[PATCH v2] drm/xe: Add timeout to preempt fences
Matthew Auld
matthew.auld at intel.com
Tue Jun 25 13:03:38 UTC 2024
Hi,
On 25/06/2024 06:51, Matthew Brost wrote:
> To adhere to dma fencing rules that fences must signal within a
> reasonable amount of time, add a 5 second timeout to preempt fences. If
> this timeout occurs, kill the associated VM as this fatal to the VM.
>
> v2:
> - Add comment for smp_wmb (Checkpatch)
> - Fix kernel doc typo (Inspection)
> - Add comment for killed check (Niranjana)
>
> Cc: Niranjana Vishwanathapura <niranjana.vishwanathapura at intel.com>
> Signed-off-by: Matthew Brost <matthew.brost at intel.com>
> Reviewed-by: Niranjana Vishwanathapura <niranjana.vishwanathapura at intel.com>
> ---
> drivers/gpu/drm/xe/xe_exec_queue_types.h | 6 ++--
> drivers/gpu/drm/xe/xe_execlist.c | 3 +-
> drivers/gpu/drm/xe/xe_guc_submit.c | 41 ++++++++++++++++++++----
> drivers/gpu/drm/xe/xe_preempt_fence.c | 14 +++++++-
> drivers/gpu/drm/xe/xe_vm.c | 10 +++++-
> drivers/gpu/drm/xe/xe_vm.h | 2 ++
> 6 files changed, 65 insertions(+), 11 deletions(-)
>
> diff --git a/drivers/gpu/drm/xe/xe_exec_queue_types.h b/drivers/gpu/drm/xe/xe_exec_queue_types.h
> index 201588ec33c3..1e51c978db7a 100644
> --- a/drivers/gpu/drm/xe/xe_exec_queue_types.h
> +++ b/drivers/gpu/drm/xe/xe_exec_queue_types.h
> @@ -172,9 +172,11 @@ struct xe_exec_queue_ops {
> int (*suspend)(struct xe_exec_queue *q);
> /**
> * @suspend_wait: Wait for an exec queue to suspend executing, should be
> - * call after suspend.
> + * call after suspend. In dma-fencing path thus must return within a
> + * reasonable amount of time. A non-zero return shall indicate an error
> + * waiting for suspend.
> */
> - void (*suspend_wait)(struct xe_exec_queue *q);
> + int (*suspend_wait)(struct xe_exec_queue *q);
> /**
> * @resume: Resume exec queue execution, exec queue must be in a suspended
> * state and dma fence returned from most recent suspend call must be
> diff --git a/drivers/gpu/drm/xe/xe_execlist.c b/drivers/gpu/drm/xe/xe_execlist.c
> index db906117db6d..7502e3486eaf 100644
> --- a/drivers/gpu/drm/xe/xe_execlist.c
> +++ b/drivers/gpu/drm/xe/xe_execlist.c
> @@ -422,10 +422,11 @@ static int execlist_exec_queue_suspend(struct xe_exec_queue *q)
> return 0;
> }
>
> -static void execlist_exec_queue_suspend_wait(struct xe_exec_queue *q)
> +static int execlist_exec_queue_suspend_wait(struct xe_exec_queue *q)
>
> {
> /* NIY */
> + return 0;
> }
>
> static void execlist_exec_queue_resume(struct xe_exec_queue *q)
> diff --git a/drivers/gpu/drm/xe/xe_guc_submit.c b/drivers/gpu/drm/xe/xe_guc_submit.c
> index 373447758a60..9df97ee94fca 100644
> --- a/drivers/gpu/drm/xe/xe_guc_submit.c
> +++ b/drivers/gpu/drm/xe/xe_guc_submit.c
> @@ -1301,6 +1301,17 @@ static void __guc_exec_queue_process_msg_set_sched_props(struct xe_sched_msg *ms
> kfree(msg);
> }
>
> +static void __suspend_fence_signal(struct xe_exec_queue *q)
> +{
> + if (!q->guc->suspend_pending)
> + return;
> +
> + q->guc->suspend_pending = false;
> + smp_wmb(); /* Ensure suspend_pending change is visible */
I guess it was already like that, but where is the matching smp_rmb()?
If adding smp_wmb() there should usually always be a barrier on the
reader side.
If this is just simple wake_up() / wait_event() pattern with single
dependant store/load vs wait/wakeup then I don't think we need explicit
barrier, it should be handled already by the api IIRC.
> +
> + wake_up(&q->guc->suspend_wait);
> +}
> +
> static void suspend_fence_signal(struct xe_exec_queue *q)
> {
> struct xe_guc *guc = exec_queue_to_guc(q);
> @@ -1310,9 +1321,7 @@ static void suspend_fence_signal(struct xe_exec_queue *q)
> guc_read_stopped(guc));
> xe_assert(xe, q->guc->suspend_pending);
>
> - q->guc->suspend_pending = false;
> - smp_wmb();
> - wake_up(&q->guc->suspend_wait);
> + __suspend_fence_signal(q);
> }
>
> static void __guc_exec_queue_process_msg_suspend(struct xe_sched_msg *msg)
> @@ -1465,6 +1474,7 @@ static void guc_exec_queue_kill(struct xe_exec_queue *q)
> {
> trace_xe_exec_queue_kill(q);
> set_exec_queue_killed(q);
> + __suspend_fence_signal(q);
> xe_guc_exec_queue_trigger_cleanup(q);
> }
>
> @@ -1561,12 +1571,31 @@ static int guc_exec_queue_suspend(struct xe_exec_queue *q)
> return 0;
> }
>
> -static void guc_exec_queue_suspend_wait(struct xe_exec_queue *q)
> +static int guc_exec_queue_suspend_wait(struct xe_exec_queue *q)
> {
> struct xe_guc *guc = exec_queue_to_guc(q);
> + int ret;
> +
> + /*
> + * Likely don't need to check exec_queue_killed() as we clear
> + * suspend_pending upon kill but to be paranoid but races in which
> + * suspend_pending is set after kill also check kill here.
> + */
> + ret = wait_event_timeout(q->guc->suspend_wait,
> + !q->guc->suspend_pending ||
> + exec_queue_killed(q) ||
> + guc_read_stopped(guc),
> + HZ * 5);
>
> - wait_event(q->guc->suspend_wait, !q->guc->suspend_pending ||
> - guc_read_stopped(guc));
> + if (!ret) {
> + xe_gt_warn(guc_to_gt(guc),
> + "Suspend fence, guc_id=%d, failed to respond",
> + q->guc->id);
> + /* XXX: Trigger GT reset? */
> + return -ETIME;
> + }
> +
> + return 0;
> }
>
> static void guc_exec_queue_resume(struct xe_exec_queue *q)
> diff --git a/drivers/gpu/drm/xe/xe_preempt_fence.c b/drivers/gpu/drm/xe/xe_preempt_fence.c
> index e8b8ae5c6485..8356d9798206 100644
> --- a/drivers/gpu/drm/xe/xe_preempt_fence.c
> +++ b/drivers/gpu/drm/xe/xe_preempt_fence.c
> @@ -16,11 +16,23 @@ static void preempt_fence_work_func(struct work_struct *w)
> struct xe_preempt_fence *pfence =
> container_of(w, typeof(*pfence), preempt_work);
> struct xe_exec_queue *q = pfence->q;
> + int err = 0;
>
> if (pfence->error)
> dma_fence_set_error(&pfence->base, pfence->error);
> + else if (!q->ops->reset_status(q))
> + err = q->ops->suspend_wait(q);
> else
> - q->ops->suspend_wait(q);
> + dma_fence_set_error(&pfence->base, -ENOENT);
> +
> + if (err) {
> + dma_fence_set_error(&pfence->base, err);
> +
> + down_write(&q->vm->lock);
> + xe_vm_kill(q->vm, false);
> + up_write(&q->vm->lock);
I think grabbing vm->lock will deadlock here, right? Calling vm_kill
might also be scary? lockdep will not see it unless we have some way of
triggering the error path here. For reference:
3cd1585e57908b6efcd967465ef7685f40b2a294
> + }
> +
>
> dma_fence_signal(&pfence->base);
> /*
> diff --git a/drivers/gpu/drm/xe/xe_vm.c b/drivers/gpu/drm/xe/xe_vm.c
> index 5b166fa03684..e7c15b7877b1 100644
> --- a/drivers/gpu/drm/xe/xe_vm.c
> +++ b/drivers/gpu/drm/xe/xe_vm.c
> @@ -311,7 +311,15 @@ int __xe_vm_userptr_needs_repin(struct xe_vm *vm)
>
> #define XE_VM_REBIND_RETRY_TIMEOUT_MS 1000
>
> -static void xe_vm_kill(struct xe_vm *vm, bool unlocked)
> +/**
> + * xe_vm_kill() - VM Kill
> + * @vm: The VM.
> + * @unlocked: Flag indicates the VM's dma-resv is not held
> + *
> + * Kill the VM by setting banned flag indicated VM is no longer available for
> + * use. If in preempt fence mode, also kill all exec queue attached to the VM.
> + */
> +void xe_vm_kill(struct xe_vm *vm, bool unlocked)
> {
> struct xe_exec_queue *q;
>
> diff --git a/drivers/gpu/drm/xe/xe_vm.h b/drivers/gpu/drm/xe/xe_vm.h
> index b481608b12f1..c864dba35e1d 100644
> --- a/drivers/gpu/drm/xe/xe_vm.h
> +++ b/drivers/gpu/drm/xe/xe_vm.h
> @@ -259,6 +259,8 @@ static inline struct dma_resv *xe_vm_resv(struct xe_vm *vm)
> return drm_gpuvm_resv(&vm->gpuvm);
> }
>
> +void xe_vm_kill(struct xe_vm *vm, bool unlocked);
> +
> /**
> * xe_vm_assert_held(vm) - Assert that the vm's reservation object is held.
> * @vm: The vm
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