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Tue, 25 Nov 2025 04:37:00 -0800 Date: Tue, 25 Nov 2025 14:36:59 +0200 From: Zhi Wang To: Christian =?UTF-8?B?S8O2bmln?= CC: John Hubbard , Dave Airlie , "Joel Fernandes" , , "Maarten Lankhorst" , Maxime Ripard , Thomas Zimmermann , "Simona Vetter" , Jonathan Corbet , Alex Deucher , Jani Nikula , Joonas Lahtinen , Rodrigo Vivi , Tvrtko Ursulin , Huang Rui , Matthew Auld , Matthew Brost , Lucas De Marchi , Thomas =?UTF-8?B?SGVsbHN0csO2bQ==?= , Helge Deller , Danilo Krummrich , Alice Ryhl , Miguel Ojeda , Alex Gaynor , Boqun Feng , Gary Guo , =?UTF-8?B?QmrDtnJu?= Roy Baron , Benno Lossin , "Andreas Hindborg" , Trevor Gross , "Alistair Popple" , Timur Tabi , Edwin Peer , Alexandre Courbot , , , , , , , , Subject: Re: [PATCH] gpu: Move DRM buddy allocator one level up Message-ID: <20251125143339.361cc3bb.zhiw@nvidia.com> In-Reply-To: <9f433dee-7ad9-4d0f-8ac1-e67deb409b70@amd.com> References: <20251124234432.1988476-1-joelagnelf@nvidia.com> <24d4f02b-8ecd-4512-a1f0-ba41684ede1d@amd.com> <9f433dee-7ad9-4d0f-8ac1-e67deb409b70@amd.com> Organization: NVIDIA X-Mailer: Claws Mail 4.3.1 (GTK 3.24.33; 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X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 25 Nov 2025 12:37:25.6225 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 578f5653-2621-4fa1-b357-08de2c1f6379 X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=43083d15-7273-40c1-b7db-39efd9ccc17a;Ip=[216.228.117.160];Helo=[mail.nvidia.com] X-MS-Exchange-CrossTenant-AuthSource: BN1PEPF00006003.namprd05.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: LV3PR12MB9329 On Tue, 25 Nov 2025 09:10:54 +0100 Christian K=C3=B6nig wrote: > On 11/25/25 08:59, John Hubbard wrote: > > On 11/24/25 11:54 PM, Christian K=C3=B6nig wrote: > >> On 11/25/25 08:49, Dave Airlie wrote: > >>> On Tue, 25 Nov 2025 at 17:45, Christian K=C3=B6nig > >>> wrote: > > ... > >> My question is why exactly is nova separated into nova-core and > >> nova-drm? That doesn't seem to be necessary in the first place. > >> > > The idea is that nova-core allows building up a separate software > > stack for VFIO, without pulling in any DRM-specific code that a > > hypervisor (for example) wouldn't need. That makes for a smaller, > > more security-auditable set of code for that case. >=20 > Well that is the same argument used by some AMD team to maintain a > separate out of tree hypervisor for nearly a decade. >=20 I guess you mean the VFIO driver? [1] In the code, it is bascially to support the migration, which is simiar as any other in-tree VFIO drivers. The questionable parts might be how to clean up those callbacks supporting migration and get them into mainline. Those callbacks stays in the PF driver, either talks to HW or firmware interface to control VF states, obtain the bitstream, which contains VF states and data. IMO, they should be quite self-contained and userspace shouldn't be invovled. Userspace (QEMU) only talks to VFIO. This is just my initial impression from briefly looking at the code. :) [1] https://github.com/amd/MxGPU-Virtualization/blob/staging/amd-vfio-pci/amd-v= fio.c > Additional to that the same argument has also been used to justify > the KFD node as alternative API to DRM for compute. >=20 > Both cases have proven to be extremely bad ideas. >=20 > Background is that except for all the legacy stuff the DRM API is > actually very well thought through and it is actually quite hard to > come up with something similarly well. >=20 > Regards, > Christian.=20 >=20 > >=20 > > thanks, >=20 >=20