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See http://www.infradead.org/rpr.html X-Rspam-User: X-Rspamd-Queue-Id: 7AC10120009 X-Rspamd-Server: rspam06 X-Stat-Signature: noequet9qjfinqsfrm3f1obef7efz1an X-HE-Tag: 1753081153-830267 X-HE-Meta: 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 SZR0LoHz Xx10p4PmRxKiA3FLdqPP/B1ZZSe1iZXa0sCx6wx1EcW5fJP6k15+WrV4iacyOouTlxfNHoThLUtjLJc7fFpME1FODDQg8YwhZvNvMcFDlsk16L+XlIw/t/Rjg62EW580b37vWPtqWipQaYH7vOz3csgmXfvxgr28nJPHjWho//Hj69LSGmYD7Q7EFkXIzia59Vd4adey4sDl1x7Uq26yqcWfKzxikxPgHNSzlMWPS5lfGbl6t9Thv2wnb1jn58ksv/wO7loCjr2tAARcSvYmEelYYbuNdTUoxL5zeaaJMSRCXqrSQ3pPD+82LxT/CeVW65MOvd5LhHSWlnyKPn27e/zZmsbErAKOaL2KTKG68OuDvp1d23A+cwiZctLom5LINYajZdke5pXZpiT85dw2yKiYr58f+TM5y2hraIqZ3hnzIJHRE+QNhNj6heanMFXZWis6X93bUjXGPHWA= 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: On Fri, Jul 18, 2025 at 02:51:08PM +0300, Yonatan Maman wrote: > From: Yonatan Maman > > hmm_range_fault() by default triggered a page fault on device private > when HMM_PFN_REQ_FAULT flag was set. pages, migrating them to RAM. In some > cases, such as with RDMA devices, the migration overhead between the > device (e.g., GPU) and the CPU, and vice-versa, significantly degrades > performance. Thus, enabling Peer-to-Peer (P2P) DMA access for device > private page might be crucial for minimizing data transfer overhead. You don't enable DMA for device private pages. You allow discovering a DMAable alias for device private pages. Also absolutely nothing GPU specific here. > + /* > + * Don't fault in device private pages owned by the caller, > + * just report the PFN. > + */ > + if (pgmap->owner == range->dev_private_owner) { > + *hmm_pfn = swp_offset_pfn(entry); > + goto found; This is dangerous because it mixes actual DMAable alias PFNs with the device private fake PFNs. Maybe your hardware / driver can handle it, but just leaking this out is not a good idea. > + hmm_handle_device_private(range, pfn_req_flags, entry, hmm_pfn)) Overly long line here.