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=?utf-8?B?TlhPbC9RbFhaK0M3eFFnaU1LNERvbDlGck5QSmZXam1tM3VnNTB1UT09?= X-Exchange-RoutingPolicyChecked: N3ZEiL8QnTAp7s6ze7LFueD4i7l0v+6HQiqn10zt8uI0mQ1APwbhjx5eTS+XSFy7+nwvyQ6XLvU3aPh3TV+2TICKqN+yug0Jiuz5cSktCNNH0ZlejaALm91/16wh4M8LnPtNZDhJkpS/7IehwTWqOpbdfTCFOHjkwQoaU4XA8ipRweH+r8YBICDnn7Jz+dk3H8nlRxnlh8rsCT7dPbCc6MXNetguey6TBhjx+1y0YkRIwb94nPMYl4vn6IlfBiph7FXjdw387PDhcyd/H1Yf3/CUqYPcjy2RuP3c17GNqjwn9zZSTYpqbuvNsTs9H1TkhE5/YoeO2g9PdXbqk2SnDg== X-MS-Exchange-CrossTenant-Network-Message-Id: ded61410-cb88-4ecf-8b89-08de9f71fadd X-MS-Exchange-CrossTenant-AuthSource: DM4PR11MB6527.namprd11.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 21 Apr 2026 06:48:22.3975 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 46c98d88-e344-4ed4-8496-4ed7712e255d X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: nu1IU72um9ty3yi4NVzkWu5v2aGPFGkj9EDwAVEPgKRPGpDIjCYnTzBAZNhTFTjyUKabxDDg+s4NQc92uS6yJg== X-MS-Exchange-Transport-CrossTenantHeadersStamped: IA3PR11MB9207 X-OriginatorOrg: intel.com X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" On Tue, Apr 21, 2026 at 08:19:54AM +0200, Christian König wrote: > On 4/21/26 07:08, Matthew Brost wrote: > > On Mon, Apr 20, 2026 at 08:07:38PM +0200, Christian König wrote: > >> On 4/20/26 18:06, Matthew Brost wrote: > >>> On Mon, Apr 20, 2026 at 05:37:43PM +0200, Christian König wrote: > >>>> On 4/20/26 15:30, Huang, Honglei1 wrote: > >>>>> On 4/20/2026 8:15 PM, Christian König wrote: > ... > >> Either you set the information per-device and then each device only gets the information if it needs to migrate the page to it's own local memory or you have global information. > >> > >> So why does a device fd needs to know about remote pgmap? > >> > > > > Simplest example: > > > > Devices A and B. The user sets the preferred placement to Device A. > > Device B faults first, and Device B moves memory to Device A via remote > > pull and can access locally via P2P, scale-up, etc. Avoid a double > > bounce once Device A faults. > > So you basically tell the device as soon as you want to access this VA please push the underlying memory away to a different device? > Yes. GPU SVM supports remote pulls. > I didn't thought that would be a valid use case. As far as I can see the only thing you avoid is updating your page tables on the faulting device twice. > TBH, I’m unsure if this will happen in practice, but it also seems entirely possible. Computers are asynchronous, have random thread stalls, etc., so out-of-order from expected access isn’t far-fetched. No on 'updating your page tables twice' being only bad thing. In my example, let’s say Device B moves memory to itself initially. Then Device A faults and tries to move the memory to itself. Bad things: - Two copies (one from sys->Device B, then Device B -> A) - Device B faults again after move to Device A - this stalls B's execution pipeline Matt > Thanks for the explanation, that was absolutely not obvious. Going to discuss that with the team on the next meeting. > > Christian. > > > > > Matt