Re: [PATCH v8 11/12] drm/xe: batch CT pagefault acks with periodic flush

[Francois Dugast <francois.dugast@intel.com>]

On Tue, Aug 04, 2026 at 10:53:05AM -0700, Matthew Brost wrote:
> On Tue, Aug 04, 2026 at 02:55:41PM +0200, Francois Dugast wrote:
> > LGTM, just a couple of nits below.
> > 
> > On Fri, Jul 24, 2026 at 04:26:00PM -0700, Matthew Brost wrote:
> > > Pagefault storms can generate long chains of acknowledgments back to the
> > > GuC. Sending each ack as a full CT submission forces a barrier,
> > > descriptor update and doorbell per fault.
> > > 
> > > Extend xe_guc_ct_send_locked() with a “write-only” mode that copies the
> > 
> > Wondering if calling the argument "defer_flush" instead of "write_only" would
> > be a better fit, and also hint the caller to call xe_guc_ct_send_flush().
> > 
> > > message into the H2G ring but defers publishing the descriptor and
> > > ringing the doorbell. Add xe_guc_ct_send_flush() to publish pending
> > > writes and notify GuC once per batch. Wire this into the pagefault
> > > producer via new ack_fault_begin/ack_fault_end callbacks and CT lock
> > > wrappers.
> > > 
> > > To avoid excessive flush latency while still amortizing MMIO costs, use
> > > a simple periodic flush heuristic for GuC pagefault acks: batch most
> > > acks as write-only and force a publish at a fixed interval (e.g., every
> > > 16th ack), with a final flush at end-of-batch.
> > > 
> > > Also increase the H2G CTB size to 16K to better absorb bursts.
> > > 
> > > Assisted-by: ChatGPT:gpt-5 # Documentation
> > > Signed-off-by: Matthew Brost <matthew.brost@intel.com>
> > > ---
> > >  drivers/gpu/drm/xe/xe_guc_ct.c          | 95 +++++++++++++++++++------
> > >  drivers/gpu/drm/xe/xe_guc_ct.h          | 36 +++++++++-
> > >  drivers/gpu/drm/xe/xe_guc_pagefault.c   | 32 ++++++++-
> > >  drivers/gpu/drm/xe/xe_guc_types.h       |  6 ++
> > >  drivers/gpu/drm/xe/xe_pagefault.c       | 12 +++-
> > >  drivers/gpu/drm/xe/xe_pagefault_types.h | 14 ++++
> > >  6 files changed, 170 insertions(+), 25 deletions(-)
> > > 
> > > diff --git a/drivers/gpu/drm/xe/xe_guc_ct.c b/drivers/gpu/drm/xe/xe_guc_ct.c
> > > index fe70c0fd85c5..686611ddabc8 100644
> > > --- a/drivers/gpu/drm/xe/xe_guc_ct.c
> > > +++ b/drivers/gpu/drm/xe/xe_guc_ct.c
> > > @@ -265,7 +265,7 @@ static bool g2h_fence_needs_alloc(struct g2h_fence *g2h_fence)
> > >  #define CTB_DESC_SIZE		ALIGN(sizeof(struct guc_ct_buffer_desc), SZ_2K)
> > >  #define CTB_H2G_BUFFER_OFFSET	(CTB_DESC_SIZE * 2)
> > >  #define CTB_G2H_BUFFER_OFFSET	(CTB_DESC_SIZE * 2)
> > > -#define CTB_H2G_BUFFER_SIZE	(SZ_4K)
> > > +#define CTB_H2G_BUFFER_SIZE	(SZ_16K)
> > >  #define CTB_H2G_BUFFER_DWORDS	(CTB_H2G_BUFFER_SIZE / sizeof(u32))
> > >  #define CTB_G2H_BUFFER_SIZE	(SZ_128K)
> > >  #define CTB_G2H_BUFFER_DWORDS	(CTB_G2H_BUFFER_SIZE / sizeof(u32))
> > > @@ -939,7 +939,7 @@ static bool vf_action_can_safely_fail(struct xe_device *xe, u32 action)
> > >  #define H2G_CT_HEADERS (GUC_CTB_HDR_LEN + 1) /* one DW CTB header and one DW HxG header */
> > >  
> > >  static int h2g_write(struct xe_guc_ct *ct, const u32 *action, u32 len,
> > > -		     u32 ct_fence_value, bool want_response)
> > > +		     u32 ct_fence_value, bool want_response, bool write_only)
> > >  {
> > >  	struct xe_device *xe = ct_to_xe(ct);
> > >  	struct xe_gt *gt = ct_to_gt(ct);
> > > @@ -956,7 +956,6 @@ static int h2g_write(struct xe_guc_ct *ct, const u32 *action, u32 len,
> > >  	xe_gt_assert(gt, full_len <= GUC_CTB_MSG_MAX_LEN);
> > >  
> > >  	if (IS_ENABLED(CONFIG_DRM_XE_DEBUG)) {
> > > -		u32 desc_tail = desc_read(xe, h2g, tail);
> > >  		u32 desc_head = desc_read(xe, h2g, head);
> > >  		u32 desc_status;
> > >  
> > > @@ -966,12 +965,6 @@ static int h2g_write(struct xe_guc_ct *ct, const u32 *action, u32 len,
> > >  			goto corrupted;
> > >  		}
> > >  
> > > -		if (tail != desc_tail) {
> > > -			desc_write(xe, h2g, status, desc_status | GUC_CTB_STATUS_MISMATCH);
> > > -			xe_gt_err(gt, "CT write: tail was modified %u != %u\n", desc_tail, tail);
> > > -			goto corrupted;
> > > -		}
> > 
> > Could we keep that check when !write_only?
> > 
> 
> Not without a bigger change. Consider write_only followed by
> !write_only, the tail != desc_tail immediately mismatches.
> 
> We'd have to add 3 states:
> 
> - Normal (check)
> - Defer flush (no check)
> - Issue flush (no check)
> 
> Not sure if it is worth the complexity, but change add if this if you
> want.

Agreed, probably not worth the extra complexity in that case.

Francois

> 
> > > -
> > >  		if (tail > h2g->info.size) {
> > >  			desc_write(xe, h2g, status, desc_status | GUC_CTB_STATUS_OVERFLOW);
> > >  			xe_gt_err(gt, "CT write: tail out of range: %u vs %u\n",
> > > @@ -993,7 +986,10 @@ static int h2g_write(struct xe_guc_ct *ct, const u32 *action, u32 len,
> > >  			      (h2g->info.size - tail) * sizeof(u32));
> > >  		h2g_reserve_space(ct, (h2g->info.size - tail));
> > >  		h2g->info.tail = 0;
> > > -		desc_write(xe, h2g, tail, h2g->info.tail);
> > > +		if (!write_only) {
> > > +			xe_device_wmb(xe);
> > > +			desc_write(xe, h2g, tail, h2g->info.tail);
> > > +		}
> > >  
> > >  		return -EAGAIN;
> > >  	}
> > > @@ -1024,14 +1020,15 @@ static int h2g_write(struct xe_guc_ct *ct, const u32 *action, u32 len,
> > >  	/* Write H2G ensuring visible before descriptor update */
> > >  	xe_map_memcpy_to(xe, &map, 0, cmd, H2G_CT_HEADERS * sizeof(u32));
> > >  	xe_map_memcpy_to(xe, &map, H2G_CT_HEADERS * sizeof(u32), action, len * sizeof(u32));
> > > -	xe_device_wmb(xe);
> > > -
> > >  	/* Update local copies */
> > >  	h2g->info.tail = (tail + full_len) % h2g->info.size;
> > >  	h2g_reserve_space(ct, full_len);
> > >  
> > >  	/* Update descriptor */
> > > -	desc_write(xe, h2g, tail, h2g->info.tail);
> > > +	if (!write_only) {
> > > +		xe_device_wmb(xe);
> > > +		desc_write(xe, h2g, tail, h2g->info.tail);
> > > +	}
> > >  
> > >  	/*
> > >  	 * desc_read() performs an VRAM read which serializes the CPU and drains
> > > @@ -1052,7 +1049,7 @@ static int h2g_write(struct xe_guc_ct *ct, const u32 *action, u32 len,
> > >  
> > >  static int __guc_ct_send_locked(struct xe_guc_ct *ct, const u32 *action,
> > >  				u32 len, u32 g2h_len, u32 num_g2h,
> > > -				struct g2h_fence *g2h_fence)
> > > +				struct g2h_fence *g2h_fence, bool write_only)
> > >  {
> > >  	struct xe_gt *gt = ct_to_gt(ct);
> > >  	u16 seqno;
> > > @@ -1112,7 +1109,7 @@ static int __guc_ct_send_locked(struct xe_guc_ct *ct, const u32 *action,
> > >  	if (unlikely(ret))
> > >  		goto out_unlock;
> > >  
> > > -	ret = h2g_write(ct, action, len, seqno, !!g2h_fence);
> > > +	ret = h2g_write(ct, action, len, seqno, !!g2h_fence, write_only);
> > >  	if (unlikely(ret)) {
> > >  		if (ret == -EAGAIN)
> > >  			goto retry;
> > > @@ -1120,7 +1117,8 @@ static int __guc_ct_send_locked(struct xe_guc_ct *ct, const u32 *action,
> > >  	}
> > >  
> > >  	__g2h_reserve_space(ct, g2h_len, num_g2h);
> > > -	xe_guc_notify(ct_to_guc(ct));
> > > +	if (!write_only)
> > > +		xe_guc_notify(ct_to_guc(ct));
> > >  out_unlock:
> > >  	if (g2h_len)
> > >  		spin_unlock_irq(&ct->fast_lock);
> > > @@ -1196,7 +1194,7 @@ static bool guc_ct_send_wait_for_retry(struct xe_guc_ct *ct, u32 len,
> > >  
> > >  static int guc_ct_send_locked(struct xe_guc_ct *ct, const u32 *action, u32 len,
> > >  			      u32 g2h_len, u32 num_g2h,
> > > -			      struct g2h_fence *g2h_fence)
> > > +			      struct g2h_fence *g2h_fence, bool write_only)
> > >  {
> > >  	struct xe_gt *gt = ct_to_gt(ct);
> > >  	unsigned int sleep_period_ms = 1;
> > > @@ -1209,9 +1207,10 @@ static int guc_ct_send_locked(struct xe_guc_ct *ct, const u32 *action, u32 len,
> > >  
> > >  try_again:
> > >  	ret = __guc_ct_send_locked(ct, action, len, g2h_len, num_g2h,
> > > -				   g2h_fence);
> > > +				   g2h_fence, write_only);
> > >  
> > >  	if (unlikely(ret == -EBUSY)) {
> > > +		xe_guc_ct_send_flush(ct);
> > >  		if (!guc_ct_send_wait_for_retry(ct, len, g2h_len, g2h_fence,
> > >  						&sleep_period_ms, &sleep_total_ms))
> > >  			goto broken;
> > > @@ -1235,7 +1234,8 @@ static int guc_ct_send(struct xe_guc_ct *ct, const u32 *action, u32 len,
> > >  	xe_gt_assert(ct_to_gt(ct), !g2h_len || !g2h_fence);
> > >  
> > >  	mutex_lock(&ct->lock);
> > > -	ret = guc_ct_send_locked(ct, action, len, g2h_len, num_g2h, g2h_fence);
> > > +	ret = guc_ct_send_locked(ct, action, len, g2h_len, num_g2h, g2h_fence,
> > > +				 false);
> > >  	mutex_unlock(&ct->lock);
> > >  
> > >  	return ret;
> > > @@ -1283,25 +1283,76 @@ int xe_guc_ct_send(struct xe_guc_ct *ct, const u32 *action, u32 len,
> > >  	return ret;
> > >  }
> > >  
> > > +/**
> > > + * xe_guc_ct_send_locked() - submit a GuC CT H2G message with CT lock held
> > > + * @ct: GuC CT object
> > > + * @action: payload dwords (HxG header dword is expected at @action[-1])
> > > + * @len: number of payload dwords in @action
> > > + * @write_only: defer publishing/doorbell for batching
> > > + *
> > > + * Sends a single H2G message to the GuC CT buffer while the caller already
> > > + * holds @ct->lock.
> > > + *
> > > + * If @write_only is false, the function completes the submission immediately:
> > > + * it makes the payload visible to the device, updates the H2G descriptor and
> > > + * rings the GuC doorbell.
> > > + *
> > > + * If @write_only is true, the message payload is copied into the H2G ring and
> > > + * the software tail is advanced, but the descriptor update and doorbell are
> > > + * deferred so multiple messages can be batched. In this mode, the caller must
> > > + * eventually call xe_guc_ct_send_flush() (still holding @ct->lock) to publish
> > > + * the descriptor and notify the GuC. On internal retry paths (-EBUSY), the
> > > + * implementation may force a flush to ensure forward progress.
> > > + *
> > > + * Return: 0 on success, negative errno on failure.
> > > + *
> > > + * Locking:
> > > + *   Must be called with @ct->lock held.
> > > + */
> > >  int xe_guc_ct_send_locked(struct xe_guc_ct *ct, const u32 *action, u32 len,
> > > -			  u32 g2h_len, u32 num_g2h)
> > > +			  bool write_only)
> > >  {
> > >  	int ret;
> > >  
> > > -	ret = guc_ct_send_locked(ct, action, len, g2h_len, num_g2h, NULL);
> > > +	ret = guc_ct_send_locked(ct, action, len, 0, 0, NULL, write_only);
> > >  	if (ret == -EDEADLK)
> > >  		kick_reset(ct);
> > >  
> > >  	return ret;
> > >  }
> > >  
> > > +/**
> > > + * xe_guc_ct_send_flush() - flush pending GuC CT H2G writes
> > > + * @ct: GuC CT instance
> > > + *
> > > + * Some callers batch multiple H2G writes using xe_guc_ct_send_locked() in
> > > + * "write-only" mode (i.e., queue the message payloads but defer ringing the
> > > + * doorbell / updating the CT descriptor). This helper completes the submission
> > > + * by ensuring the payload writes are visible to the device, updating the H2G
> > > + * descriptor, and ringing the GuC CT doorbell.
> > > + *
> > > + * Locking:
> > > + *   Must be called with @ct->lock held.
> > > + */
> > > +void xe_guc_ct_send_flush(struct xe_guc_ct *ct)
> > > +{
> > > +	struct xe_device *xe = ct_to_xe(ct);
> > > +	struct guc_ctb *h2g = &ct->ctbs.h2g;
> > > +
> > > +	lockdep_assert_held(&ct->lock);
> > > +
> > > +	xe_device_wmb(xe);
> > > +	desc_write(xe, h2g, tail, h2g->info.tail);
> > > +	xe_guc_notify(ct_to_guc(ct));
> > > +}
> > > +
> > >  int xe_guc_ct_send_g2h_handler(struct xe_guc_ct *ct, const u32 *action, u32 len)
> > >  {
> > >  	int ret;
> > >  
> > >  	lockdep_assert_held(&ct->lock);
> > >  
> > > -	ret = guc_ct_send_locked(ct, action, len, 0, 0, NULL);
> > > +	ret = guc_ct_send_locked(ct, action, len, 0, 0, NULL, false);
> > >  	if (ret == -EDEADLK)
> > >  		kick_reset(ct);
> > >  
> > > diff --git a/drivers/gpu/drm/xe/xe_guc_ct.h b/drivers/gpu/drm/xe/xe_guc_ct.h
> > > index 767365a33dee..b30c1f34be39 100644
> > > --- a/drivers/gpu/drm/xe/xe_guc_ct.h
> > > +++ b/drivers/gpu/drm/xe/xe_guc_ct.h
> > > @@ -54,7 +54,7 @@ static inline void xe_guc_ct_irq_handler(struct xe_guc_ct *ct)
> > >  int xe_guc_ct_send(struct xe_guc_ct *ct, const u32 *action, u32 len,
> > >  		   u32 g2h_len, u32 num_g2h);
> > >  int xe_guc_ct_send_locked(struct xe_guc_ct *ct, const u32 *action, u32 len,
> > > -			  u32 g2h_len, u32 num_g2h);
> > > +			  bool write_only);
> > >  int xe_guc_ct_send_recv(struct xe_guc_ct *ct, const u32 *action, u32 len,
> > >  			u32 *response_buffer);
> > >  static inline int
> > > @@ -63,6 +63,8 @@ xe_guc_ct_send_block(struct xe_guc_ct *ct, const u32 *action, u32 len)
> > >  	return xe_guc_ct_send_recv(ct, action, len, NULL);
> > >  }
> > >  
> > > +void xe_guc_ct_send_flush(struct xe_guc_ct *ct);
> > > +
> > >  /* This is only version of the send CT you can call from a G2H handler */
> > >  int xe_guc_ct_send_g2h_handler(struct xe_guc_ct *ct, const u32 *action,
> > >  			       u32 len);
> > > @@ -87,4 +89,36 @@ static inline void xe_guc_ct_wake_waiters(struct xe_guc_ct *ct)
> > >  	wake_up_all(&ct->wq);
> > >  }
> > >  
> > > +/**
> > > + * xe_guc_ct_lock() - take the GuC CT mutex
> > > + * @ct: GuC CT object
> > > + *
> > > + * Wrapper around mutex_lock(&ct->lock) for cases where CT operations need to be
> > > + * performed from contexts that want an explicit "CT locked" pair without
> > > + * exporting the lock itself.
> > > + *
> > > + * Return/Locking:
> > > + *   Acquires @ct->lock.
> > > + */
> > > +static inline void xe_guc_ct_lock(struct xe_guc_ct *ct)
> > > +__acquires(&ct->lock)
> > > +{
> > > +	mutex_lock(&ct->lock);
> > 
> > Now it would be cleaner to add "#include <linux/mutex.h>" in xe_guc_ct.h.
> > 
> 
> Sure.
> 
> Matt
> 
> > Francois
> > 
> > > +}
> > > +
> > > +/**
> > > + * xe_guc_ct_unlock() - release the GuC CT mutex
> > > + * @ct: GuC CT object
> > > + *
> > > + * Counterpart to xe_guc_ct_lock().
> > > + *
> > > + * Locking:
> > > + *   Releases @ct->lock.
> > > + */
> > > +static inline void xe_guc_ct_unlock(struct xe_guc_ct *ct)
> > > +__releases(&ct->lock)
> > > +{
> > > +	mutex_unlock(&ct->lock);
> > > +}
> > > +
> > >  #endif
> > > diff --git a/drivers/gpu/drm/xe/xe_guc_pagefault.c b/drivers/gpu/drm/xe/xe_guc_pagefault.c
> > > index 2470faf3d5d8..8f8210a732e9 100644
> > > --- a/drivers/gpu/drm/xe/xe_guc_pagefault.c
> > > +++ b/drivers/gpu/drm/xe/xe_guc_pagefault.c
> > > @@ -10,6 +10,22 @@
> > >  #include "xe_pagefault.h"
> > >  #include "xe_pagefault_types.h"
> > >  
> > > +#define XE_GUC_PAGEFAULT_FLUSH_PERIOD	BIT(4)	/* Sixteen */
> > > +
> > > +static void guc_ack_fault_begin(void *private)
> > > +{
> > > +	struct xe_guc *guc = private;
> > > +
> > > +	xe_guc_ct_lock(&guc->ct);
> > > +
> > > +	BUILD_BUG_ON(((XE_GUC_PAGEFAULT_FLUSH_PERIOD - 1) &
> > > +		     XE_GUC_PAGEFAULT_FLUSH_PERIOD) != 0);
> > > +
> > > +	/* Ack the 2nd, then 18th, etc... */
> > > +	guc->pagefault_ack_counter =
> > > +		XE_GUC_PAGEFAULT_FLUSH_PERIOD - 1;
> > > +}
> > > +
> > >  static void guc_ack_fault(struct xe_pagefault *pf, int err)
> > >  {
> > >  	u32 vfid = FIELD_GET(PFD_VFID, pf->producer.msg[2]);
> > > @@ -36,12 +52,26 @@ static void guc_ack_fault(struct xe_pagefault *pf, int err)
> > >  		FIELD_PREP(PFR_PDATA, pdata),
> > >  	};
> > >  	struct xe_guc *guc = pf->producer.private;
> > > +	bool write_only = guc->pagefault_ack_counter++ &
> > > +		(XE_GUC_PAGEFAULT_FLUSH_PERIOD - 1);
> > > +
> > > +	xe_guc_ct_send_locked(&guc->ct, action, ARRAY_SIZE(action),
> > > +			      write_only);
> > > +}
> > > +
> > > +static void guc_ack_fault_end(void *private)
> > > +{
> > > +	struct xe_guc *guc = private;
> > >  
> > > -	xe_guc_ct_send(&guc->ct, action, ARRAY_SIZE(action), 0, 0);
> > > +	if ((guc->pagefault_ack_counter & (XE_GUC_PAGEFAULT_FLUSH_PERIOD - 1)) != 1)
> > > +		xe_guc_ct_send_flush(&guc->ct);
> > > +	xe_guc_ct_unlock(&guc->ct);
> > >  }
> > >  
> > >  static const struct xe_pagefault_ops guc_pagefault_ops = {
> > > +	.ack_fault_begin = guc_ack_fault_begin,
> > >  	.ack_fault = guc_ack_fault,
> > > +	.ack_fault_end = guc_ack_fault_end,
> > >  };
> > >  
> > >  /**
> > > diff --git a/drivers/gpu/drm/xe/xe_guc_types.h b/drivers/gpu/drm/xe/xe_guc_types.h
> > > index 31a2acb63ac3..3dbcb1331690 100644
> > > --- a/drivers/gpu/drm/xe/xe_guc_types.h
> > > +++ b/drivers/gpu/drm/xe/xe_guc_types.h
> > > @@ -122,6 +122,12 @@ struct xe_guc {
> > >  	struct xe_reg notify_reg;
> > >  	/** @params: Control params for fw initialization */
> > >  	u32 params[GUC_CTL_MAX_DWORDS];
> > > +
> > > +	/**
> > > +	 * @pagefault_ack_counter: Counter to determine when periodically ack
> > > +	 * pagefaults in a batch.
> > > +	 */
> > > +	u32 pagefault_ack_counter;
> > >  };
> > >  
> > >  #endif
> > > diff --git a/drivers/gpu/drm/xe/xe_pagefault.c b/drivers/gpu/drm/xe/xe_pagefault.c
> > > index caa39a024ae6..917884c49e1d 100644
> > > --- a/drivers/gpu/drm/xe/xe_pagefault.c
> > > +++ b/drivers/gpu/drm/xe/xe_pagefault.c
> > > @@ -412,6 +412,10 @@ static bool xe_pagefault_try_chain(struct xe_pagefault_queue *pf_queue,
> > >  			xe_assert(xe, pf_work->cache.pf->consumer.alloc_state ==
> > >  				  XE_PAGEFAULT_ALLOC_STATE_ACTIVE);
> > >  
> > > +			if (pf->producer.private !=
> > > +			    pf_work->cache.pf->producer.private)
> > > +				continue;
> > > +
> > >  			xe_gt_stats_incr(pf->gt,
> > >  					 XE_GT_STATS_ID_CHAIN_PAGEFAULT_COUNT,
> > >  					 1);
> > > @@ -585,6 +589,8 @@ static void xe_pagefault_queue_work(struct work_struct *w)
> > >  	threshold = jiffies + msecs_to_jiffies(USM_QUEUE_MAX_RUNTIME_MS);
> > >  
> > >  	while (xe_pagefault_queue_pop(pf_queue, &pf, pf_work->id)) {
> > > +		const struct xe_pagefault_ops *ops = pf->producer.ops;
> > > +		void *private = pf->producer.private;
> > >  		struct xe_gt *gt = pf->gt;
> > >  		u32 asid = pf->consumer.asid;
> > >  		int err = 0;
> > > @@ -622,11 +628,14 @@ static void xe_pagefault_queue_work(struct work_struct *w)
> > >  			  XE_PAGEFAULT_ALLOC_STATE_ACTIVE);
> > >  		xe_assert(xe, pf == pf_work->cache.pf);
> > >  
> > > +		ops->ack_fault_begin(private);
> > >  		while (pf) {
> > >  			xe_assert(xe, pf->consumer.alloc_state ==
> > >  				  XE_PAGEFAULT_ALLOC_STATE_ACTIVE);
> > > +			xe_assert(xe, ops == pf->producer.ops);
> > > +			xe_assert(xe, gt == pf->gt);
> > >  
> > > -			pf->producer.ops->ack_fault(pf, err);
> > > +			ops->ack_fault(pf, err);
> > >  
> > >  			spin_lock_irq(&pf_queue->lock);
> > >  
> > > @@ -654,6 +663,7 @@ static void xe_pagefault_queue_work(struct work_struct *w)
> > >  					XE_PAGEFAULT_ALLOC_STATE_ACTIVE;
> > >  			spin_unlock_irq(&pf_queue->lock);
> > >  		}
> > > +		ops->ack_fault_end(private);
> > >  
> > >  		if (time_after(jiffies, threshold)) {
> > >  			queue_work(xe->usm.pagefault_wq, w);
> > > diff --git a/drivers/gpu/drm/xe/xe_pagefault_types.h b/drivers/gpu/drm/xe/xe_pagefault_types.h
> > > index a1fff0e47fa5..efeba5c3a58b 100644
> > > --- a/drivers/gpu/drm/xe/xe_pagefault_types.h
> > > +++ b/drivers/gpu/drm/xe/xe_pagefault_types.h
> > > @@ -33,6 +33,13 @@ enum xe_pagefault_type {
> > >  
> > >  /** struct xe_pagefault_ops - Xe pagefault ops (producer) */
> > >  struct xe_pagefault_ops {
> > > +	/**
> > > +	 * @ack_fault_begin: Ack fault begin
> > > +	 * @private: producer private data
> > > +	 *
> > > +	 * Page fault producer begins acknowledgment from the consumer.
> > > +	 */
> > > +	void (*ack_fault_begin)(void *private);
> > >  	/**
> > >  	 * @ack_fault: Ack fault
> > >  	 * @pf: Page fault
> > > @@ -42,6 +49,13 @@ struct xe_pagefault_ops {
> > >  	 * sends the result to the HW/FW interface.
> > >  	 */
> > >  	void (*ack_fault)(struct xe_pagefault *pf, int err);
> > > +	/**
> > > +	 * @ack_fault_end: Ack fault end
> > > +	 * @private: producer private data
> > > +	 *
> > > +	 * Page fault producer ends acknowledgment from the consumer.
> > > +	 */
> > > +	void (*ack_fault_end)(void *private);
> > >  };
> > >  
> > >  /**
> > > -- 
> > > 2.34.1
> > >