On Thursday 10 June 2021 08:43:06 Christian König wrote: > > Am 09.06.21 um 22:00 schrieb Ondrej Zary: > > On Wednesday 09 June 2021 11:21:05 Christian König wrote: > >> Am 09.06.21 um 09:10 schrieb Ondrej Zary: > >>> On Wednesday 09 June 2021, Christian König wrote: > >>>> Am 09.06.21 um 08:57 schrieb Ondrej Zary: > >>>>> [SNIP] > >>>>>> Thanks for the heads up. So the problem with my patch is already fixed, > >>>>>> isn't it? > >>>>> The NULL pointer dereference in nouveau_bo_wr16 introduced in > >>>>> 141b15e59175aa174ca1f7596188bd15a7ca17ba was fixed by > >>>>> aea656b0d05ec5b8ed5beb2f94c4dd42ea834e9d. > >>>>> > >>>>> That's the bug I hit when bisecting the original problem: > >>>>> NULL pointer dereference in nouveau_bo_sync_for_device > >>>>> It's caused by: > >>>>> # first bad commit: [e34b8feeaa4b65725b25f49c9b08a0f8707e8e86] drm/ttm: merge ttm_dma_tt back into ttm_tt > >>>> Good that I've asked :) > >>>> > >>>> Ok that's a bit strange. e34b8feeaa4b65725b25f49c9b08a0f8707e8e86 was > >>>> created mostly automated. > >>>> > >>>> Do you have the original backtrace of that NULL pointer deref once more? > >>> The original backtrace is here: https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Flkml.org%2Flkml%2F2021%2F6%2F5%2F350&data=04%7C01%7Cchristian.koenig%40amd.com%7C4309ff021d5e4cbe948b08d92b813106%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C637588657045383056%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000&sdata=t70c9ktzPJzDaEAcO4wpQMv3TUo5b53cUy66AkLeVwE%3D&reserved=0 > >> And the problem is that ttm_dma->dma_address is NULL, right? Mhm, I > >> don't see how that can happen since nouveau is using ttm_sg_tt_init(). > >> > >> Apart from that what nouveau does here is rather questionable since you > >> need a coherent architecture for most things anyway, but that's not what > >> we are trying to fix here. > >> > >> Can you try to narrow down if ttm_sg_tt_init is called before calling > >> this function for the tt object in question? > > ttm_sg_tt_init is not called: > > [ 12.150124] nouveau 0000:01:00.0: DRM: VRAM: 31 MiB > > [ 12.150133] nouveau 0000:01:00.0: DRM: GART: 128 MiB > > [ 12.150143] nouveau 0000:01:00.0: DRM: BMP version 5.6 > > [ 12.150151] nouveau 0000:01:00.0: DRM: No DCB data found in VBIOS > > [ 12.151362] ttm_tt_init > > [ 12.151370] ttm_tt_init_fields > > [ 12.151374] ttm_tt_alloc_page_directory > > [ 12.151615] BUG: kernel NULL pointer dereference, address: 00000000 > > Please add dump_stack(); to ttm_tt_init() and report back with the > backtrace. > > I can't see how this is called from the nouveau code, only possibility I > see is that it is maybe called through the AGP code somehow. Yes, you're right: [ 13.192663] Call Trace: [ 13.192678] dump_stack+0x54/0x68 [ 13.192690] ttm_tt_init+0x11/0x8a [ttm] [ 13.192699] ttm_agp_tt_create+0x39/0x51 [ttm] [ 13.192840] nouveau_ttm_tt_create+0x17/0x22 [nouveau] [ 13.192856] ttm_tt_create+0x78/0x8c [ttm] [ 13.192864] ttm_bo_handle_move_mem+0x7d/0xca [ttm] [ 13.192873] ttm_bo_validate+0x92/0xc8 [ttm] [ 13.192883] ttm_bo_init_reserved+0x216/0x243 [ttm] [ 13.192892] ttm_bo_init+0x45/0x65 [ttm] [ 13.193018] ? nouveau_bo_del_io_reserve_lru+0x48/0x48 [nouveau] [ 13.193150] nouveau_bo_init+0x8c/0x94 [nouveau] [ 13.193273] ? nouveau_bo_del_io_reserve_lru+0x48/0x48 [nouveau] [ 13.193407] nouveau_bo_new+0x44/0x57 [nouveau] [ 13.193537] nouveau_channel_prep+0xa3/0x269 [nouveau] [ 13.193665] nouveau_channel_new+0x3c/0x5f7 [nouveau] [ 13.193679] ? slab_free_freelist_hook+0x3b/0xa7 [ 13.193686] ? kfree+0x9e/0x11a [ 13.193781] ? nvif_object_sclass_put+0xd/0x16 [nouveau] [ 13.193908] nouveau_drm_device_init+0x2e2/0x646 [nouveau] [ 13.193924] ? pci_enable_device_flags+0x1e/0xac [ 13.194052] nouveau_drm_probe+0xeb/0x188 [nouveau] [ 13.194182] ? nouveau_drm_device_init+0x646/0x646 [nouveau] [ 13.194195] pci_device_probe+0x89/0xe9 [ 13.194205] really_probe+0x127/0x2a7 [ 13.194212] driver_probe_device+0x5b/0x87 [ 13.194219] device_driver_attach+0x2e/0x41 [ 13.194226] __driver_attach+0x7c/0x83 [ 13.194232] bus_for_each_dev+0x4c/0x66 [ 13.194238] driver_attach+0x14/0x16 [ 13.194244] ? device_driver_attach+0x41/0x41 [ 13.194251] bus_add_driver+0xc5/0x16c [ 13.194258] driver_register+0x87/0xb9 [ 13.194265] __pci_register_driver+0x38/0x3b [ 13.194271] ? 0xf0c0d000 [ 13.194362] nouveau_drm_init+0x14c/0x1000 [nouveau] How is ttm_dma_tt->dma_address allocated? I cannot find any assignment executed (in the working code): $ git grep dma_address\ = drivers/gpu/ drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c: sg->sgl->dma_address = addr; drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c: dma_address = &dma->dma_address[offset >> PAGE_SHIFT]; drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c: dma_address = (mm_node->start << PAGE_SHIFT) + offset; drivers/gpu/drm/i915/gvt/scheduler.c: sg->dma_address = addr; drivers/gpu/drm/i915/i915_gpu_error.c: sg->dma_address = it; drivers/gpu/drm/ttm/ttm_tt.c: ttm->dma_address = (void *) (ttm->ttm.pages + ttm->ttm.num_pages); drivers/gpu/drm/ttm/ttm_tt.c: ttm->dma_address = kvmalloc_array(ttm->ttm.num_pages, drivers/gpu/drm/ttm/ttm_tt.c: ttm_dma->dma_address = NULL; drivers/gpu/drm/vmwgfx/vmwgfx_ttm_buffer.c: viter->dma_address = &__vmw_piter_phys_addr; drivers/gpu/drm/vmwgfx/vmwgfx_ttm_buffer.c: viter->dma_address = &__vmw_piter_dma_addr; drivers/gpu/drm/vmwgfx/vmwgfx_ttm_buffer.c: viter->dma_address = &__vmw_piter_sg_addr; The 2 cases in ttm_tt.c are in ttm_dma_tt_alloc_page_directory() and ttm_sg_tt_alloc_page_directory(). Confirmed by adding printk()s that they're NOT called. -- Ondrej Zary
