1 files changed, 445 insertions, 0 deletions
diff --git a/drivers/gpu/drm/xe/xe_pagefault.c b/drivers/gpu/drm/xe/xe_pagefault.c
new file mode 100644
index 000000000000..fe3e40145012
--- /dev/null
+++ b/drivers/gpu/drm/xe/xe_pagefault.c
@@ -0,0 +1,445 @@
+// SPDX-License-Identifier: MIT
+/*
+ * Copyright © 2025 Intel Corporation
+ */
+
+#include <linux/circ_buf.h>
+
+#include <drm/drm_exec.h>
+#include <drm/drm_managed.h>
+
+#include "xe_bo.h"
+#include "xe_device.h"
+#include "xe_gt_printk.h"
+#include "xe_gt_types.h"
+#include "xe_gt_stats.h"
+#include "xe_hw_engine.h"
+#include "xe_pagefault.h"
+#include "xe_pagefault_types.h"
+#include "xe_svm.h"
+#include "xe_trace_bo.h"
+#include "xe_vm.h"
+
+/**
+ * DOC: Xe page faults
+ *
+ * Xe page faults are handled in two layers. The producer layer interacts with
+ * hardware or firmware to receive and parse faults into struct xe_pagefault,
+ * then forwards them to the consumer. The consumer layer services the faults
+ * (e.g., memory migration, page table updates) and acknowledges the result back
+ * to the producer, which then forwards the results to the hardware or firmware.
+ * The consumer uses a page fault queue sized to absorb all potential faults and
+ * a multi-threaded worker to process them. Multiple producers are supported,
+ * with a single shared consumer.
+ *
+ * xe_pagefault.c implements the consumer layer.
+ */
+
+static int xe_pagefault_entry_size(void)
+{
+	/*
+	 * Power of two alignment is not a hardware requirement, rather a
+	 * software restriction which makes the math for page fault queue
+	 * management simplier.
+	 */
+	return roundup_pow_of_two(sizeof(struct xe_pagefault));
+}
+
+static int xe_pagefault_begin(struct drm_exec *exec, struct xe_vma *vma,
+			      struct xe_vram_region *vram, bool need_vram_move)
+{
+	struct xe_bo *bo = xe_vma_bo(vma);
+	struct xe_vm *vm = xe_vma_vm(vma);
+	int err;
+
+	err = xe_vm_lock_vma(exec, vma);
+	if (err)
+		return err;
+
+	if (!bo)
+		return 0;
+
+	return need_vram_move ? xe_bo_migrate(bo, vram->placement, NULL, exec) :
+		xe_bo_validate(bo, vm, true, exec);
+}
+
+static int xe_pagefault_handle_vma(struct xe_gt *gt, struct xe_vma *vma,
+				   bool atomic)
+{
+	struct xe_vm *vm = xe_vma_vm(vma);
+	struct xe_tile *tile = gt_to_tile(gt);
+	struct xe_validation_ctx ctx;
+	struct drm_exec exec;
+	struct dma_fence *fence;
+	int err, needs_vram;
+
+	lockdep_assert_held_write(&vm->lock);
+
+	needs_vram = xe_vma_need_vram_for_atomic(vm->xe, vma, atomic);
+	if (needs_vram < 0 || (needs_vram && xe_vma_is_userptr(vma)))
+		return needs_vram < 0 ? needs_vram : -EACCES;
+
+	xe_gt_stats_incr(gt, XE_GT_STATS_ID_VMA_PAGEFAULT_COUNT, 1);
+	xe_gt_stats_incr(gt, XE_GT_STATS_ID_VMA_PAGEFAULT_KB,
+			 xe_vma_size(vma) / SZ_1K);
+
+	trace_xe_vma_pagefault(vma);
+
+	/* Check if VMA is valid, opportunistic check only */
+	if (xe_vm_has_valid_gpu_mapping(tile, vma->tile_present,
+					vma->tile_invalidated) && !atomic)
+		return 0;
+
+retry_userptr:
+	if (xe_vma_is_userptr(vma) &&
+	    xe_vma_userptr_check_repin(to_userptr_vma(vma))) {
+		struct xe_userptr_vma *uvma = to_userptr_vma(vma);
+
+		err = xe_vma_userptr_pin_pages(uvma);
+		if (err)
+			return err;
+	}
+
+	/* Lock VM and BOs dma-resv */
+	xe_validation_ctx_init(&ctx, &vm->xe->val, &exec, (struct xe_val_flags) {});
+	drm_exec_init(&exec, 0, 0);
+	drm_exec_until_all_locked(&exec) {
+		err = xe_pagefault_begin(&exec, vma, tile->mem.vram,
+					 needs_vram == 1);
+		drm_exec_retry_on_contention(&exec);
+		xe_validation_retry_on_oom(&ctx, &err);
+		if (err)
+			goto unlock_dma_resv;
+
+		/* Bind VMA only to the GT that has faulted */
+		trace_xe_vma_pf_bind(vma);
+		xe_vm_set_validation_exec(vm, &exec);
+		fence = xe_vma_rebind(vm, vma, BIT(tile->id));
+		xe_vm_set_validation_exec(vm, NULL);
+		if (IS_ERR(fence)) {
+			err = PTR_ERR(fence);
+			xe_validation_retry_on_oom(&ctx, &err);
+			goto unlock_dma_resv;
+		}
+	}
+
+	dma_fence_wait(fence, false);
+	dma_fence_put(fence);
+
+unlock_dma_resv:
+	xe_validation_ctx_fini(&ctx);
+	if (err == -EAGAIN)
+		goto retry_userptr;
+
+	return err;
+}
+
+static bool
+xe_pagefault_access_is_atomic(enum xe_pagefault_access_type access_type)
+{
+	return access_type == XE_PAGEFAULT_ACCESS_TYPE_ATOMIC;
+}
+
+static struct xe_vm *xe_pagefault_asid_to_vm(struct xe_device *xe, u32 asid)
+{
+	struct xe_vm *vm;
+
+	down_read(&xe->usm.lock);
+	vm = xa_load(&xe->usm.asid_to_vm, asid);
+	if (vm && xe_vm_in_fault_mode(vm))
+		xe_vm_get(vm);
+	else
+		vm = ERR_PTR(-EINVAL);
+	up_read(&xe->usm.lock);
+
+	return vm;
+}
+
+static int xe_pagefault_service(struct xe_pagefault *pf)
+{
+	struct xe_gt *gt = pf->gt;
+	struct xe_device *xe = gt_to_xe(gt);
+	struct xe_vm *vm;
+	struct xe_vma *vma = NULL;
+	int err;
+	bool atomic;
+
+	/* Producer flagged this fault to be nacked */
+	if (pf->consumer.fault_level == XE_PAGEFAULT_LEVEL_NACK)
+		return -EFAULT;
+
+	vm = xe_pagefault_asid_to_vm(xe, pf->consumer.asid);
+	if (IS_ERR(vm))
+		return PTR_ERR(vm);
+
+	/*
+	 * TODO: Change to read lock? Using write lock for simplicity.
+	 */
+	down_write(&vm->lock);
+
+	if (xe_vm_is_closed(vm)) {
+		err = -ENOENT;
+		goto unlock_vm;
+	}
+
+	vma = xe_vm_find_vma_by_addr(vm, pf->consumer.page_addr);
+	if (!vma) {
+		err = -EINVAL;
+		goto unlock_vm;
+	}
+
+	atomic = xe_pagefault_access_is_atomic(pf->consumer.access_type);
+
+	if (xe_vma_is_cpu_addr_mirror(vma))
+		err = xe_svm_handle_pagefault(vm, vma, gt,
+					      pf->consumer.page_addr, atomic);
+	else
+		err = xe_pagefault_handle_vma(gt, vma, atomic);
+
+unlock_vm:
+	if (!err)
+		vm->usm.last_fault_vma = vma;
+	up_write(&vm->lock);
+	xe_vm_put(vm);
+
+	return err;
+}
+
+static bool xe_pagefault_queue_pop(struct xe_pagefault_queue *pf_queue,
+				   struct xe_pagefault *pf)
+{
+	bool found_fault = false;
+
+	spin_lock_irq(&pf_queue->lock);
+	if (pf_queue->tail != pf_queue->head) {
+		memcpy(pf, pf_queue->data + pf_queue->tail, sizeof(*pf));
+		pf_queue->tail = (pf_queue->tail + xe_pagefault_entry_size()) %
+			pf_queue->size;
+		found_fault = true;
+	}
+	spin_unlock_irq(&pf_queue->lock);
+
+	return found_fault;
+}
+
+static void xe_pagefault_print(struct xe_pagefault *pf)
+{
+	xe_gt_dbg(pf->gt, "\n\tASID: %d\n"
+		  "\tFaulted Address: 0x%08x%08x\n"
+		  "\tFaultType: %d\n"
+		  "\tAccessType: %d\n"
+		  "\tFaultLevel: %d\n"
+		  "\tEngineClass: %d %s\n"
+		  "\tEngineInstance: %d\n",
+		  pf->consumer.asid,
+		  upper_32_bits(pf->consumer.page_addr),
+		  lower_32_bits(pf->consumer.page_addr),
+		  pf->consumer.fault_type,
+		  pf->consumer.access_type,
+		  pf->consumer.fault_level,
+		  pf->consumer.engine_class,
+		  xe_hw_engine_class_to_str(pf->consumer.engine_class),
+		  pf->consumer.engine_instance);
+}
+
+static void xe_pagefault_queue_work(struct work_struct *w)
+{
+	struct xe_pagefault_queue *pf_queue =
+		container_of(w, typeof(*pf_queue), worker);
+	struct xe_pagefault pf;
+	unsigned long threshold;
+
+#define USM_QUEUE_MAX_RUNTIME_MS      20
+	threshold = jiffies + msecs_to_jiffies(USM_QUEUE_MAX_RUNTIME_MS);
+
+	while (xe_pagefault_queue_pop(pf_queue, &pf)) {
+		int err;
+
+		if (!pf.gt)	/* Fault squashed during reset */
+			continue;
+
+		err = xe_pagefault_service(&pf);
+		if (err) {
+			xe_pagefault_print(&pf);
+			xe_gt_dbg(pf.gt, "Fault response: Unsuccessful %pe\n",
+				  ERR_PTR(err));
+		}
+
+		pf.producer.ops->ack_fault(&pf, err);
+
+		if (time_after(jiffies, threshold)) {
+			queue_work(gt_to_xe(pf.gt)->usm.pf_wq, w);
+			break;
+		}
+	}
+#undef USM_QUEUE_MAX_RUNTIME_MS
+}
+
+static int xe_pagefault_queue_init(struct xe_device *xe,
+				   struct xe_pagefault_queue *pf_queue)
+{
+	struct xe_gt *gt;
+	int total_num_eus = 0;
+	u8 id;
+
+	for_each_gt(gt, xe, id) {
+		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;
+
+		total_num_eus += num_eus;
+	}
+
+	xe_assert(xe, total_num_eus);
+
+	/*
+	 * user can issue separate page faults per EU and per CS
+	 *
+	 * XXX: Multiplier required as compute UMD are getting PF queue errors
+	 * without it. Follow on why this multiplier is required.
+	 */
+#define PF_MULTIPLIER	8
+	pf_queue->size = (total_num_eus + XE_NUM_HW_ENGINES) *
+		xe_pagefault_entry_size() * PF_MULTIPLIER;
+	pf_queue->size = roundup_pow_of_two(pf_queue->size);
+#undef PF_MULTIPLIER
+
+	drm_dbg(&xe->drm, "xe_pagefault_entry_size=%d, total_num_eus=%d, pf_queue->size=%u",
+		xe_pagefault_entry_size(), total_num_eus, pf_queue->size);
+
+	spin_lock_init(&pf_queue->lock);
+	INIT_WORK(&pf_queue->worker, xe_pagefault_queue_work);
+
+	pf_queue->data = drmm_kzalloc(&xe->drm, pf_queue->size, GFP_KERNEL);
+	if (!pf_queue->data)
+		return -ENOMEM;
+
+	return 0;
+}
+
+static void xe_pagefault_fini(void *arg)
+{
+	struct xe_device *xe = arg;
+
+	destroy_workqueue(xe->usm.pf_wq);
+}
+
+/**
+ * xe_pagefault_init() - Page fault init
+ * @xe: xe device instance
+ *
+ * Initialize Xe page fault state. Must be done after reading fuses.
+ *
+ * Return: 0 on Success, errno on failure
+ */
+int xe_pagefault_init(struct xe_device *xe)
+{
+	int err, i;
+
+	if (!xe->info.has_usm)
+		return 0;
+
+	xe->usm.pf_wq = alloc_workqueue("xe_page_fault_work_queue",
+					WQ_UNBOUND | WQ_HIGHPRI,
+					XE_PAGEFAULT_QUEUE_COUNT);
+	if (!xe->usm.pf_wq)
+		return -ENOMEM;
+
+	for (i = 0; i < XE_PAGEFAULT_QUEUE_COUNT; ++i) {
+		err = xe_pagefault_queue_init(xe, xe->usm.pf_queue + i);
+		if (err)
+			goto err_out;
+	}
+
+	return devm_add_action_or_reset(xe->drm.dev, xe_pagefault_fini, xe);
+
+err_out:
+	destroy_workqueue(xe->usm.pf_wq);
+	return err;
+}
+
+static void xe_pagefault_queue_reset(struct xe_device *xe, struct xe_gt *gt,
+				     struct xe_pagefault_queue *pf_queue)
+{
+	u32 i;
+
+	/* Driver load failure guard / USM not enabled guard */
+	if (!pf_queue->data)
+		return;
+
+	/* Squash all pending faults on the GT */
+
+	spin_lock_irq(&pf_queue->lock);
+	for (i = pf_queue->tail; i != pf_queue->head;
+	     i = (i + xe_pagefault_entry_size()) % pf_queue->size) {
+		struct xe_pagefault *pf = pf_queue->data + i;
+
+		if (pf->gt == gt)
+			pf->gt = NULL;
+	}
+	spin_unlock_irq(&pf_queue->lock);
+}
+
+/**
+ * xe_pagefault_reset() - Page fault reset for a GT
+ * @xe: xe device instance
+ * @gt: GT being reset
+ *
+ * Reset the Xe page fault state for a GT; that is, squash any pending faults on
+ * the GT.
+ */
+void xe_pagefault_reset(struct xe_device *xe, struct xe_gt *gt)
+{
+	int i;
+
+	for (i = 0; i < XE_PAGEFAULT_QUEUE_COUNT; ++i)
+		xe_pagefault_queue_reset(xe, gt, xe->usm.pf_queue + i);
+}
+
+static bool xe_pagefault_queue_full(struct xe_pagefault_queue *pf_queue)
+{
+	lockdep_assert_held(&pf_queue->lock);
+
+	return CIRC_SPACE(pf_queue->head, pf_queue->tail, pf_queue->size) <=
+		xe_pagefault_entry_size();
+}
+
+/**
+ * xe_pagefault_handler() - Page fault handler
+ * @xe: xe device instance
+ * @pf: Page fault
+ *
+ * Sink the page fault to a queue (i.e., a memory buffer) and queue a worker to
+ * service it. Safe to be called from IRQ or process context. Reclaim safe.
+ *
+ * Return: 0 on success, errno on failure
+ */
+int xe_pagefault_handler(struct xe_device *xe, struct xe_pagefault *pf)
+{
+	struct xe_pagefault_queue *pf_queue = xe->usm.pf_queue +
+		(pf->consumer.asid % XE_PAGEFAULT_QUEUE_COUNT);
+	unsigned long flags;
+	bool full;
+
+	spin_lock_irqsave(&pf_queue->lock, flags);
+	full = xe_pagefault_queue_full(pf_queue);
+	if (!full) {
+		memcpy(pf_queue->data + pf_queue->head, pf, sizeof(*pf));
+		pf_queue->head = (pf_queue->head + xe_pagefault_entry_size()) %
+			pf_queue->size;
+		queue_work(xe->usm.pf_wq, &pf_queue->worker);
+	} else {
+		drm_warn(&xe->drm,
+			 "PageFault Queue (%d) full, shouldn't be possible\n",
+			 pf->consumer.asid % XE_PAGEFAULT_QUEUE_COUNT);
+	}
+	spin_unlock_irqrestore(&pf_queue->lock, flags);
+
+	return full ? -ENOSPC : 0;
+}