[PATCH v3] drm/xe/devcoredump: Defer devcoredump initialization during probe
Summers, Stuart
stuart.summers at intel.com
Thu Jul 31 16:37:20 UTC 2025
On Thu, 2025-07-31 at 11:43 +0530, Balasubramani Vivekanandan wrote:
> Doing devcoredump initializing before GT though look harmless, it
> leads
> to problem during driver unbind. Because of this order, GT/Engine
> release functions will be called before xe devcoredump release
> function
> (xe_driver_devcoredump_fini) leading to the following kernel crash[1]
> because the devcoredump functions might still use GT/Engine
> datastructures after those are freed.
>
> The following crash is observed while running the IGT
> xe_wedged at wedged-at-any-timeout. The test forces a wedged state by
> submitting a worload which hangs. Then does a unbind/rebind of the
/s/worload/workload/
> driver to recover from the wedged state.
> The hanged worload leads to a devcoredump. The following crash is
same
Otherwise looks great:
Reviewed-by: Stuart Summers <stuart.summers at intel.com>
> noticed when the devcoredump capture races with the driver unbind.
> During driver unbind, the release function hw_engine_fini() will be
> called which assigns NULL to hwe->gt. But the same data structure is
> accessed during the coredump capture in the function
> xe_engine_snapshot_print by reading snapshot->hwe->gt.
>
> With this patch, we make sure the devcoredump is stopped before
> deinitializing the core driver functions.
>
> [1]:
> BUG: kernel NULL pointer dereference, address: 0000000000000000
> Workqueue: events_unbound xe_devcoredump_deferred_snap_work [xe]
> RIP: 0010:xe_engine_snapshot_print+0x47/0x420 [xe]
> Call Trace:
> <TASK>
> ? drm_printf+0x64/0x90
> __xe_devcoredump_read+0x23f/0x2d0 [xe]
> ? __pfx___drm_printfn_coredump+0x10/0x10
> ? __pfx___drm_puts_coredump+0x10/0x10
> xe_devcoredump_deferred_snap_work+0x17a/0x190 [xe]
> process_one_work+0x22e/0x6f0
> worker_thread+0x1e8/0x3d0
> ? __pfx_worker_thread+0x10/0x10
> kthread+0x11f/0x250
> ? __pfx_kthread+0x10/0x10
> ret_from_fork+0x47/0x70
> ? __pfx_kthread+0x10/0x10
> ret_from_fork_asm+0x1a/0x30
>
> v2: Detailed commit description (Rodrigo)
> v3: FIXME added (Rodrigo, Stuart)
>
> Fixes: 4209d635a823 ("drm/xe: Remove devcoredump during driver
> release")
> Signed-off-by: Balasubramani Vivekanandan
> <balasubramani.vivekanandan at intel.com>
> ---
> drivers/gpu/drm/xe/xe_device.c | 8 ++++----
> drivers/gpu/drm/xe/xe_guc_capture.c | 6 ++++++
> 2 files changed, 10 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/gpu/drm/xe/xe_device.c
> b/drivers/gpu/drm/xe/xe_device.c
> index d04a0ae018e6..ae48cd3c7bf0 100644
> --- a/drivers/gpu/drm/xe/xe_device.c
> +++ b/drivers/gpu/drm/xe/xe_device.c
> @@ -821,10 +821,6 @@ int xe_device_probe(struct xe_device *xe)
> return err;
> }
>
> - err = xe_devcoredump_init(xe);
> - if (err)
> - return err;
> -
> /*
> * From here on, if a step fails, make sure a Driver-FLR is
> triggereed
> */
> @@ -889,6 +885,10 @@ int xe_device_probe(struct xe_device *xe)
> XE_WA(xe->tiles->media_gt, 15015404425_disable))
> XE_DEVICE_WA_DISABLE(xe, 15015404425);
>
> + err = xe_devcoredump_init(xe);
> + if (err)
> + return err;
> +
> xe_nvm_init(xe);
>
> err = xe_heci_gsc_init(xe);
> diff --git a/drivers/gpu/drm/xe/xe_guc_capture.c
> b/drivers/gpu/drm/xe/xe_guc_capture.c
> index 859a3ba91be5..243dad3e2418 100644
> --- a/drivers/gpu/drm/xe/xe_guc_capture.c
> +++ b/drivers/gpu/drm/xe/xe_guc_capture.c
> @@ -1817,6 +1817,12 @@ void xe_engine_snapshot_print(struct
> xe_hw_engine_snapshot *snapshot, struct drm
> str_yes_no(snapshot->kernel_reserved));
>
> for (type = GUC_STATE_CAPTURE_TYPE_GLOBAL; type <
> GUC_STATE_CAPTURE_TYPE_MAX; type++) {
> + /*
> + * FIXME: During devcoredump print we should avoid
> accessing the
> + * driver pointers for gt or engine. Printing should
> be done only
> + * using the snapshot captured. Here we are accessing
> the gt
> + * pointer. It should be fixed.
> + */
> list = xe_guc_capture_get_reg_desc_list(gt,
> GUC_CAPTURE_LIST_INDEX_PF, type,
> capture_class
> , false);
> snapshot_print_by_list_order(snapshot, p, type,
> list);
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