On 15/02/2025 01:23, Matthew Brost wrote:
On Fri, Feb 14, 2025 at 05:05:29PM +0000, Matthew Auld wrote:
Currently we treat EFAULT from hmm_range_fault() as a non-fatal error when called from xe_vm_userptr_pin() with the idea that we want to avoid killing the entire vm and chucking an error, under the assumption that the user just did an unmap or something, and has no intention of actually touching that memory from the GPU. At this point we have already zapped the PTEs so any access should generate a page fault, and if the pin fails there also it will then become fatal.
However it looks like it's possible for the userptr vma to still be on the rebind list in preempt_rebind_work_func(), if we had to retry the pin again due to something happening in the caller before we did the rebind step, but in the meantime needing to re-validate the userptr and this time hitting the EFAULT.
This might explain an internal user report of hitting:
[ 191.738349] WARNING: CPU: 1 PID: 157 at drivers/gpu/drm/xe/xe_res_cursor.h:158 xe_pt_stage_bind.constprop.0+0x60a/0x6b0 [xe] [ 191.738551] Workqueue: xe-ordered-wq preempt_rebind_work_func [xe] [ 191.738616] RIP: 0010:xe_pt_stage_bind.constprop.0+0x60a/0x6b0 [xe] [ 191.738690] Call Trace: [ 191.738692] <TASK> [ 191.738694] ? show_regs+0x69/0x80 [ 191.738698] ? __warn+0x93/0x1a0 [ 191.738703] ? xe_pt_stage_bind.constprop.0+0x60a/0x6b0 [xe] [ 191.738759] ? report_bug+0x18f/0x1a0 [ 191.738764] ? handle_bug+0x63/0xa0 [ 191.738767] ? exc_invalid_op+0x19/0x70 [ 191.738770] ? asm_exc_invalid_op+0x1b/0x20 [ 191.738777] ? xe_pt_stage_bind.constprop.0+0x60a/0x6b0 [xe] [ 191.738834] ? ret_from_fork_asm+0x1a/0x30 [ 191.738849] bind_op_prepare+0x105/0x7b0 [xe] [ 191.738906] ? dma_resv_reserve_fences+0x301/0x380 [ 191.738912] xe_pt_update_ops_prepare+0x28c/0x4b0 [xe] [ 191.738966] ? kmemleak_alloc+0x4b/0x80 [ 191.738973] ops_execute+0x188/0x9d0 [xe] [ 191.739036] xe_vm_rebind+0x4ce/0x5a0 [xe] [ 191.739098] ? trace_hardirqs_on+0x4d/0x60 [ 191.739112] preempt_rebind_work_func+0x76f/0xd00 [xe]
Followed by NPD, when running some workload, since the sg was never actually populated but the vma is still marked for rebind when it should be skipped for this special EFAULT case. And from the logs it does seem like we hit this special EFAULT case before the explosions.
It would be nice to verify if this fixes the bug report.
Yes, reporter said it fixes it. Or at least the previous version did. See GSD-10562 if you are curious. Will re-phrase the commit message to make that clear.
v2 (MattB):
- Move earlier
Fixes: 521db22a1d70 ("drm/xe: Invalidate userptr VMA on page pin fault") Signed-off-by: Matthew Auld matthew.auld@intel.com Cc: Matthew Brost matthew.brost@intel.com
Anyways, LGTM: Reviewed-by: Matthew Brost matthew.brost@intel.com
Thanks.
Cc: Thomas Hellström thomas.hellstrom@linux.intel.com Cc: stable@vger.kernel.org # v6.10+
drivers/gpu/drm/xe/xe_vm.c | 12 ++++++++++++ 1 file changed, 12 insertions(+)
diff --git a/drivers/gpu/drm/xe/xe_vm.c b/drivers/gpu/drm/xe/xe_vm.c index 668b0bde7822..f36e2cc1d155 100644 --- a/drivers/gpu/drm/xe/xe_vm.c +++ b/drivers/gpu/drm/xe/xe_vm.c @@ -681,6 +681,18 @@ int xe_vm_userptr_pin(struct xe_vm *vm) err = xe_vma_userptr_pin_pages(uvma); if (err == -EFAULT) { list_del_init(&uvma->userptr.repin_link);
/** We might have already done the pin once already, but* then had to retry before the re-bind happened, due* some other condition in the caller, but in the* meantime the userptr got dinged by the notifier such* that we need to revalidate here, but this time we hit* the EFAULT. In such a case make sure we remove* ourselves from the rebind list to avoid going down in* flames.*/if (!list_empty(&uvma->vma.combined_links.rebind))list_del_init(&uvma->vma.combined_links.rebind);/* Wait for pending binds */ xe_vm_lock(vm, false); -- 2.48.1