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Message-ID: <9792c6c3-a2b8-4b2b-b5ba-fba19b153e21@suse.de>
Date: Wed, 13 Aug 2025 11:25:13 +0200
From: Thomas Zimmermann <tzimmermann@...e.de>
To: Shixiong Ou <oushixiong1025@....com>,
Christian König <christian.koenig@....com>
Cc: Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
Maxime Ripard <mripard@...nel.org>, David Airlie <airlied@...il.com>,
Simona Vetter <simona@...ll.ch>, Sean Paul <sean@...rly.run>,
Jocelyn Falempe <jfalempe@...hat.com>, dri-devel@...ts.freedesktop.org,
linux-kernel@...r.kernel.org, Shixiong Ou <oushixiong@...inos.cn>
Subject: Re: [PATCH v5 RESEND 1/3] drm/shmem-helper: Import dmabuf without
mapping its sg_table
Hi
Am 14.07.25 um 12:16 schrieb Shixiong Ou:
>
>
> 在 2025/7/11 22:16, Thomas Zimmermann 写道:
>> Hi
>>
>> this patch regresses buffer sharing between udl and amdgpu. The
>> latter uses TTM. When udl imports a dma_buf from amdgpu, vmap returns
>> a kernel address, but pagefaults on the buffer cannot be handled. A
>> full error message is attached. It fails right at [1], where udl read
>> the first pixel from the buffer. That pixel address is the vmap'ed
>> buffer.
>>
>> [1]
>> https://elixir.bootlin.com/linux/v6.15.5/source/drivers/gpu/drm/udl/udl_transfer.c#L109
>>
>> Buffer sharing works with SHMEM-based drivers, which have their
>> buffers in system memory though. I assume that amdgpu's buffer is
>> located in I/O memory or scanout.
>>
>> Best regards
>> Thomas
>>
>
> Hi,
> I haven't been able to reproduce this issue yet.
> Did the driver not pin the buffer into GTT?
>
Any updates here? If we cannot fix the problem, we have to revert the
sg_table change.
Best regards
Thomas
>
> Best regards,
> Shixiong
>
>
>>
>> [ 168.785445] BUG: unable to handle page fault for address:
>> ffffc9012b800000
>> [ 168.792311] #PF: supervisor read access in kernel mode
>> [ 168.797452] #PF: error_code(0x0000) - not-present page
>> [ 168.802586] PGD 100000067 P4D 100000067 PUD 0
>> [ 168.807042] Oops: Oops: 0000 [#1] SMP KASAN PTI
>> [ 168.811573] CPU: 2 UID: 1000 PID: 2380 Comm: KMS thread Tainted:
>> G E 6.16.0-rc5-1-default+ #4080 PREEMPT(voluntary)
>> [ 168.823537] Tainted: [E]=UNSIGNED_MODULE
>> [ 168.827458] Hardware name: System manufacturer System Product
>> Name/Z170-A, BIOS 3802 03/15/2018
>> [ 168.836125] RIP: 0010:udl_compress_hline16+0x219/0x940 [udl]
>> [ 168.841779] Code: 0f b6 34 28 4c 89 d8 49 d3 e5 83 e0 07 4d 01 dd
>> 83 f9 01 0f 84 4a 03 00 00 83 c0 03 40 38 f0 7c 09 40 84 f6 0f 85 82
>> 05 00 00 <41> 8b 03 4c 63 7c 24 78 4c 89 5c 24 08 89 c6 41 89 c4 c1
>> e8 08
>> c1
>> [ 168.860476] RSP: 0018:ffff88811c7e75c0 EFLAGS: 00010246
>> [ 168.865697] RAX: 0000000000000003 RBX: 0000000000000000 RCX:
>> 0000000000000002
>> [ 168.872815] RDX: 0000000000000000 RSI: 0000000000000000 RDI:
>> 0000000000000100
>> [ 168.879934] RBP: dffffc0000000000 R08: ffff8881082efe00 R09:
>> ffff8881082e0000
>> [ 168.887046] R10: 0000000000000002 R11: ffffc9012b800000 R12:
>> ffff88811c7e76f8
>> [ 168.894155] R13: ffffc9012b800400 R14: ffff8881082e0007 R15:
>> 0000000000000000
>> [ 168.901266] FS: 00007f4685f3b6c0(0000) GS:ffff88846c690000(0000)
>> knlGS:0000000000000000
>> [ 168.909330] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>> [ 168.915058] CR2: ffffc9012b800000 CR3: 0000000117944004 CR4:
>> 00000000003706f0
>> [ 168.922170] Call Trace:
>> [ 168.924616] <TASK>
>> [ 168.926714] ? validate_chain+0x24e/0x5e0
>> [ 168.930718] ? __lock_acquire+0x568/0xae0
>> [ 168.934725] udl_render_hline+0x165/0x33b [udl]
>> [ 168.939256] ? __pfx_udl_render_hline+0x10/0x10 [udl]
>> [ 168.944297] ? local_clock_noinstr+0xb/0x100
>> [ 168.948557] ? __lock_release.isra.0+0x16c/0x2e0
>> [ 168.953162] ? mark_held_locks+0x40/0x70
>> [ 168.957077] ? lockdep_hardirqs_on_prepare.part.0+0x92/0x170
>> [ 168.962721] udl_primary_plane_helper_atomic_update+0x432/0x670 [udl]
>> [ 168.969145] ?
>> __pfx_udl_primary_plane_helper_atomic_update+0x10/0x10 [udl]
>> [ 168.976089] ? __pfx___drm_dev_dbg+0x10/0x10
>> [ 168.980357] ?
>> drm_atomic_helper_calc_timestamping_constants+0x141/0x200
>> [ 168.987044] ? drm_atomic_helper_commit_planes+0x3b6/0x1030
>> [ 168.992599] drm_atomic_helper_commit_planes+0x3b6/0x1030
>> [ 168.997987] drm_atomic_helper_commit_tail+0x41/0xb0
>> [ 169.002943] commit_tail+0x204/0x330
>> [ 169.006513] drm_atomic_helper_commit+0x242/0x2e0
>> [ 169.011203] ? __pfx_drm_atomic_helper_commit+0x10/0x10
>> [ 169.016413] drm_atomic_commit+0x1e1/0x290
>> [ 169.020500] ? prepare_signaling+0x355/0xda0
>> [ 169.024769] ? __pfx_drm_atomic_commit+0x10/0x10
>> [ 169.029372] ? __pfx___drm_printfn_info+0x10/0x10
>> [ 169.034069] drm_mode_atomic_ioctl+0x8ff/0xe40
>> [ 169.038510] ? __pfx_drm_mode_atomic_ioctl+0x10/0x10
>> [ 169.043466] ? find_held_lock+0x2b/0x80
>> [ 169.047295] ? __lock_acquire+0x568/0xae0
>> [ 169.051293] ? mark_usage+0x65/0x180
>> [ 169.054870] ? __pfx_drm_mode_atomic_ioctl+0x10/0x10
>> [ 169.059823] ? do_raw_spin_unlock+0x55/0x230
>> [ 169.064081] ? drm_is_current_master+0x26/0x30
>> [ 169.068517] ? __pfx_drm_mode_atomic_ioctl+0x10/0x10
>> [ 169.073465] drm_ioctl_kernel+0x141/0x2b0
>> [ 169.077468] ? __pfx_drm_ioctl_kernel+0x10/0x10
>> [ 169.081987] ? lock_release.part.0+0x47/0x90
>> [ 169.086249] drm_ioctl+0x481/0xb50
>> [ 169.089653] ? __pfx_drm_mode_atomic_ioctl+0x10/0x10
>> [ 169.094610] ? __pfx_drm_ioctl+0x10/0x10
>> [ 169.098525] ? find_held_lock+0x2b/0x80
>> [ 169.102356] ? lock_release.part.0+0x47/0x90
>> [ 169.106621] ? __fget_files+0x1aa/0x2f0
>> [ 169.110450] ? __fget_files+0x1b4/0x2f0
>> [ 169.114281] __x64_sys_ioctl+0x135/0x1c0
>> [ 169.118201] do_syscall_64+0x68/0x2a0
>> [ 169.121856] entry_SYSCALL_64_after_hwframe+0x76/0x7e
>> [ 169.126892] RIP: 0033:0x7f469391a53f
>> [ 169.130460] Code: 00 48 89 44 24 18 31 c0 48 8d 44 24 60 c7 04 24
>> 10 00 00 00 48 89 44 24 08 48 8d 44 24 20 48 89 44 24 10 b8 10 00 00
>> 00 0f 05 <89> c2 3d 00 f0 ff ff 77 18 48 8b 44 24 18 64 48 2b 04 25
>> 28 00
>> 00
>> [ 169.149151] RSP: 002b:00007f4685f39a80 EFLAGS: 00000246 ORIG_RAX:
>> 0000000000000010
>> [ 169.156703] RAX: ffffffffffffffda RBX: 00007f465c002da0 RCX:
>> 00007f469391a53f
>> [ 169.163868] RDX: 00007f4685f39b20 RSI: 00000000c03864bc RDI:
>> 0000000000000010
>> [ 169.171029] RBP: 00007f4685f39b20 R08: 0000000000001310 R09:
>> 00007f465c044cf0
>> [ 169.178194] R10: 0000000000000002 R11: 0000000000000246 R12:
>> 00000000c03864bc
>> [ 169.185358] R13: 0000000000000010 R14: 00007f465c0284b0 R15:
>> 00007f45d402b110
>> [ 169.192525] </TASK>
>> [ 169.194732] Modules linked in: udl(E) snd_seq_dummy(E)
>> snd_hrtimer(E) snd_seq(E) snd_seq_device(E) af_packet(E) nf_tables(E)
>> iptable_filter(E) binfmt_misc(E) intel_rapl_msr(E) nls_iso8859_1(E)
>> eeepc_wmi(E) nls
>> _cp437(E) intel_rapl_common(E) snd_hda_codec_realtek(E) asus_wmi(E)
>> iTCO_wdt(E) vfat(E) ee1004(E) snd_hda_codec_generic(E)
>> sparse_keymap(E) x86_pkg_temp_thermal(E) iTCO_vendor_support(E)
>> snd_hda_scodec_component(
>> E) intel_powerclamp(E) snd_hda_codec_hdmi(E) platform_profile(E)
>> fat(E) e1000e(E) i2c_i801(E) ptp(E) battery(E) snd_hda_intel(E)
>> i2c_smbus(E) snd_intel_dspcfg(E) mxm_wmi(E) rfkill(E) wmi_bmof(E)
>> intel_wmi_thunder
>> bolt(E) coretemp(E) pps_core(E) i2c_mux(E) pcspkr(E) snd_hda_codec(E)
>> xfs(E) snd_hda_core(E) snd_hwdep(E) snd_pcm(E) snd_timer(E) snd(E)
>> soundcore(E) mei_me(E) acpi_pad(E) button(E) mei(E) joydev(E)
>> nvme_fabrics(
>> E) loop(E) fuse(E) efi_pstore(E) dm_mod(E) configfs(E) nfnetlink(E)
>> ip_tables(E) x_tables(E) amdgpu(E) amdxcp(E) i2c_algo_bit(E)
>> drm_ttm_helper(E) ttm(E) drm_exec(E) hid_generic(E)
>> [ 169.194874] gpu_sched(E) drm_suballoc_helper(E)
>> ghash_clmulni_intel(E) sha512_ssse3(E) video(E) sha1_ssse3(E)
>> aesni_intel(E) usbhid(E) drm_panel_backlight_quirks(E) drm_buddy(E)
>> drm_display_helper(E) cec(E) w
>> mi(E) btrfs(E) blake2b_generic(E) xor(E) raid6_pq(E) msr(E)
>> i2c_dev(E) efivarfs(E) dmi_sysfs(E)
>> [ 169.311501] CR2: ffffc9012b800000
>> [ 169.314835] ---[ end trace 0000000000000000 ]---
>> [ 169.434549] RIP: 0010:udl_compress_hline16+0x219/0x940 [udl]
>> [ 169.440237] Code: 0f b6 34 28 4c 89 d8 49 d3 e5 83 e0 07 4d 01 dd
>> 83 f9 01 0f 84 4a 03 00 00 83 c0 03 40 38 f0 7c 09 40 84 f6 0f 85 82
>> 05 00 00 <41> 8b 03 4c 63 7c 24 78 4c 89 5c 24 08 89 c6 41 89 c4 c1
>> e8 08
>> c1
>> [ 169.459062] RSP: 0018:ffff88811c7e75c0 EFLAGS: 00010246
>> [ 169.464309] RAX: 0000000000000003 RBX: 0000000000000000 RCX:
>> 0000000000000002
>> [ 169.471474] RDX: 0000000000000000 RSI: 0000000000000000 RDI:
>> 0000000000000100
>> [ 169.478635] RBP: dffffc0000000000 R08: ffff8881082efe00 R09:
>> ffff8881082e0000
>> [ 169.485800] R10: 0000000000000002 R11: ffffc9012b800000 R12:
>> ffff88811c7e76f8
>> [ 169.492962] R13: ffffc9012b800400 R14: ffff8881082e0007 R15:
>> 0000000000000000
>> [ 169.500126] FS: 00007f4685f3b6c0(0000) GS:ffff88846c690000(0000)
>> knlGS:0000000000000000
>> [ 169.508246] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>> [ 169.514014] CR2: ffffc9012b800000 CR3: 0000000117944004 CR4:
>> 00000000003706f0
>> [ 169.521180] note: KMS thread[2380] exited with irqs disabled
>> [ 175.343111]
>> ==================================================================
>> [ 175.350342] BUG: KASAN: slab-use-after-free in
>> mutex_can_spin_on_owner+0x1a6/0x1c0
>> [ 175.357886] Read of size 4 at addr ffff8881172daff4 by task
>> kworker/5:0/49
>> [ 175.364738]
>> [ 175.366235] CPU: 5 UID: 0 PID: 49 Comm: kworker/5:0 Tainted:
>> G D E 6.16.0-rc5-1-default+ #4080 PREEMPT(voluntary)
>> [ 175.366240] Tainted: [D]=DIE, [E]=UNSIGNED_MODULE
>> [ 175.366242] Hardware name: System manufacturer System Product
>> Name/Z170-A, BIOS 3802 03/15/2018
>> [ 175.366244] Workqueue: events output_poll_execute
>> [ 175.366249] Call Trace:
>> [ 175.366251] <TASK>
>> [ 175.366254] dump_stack_lvl+0x68/0x90
>> [ 175.366259] ? mutex_can_spin_on_owner+0x1a6/0x1c0
>> [ 175.366261] print_address_description.constprop.0+0x88/0x380
>> [ 175.366266] ? lock_acquire+0xf2/0x140
>> [ 175.366269] ? mutex_can_spin_on_owner+0x1a6/0x1c0
>> [ 175.366272] print_report+0xf8/0x1e2
>> [ 175.366275] ? __virt_addr_valid+0x22e/0x500
>> [ 175.366279] ? kasan_addr_to_slab+0x9/0x90
>> [ 175.366282] ? mutex_can_spin_on_owner+0x1a6/0x1c0
>> [ 175.366284] kasan_report+0xd8/0x190
>> [ 175.366288] ? mutex_can_spin_on_owner+0x1a6/0x1c0
>> [ 175.366294] mutex_can_spin_on_owner+0x1a6/0x1c0
>> [ 175.366297] __ww_mutex_lock.constprop.0+0x2f8/0x34d0
>> [ 175.366301] ? do_raw_spin_trylock+0xa2/0x160
>> [ 175.366304] ? __pfx_do_raw_spin_trylock+0x10/0x10
>> [ 175.366308] ? get_nohz_timer_target+0x28/0x3d0
>> [ 175.366311] ? modeset_lock+0x3c6/0x640
>> [ 175.366316] ? __pfx___ww_mutex_lock.constprop.0+0x10/0x10
>> [ 175.366320] ? rcu_is_watching+0x11/0xb0
>> [ 175.366323] ? timerqueue_add+0x154/0x3c0
>> [ 175.366328] ? __hrtimer_start_range_ns+0x2e1/0x750
>> [ 175.366331] ? rcu_is_watching+0x11/0xb0
>> [ 175.366334] ? lock_acquired+0xb6/0xf0
>> [ 175.366337] ? rcu_is_watching+0x11/0xb0
>> [ 175.366340] ? rcu_is_watching+0x11/0xb0
>> [ 175.366342] ? drm_helper_probe_detect_ctx+0x6d/0x1a0
>> [ 175.366345] ? lock_acquire+0xf2/0x140
>> [ 175.366349] ? ww_mutex_lock+0x27/0x150
>> [ 175.366352] ? drm_helper_probe_detect_ctx+0x6d/0x1a0
>> [ 175.366355] ww_mutex_lock+0x27/0x150
>> [ 175.366358] modeset_lock+0x3c6/0x640
>> [ 175.366362] drm_helper_probe_detect_ctx+0xa6/0x1a0
>> [ 175.366366] ? __pfx_drm_helper_probe_detect_ctx+0x10/0x10
>> [ 175.366375] ? __pfx_drm_connector_list_iter_next+0x10/0x10
>> [ 175.366381] output_poll_execute+0x29b/0x760
>> [ 175.366387] ? trace_hardirqs_on+0x14/0x150
>> [ 175.366391] ? __pfx_output_poll_execute+0x10/0x10
>> [ 175.366396] process_one_work+0x7b5/0x1390
>> [ 175.366404] ? __pfx_process_one_work+0x10/0x10
>> [ 175.366409] ? assign_work+0x156/0x390
>> [ 175.366413] worker_thread+0x58d/0xf60
>> [ 175.366420] ? __pfx_worker_thread+0x10/0x10
>> [ 175.366422] kthread+0x370/0x720
>> [ 175.366425] ? __pfx_kthread+0x10/0x10
>> [ 175.366428] ? local_clock_noinstr+0x56/0x100
>> [ 175.366431] ? local_clock+0x11/0x30
>> [ 175.366433] ? __lock_release.isra.0+0x16c/0x2e0
>> [ 175.366437] ? rcu_is_watching+0x11/0xb0
>> [ 175.366439] ? lockdep_hardirqs_on_prepare.part.0+0x92/0x170
>> [ 175.366442] ? __pfx_kthread+0x10/0x10
>> [ 175.366445] ret_from_fork+0x1f4/0x2f0
>> [ 175.366448] ? __pfx_kthread+0x10/0x10
>> [ 175.366450] ret_from_fork_asm+0x1a/0x30
>> [ 175.366459] </TASK>
>> [ 175.366460]
>> [ 175.632772] Allocated by task 2342:
>> [ 175.636282] kasan_save_stack+0x1c/0x40
>> [ 175.640137] kasan_save_track+0x10/0x30
>> [ 175.643992] __kasan_slab_alloc+0x5f/0x70
>> [ 175.648023] kmem_cache_alloc_node_noprof+0x13a/0x380
>> [ 175.653097] dup_task_struct+0x32/0x730
>> [ 175.656952] copy_process+0x2d8/0x5380
>> [ 175.660720] kernel_clone+0x9f/0x5e0
>> [ 175.664318] __do_sys_clone3+0x135/0x180
>> [ 175.668258] do_syscall_64+0x68/0x2a0
>> [ 175.671940] entry_SYSCALL_64_after_hwframe+0x76/0x7e
>> [ 175.677014]
>> [ 175.678520] Freed by task 0:
>> [ 175.681418] kasan_save_stack+0x1c/0x40
>> [ 175.685273] kasan_save_track+0x10/0x30
>> [ 175.689130] kasan_save_free_info+0x37/0x70
>> [ 175.693333] __kasan_slab_free+0x33/0x40
>> [ 175.697278] kmem_cache_free+0x10b/0x4d0
>> [ 175.701221] delayed_put_task_struct+0x15e/0x1e0
>> [ 175.705858] rcu_do_batch+0x2e3/0xb30
>> [ 175.709542] rcu_core+0x51d/0xb60
>> [ 175.712873] handle_softirqs+0x1a2/0x6b0
>> [ 175.716817] __irq_exit_rcu+0xf7/0x160
>> [ 175.720585] irq_exit_rcu+0xa/0x30
>> [ 175.724006] sysvec_apic_timer_interrupt+0x9d/0xc0
>> [ 175.728820] asm_sysvec_apic_timer_interrupt+0x16/0x20
>> [ 175.733980]
>> [ 175.735486] Last potentially related work creation:
>> [ 175.740385] kasan_save_stack+0x1c/0x40
>> [ 175.744243] kasan_record_aux_stack+0x88/0xa0
>> [ 175.748618] __call_rcu_common.constprop.0+0x77/0x850
>> [ 175.753693] __schedule+0x887/0x1d00
>> [ 175.757287] schedule+0xd0/0x260
>> [ 175.760533] smpboot_thread_fn+0x583/0x7a0
>> [ 175.764650] kthread+0x370/0x720
>> [ 175.767896] ret_from_fork+0x1f4/0x2f0
>> [ 175.771665] ret_from_fork_asm+0x1a/0x30
>> [ 175.775608]
>> [ 175.777113] Second to last potentially related work creation:
>> [ 175.782886] kasan_save_stack+0x1c/0x40
>> [ 175.786739] kasan_record_aux_stack+0x88/0xa0
>> [ 175.791118] task_work_add+0x1b1/0x270
>> [ 175.794886] sched_tick+0x226/0x6f0
>> [ 175.798394] update_process_times+0xe9/0x1f0
>> [ 175.802685] tick_nohz_handler+0x1a6/0x4b0
>> [ 175.806801] __hrtimer_run_queues+0x161/0x960
>> [ 175.811181] hrtimer_interrupt+0x33e/0x880
>> [ 175.815295] __sysvec_apic_timer_interrupt+0xf6/0x390
>> [ 175.820370] sysvec_apic_timer_interrupt+0x98/0xc0
>> [ 175.825183] asm_sysvec_apic_timer_interrupt+0x16/0x20
>> [ 175.830343]
>> [ 175.831849] The buggy address belongs to the object at
>> ffff8881172dafc0
>> [ 175.831849] which belongs to the cache task_struct of size 11968
>> [ 175.844582] The buggy address is located 52 bytes inside of
>> [ 175.844582] freed 11968-byte region [ffff8881172dafc0,
>> ffff8881172dde80)
>> [ 175.856969]
>> [ 175.858474] The buggy address belongs to the physical page:
>> [ 175.864070] page: refcount:0 mapcount:0 mapping:0000000000000000
>> index:0x0 pfn:0x1172d8
>> [ 175.872104] head: order:3 mapcount:0 entire_mapcount:0
>> nr_pages_mapped:0 pincount:0
>> [ 175.879788] memcg:ffff88811068a301
>> [ 175.883209] anon flags:
>> 0x2ffff800000040(head|node=0|zone=2|lastcpupid=0x1ffff)
>> [ 175.890547] page_type: f5(slab)
>> [ 175.893706] raw: 002ffff800000040 ffff888100930500
>> 0000000000000000 0000000000000001
>> [ 175.901479] raw: 0000000000000000 0000000000020002
>> 00000000f5000000 ffff88811068a301
>> [ 175.909249] head: 002ffff800000040 ffff888100930500
>> 0000000000000000 0000000000000001
>> [ 175.917109] head: 0000000000000000 0000000000020002
>> 00000000f5000000 ffff88811068a301
>> [ 175.924968] head: 002ffff800000003 ffffea00045cb601
>> 00000000ffffffff 00000000ffffffff
>> [ 175.932827] head: ffffffffffffffff 0000000000000000
>> 00000000ffffffff 0000000000000008
>> [ 175.940685] page dumped because: kasan: bad access detected
>> [ 175.946283]
>> [ 175.947787] Memory state around the buggy address:
>> [ 175.952603] ffff8881172dae80: fb fb fb fb fb fb fb fb fc fc fc fc
>> fc fc fc fc
>> [ 175.959854] ffff8881172daf00: fc fc fc fc fc fc fc fc fc fc fc fc
>> fc fc fc fc
>> [ 175.967101] >ffff8881172daf80: fc fc fc fc fc fc fc fc fa fb fb fb
>> fb fb fb fb
>> [ 175.974353] ^
>> [ 175.981256] ffff8881172db000: fb fb fb fb fb fb fb fb fb fb fb fb
>> fb fb fb fb
>> [ 175.988504] ffff8881172db080: fb fb fb fb fb fb fb fb fb fb fb fb
>> fb fb fb fb
>> [ 175.995755]
>> ==================================================================
>>
>>
>>
>>
>>
>>
>>
>> Am 22.05.25 um 09:07 schrieb oushixiong1025@....com:
>>> From: Shixiong Ou <oushixiong@...inos.cn>
>>>
>>> [WHY]
>>> 1. Drivers using DRM_GEM_SHADOW_PLANE_HELPER_FUNCS and
>>> DRM_GEM_SHMEM_DRIVER_OPS (e.g., udl, ast) do not require
>>> sg_table import.
>>> They only need dma_buf_vmap() to access the shared buffer's
>>> kernel virtual address.
>>>
>>> 2. On certain Aspeed-based boards, a dma_mask of 0xffff_ffff may
>>> trigger SWIOTLB during dmabuf import. However, IO_TLB_SEGSIZE
>>> restricts the maximum DMA streaming mapping memory, resulting in
>>> errors like:
>>>
>>> ast 0000:07:00.0: swiotlb buffer is full (sz: 3145728 bytes),
>>> total 32768 (slots), used 0 (slots)
>>>
>>> [HOW]
>>> Provide a gem_prime_import implementation without sg_table mapping
>>> to avoid issues (e.g., "swiotlb buffer is full"). Drivers that do not
>>> require sg_table can adopt this.
>>>
>>> Signed-off-by: Shixiong Ou <oushixiong@...inos.cn>
>>> ---
>>> v1->v2:
>>> Patch rebase.
>>> v2->v3:
>>> Rename the import callback function.
>>> Remove drm_gem_shmem_prime_export() and separate some codes
>>> to drm_gem_prime_import_self().
>>> v3->v4:
>>> Separate the test from the policy.
>>> Rename the macro.
>>> v4->v5:
>>> Rename some functions.
>>>
>>> drivers/gpu/drm/drm_gem_shmem_helper.c | 57
>>> ++++++++++++++++++++++++++
>>> drivers/gpu/drm/drm_prime.c | 36 ++++++++++++----
>>> include/drm/drm_gem_shmem_helper.h | 15 +++++++
>>> include/drm/drm_prime.h | 3 ++
>>> 4 files changed, 102 insertions(+), 9 deletions(-)
>>>
>>> diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c
>>> b/drivers/gpu/drm/drm_gem_shmem_helper.c
>>> index aa43265f4f4f..126aa79042ad 100644
>>> --- a/drivers/gpu/drm/drm_gem_shmem_helper.c
>>> +++ b/drivers/gpu/drm/drm_gem_shmem_helper.c
>>> @@ -800,6 +800,63 @@ drm_gem_shmem_prime_import_sg_table(struct
>>> drm_device *dev,
>>> }
>>> EXPORT_SYMBOL_GPL(drm_gem_shmem_prime_import_sg_table);
>>> +/**
>>> + * drm_gem_shmem_prime_import_no_map - Import dmabuf without
>>> mapping its sg_table
>>> + * @dev: Device to import into
>>> + * @dma_buf: dma-buf object to import
>>> + *
>>> + * Drivers that use the shmem helpers but also wants to import
>>> dmabuf without
>>> + * mapping its sg_table can use this as their
>>> &drm_driver.gem_prime_import
>>> + * implementation.
>>> + */
>>> +struct drm_gem_object *drm_gem_shmem_prime_import_no_map(struct
>>> drm_device *dev,
>>> + struct dma_buf *dma_buf)
>>> +{
>>> + struct dma_buf_attachment *attach;
>>> + struct drm_gem_shmem_object *shmem;
>>> + struct drm_gem_object *obj;
>>> + size_t size;
>>> + int ret;
>>> +
>>> + if (drm_gem_is_prime_exported_dma_buf(dev, dma_buf)) {
>>> + /*
>>> + * Importing dmabuf exported from our own gem increases
>>> + * refcount on gem itself instead of f_count of dmabuf.
>>> + */
>>> + obj = dma_buf->priv;
>>> + drm_gem_object_get(obj);
>>> + return obj;
>>> + }
>>> +
>>> + attach = dma_buf_attach(dma_buf, dev->dev);
>>> + if (IS_ERR(attach))
>>> + return ERR_CAST(attach);
>>> +
>>> + get_dma_buf(dma_buf);
>>> +
>>> + size = PAGE_ALIGN(attach->dmabuf->size);
>>> +
>>> + shmem = __drm_gem_shmem_create(dev, size, true, NULL);
>>> + if (IS_ERR(shmem)) {
>>> + ret = PTR_ERR(shmem);
>>> + goto fail_detach;
>>> + }
>>> +
>>> + drm_dbg_prime(dev, "size = %zu\n", size);
>>> +
>>> + shmem->base.import_attach = attach;
>>> + shmem->base.resv = dma_buf->resv;
>>> +
>>> + return &shmem->base;
>>> +
>>> +fail_detach:
>>> + dma_buf_detach(dma_buf, attach);
>>> + dma_buf_put(dma_buf);
>>> +
>>> + return ERR_PTR(ret);
>>> +}
>>> +EXPORT_SYMBOL_GPL(drm_gem_shmem_prime_import_no_map);
>>> +
>>> MODULE_DESCRIPTION("DRM SHMEM memory-management helpers");
>>> MODULE_IMPORT_NS("DMA_BUF");
>>> MODULE_LICENSE("GPL v2");
>>> diff --git a/drivers/gpu/drm/drm_prime.c b/drivers/gpu/drm/drm_prime.c
>>> index d828502268b8..b825b71038d6 100644
>>> --- a/drivers/gpu/drm/drm_prime.c
>>> +++ b/drivers/gpu/drm/drm_prime.c
>>> @@ -910,6 +910,26 @@ struct dma_buf *drm_gem_prime_export(struct
>>> drm_gem_object *obj,
>>> }
>>> EXPORT_SYMBOL(drm_gem_prime_export);
>>> +
>>> +/**
>>> + * drm_gem_is_prime_exported_dma_buf -
>>> + * checks if the DMA-BUF was exported from a GEM object belonging
>>> to @dev.
>>> + * @dev: drm_device to check against
>>> + * @dma_buf: dma-buf object to import
>>> + *
>>> + * Return: true if the DMA-BUF was exported from a GEM object
>>> belonging
>>> + * to @dev, false otherwise.
>>> + */
>>> +
>>> +bool drm_gem_is_prime_exported_dma_buf(struct drm_device *dev,
>>> + struct dma_buf *dma_buf)
>>> +{
>>> + struct drm_gem_object *obj = dma_buf->priv;
>>> +
>>> + return (dma_buf->ops == &drm_gem_prime_dmabuf_ops) && (obj->dev
>>> == dev);
>>> +}
>>> +EXPORT_SYMBOL(drm_gem_is_prime_exported_dma_buf);
>>> +
>>> /**
>>> * drm_gem_prime_import_dev - core implementation of the import
>>> callback
>>> * @dev: drm_device to import into
>>> @@ -933,16 +953,14 @@ struct drm_gem_object
>>> *drm_gem_prime_import_dev(struct drm_device *dev,
>>> struct drm_gem_object *obj;
>>> int ret;
>>> - if (dma_buf->ops == &drm_gem_prime_dmabuf_ops) {
>>> + if (drm_gem_is_prime_exported_dma_buf(dev, dma_buf)) {
>>> + /*
>>> + * Importing dmabuf exported from our own gem increases
>>> + * refcount on gem itself instead of f_count of dmabuf.
>>> + */
>>> obj = dma_buf->priv;
>>> - if (obj->dev == dev) {
>>> - /*
>>> - * Importing dmabuf exported from our own gem increases
>>> - * refcount on gem itself instead of f_count of dmabuf.
>>> - */
>>> - drm_gem_object_get(obj);
>>> - return obj;
>>> - }
>>> + drm_gem_object_get(obj);
>>> + return obj;
>>> }
>>> if (!dev->driver->gem_prime_import_sg_table)
>>> diff --git a/include/drm/drm_gem_shmem_helper.h
>>> b/include/drm/drm_gem_shmem_helper.h
>>> index b4f993da3cae..35f7466dca84 100644
>>> --- a/include/drm/drm_gem_shmem_helper.h
>>> +++ b/include/drm/drm_gem_shmem_helper.h
>>> @@ -287,6 +287,8 @@ drm_gem_shmem_prime_import_sg_table(struct
>>> drm_device *dev,
>>> struct sg_table *sgt);
>>> int drm_gem_shmem_dumb_create(struct drm_file *file, struct
>>> drm_device *dev,
>>> struct drm_mode_create_dumb *args);
>>> +struct drm_gem_object *drm_gem_shmem_prime_import_no_map(struct
>>> drm_device *dev,
>>> + struct dma_buf *buf);
>>> /**
>>> * DRM_GEM_SHMEM_DRIVER_OPS - Default shmem GEM operations
>>> @@ -298,4 +300,17 @@ int drm_gem_shmem_dumb_create(struct drm_file
>>> *file, struct drm_device *dev,
>>> .gem_prime_import_sg_table =
>>> drm_gem_shmem_prime_import_sg_table, \
>>> .dumb_create = drm_gem_shmem_dumb_create
>>> +/**
>>> + * DRM_GEM_SHMEM_DRIVER_OPS_NO_MAP_SGT - shmem GEM operations
>>> + * without mapping sg_table on
>>> + * imported buffer.
>>> + *
>>> + * This macro provides a shortcut for setting the shmem GEM
>>> operations in
>>> + * the &drm_driver structure for drivers that do not require a
>>> sg_table on
>>> + * imported buffers.
>>> + */
>>> +#define DRM_GEM_SHMEM_DRIVER_OPS_NO_MAP_SGT \
>>> + .gem_prime_import = drm_gem_shmem_prime_import_no_map, \
>>> + .dumb_create = drm_gem_shmem_dumb_create
>>> +
>>> #endif /* __DRM_GEM_SHMEM_HELPER_H__ */
>>> diff --git a/include/drm/drm_prime.h b/include/drm/drm_prime.h
>>> index fa085c44d4ca..f50f862f0d8b 100644
>>> --- a/include/drm/drm_prime.h
>>> +++ b/include/drm/drm_prime.h
>>> @@ -100,6 +100,9 @@ struct dma_buf *drm_gem_prime_export(struct
>>> drm_gem_object *obj,
>>> unsigned long drm_prime_get_contiguous_size(struct sg_table *sgt);
>>> /* helper functions for importing */
>>> +bool drm_gem_is_prime_exported_dma_buf(struct drm_device *dev,
>>> + struct dma_buf *dma_buf);
>>> +
>>> struct drm_gem_object *drm_gem_prime_import_dev(struct drm_device
>>> *dev,
>>> struct dma_buf *dma_buf,
>>> struct device *attach_dev);
>>
--
--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Frankenstrasse 146, 90461 Nuernberg, Germany
GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman
HRB 36809 (AG Nuernberg)
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