[PATCH v2] drm/xe: Add timeout to preempt fences
Matthew Brost
matthew.brost at intel.com
Tue Jun 25 15:46:17 UTC 2024
On Tue, Jun 25, 2024 at 02:03:38PM +0100, Matthew Auld wrote:
> 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.
>
Yea, I knew some smp_* barrier usage was wrong. Let me drop this.
> > +
> > + 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
>
Yea I think you are right. I was thinking we could grab this here as I
thought having a dedicated ordered work queue here allowed the vm->lock
to be safely taken about that thinking is wrong. Hmm, I need to rethink
this design. I might be able to refactor xe_vm_kill to not require the
vm->lock... Let me play around with this.
Matt
> > + }
> > +
> > 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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