From: Matthew Brost Date: Thu, 2 Jul 2026 21:48:15 +0000 (-0700) Subject: drm/ttm: Account for NULL and handle pages in ttm_pool_backup X-Git-Tag: v7.2-rc4~13^2~3^2~5 X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=5b7b3b6595ee77d01c7463757baed114786094dd;p=thirdparty%2Fkernel%2Flinux.git drm/ttm: Account for NULL and handle pages in ttm_pool_backup Pages in ttm_pool_backup can be NULL or backup handles (ttm_backup_page_ptr_is_handle()), neither of which can be passed to set_pages_array_wb() or freed. Add a dedicated WB pass before the dma/purge loop that walks allocations using the same i += num_pages stride, skipping NULL and handle entries, and calls set_pages_array_wb() once per contiguous run of real pages. Apply the same NULL/handle guard to the dma/purge loop. Fixes the following oops: Oops: general protection fault, kernel NULL pointer dereference 0x0: 0000 [#1] SMP NOPTI RIP: 0010:__cpa_process_fault+0xf8/0x770 RSP: 0018:ffffc90000a87718 EFLAGS: 00010287 RAX: 0000000000000000 RBX: ffffc90000a87868 RCX: 0000000000000000 RDX: 0000000000001000 RSI: 0005088000000000 RDI: ffffffff827c5f34 RBP: 0005088000000000 R08: ffffc90000a877cb R09: ffffc90000a877d0 R10: 0000000000000000 R11: 000000000000001b R12: 000ffffffffff000 R13: ffffc90000a87868 R14: ffffc90000a87868 R15: ffff88815b882ae0 FS: 0000000000000000(0000) GS:ffff8884ec840000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f930b844000 CR3: 000000000262e003 CR4: 0000000008f70ef0 PKRU: 55555554 Call Trace: __change_page_attr_set_clr+0x989/0xe90 ? __purge_vmap_area_lazy+0x6c/0x3a0 ? _vm_unmap_aliases+0x250/0x2a0 set_pages_array_wb+0x7f/0x120 ttm_pool_backup+0x4c9/0x5b0 [ttm] ? dma_resv_wait_timeout+0x3b/0xf0 ttm_tt_backup+0x32/0x60 [ttm] ttm_bo_shrink+0x66/0x110 [ttm] xe_bo_shrink_purge+0x12b/0x1b0 [xe] xe_bo_shrink+0xbb/0x270 [xe] __xe_shrinker_walk+0xf7/0x160 [xe] xe_shrinker_walk+0x9d/0xc0 [xe] xe_shrinker_scan+0x11f/0x210 [xe] do_shrink_slab+0x13b/0x270 shrink_slab+0xf1/0x400 shrink_node+0x352/0x8a0 balance_pgdat+0x32c/0x700 kswapd+0x205/0x2f0 ? __pfx_autoremove_wake_function+0x10/0x10 ? __pfx_kswapd+0x10/0x10 kthread+0xd1/0x110 ? __pfx_kthread+0x10/0x10 ret_from_fork+0x1b1/0x200 ? __pfx_kthread+0x10/0x10 ret_from_fork_asm+0x1a/0x30 Cc: Christian Koenig Cc: Huang Rui Cc: Matthew Auld Cc: Matthew Brost Cc: Maarten Lankhorst Cc: Maxime Ripard Cc: Thomas Zimmermann Cc: David Airlie Cc: Simona Vetter Cc: Thomas Hellström Cc: dri-devel@lists.freedesktop.org Cc: linux-kernel@vger.kernel.org Cc: stable@vger.kernel.org Fixes: b63d715b8090 ("drm/ttm/pool, drm/ttm/tt: Provide a helper to shrink pages") Cc: stable@vger.kernel.org Assisted-by: GitHub_Copilot:claude-opus-4.8 Signed-off-by: Matthew Brost Reviewed-by: Thomas Hellström Link: https://patch.msgid.link/20260702214815.4009271-1-matthew.brost@intel.com --- diff --git a/drivers/gpu/drm/ttm/ttm_pool.c b/drivers/gpu/drm/ttm/ttm_pool.c index 278bbe7a11add..46983e7de7a33 100644 --- a/drivers/gpu/drm/ttm/ttm_pool.c +++ b/drivers/gpu/drm/ttm/ttm_pool.c @@ -1051,9 +1051,31 @@ long ttm_pool_backup(struct ttm_pool *pool, struct ttm_tt *tt, return -EBUSY; #ifdef CONFIG_X86 - /* Anything returned to the system needs to be cached. */ - if (tt->caching != ttm_cached) - set_pages_array_wb(tt->pages, tt->num_pages); + /* Anything returned to the system needs to be cached. Walk allocations + * skipping NULL pages and issue set_pages_array_wb() per contiguous run. + */ + if (tt->caching != ttm_cached) { + pgoff_t run_start = 0, run_count = 0; + + for (i = 0; i < tt->num_pages; i += num_pages) { + page = tt->pages[i]; + if (unlikely(!page || ttm_backup_page_ptr_is_handle(page))) { + if (run_count) { + set_pages_array_wb(&tt->pages[run_start], + run_count); + run_count = 0; + } + num_pages = 1; + continue; + } + num_pages = 1UL << ttm_pool_page_order(pool, page); + if (!run_count) + run_start = i; + run_count += num_pages; + } + if (run_count) + set_pages_array_wb(&tt->pages[run_start], run_count); + } #endif if (tt->dma_address || flags->purge) { @@ -1061,7 +1083,7 @@ long ttm_pool_backup(struct ttm_pool *pool, struct ttm_tt *tt, unsigned int order; page = tt->pages[i]; - if (unlikely(!page)) { + if (unlikely(!page || ttm_backup_page_ptr_is_handle(page))) { num_pages = 1; continue; } @@ -1104,6 +1126,10 @@ long ttm_pool_backup(struct ttm_pool *pool, struct ttm_tt *tt, if (unlikely(!page)) continue; + /* Already-handled entry from a previous attempt. */ + if (unlikely(ttm_backup_page_ptr_is_handle(page))) + continue; + ttm_pool_split_for_swap(pool, page); shandle = ttm_backup_backup_page(backup, page, flags->writeback, i,