?Q?+NREwv4TdTRck4CFdchOtToNAVaFsdjRNTXm6iC4oYgvGhvrKLBErUBPlCJI?= =?us-ascii?Q?wM6BKktsOqabF1AcVFQDveUBB2ClsKavMm1QNxk7j1UDVX6t0mZUvW8c0AWL?= =?us-ascii?Q?WLBJfWnMeOHkFjgkxv8t8rAbh6zXRa4kufED8fRgRu6RJ8Q0rg4V81zwsWQT?= =?us-ascii?Q?MwbMgIvsOD+RH4YMG85gaI87L8e4duL2bwy3WNN0OLmdqp33FDZ/e4D97/GJ?= =?us-ascii?Q?0CXch8MTyrNJvUgn3Ngw98JmGAOCsAAcutZbuaLFNbdfEBQVicuoUpHDnIyg?= =?us-ascii?Q?QGZFX8AolMrtqoIKanyrjxkT9NbIT+G0mDhu5k2puPxH+HKCAAqSUi7cmpiC?= =?us-ascii?Q?0yMmruH1U6FSi9mmYUfHUd5wY9LGYJGPiGtc2LQZx6wYSmVeVdp8bWT04woR?= =?us-ascii?Q?Y2RtqT6jhSLWiIxIAfZJE+xzPzLHyCBCRVL1/0s1ZJyqd54qkpczi5Ee4MhE?= =?us-ascii?Q?EhR+5d9FZQG6oAWosn95jIuApoA/2+iVxkRbpYQMoQJDUzegBmVqovtmhCbS?= =?us-ascii?Q?G9bErnrTylhfFf0su/qLKauImRiYfpG2bv15tp1wxP6EIrokn7NqJBrpF2fV?= =?us-ascii?Q?dsytqeOyByJ1NKoQ3EBtGBe2ts4yIFdPjYbAd7U5CCARf9OsQF01liBQECFV?= =?us-ascii?Q?lmxnQJL/+8WPn4LrX61pDLzje5ZofXzt0MPyPqqFj6keh/m1o8Rf/X29YzX7?= =?us-ascii?Q?pyTTDKVvBwcaN+fjkt4=3D?= X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-Network-Message-Id: a297ed27-88a7-4d5b-a32b-08ddeed59743 X-MS-Exchange-CrossTenant-AuthSource: PH7PR12MB5757.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 08 Sep 2025 12:45:29.4369 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: MpjeEYUBSzxhLqO+CFbT2nbSUFImadVFjjLPJK1baSpu1/pO2lfM5uOGwpCMQBKu X-MS-Exchange-Transport-CrossTenantHeadersStamped: BN7PPF915F74166 On Sun, Sep 07, 2025 at 11:25:09PM +0900, Takashi Sakamoto wrote: > Hi, > > I'm a present maintainer of Linux FireWire subsystem, and recent years > have been working to modernize the subsystem. > > On Fri, Sep 05, 2025 at 14:43:24PM -0300, Jason Gunthorpe wrote: > > There is only one user I found of alloc_pages: > > > > drivers/firewire/ohci.c: ctx->pages[i] = dma_alloc_pages(dev, PAGE_SIZE, &dma_addr, > > > > And it deliberately uses page->private: > > > > set_page_private(ctx->pages[i], dma_addr); > > > > So it is correct to use the struct page API. > > I've already realized it, and it is in my TODO list to use modern > alternative APIs to replace it (but not yet). If you know some > candidates for this purpose, it is really helpful to accomplish it. I think for now it is probably OKish, but in the medium/longer term this probably wants to have its own memdesc like other cases. Ie instead of using page->private you'd have a struct ohci_desc { unsigned long __page_flags; dma_addr_t dma_addr; [..] }; And instead of using page->private you'd use ohci_desc::dma_addr. This would require changing dma_alloc_pages() to be able to allocate the frozen memdescs.. Which we are not quite there yet, but maybe come back to this in 2026? Jason