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From: Felix Kuehling <felix.kuehling@amd.com>
To: Andrey Grodzovsky <andrey.grodzovsky@amd.com>,
	Daniel Vetter <daniel@ffwll.ch>
Cc: ckoenig.leichtzumerken@gmail.com, gregkh@linuxfoundation.org,
	daniel.vetter@ffwll.ch, amd-gfx@lists.freedesktop.org,
	helgaas@kernel.org, dri-devel@lists.freedesktop.org,
	linux-pci@vger.kernel.org, Alexander.Deucher@amd.com
Subject: Re: [PATCH v5 20/27] drm: Scope all DRM IOCTLs with drm_dev_enter/exit
Date: Thu, 29 Apr 2021 12:15:45 -0400	[thread overview]
Message-ID: <e760ada9-b4a7-c6ab-18f7-0bcc1b5442c2@amd.com> (raw)
In-Reply-To: <95935e46-408b-4fee-a7b4-691e9db4f455@amd.com>

Am 2021-04-29 um 12:04 p.m. schrieb Andrey Grodzovsky:
> So as I understand your preferred approach is that I scope any
> back_end, HW specific function with drm_dev_enter/exit because that
> where MMIO
> access takes place. But besides explicit MMIO access thorough
> register accessors in the HW back-end there is also indirect MMIO access
> taking place throughout the code in the driver because of various VRAM
> BOs which provide CPU access to VRAM through the VRAM BAR. This kind of
> access is spread all over in the driver and even in mid-layers such as
> TTM and not limited to HW back-end functions. It means it's much harder
> to spot such places to surgically scope them with drm_dev_enter/exit and
> also that any new such code introduced will immediately break hot unplug
> because the developers can't be expected to remember making their code
> robust to this specific use case. That why when we discussed internally
> what approach to take to protecting code with drm_dev_enter/exit we
> opted for using the widest available scope.

VRAM can also be mapped in user mode. Is there anything preventing user
mode from accessing the memory after unplug? I guess the best you could
do is unmap it from the CPU page table and let the application segfault
on the next access. Or replace the mapping with a dummy page in system
memory?

Regards,
  Felix


>
> Andrey 
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  reply	other threads:[~2021-04-29 16:15 UTC|newest]

Thread overview: 82+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-04-28 15:11 [PATCH v5 00/27] RFC Support hot device unplug in amdgpu Andrey Grodzovsky
2021-04-28 15:11 ` [PATCH v5 01/27] drm/ttm: Remap all page faults to per process dummy page Andrey Grodzovsky
2021-04-28 15:11 ` [PATCH v5 02/27] drm/ttm: Expose ttm_tt_unpopulate for driver use Andrey Grodzovsky
2021-04-28 15:11 ` [PATCH v5 03/27] drm/amdgpu: Split amdgpu_device_fini into early and late Andrey Grodzovsky
2021-04-29  7:04   ` Christian König
2021-04-30  3:10     ` Alex Deucher
2021-04-30  5:19   ` Lazar, Lijo
2021-04-30  5:39     ` Andrey Grodzovsky
2021-04-30  5:49       ` Lazar, Lijo
2021-04-28 15:11 ` [PATCH v5 04/27] drm/amdkfd: Split kfd suspend from devie exit Andrey Grodzovsky
2021-04-28 15:11 ` [PATCH v5 05/27] drm/amdgpu: Add early fini callback Andrey Grodzovsky
2021-04-28 15:11 ` [PATCH v5 06/27] drm/amdgpu: Handle IOMMU enabled case Andrey Grodzovsky
2021-04-29  7:08   ` Christian König
2021-05-03 20:43     ` Andrey Grodzovsky
2021-05-04  7:03       ` Christian König
2021-05-04 15:43         ` Andrey Grodzovsky
2021-05-05 14:51           ` Andrey Grodzovsky
2021-04-30  3:13   ` Alex Deucher
2021-05-03 18:00     ` Andrey Grodzovsky
2021-05-04 17:05   ` Felix Kuehling
2021-05-05 14:05     ` Andrey Grodzovsky
2021-04-28 15:11 ` [PATCH v5 07/27] drm/amdgpu: Remap all page faults to per process dummy page Andrey Grodzovsky
2021-04-29  7:09   ` Christian König
2021-04-28 15:11 ` [PATCH v5 08/27] PCI: add support for dev_groups to struct pci_device_driver Andrey Grodzovsky
2021-04-28 16:53   ` Bjorn Helgaas
2021-04-29 16:53     ` Andrey Grodzovsky
2021-04-29 19:23       ` Bjorn Helgaas
2021-04-29 20:36         ` Andrey Grodzovsky
2021-04-28 15:11 ` [PATCH v5 09/27] dmr/amdgpu: Move some sysfs attrs creation to default_attr Andrey Grodzovsky
2021-04-28 17:23   ` Bjorn Helgaas
2021-04-29  7:11   ` Christian König
2021-04-28 15:11 ` [PATCH v5 10/27] drm/amdgpu: Guard against write accesses after device removal Andrey Grodzovsky
2021-04-29  7:14   ` Christian König
2021-04-28 15:11 ` [PATCH v5 11/27] drm/sched: Make timeout timer rearm conditional Andrey Grodzovsky
2021-04-28 15:11 ` [PATCH v5 12/27] drm/amdgpu: Prevent any job recoveries after device is unplugged Andrey Grodzovsky
2021-04-28 15:11 ` [PATCH v5 13/27] drm/amdgpu: When filizing the fence driver. stop scheduler first Andrey Grodzovsky
2021-04-29  7:15   ` Christian König
2021-04-29 17:12     ` Andrey Grodzovsky
2021-04-28 15:11 ` [PATCH v5 14/27] drm/amdgpu: Fix hang on device removal Andrey Grodzovsky
2021-04-28 15:11 ` [PATCH v5 15/27] drm/scheduler: Fix hang when sched_entity released Andrey Grodzovsky
2021-04-29  7:18   ` Christian König
2021-04-29 17:06     ` Andrey Grodzovsky
2021-04-30  6:47       ` Christian König
2021-04-30 16:10         ` Andrey Grodzovsky
2021-05-05 13:57           ` Andrey Grodzovsky
2021-05-07 16:29           ` Daniel Vetter
2021-05-07 16:32             ` Andrey Grodzovsky
2021-04-28 15:11 ` [PATCH v5 16/27] drm/amdgpu: Unmap all MMIO mappings Andrey Grodzovsky
2021-04-29  7:19   ` Christian König
2021-04-29 16:55     ` Andrey Grodzovsky
2021-04-28 15:11 ` [PATCH v5 17/27] drm/amdgpu: Add rw_sem to pushing job into sched queue Andrey Grodzovsky
2021-04-28 15:11 ` [PATCH v5 18/27] drm/sched: Expose drm_sched_entity_kill_jobs Andrey Grodzovsky
2021-04-28 15:11 ` [PATCH v5 19/27] drm/amdgpu: Finilise device fences on device remove Andrey Grodzovsky
2021-04-28 15:20   ` Andrey Grodzovsky
2021-04-28 15:12 ` [PATCH v5 20/27] drm: Scope all DRM IOCTLs with drm_dev_enter/exit Andrey Grodzovsky
2021-04-29 11:23   ` Daniel Vetter
2021-04-29 11:32     ` Daniel Vetter
2021-04-29 16:04       ` Andrey Grodzovsky
2021-04-29 16:15         ` Felix Kuehling [this message]
2021-04-29 16:21           ` Andrey Grodzovsky
2021-04-29 16:29             ` Felix Kuehling
2021-04-29 16:33               ` Andrey Grodzovsky
2021-04-29 19:05         ` Daniel Vetter
2021-04-29 20:34           ` Andrey Grodzovsky
2021-04-30 10:25             ` Daniel Vetter
2021-04-30 17:27               ` Andrey Grodzovsky
2021-05-05 13:57                 ` Andrey Grodzovsky
2021-05-06  9:40                 ` Daniel Vetter
2021-05-06 16:25                   ` Andrey Grodzovsky
2021-05-07  9:11                     ` Daniel Vetter
2021-05-07 15:39                       ` Andrey Grodzovsky
2021-05-07 16:24                         ` Daniel Vetter
2021-05-07 18:00                           ` Andrey Grodzovsky
2021-05-10 15:46                             ` Daniel Vetter
2021-04-28 15:12 ` [PATCH v5 21/27] drm/amdgpu: Add support for hot-unplug feature at DRM level Andrey Grodzovsky
2021-04-28 15:12 ` [PATCH v5 22/27] drm/amd/display: Scope all DM queued work with drm_dev_enter/exit Andrey Grodzovsky
2021-04-28 15:12 ` [PATCH v5 23/27] drm/amd/powerplay: Scope all PM " Andrey Grodzovsky
2021-04-28 15:12 ` [PATCH v5 24/27] drm/amdkfd: Scope all KFD " Andrey Grodzovsky
2021-04-28 15:12 ` [PATCH v5 25/27] drm/amdgpu: Scope all amdgpu " Andrey Grodzovsky
2021-04-28 15:12 ` [PATCH v5 26/27] drm/amd/display: Remove superflous drm_mode_config_cleanup Andrey Grodzovsky
2021-04-28 15:12 ` [PATCH v5 27/27] drm/amdgpu: Verify DMA opearations from device are done Andrey Grodzovsky
2021-04-28 17:07 ` [PATCH v5 00/27] RFC Support hot device unplug in amdgpu Bjorn Helgaas

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