drivers/accel/amdxdna/amdxdna_ubuf.c

// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright (C) 2025, Advanced Micro Devices, Inc.
 */

#include <drm/amdxdna_accel.h>
#include <drm/drm_device.h>
#include <drm/drm_print.h>
#include <linux/dma-buf.h>
#include <linux/overflow.h>
#include <linux/pagemap.h>
#include <linux/vmalloc.h>

#include "amdxdna_pci_drv.h"
#include "amdxdna_ubuf.h"

struct amdxdna_ubuf_priv {
	struct page **pages;
	u64 nr_pages;
	struct mm_struct *mm;
};

static struct sg_table *amdxdna_ubuf_map(struct dma_buf_attachment *attach,
					 enum dma_data_direction direction)
{
	struct amdxdna_ubuf_priv *ubuf = attach->dmabuf->priv;
	struct sg_table *sg;
	int ret;

	sg = kzalloc_obj(*sg);
	if (!sg)
		return ERR_PTR(-ENOMEM);

	ret = sg_alloc_table_from_pages(sg, ubuf->pages, ubuf->nr_pages, 0,
					ubuf->nr_pages << PAGE_SHIFT, GFP_KERNEL);
	if (ret)
		goto err_free_sg;

	ret = dma_map_sgtable(attach->dev, sg, direction, 0);
	if (ret)
		goto err_free_table;

	return sg;

err_free_table:
	sg_free_table(sg);
err_free_sg:
	kfree(sg);
	return ERR_PTR(ret);
}

static void amdxdna_ubuf_unmap(struct dma_buf_attachment *attach,
			       struct sg_table *sg,
			       enum dma_data_direction direction)
{
	dma_unmap_sgtable(attach->dev, sg, direction, 0);
	sg_free_table(sg);
	kfree(sg);
}

static void amdxdna_ubuf_release(struct dma_buf *dbuf)
{
	struct amdxdna_ubuf_priv *ubuf = dbuf->priv;

	unpin_user_pages(ubuf->pages, ubuf->nr_pages);
	kvfree(ubuf->pages);
	atomic64_sub(ubuf->nr_pages, &ubuf->mm->pinned_vm);
	mmdrop(ubuf->mm);
	kfree(ubuf);
}

static const struct dma_buf_ops amdxdna_ubuf_dmabuf_ops = {
	.map_dma_buf = amdxdna_ubuf_map,
	.unmap_dma_buf = amdxdna_ubuf_unmap,
	.release = amdxdna_ubuf_release,
};

struct dma_buf *amdxdna_get_ubuf(struct drm_device *dev,
				 u32 num_entries, void __user *va_entries)
{
	struct amdxdna_dev *xdna = to_xdna_dev(dev);
	unsigned long lock_limit, new_pinned;
	struct amdxdna_drm_va_entry *va_ent;
	struct amdxdna_ubuf_priv *ubuf;
	u32 npages, start = 0;
	struct dma_buf *dbuf;
	int i, ret;
	DEFINE_DMA_BUF_EXPORT_INFO(exp_info);

	if (!can_do_mlock())
		return ERR_PTR(-EPERM);

	ubuf = kzalloc_obj(*ubuf);
	if (!ubuf)
		return ERR_PTR(-ENOMEM);

	ubuf->mm = current->mm;
	mmgrab(ubuf->mm);

	va_ent = kvzalloc_objs(*va_ent, num_entries);
	if (!va_ent) {
		ret = -ENOMEM;
		goto free_ubuf;
	}

	if (copy_from_user(va_ent, va_entries, sizeof(*va_ent) * num_entries)) {
		XDNA_DBG(xdna, "Access va entries failed");
		ret = -EINVAL;
		goto free_ent;
	}

	for (i = 0, exp_info.size = 0; i < num_entries; i++) {
		if (!IS_ALIGNED(va_ent[i].vaddr, PAGE_SIZE) ||
		    !IS_ALIGNED(va_ent[i].len, PAGE_SIZE)) {
			XDNA_ERR(xdna, "Invalid address or len %llx, %llx",
				 va_ent[i].vaddr, va_ent[i].len);
			ret = -EINVAL;
			goto free_ent;
		}

		if (check_add_overflow(exp_info.size, va_ent[i].len, &exp_info.size)) {
			ret = -EINVAL;
			goto free_ent;
		}
	}

	ubuf->nr_pages = exp_info.size >> PAGE_SHIFT;
	lock_limit = rlimit(RLIMIT_MEMLOCK) >> PAGE_SHIFT;
	new_pinned = atomic64_add_return(ubuf->nr_pages, &ubuf->mm->pinned_vm);
	if (new_pinned > lock_limit && !capable(CAP_IPC_LOCK)) {
		XDNA_DBG(xdna, "New pin %ld, limit %ld, cap %d",
			 new_pinned, lock_limit, capable(CAP_IPC_LOCK));
		ret = -ENOMEM;
		goto sub_pin_cnt;
	}

	ubuf->pages = kvmalloc_objs(*ubuf->pages, ubuf->nr_pages);
	if (!ubuf->pages) {
		ret = -ENOMEM;
		goto sub_pin_cnt;
	}

	for (i = 0; i < num_entries; i++) {
		npages = va_ent[i].len >> PAGE_SHIFT;

		ret = pin_user_pages_fast(va_ent[i].vaddr, npages,
					  FOLL_WRITE | FOLL_LONGTERM,
					  &ubuf->pages[start]);
		if (ret >= 0) {
			start += ret;
			if (ret != npages) {
				XDNA_ERR(xdna, "Partially pinned pages %d/%u", ret, npages);
				ret = -ENOMEM;
				goto destroy_pages;
			}
		} else {
			XDNA_ERR(xdna, "Failed to pin pages ret %d", ret);
			goto destroy_pages;
		}
	}

	exp_info.ops = &amdxdna_ubuf_dmabuf_ops;
	exp_info.priv = ubuf;
	exp_info.flags = O_RDWR | O_CLOEXEC;

	dbuf = dma_buf_export(&exp_info);
	if (IS_ERR(dbuf)) {
		ret = PTR_ERR(dbuf);
		goto destroy_pages;
	}
	kvfree(va_ent);

	return dbuf;

destroy_pages:
	if (start)
		unpin_user_pages(ubuf->pages, start);
	kvfree(ubuf->pages);
sub_pin_cnt:
	atomic64_sub(ubuf->nr_pages, &ubuf->mm->pinned_vm);
free_ent:
	kvfree(va_ent);
free_ubuf:
	mmdrop(ubuf->mm);
	kfree(ubuf);
	return ERR_PTR(ret);
}