1 files changed, 325 insertions, 0 deletions
diff --git a/drivers/gpu/drm/xe/xe_hmm.c b/drivers/gpu/drm/xe/xe_hmm.c
new file mode 100644
index 000000000000..57b71956ddf4
--- /dev/null
+++ b/drivers/gpu/drm/xe/xe_hmm.c
@@ -0,0 +1,325 @@
+// SPDX-License-Identifier: MIT
+/*
+ * Copyright © 2024 Intel Corporation
+ */
+
+#include <linux/scatterlist.h>
+#include <linux/mmu_notifier.h>
+#include <linux/dma-mapping.h>
+#include <linux/memremap.h>
+#include <linux/swap.h>
+#include <linux/hmm.h>
+#include <linux/mm.h>
+#include "xe_hmm.h"
+#include "xe_vm.h"
+#include "xe_bo.h"
+
+static u64 xe_npages_in_range(unsigned long start, unsigned long end)
+{
+	return (end - start) >> PAGE_SHIFT;
+}
+
+static int xe_alloc_sg(struct xe_device *xe, struct sg_table *st,
+		       struct hmm_range *range, struct rw_semaphore *notifier_sem)
+{
+	unsigned long i, npages, hmm_pfn;
+	unsigned long num_chunks = 0;
+	int ret;
+
+	/* HMM docs says this is needed. */
+	ret = down_read_interruptible(notifier_sem);
+	if (ret)
+		return ret;
+
+	if (mmu_interval_read_retry(range->notifier, range->notifier_seq)) {
+		up_read(notifier_sem);
+		return -EAGAIN;
+	}
+
+	npages = xe_npages_in_range(range->start, range->end);
+	for (i = 0; i < npages;) {
+		unsigned long len;
+
+		hmm_pfn = range->hmm_pfns[i];
+		xe_assert(xe, hmm_pfn & HMM_PFN_VALID);
+
+		len = 1UL << hmm_pfn_to_map_order(hmm_pfn);
+
+		/* If order > 0 the page may extend beyond range->start */
+		len -= (hmm_pfn & ~HMM_PFN_FLAGS) & (len - 1);
+		i += len;
+		num_chunks++;
+	}
+	up_read(notifier_sem);
+
+	return sg_alloc_table(st, num_chunks, GFP_KERNEL);
+}
+
+/**
+ * xe_build_sg() - build a scatter gather table for all the physical pages/pfn
+ * in a hmm_range. dma-map pages if necessary. dma-address is save in sg table
+ * and will be used to program GPU page table later.
+ * @xe: the xe device who will access the dma-address in sg table
+ * @range: the hmm range that we build the sg table from. range->hmm_pfns[]
+ * has the pfn numbers of pages that back up this hmm address range.
+ * @st: pointer to the sg table.
+ * @notifier_sem: The xe notifier lock.
+ * @write: whether we write to this range. This decides dma map direction
+ * for system pages. If write we map it bi-diretional; otherwise
+ * DMA_TO_DEVICE
+ *
+ * All the contiguous pfns will be collapsed into one entry in
+ * the scatter gather table. This is for the purpose of efficiently
+ * programming GPU page table.
+ *
+ * The dma_address in the sg table will later be used by GPU to
+ * access memory. So if the memory is system memory, we need to
+ * do a dma-mapping so it can be accessed by GPU/DMA.
+ *
+ * FIXME: This function currently only support pages in system
+ * memory. If the memory is GPU local memory (of the GPU who
+ * is going to access memory), we need gpu dpa (device physical
+ * address), and there is no need of dma-mapping. This is TBD.
+ *
+ * FIXME: dma-mapping for peer gpu device to access remote gpu's
+ * memory. Add this when you support p2p
+ *
+ * This function allocates the storage of the sg table. It is
+ * caller's responsibility to free it calling sg_free_table.
+ *
+ * Returns 0 if successful; -ENOMEM if fails to allocate memory
+ */
+static int xe_build_sg(struct xe_device *xe, struct hmm_range *range,
+		       struct sg_table *st,
+		       struct rw_semaphore *notifier_sem,
+		       bool write)
+{
+	unsigned long npages = xe_npages_in_range(range->start, range->end);
+	struct device *dev = xe->drm.dev;
+	struct scatterlist *sgl;
+	struct page *page;
+	unsigned long i, j;
+
+	lockdep_assert_held(notifier_sem);
+
+	i = 0;
+	for_each_sg(st->sgl, sgl, st->nents, j) {
+		unsigned long hmm_pfn, size;
+
+		hmm_pfn = range->hmm_pfns[i];
+		page = hmm_pfn_to_page(hmm_pfn);
+		xe_assert(xe, !is_device_private_page(page));
+
+		size = 1UL << hmm_pfn_to_map_order(hmm_pfn);
+		size -= page_to_pfn(page) & (size - 1);
+		i += size;
+
+		if (unlikely(j == st->nents - 1)) {
+			xe_assert(xe, i >= npages);
+			if (i > npages)
+				size -= (i - npages);
+
+			sg_mark_end(sgl);
+		} else {
+			xe_assert(xe, i < npages);
+		}
+
+		sg_set_page(sgl, page, size << PAGE_SHIFT, 0);
+	}
+
+	return dma_map_sgtable(dev, st, write ? DMA_BIDIRECTIONAL : DMA_TO_DEVICE,
+			       DMA_ATTR_SKIP_CPU_SYNC | DMA_ATTR_NO_KERNEL_MAPPING);
+}
+
+static void xe_hmm_userptr_set_mapped(struct xe_userptr_vma *uvma)
+{
+	struct xe_userptr *userptr = &uvma->userptr;
+	struct xe_vm *vm = xe_vma_vm(&uvma->vma);
+
+	lockdep_assert_held_write(&vm->lock);
+	lockdep_assert_held(&vm->userptr.notifier_lock);
+
+	mutex_lock(&userptr->unmap_mutex);
+	xe_assert(vm->xe, !userptr->mapped);
+	userptr->mapped = true;
+	mutex_unlock(&userptr->unmap_mutex);
+}
+
+void xe_hmm_userptr_unmap(struct xe_userptr_vma *uvma)
+{
+	struct xe_userptr *userptr = &uvma->userptr;
+	struct xe_vma *vma = &uvma->vma;
+	bool write = !xe_vma_read_only(vma);
+	struct xe_vm *vm = xe_vma_vm(vma);
+	struct xe_device *xe = vm->xe;
+
+	if (!lockdep_is_held_type(&vm->userptr.notifier_lock, 0) &&
+	    !lockdep_is_held_type(&vm->lock, 0) &&
+	    !(vma->gpuva.flags & XE_VMA_DESTROYED)) {
+		/* Don't unmap in exec critical section. */
+		xe_vm_assert_held(vm);
+		/* Don't unmap while mapping the sg. */
+		lockdep_assert_held(&vm->lock);
+	}
+
+	mutex_lock(&userptr->unmap_mutex);
+	if (userptr->sg && userptr->mapped)
+		dma_unmap_sgtable(xe->drm.dev, userptr->sg,
+				  write ? DMA_BIDIRECTIONAL : DMA_TO_DEVICE, 0);
+	userptr->mapped = false;
+	mutex_unlock(&userptr->unmap_mutex);
+}
+
+/**
+ * xe_hmm_userptr_free_sg() - Free the scatter gather table of userptr
+ * @uvma: the userptr vma which hold the scatter gather table
+ *
+ * With function xe_userptr_populate_range, we allocate storage of
+ * the userptr sg table. This is a helper function to free this
+ * sg table, and dma unmap the address in the table.
+ */
+void xe_hmm_userptr_free_sg(struct xe_userptr_vma *uvma)
+{
+	struct xe_userptr *userptr = &uvma->userptr;
+
+	xe_assert(xe_vma_vm(&uvma->vma)->xe, userptr->sg);
+	xe_hmm_userptr_unmap(uvma);
+	sg_free_table(userptr->sg);
+	userptr->sg = NULL;
+}
+
+/**
+ * xe_hmm_userptr_populate_range() - Populate physical pages of a virtual
+ * address range
+ *
+ * @uvma: userptr vma which has information of the range to populate.
+ * @is_mm_mmap_locked: True if mmap_read_lock is already acquired by caller.
+ *
+ * This function populate the physical pages of a virtual
+ * address range. The populated physical pages is saved in
+ * userptr's sg table. It is similar to get_user_pages but call
+ * hmm_range_fault.
+ *
+ * This function also read mmu notifier sequence # (
+ * mmu_interval_read_begin), for the purpose of later
+ * comparison (through mmu_interval_read_retry).
+ *
+ * This must be called with mmap read or write lock held.
+ *
+ * This function allocates the storage of the userptr sg table.
+ * It is caller's responsibility to free it calling sg_free_table.
+ *
+ * returns: 0 for success; negative error no on failure
+ */
+int xe_hmm_userptr_populate_range(struct xe_userptr_vma *uvma,
+				  bool is_mm_mmap_locked)
+{
+	unsigned long timeout =
+		jiffies + msecs_to_jiffies(HMM_RANGE_DEFAULT_TIMEOUT);
+	unsigned long *pfns;
+	struct xe_userptr *userptr;
+	struct xe_vma *vma = &uvma->vma;
+	u64 userptr_start = xe_vma_userptr(vma);
+	u64 userptr_end = userptr_start + xe_vma_size(vma);
+	struct xe_vm *vm = xe_vma_vm(vma);
+	struct hmm_range hmm_range = {
+		.pfn_flags_mask = 0, /* ignore pfns */
+		.default_flags = HMM_PFN_REQ_FAULT,
+		.start = userptr_start,
+		.end = userptr_end,
+		.notifier = &uvma->userptr.notifier,
+		.dev_private_owner = vm->xe,
+	};
+	bool write = !xe_vma_read_only(vma);
+	unsigned long notifier_seq;
+	u64 npages;
+	int ret;
+
+	userptr = &uvma->userptr;
+
+	if (is_mm_mmap_locked)
+		mmap_assert_locked(userptr->notifier.mm);
+
+	if (vma->gpuva.flags & XE_VMA_DESTROYED)
+		return 0;
+
+	notifier_seq = mmu_interval_read_begin(&userptr->notifier);
+	if (notifier_seq == userptr->notifier_seq)
+		return 0;
+
+	if (userptr->sg)
+		xe_hmm_userptr_free_sg(uvma);
+
+	npages = xe_npages_in_range(userptr_start, userptr_end);
+	pfns = kvmalloc_array(npages, sizeof(*pfns), GFP_KERNEL);
+	if (unlikely(!pfns))
+		return -ENOMEM;
+
+	if (write)
+		hmm_range.default_flags |= HMM_PFN_REQ_WRITE;
+
+	if (!mmget_not_zero(userptr->notifier.mm)) {
+		ret = -EFAULT;
+		goto free_pfns;
+	}
+
+	hmm_range.hmm_pfns = pfns;
+
+	while (true) {
+		hmm_range.notifier_seq = mmu_interval_read_begin(&userptr->notifier);
+
+		if (!is_mm_mmap_locked)
+			mmap_read_lock(userptr->notifier.mm);
+
+		ret = hmm_range_fault(&hmm_range);
+
+		if (!is_mm_mmap_locked)
+			mmap_read_unlock(userptr->notifier.mm);
+
+		if (ret == -EBUSY) {
+			if (time_after(jiffies, timeout))
+				break;
+
+			continue;
+		}
+		break;
+	}
+
+	mmput(userptr->notifier.mm);
+
+	if (ret)
+		goto free_pfns;
+
+	ret = xe_alloc_sg(vm->xe, &userptr->sgt, &hmm_range, &vm->userptr.notifier_lock);
+	if (ret)
+		goto free_pfns;
+
+	ret = down_read_interruptible(&vm->userptr.notifier_lock);
+	if (ret)
+		goto free_st;
+
+	if (mmu_interval_read_retry(hmm_range.notifier, hmm_range.notifier_seq)) {
+		ret = -EAGAIN;
+		goto out_unlock;
+	}
+
+	ret = xe_build_sg(vm->xe, &hmm_range, &userptr->sgt,
+			  &vm->userptr.notifier_lock, write);
+	if (ret)
+		goto out_unlock;
+
+	userptr->sg = &userptr->sgt;
+	xe_hmm_userptr_set_mapped(uvma);
+	userptr->notifier_seq = hmm_range.notifier_seq;
+	up_read(&vm->userptr.notifier_lock);
+	kvfree(pfns);
+	return 0;
+
+out_unlock:
+	up_read(&vm->userptr.notifier_lock);
+free_st:
+	sg_free_table(&userptr->sgt);
+free_pfns:
+	kvfree(pfns);
+	return ret;
+}