drm/xe: Use topology to determine page fault queue size

BugLink: https://bugs.launchpad.net/bugs/2089884

[ Upstream commit 3338e4f90c143cf32f77d64f464cb7f2c2d24700 ]

Currently the page fault queue size is hard coded. However
the hardware supports faulting for each EU and each CS.
For some applications running on hardware with a large
number of EUs and CSs, this can result in an overflow of
the page fault queue.

Add a small calculation to determine the page fault queue
size based on the number of EUs and CSs in the platform as
detmined by fuses.

Signed-off-by: Stuart Summers <stuart.summers@intel.com>
Reviewed-by: Matthew Brost <matthew.brost@intel.com>
Signed-off-by: Matthew Brost <matthew.brost@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/24d582a3b48c97793b8b6a402f34b4b469471636.1723862633.git.stuart.summers@intel.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
[koichiroden: adjusted context due to missing commit:
6240c2c43fd0 ("drm/xe: Document nested struct members according to guidelines")]
Signed-off-by: Koichiro Den <koichiro.den@canonical.com>
Signed-off-by: Roxana Nicolescu <roxana.nicolescu@canonical.com>

drivers/gpu/drm/xe/xe_gt_pagefault.c

@@ -308,7 +308,7 @@ static bool get_pagefault(struct pf_queue *pf_queue, struct pagefault *pf)
 			PFD_VIRTUAL_ADDR_LO_SHIFT;
 
 		pf_queue->tail = (pf_queue->tail + PF_MSG_LEN_DW) %
-			PF_QUEUE_NUM_DW;
+			pf_queue->num_dw;
 		ret = true;
 	}
 	spin_unlock_irq(&pf_queue->lock);
@@ -320,7 +320,8 @@ static bool pf_queue_full(struct pf_queue *pf_queue)
 {
 	lockdep_assert_held(&pf_queue->lock);
 
-	return CIRC_SPACE(pf_queue->head, pf_queue->tail, PF_QUEUE_NUM_DW) <=
+	return CIRC_SPACE(pf_queue->head, pf_queue->tail,
+			  pf_queue->num_dw) <=
 		PF_MSG_LEN_DW;
 }
 
@@ -339,11 +340,17 @@ int xe_guc_pagefault_handler(struct xe_guc *guc, u32 *msg, u32 len)
 	asid = FIELD_GET(PFD_ASID, msg[1]);
 	pf_queue = gt->usm.pf_queue + (asid % NUM_PF_QUEUE);
 
+	/*
+	 * The below logic doesn't work unless PF_QUEUE_NUM_DW % PF_MSG_LEN_DW == 0
+	 */
+	xe_gt_assert(gt, !(pf_queue->num_dw % PF_MSG_LEN_DW));
+
 	spin_lock_irqsave(&pf_queue->lock, flags);
 	full = pf_queue_full(pf_queue);
 	if (!full) {
 		memcpy(pf_queue->data + pf_queue->head, msg, len * sizeof(u32));
-		pf_queue->head = (pf_queue->head + len) % PF_QUEUE_NUM_DW;
+		pf_queue->head = (pf_queue->head + len) %
+			pf_queue->num_dw;
 		queue_work(gt->usm.pf_wq, &pf_queue->worker);
 	} else {
 		drm_warn(&xe->drm, "PF Queue full, shouldn't be possible");
@@ -402,26 +409,54 @@ static void pagefault_fini(void *arg)
 {
 	struct xe_gt *gt = arg;
 	struct xe_device *xe = gt_to_xe(gt);
+	int i;
 
 	if (!xe->info.has_usm)
 		return;
 
 	destroy_workqueue(gt->usm.acc_wq);
 	destroy_workqueue(gt->usm.pf_wq);
+
+	for (i = 0; i < NUM_PF_QUEUE; ++i)
+		kfree(gt->usm.pf_queue[i].data);
+}
+
+static int xe_alloc_pf_queue(struct xe_gt *gt, struct pf_queue *pf_queue)
+{
+	xe_dss_mask_t all_dss;
+	int num_dss, num_eus;
+
+	bitmap_or(all_dss, gt->fuse_topo.g_dss_mask, gt->fuse_topo.c_dss_mask,
+		  XE_MAX_DSS_FUSE_BITS);
+
+	num_dss = bitmap_weight(all_dss, XE_MAX_DSS_FUSE_BITS);
+	num_eus = bitmap_weight(gt->fuse_topo.eu_mask_per_dss,
+				XE_MAX_EU_FUSE_BITS) * num_dss;
+
+	/* user can issue separate page faults per EU and per CS */
+	pf_queue->num_dw =
+		(num_eus + XE_NUM_HW_ENGINES) * PF_MSG_LEN_DW;
+
+	pf_queue->gt = gt;
+	pf_queue->data = kzalloc(pf_queue->num_dw, GFP_KERNEL);
+	spin_lock_init(&pf_queue->lock);
+	INIT_WORK(&pf_queue->worker, pf_queue_work_func);
+
+	return 0;
 }
 
 int xe_gt_pagefault_init(struct xe_gt *gt)
 {
 	struct xe_device *xe = gt_to_xe(gt);
-	int i;
+	int i, ret = 0;
 
 	if (!xe->info.has_usm)
 		return 0;
 
 	for (i = 0; i < NUM_PF_QUEUE; ++i) {
-		gt->usm.pf_queue[i].gt = gt;
-		spin_lock_init(&gt->usm.pf_queue[i].lock);
-		INIT_WORK(&gt->usm.pf_queue[i].worker, pf_queue_work_func);
+		ret = xe_alloc_pf_queue(gt, &gt->usm.pf_queue[i]);
+		if (ret)
+			return ret;
 	}
 	for (i = 0; i < NUM_ACC_QUEUE; ++i) {
 		gt->usm.acc_queue[i].gt = gt;

drivers/gpu/drm/xe/xe_gt_types.h

@@ -224,9 +224,14 @@ struct xe_gt {
 		struct pf_queue {
 			/** @gt: back pointer to GT */
 			struct xe_gt *gt;
-#define PF_QUEUE_NUM_DW	128
 			/** @data: data in the page fault queue */
-			u32 data[PF_QUEUE_NUM_DW];
+			u32 *data;
+			/**
+			 * @usm.pf_queue.num_dw: number of DWORDS in the page
+			 * fault queue. Dynamically calculated based on the number
+			 * of compute resources available.
+			 */
+			u32 num_dw;
 			/**
 			 * @tail: tail pointer in DWs for page fault queue,
 			 * moved by worker which processes faults (consumer).