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X-MS-Exchange-CrossTenant-OriginalArrivalTime: 17 Dec 2025 12:24:46.7268 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 46c98d88-e344-4ed4-8496-4ed7712e255d X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: HdtAZDeno7bDzedLU/6UCOUWMN4nA03CYa9kWT9mWvx628il8cTB4eEG+CswdsPTWEcUZUCEbqOW8NOA5dkO8Q== X-MS-Exchange-Transport-CrossTenantHeadersStamped: IA1PR11MB7869 X-OriginatorOrg: intel.com X-BeenThere: intel-xe@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Intel Xe graphics driver List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: intel-xe-bounces@lists.freedesktop.org Sender: "Intel-xe" On 12/17/25 13:51, Matthew Auld wrote: > On 17/12/2025 10:51, Tapani Pälli wrote: >> >> On 12/17/25 12:31, Matthew Auld wrote: >>> On 17/12/2025 10:27, Matthew Auld wrote: >>>> On 17/12/2025 06:17, Tapani Pälli wrote: >>>>> Helper function xe_sync_needs_wait expects sync->fence when accessing >>>>> flags, patch makes sure we call only when sync->fence exists. >>>>> >>>>> Fixes NULL pointer dereference seen with Vulkan workloads: >>>>> >>>>> [  118.410401] RIP: 0010:xe_sync_needs_wait+0x27/0x50 [xe] >>>>> >>>>> Fixes: 4ac9048d0501 ("drm/xe: Wait on in-syncs when swicthing to >>>>> dma- fence mode") >>>>> Signed-off-by: Tapani Pälli >>>>> --- >>>>>   drivers/gpu/drm/xe/xe_exec.c | 3 ++- >>>>>   1 file changed, 2 insertions(+), 1 deletion(-) >>>>> >>>>> diff --git a/drivers/gpu/drm/xe/xe_exec.c b/drivers/gpu/drm/xe/ >>>>> xe_exec.c >>>>> index 730a5c9c2637..ea368f02cb9f 100644 >>>>> --- a/drivers/gpu/drm/xe/xe_exec.c >>>>> +++ b/drivers/gpu/drm/xe/xe_exec.c >>>>> @@ -184,7 +184,8 @@ int xe_exec_ioctl(struct drm_device *dev, void >>>>> *data, struct drm_file *file) >>>>>           if (xe_sync_is_ufence(&syncs[num_syncs])) >>>>>               num_ufence++; >>>>> -        if (!num_in_sync && xe_sync_needs_wait(&syncs[num_syncs])) >>>>> +        if (!num_in_sync && syncs[num_syncs].fence && >>>>> +            xe_sync_needs_wait(&syncs[num_syncs])) >>>> >>>> In xe_sync_entry_parse() it looks like it will always populate the >>>> fence for the !signal case, otherwise throwing an error if that is >>>> not possible. And xe_sync_needs_wait() will only touch the fence if >>>> it's the signal case? So it seems like this should not be possible? >>> >>> Sorry meant to type: >>> >>> s/touch the fence if it's the signal/touch the fence if it's the >>> !signal/ >>> >> I'm not sure of the complete flow but it is quite easy to reproduce. > > Oh, I think I see it now. > > I assume the below also fixes it? There is also the case in > xe_sync_entry_wait() which has the same bug, I think, so would also > need to handle that. > > @@ -178,6 +179,9 @@ int xe_sync_entry_parse(struct xe_device *xe, > struct xe_file *xef, > > sync_in.timeline_value); >                         if (err) >                                 return err; > + > +                       if (!sync->fence) > +                               sync->fence = dma_fence_get_stub(); > I will try this one. > So it looks like dma_fence_chain_find_seqno() can return NULL if the > seqno has already signalled. Also means we are missing some IGT > coverage for this. > > Can you resend your patch but perhaps we move the check into > needs_wait() and then add a similar check in xe_sync_entry_wait() > also? Or perhaps might be cleaner to have xe_sync_entry_wait() first > check needs_wait(), which will now also check for a NULL fence? > Yes, that sounds fine to me, I'll add null check to needs_wait(). >> >> Here is the stacktrace snippet: >> >> [  118.410401] RIP: 0010:xe_sync_needs_wait+0x27/0x50 [xe] >> [  118.410940] Code: 90 90 90 0f 1f 44 00 00 55 48 89 f1 48 89 e5 48 >> 83 ec 08 48 83 7e 08 00 0f 84 79 be 1c 00 31 c0 f6 41 4c 01 75 11 48 >> 8b 41 08 <48> 8b 40 30 48 d1 e8 83 e0 01 83 f0 01 c9 31 d2 31 c9 31 >> f6 31 ff >> [  118.410949] RSP: 0018:ffffccec8ea7bb18 EFLAGS: 00010246 >> [  118.410957] RAX: 0000000000000000 RBX: 00007ff23812f460 RCX: >> ffff8c1790db4800 >> [  118.410964] RDX: 0000000000000000 RSI: 0000000000000000 RDI: >> 0000000000000000 >> [  118.410968] RBP: ffffccec8ea7bb20 R08: 0000000000000000 R09: >> 0000000000000000 >> [  118.410973] R10: 0000000000000000 R11: 0000000000000000 R12: >> ffff8c1790db4800 >> [  118.410978] R13: 0000000000000000 R14: ffff8c178b67e000 R15: >> 0000000000000000 >> [  118.410984] FS:  0000000101aff6c0(0000) GS:ffff8c27350d1000(0000) >> knlGS:000000007fe20000 >> [  118.410992] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033 >> [  118.410998] CR2: 0000000000000030 CR3: 00000001037ef005 CR4: >> 0000000000772ef0 >> [  118.411004] PKRU: 55555554 >> [  118.411008] Call Trace: >> [  118.411013]  >> [  118.411022]  xe_exec_ioctl+0x375/0xea0 [xe] >> [  118.411377]  ? __x64_sys_ioctl+0xbd/0x100 >> [  118.411392]  ? do_syscall_64+0xa7/0x580 >> [  118.411403]  ? dma_fence_free+0x1a/0x30 >> [  118.411419]  ? __pfx_xe_exec_fn+0x10/0x10 [xe] >> [  118.411752]  ? drm_syncobj_array_free+0x56/0x80 [drm] >> [  118.411915]  ? drm_syncobj_query_ioctl+0x20f/0x460 [drm] >> [  118.412035]  ? __pfx_xe_exec_ioctl+0x10/0x10 [xe] >> [  118.412372]  drm_ioctl_kernel+0xae/0x110 [drm] >> [  118.412524]  drm_ioctl+0x2ee/0x5d0 [drm] >> [  118.412649]  ? __pfx_xe_exec_ioctl+0x10/0x10 [xe] >> [  118.412989]  ? __pm_runtime_resume+0x5f/0x90 >> [  118.413002]  xe_drm_ioctl+0x61/0xb0 [xe] >> [  118.413329]  __x64_sys_ioctl+0xa3/0x100 >> [  118.413338]  x64_sys_call+0x1060/0x2360 >> [  118.413347]  do_syscall_64+0x74/0x580 >> [  118.413355]  ? x64_sys_call+0x1060/0x2360 >> [  118.413360]  ? do_syscall_64+0xa7/0x580 >> [  118.413368]  ? __do_sys_getpid+0x1d/0x30 >> [  118.413377]  ? x64_sys_call+0xf9d/0x2360 >> [  118.413383]  ? do_syscall_64+0xa7/0x580 >> [  118.413389]  ? x64_sys_call+0x1060/0x2360 >> [  118.413395]  ? do_syscall_64+0xa7/0x580 >> [  118.413401]  ? sysvec_apic_timer_interrupt+0x54/0xd0 >> [  118.413410]  entry_SYSCALL_64_after_hwframe+0x76/0x7e >> [  118.413418] RIP: 0033:0x7ff29c93287d >> >> >> >>>> >>>>>               num_in_sync++; >>>>>       } >>>> >>> >