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Subject[Xen-devel][RFC 3/3] xen/gntdev: Add support for Linux dma buffers
Date
From: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>

Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
---
drivers/xen/gntdev.c | 954 +++++++++++++++++++++++++++++++++++++-
include/uapi/xen/gntdev.h | 101 ++++
include/xen/gntdev_exp.h | 23 +
3 files changed, 1066 insertions(+), 12 deletions(-)
create mode 100644 include/xen/gntdev_exp.h

diff --git a/drivers/xen/gntdev.c b/drivers/xen/gntdev.c
index 9510f228efe9..0ee88e193362 100644
--- a/drivers/xen/gntdev.c
+++ b/drivers/xen/gntdev.c
@@ -4,6 +4,8 @@
* Device for accessing (in user-space) pages that have been granted by other
* domains.
*
+ * DMA buffer implementation is based on drivers/gpu/drm/drm_prime.c.
+ *
* Copyright (c) 2006-2007, D G Murray.
* (c) 2009 Gerd Hoffmann <kraxel@redhat.com>
*
@@ -37,6 +39,9 @@
#include <linux/highmem.h>
#include <linux/refcount.h>

+#include <linux/dma-buf.h>
+#include <linux/of_device.h>
+
#include <xen/xen.h>
#include <xen/grant_table.h>
#include <xen/balloon.h>
@@ -61,16 +66,39 @@ static atomic_t pages_mapped = ATOMIC_INIT(0);
static int use_ptemod;
#define populate_freeable_maps use_ptemod

+#ifndef GRANT_INVALID_REF
+/*
+ * Note on usage of grant reference 0 as invalid grant reference:
+ * grant reference 0 is valid, but never exposed to a driver,
+ * because of the fact it is already in use/reserved by the PV console.
+ */
+#define GRANT_INVALID_REF 0
+#endif
+
struct gntdev_priv {
/* maps with visible offsets in the file descriptor */
struct list_head maps;
/* maps that are not visible; will be freed on munmap.
* Only populated if populate_freeable_maps == 1 */
struct list_head freeable_maps;
+ /* List of dma-bufs. */
+ struct list_head dma_bufs;
/* lock protects maps and freeable_maps */
struct mutex lock;
struct mm_struct *mm;
struct mmu_notifier mn;
+
+ /* Private data of the hyper DMA buffers. */
+
+ struct device *dev;
+ /* List of exported DMA buffers. */
+ struct list_head dmabuf_exp_list;
+ /* List of wait objects. */
+ struct list_head dmabuf_exp_wait_list;
+ /* List of imported DMA buffers. */
+ struct list_head dmabuf_imp_list;
+ /* This is the lock which protects dma_buf_xxx lists. */
+ struct mutex dmabuf_lock;
};

struct unmap_notify {
@@ -95,10 +123,65 @@ struct grant_map {
struct gnttab_unmap_grant_ref *kunmap_ops;
struct page **pages;
unsigned long pages_vm_start;
+
+ /*
+ * All the fields starting with dmabuf_ are only valid if this
+ * mapping is used for exporting a DMA buffer.
+ * If dmabuf_vaddr is not NULL then this mapping is backed by DMA
+ * capable memory.
+ */
+
+ /* Flags used to create this DMA buffer: GNTDEV_DMABUF_FLAG_XXX. */
+ bool dmabuf_flags;
+ /* Virtual/CPU address of the DMA buffer. */
+ void *dmabuf_vaddr;
+ /* Bus address of the DMA buffer. */
+ dma_addr_t dmabuf_bus_addr;
+};
+
+struct hyper_dmabuf {
+ struct gntdev_priv *priv;
+ struct dma_buf *dmabuf;
+ struct list_head next;
+ int fd;
+
+ union {
+ struct {
+ /* Exported buffers are reference counted. */
+ struct kref refcount;
+ struct grant_map *map;
+ } exp;
+ struct {
+ /* Granted references of the imported buffer. */
+ grant_ref_t *refs;
+ /* Scatter-gather table of the imported buffer. */
+ struct sg_table *sgt;
+ /* dma-buf attachment of the imported buffer. */
+ struct dma_buf_attachment *attach;
+ } imp;
+ } u;
+
+ /* Number of pages this buffer has. */
+ int nr_pages;
+ /* Pages of this buffer. */
+ struct page **pages;
+};
+
+struct hyper_dmabuf_wait_obj {
+ struct list_head next;
+ struct hyper_dmabuf *hyper_dmabuf;
+ struct completion completion;
+};
+
+struct hyper_dambuf_attachment {
+ struct sg_table *sgt;
+ enum dma_data_direction dir;
};

static int unmap_grant_pages(struct grant_map *map, int offset, int pages);

+static struct miscdevice gntdev_miscdev;
+
/* ------------------------------------------------------------------ */

static void gntdev_print_maps(struct gntdev_priv *priv,
@@ -120,8 +203,17 @@ static void gntdev_free_map(struct grant_map *map)
if (map == NULL)
return;

- if (map->pages)
+ if (map->dmabuf_vaddr) {
+ bool coherent = map->dmabuf_flags &
+ GNTDEV_DMABUF_FLAG_DMA_COHERENT;
+
+ gnttab_dma_free_pages(gntdev_miscdev.this_device,
+ coherent, map->count, map->pages,
+ map->dmabuf_vaddr, map->dmabuf_bus_addr);
+ } else if (map->pages) {
gnttab_free_pages(map->count, map->pages);
+ }
+
kfree(map->pages);
kfree(map->grants);
kfree(map->map_ops);
@@ -131,7 +223,7 @@ static void gntdev_free_map(struct grant_map *map)
kfree(map);
}

-static struct grant_map *gntdev_alloc_map(struct gntdev_priv *priv, int count)
+static struct grant_map *gntdev_alloc_map(int count, int dmabuf_flags)
{
struct grant_map *add;
int i;
@@ -154,8 +246,26 @@ static struct grant_map *gntdev_alloc_map(struct gntdev_priv *priv, int count)
NULL == add->pages)
goto err;

- if (gnttab_alloc_pages(count, add->pages))
- goto err;
+ add->dmabuf_flags = dmabuf_flags;
+
+ /*
+ * Check if this mapping is requested to be backed
+ * by a DMA buffer.
+ */
+ if (dmabuf_flags & (GNTDEV_DMABUF_FLAG_DMA_WC |
+ GNTDEV_DMABUF_FLAG_DMA_COHERENT)) {
+ bool coherent = dmabuf_flags & GNTDEV_DMABUF_FLAG_DMA_COHERENT;
+
+ if (gnttab_dma_alloc_pages(gntdev_miscdev.this_device,
+ coherent,
+ count, add->pages,
+ &add->dmabuf_vaddr,
+ &add->dmabuf_bus_addr))
+ goto err;
+ } else {
+ if (gnttab_alloc_pages(count, add->pages))
+ goto err;
+ }

for (i = 0; i < count; i++) {
add->map_ops[i].handle = -1;
@@ -233,6 +343,15 @@ static void gntdev_put_map(struct gntdev_priv *priv, struct grant_map *map)
gntdev_free_map(map);
}

+static void gntdev_put_map_unlink(struct gntdev_priv *priv,
+ struct grant_map *map)
+{
+ mutex_lock(&priv->lock);
+ list_del(&map->next);
+ gntdev_put_map(NULL /* already removed */, map);
+ mutex_unlock(&priv->lock);
+}
+
/* ------------------------------------------------------------------ */

static int find_grant_ptes(pte_t *pte, pgtable_t token,
@@ -324,6 +443,12 @@ static int map_grant_pages(struct grant_map *map)
map->unmap_ops[i].handle = map->map_ops[i].handle;
if (use_ptemod)
map->kunmap_ops[i].handle = map->kmap_ops[i].handle;
+ else if (map->dmabuf_vaddr) {
+ unsigned long mfn;
+
+ mfn = __pfn_to_mfn(page_to_pfn(map->pages[i]));
+ map->unmap_ops[i].dev_bus_addr = __pfn_to_phys(mfn);
+ }
}
return err;
}
@@ -527,19 +652,48 @@ static const struct mmu_notifier_ops gntdev_mmu_ops = {

/* ------------------------------------------------------------------ */

-static int gntdev_open(struct inode *inode, struct file *flip)
+struct gntdev_priv *gntdev_alloc_context(struct device *dev)
{
struct gntdev_priv *priv;
- int ret = 0;

priv = kzalloc(sizeof(*priv), GFP_KERNEL);
if (!priv)
- return -ENOMEM;
+ return ERR_PTR(-ENOMEM);

INIT_LIST_HEAD(&priv->maps);
INIT_LIST_HEAD(&priv->freeable_maps);
mutex_init(&priv->lock);

+ priv->dev = dev;
+ mutex_init(&priv->dmabuf_lock);
+ INIT_LIST_HEAD(&priv->dmabuf_exp_list);
+ INIT_LIST_HEAD(&priv->dmabuf_exp_wait_list);
+ INIT_LIST_HEAD(&priv->dmabuf_imp_list);
+
+ /*
+ * The device is not spawn from a device tree, so arch_setup_dma_ops
+ * is not called, thus leaving the device with dummy DMA ops.
+ * This makes the device return error on PRIME buffer import, which
+ * is not correct: to fix this call of_dma_configure() with a NULL
+ * node to set default DMA ops.
+ */
+ of_dma_configure(dev, NULL);
+
+ pr_debug("priv %p\n", priv);
+
+ return priv;
+}
+EXPORT_SYMBOL(gntdev_alloc_context);
+
+static int gntdev_open(struct inode *inode, struct file *flip)
+{
+ struct gntdev_priv *priv;
+ int ret = 0;
+
+ priv = gntdev_alloc_context(gntdev_miscdev.this_device);
+ if (IS_ERR(priv))
+ return PTR_ERR(priv);
+
if (use_ptemod) {
priv->mm = get_task_mm(current);
if (!priv->mm) {
@@ -557,14 +711,12 @@ static int gntdev_open(struct inode *inode, struct file *flip)
}

flip->private_data = priv;
- pr_debug("priv %p\n", priv);

return 0;
}

-static int gntdev_release(struct inode *inode, struct file *flip)
+void gntdev_free_context(struct gntdev_priv *priv)
{
- struct gntdev_priv *priv = flip->private_data;
struct grant_map *map;

pr_debug("priv %p\n", priv);
@@ -576,11 +728,28 @@ static int gntdev_release(struct inode *inode, struct file *flip)
gntdev_put_map(NULL /* already removed */, map);
}
WARN_ON(!list_empty(&priv->freeable_maps));
+
mutex_unlock(&priv->lock);

+ WARN(!list_empty(&priv->dmabuf_exp_list),
+ "Removing with non-empty exported DMA buffer list!\n");
+ WARN(!list_empty(&priv->dmabuf_exp_wait_list),
+ "Removing with pending wait objects!\n");
+ WARN(!list_empty(&priv->dmabuf_imp_list),
+ "Removing with non-empty imported DMA buffer list!\n");
+
+ kfree(priv);
+}
+EXPORT_SYMBOL(gntdev_free_context);
+
+static int gntdev_release(struct inode *inode, struct file *flip)
+{
+ struct gntdev_priv *priv = flip->private_data;
+
if (use_ptemod)
mmu_notifier_unregister(&priv->mn, priv->mm);
- kfree(priv);
+
+ gntdev_free_context(priv);
return 0;
}

@@ -598,7 +767,7 @@ static long gntdev_ioctl_map_grant_ref(struct gntdev_priv *priv,
return -EINVAL;

err = -ENOMEM;
- map = gntdev_alloc_map(priv, op.count);
+ map = gntdev_alloc_map(op.count, 0 /* this is not a dma-buf */);
if (!map)
return err;

@@ -949,6 +1118,755 @@ static long gntdev_ioctl_grant_copy(struct gntdev_priv *priv, void __user *u)
return ret;
}

+/* ------------------------------------------------------------------ */
+/* DMA buffer support. */
+/* ------------------------------------------------------------------ */
+
+/* ------------------------------------------------------------------ */
+/* Implementation of wait for exported DMA buffer released. */
+/* ------------------------------------------------------------------ */
+
+static void dmabuf_exp_release(struct kref *kref);
+
+static struct hyper_dmabuf_wait_obj *
+dmabuf_exp_wait_obj_new(struct gntdev_priv *priv,
+ struct hyper_dmabuf *hyper_dmabuf)
+{
+ struct hyper_dmabuf_wait_obj *obj;
+
+ obj = kzalloc(sizeof(*obj), GFP_KERNEL);
+ if (!obj)
+ return ERR_PTR(-ENOMEM);
+
+ init_completion(&obj->completion);
+ obj->hyper_dmabuf = hyper_dmabuf;
+
+ mutex_lock(&priv->dmabuf_lock);
+ list_add(&obj->next, &priv->dmabuf_exp_wait_list);
+ /* Put our reference and wait for hyper_dmabuf's release to fire. */
+ kref_put(&hyper_dmabuf->u.exp.refcount, dmabuf_exp_release);
+ mutex_unlock(&priv->dmabuf_lock);
+ return obj;
+}
+
+static void dmabuf_exp_wait_obj_free(struct gntdev_priv *priv,
+ struct hyper_dmabuf_wait_obj *obj)
+{
+ struct hyper_dmabuf_wait_obj *cur_obj, *q;
+
+ mutex_lock(&priv->dmabuf_lock);
+ list_for_each_entry_safe(cur_obj, q, &priv->dmabuf_exp_wait_list, next)
+ if (cur_obj == obj) {
+ list_del(&obj->next);
+ kfree(obj);
+ break;
+ }
+ mutex_unlock(&priv->dmabuf_lock);
+}
+
+static int dmabuf_exp_wait_obj_wait(struct hyper_dmabuf_wait_obj *obj,
+ u32 wait_to_ms)
+{
+ if (wait_for_completion_timeout(&obj->completion,
+ msecs_to_jiffies(wait_to_ms)) <= 0)
+ return -ETIMEDOUT;
+
+ return 0;
+}
+
+static void dmabuf_exp_wait_obj_signal(struct gntdev_priv *priv,
+ struct hyper_dmabuf *hyper_dmabuf)
+{
+ struct hyper_dmabuf_wait_obj *obj, *q;
+
+ list_for_each_entry_safe(obj, q, &priv->dmabuf_exp_wait_list, next)
+ if (obj->hyper_dmabuf == hyper_dmabuf) {
+ pr_debug("Found hyper_dmabuf in the wait list, wake\n");
+ complete_all(&obj->completion);
+ }
+}
+
+static struct hyper_dmabuf *
+dmabuf_exp_wait_obj_get_by_fd(struct gntdev_priv *priv, int fd)
+{
+ struct hyper_dmabuf *q, *hyper_dmabuf, *ret = ERR_PTR(-ENOENT);
+
+ mutex_lock(&priv->dmabuf_lock);
+ list_for_each_entry_safe(hyper_dmabuf, q, &priv->dmabuf_exp_list, next)
+ if (hyper_dmabuf->fd == fd) {
+ pr_debug("Found hyper_dmabuf in the wait list\n");
+ kref_get(&hyper_dmabuf->u.exp.refcount);
+ ret = hyper_dmabuf;
+ break;
+ }
+ mutex_unlock(&priv->dmabuf_lock);
+ return ret;
+}
+
+static int dmabuf_exp_wait_released(struct gntdev_priv *priv, int fd,
+ int wait_to_ms)
+{
+ struct hyper_dmabuf *hyper_dmabuf;
+ struct hyper_dmabuf_wait_obj *obj;
+ int ret;
+
+ pr_debug("Will wait for dma-buf with fd %d\n", fd);
+ /*
+ * Try to find the DMA buffer: if not found means that
+ * either the buffer has already been released or file descriptor
+ * provided is wrong.
+ */
+ hyper_dmabuf = dmabuf_exp_wait_obj_get_by_fd(priv, fd);
+ if (IS_ERR(hyper_dmabuf))
+ return PTR_ERR(hyper_dmabuf);
+
+ /*
+ * hyper_dmabuf still exists and is reference count locked by us now,
+ * so prepare to wait: allocate wait object and add it to the wait list,
+ * so we can find it on release.
+ */
+ obj = dmabuf_exp_wait_obj_new(priv, hyper_dmabuf);
+ if (IS_ERR(obj)) {
+ pr_err("Failed to setup wait object, ret %ld\n", PTR_ERR(obj));
+ return PTR_ERR(obj);
+ }
+
+ ret = dmabuf_exp_wait_obj_wait(obj, wait_to_ms);
+ dmabuf_exp_wait_obj_free(priv, obj);
+ return ret;
+}
+
+/* ------------------------------------------------------------------ */
+/* DMA buffer export support. */
+/* ------------------------------------------------------------------ */
+
+static struct sg_table *
+dmabuf_pages_to_sgt(struct page **pages, unsigned int nr_pages)
+{
+ struct sg_table *sgt;
+ int ret;
+
+ sgt = kmalloc(sizeof(struct sg_table), GFP_KERNEL);
+ if (!sgt) {
+ ret = -ENOMEM;
+ goto out;
+ }
+
+ ret = sg_alloc_table_from_pages(sgt, pages, nr_pages, 0,
+ nr_pages << PAGE_SHIFT,
+ GFP_KERNEL);
+ if (ret)
+ goto out;
+
+ return sgt;
+
+out:
+ kfree(sgt);
+ return ERR_PTR(ret);
+}
+
+static int dmabuf_exp_ops_attach(struct dma_buf *dma_buf,
+ struct device *target_dev,
+ struct dma_buf_attachment *attach)
+{
+ struct hyper_dambuf_attachment *hyper_dambuf_attach;
+
+ hyper_dambuf_attach = kzalloc(sizeof(*hyper_dambuf_attach), GFP_KERNEL);
+ if (!hyper_dambuf_attach)
+ return -ENOMEM;
+
+ hyper_dambuf_attach->dir = DMA_NONE;
+ attach->priv = hyper_dambuf_attach;
+ /* Might need to pin the pages of the buffer now. */
+ return 0;
+}
+
+static void dmabuf_exp_ops_detach(struct dma_buf *dma_buf,
+ struct dma_buf_attachment *attach)
+{
+ struct hyper_dambuf_attachment *hyper_dambuf_attach = attach->priv;
+
+ if (hyper_dambuf_attach) {
+ struct sg_table *sgt = hyper_dambuf_attach->sgt;
+
+ if (sgt) {
+ if (hyper_dambuf_attach->dir != DMA_NONE)
+ dma_unmap_sg_attrs(attach->dev, sgt->sgl,
+ sgt->nents,
+ hyper_dambuf_attach->dir,
+ DMA_ATTR_SKIP_CPU_SYNC);
+ sg_free_table(sgt);
+ }
+
+ kfree(sgt);
+ kfree(hyper_dambuf_attach);
+ attach->priv = NULL;
+ }
+ /* Might need to unpin the pages of the buffer now. */
+}
+
+static struct sg_table *
+dmabuf_exp_ops_map_dma_buf(struct dma_buf_attachment *attach,
+ enum dma_data_direction dir)
+{
+ struct hyper_dambuf_attachment *hyper_dambuf_attach = attach->priv;
+ struct hyper_dmabuf *hyper_dmabuf = attach->dmabuf->priv;
+ struct sg_table *sgt;
+
+ pr_debug("Mapping %d pages for dev %p\n", hyper_dmabuf->nr_pages,
+ attach->dev);
+
+ if (WARN_ON(dir == DMA_NONE || !hyper_dambuf_attach))
+ return ERR_PTR(-EINVAL);
+
+ /* Return the cached mapping when possible. */
+ if (hyper_dambuf_attach->dir == dir)
+ return hyper_dambuf_attach->sgt;
+
+ /*
+ * Two mappings with different directions for the same attachment are
+ * not allowed.
+ */
+ if (WARN_ON(hyper_dambuf_attach->dir != DMA_NONE))
+ return ERR_PTR(-EBUSY);
+
+ sgt = dmabuf_pages_to_sgt(hyper_dmabuf->pages, hyper_dmabuf->nr_pages);
+ if (!IS_ERR(sgt)) {
+ if (!dma_map_sg_attrs(attach->dev, sgt->sgl, sgt->nents, dir,
+ DMA_ATTR_SKIP_CPU_SYNC)) {
+ sg_free_table(sgt);
+ kfree(sgt);
+ sgt = ERR_PTR(-ENOMEM);
+ } else {
+ hyper_dambuf_attach->sgt = sgt;
+ hyper_dambuf_attach->dir = dir;
+ }
+ }
+ if (IS_ERR(sgt)
+ pr_err("Failed to map sg table for dev %p\n", attach->dev);
+ return sgt;
+}
+
+static void dmabuf_exp_ops_unmap_dma_buf(struct dma_buf_attachment *attach,
+ struct sg_table *sgt,
+ enum dma_data_direction dir)
+{
+ /* Not implemented. The unmap is done at dmabuf_exp_ops_detach(). */
+}
+
+static void dmabuf_exp_release(struct kref *kref)
+{
+ struct hyper_dmabuf *hyper_dmabuf =
+ container_of(kref, struct hyper_dmabuf,
+ u.exp.refcount);
+
+ dmabuf_exp_wait_obj_signal(hyper_dmabuf->priv, hyper_dmabuf);
+ list_del(&hyper_dmabuf->next);
+ kfree(hyper_dmabuf);
+}
+
+static void dmabuf_exp_ops_release(struct dma_buf *dma_buf)
+{
+ struct hyper_dmabuf *hyper_dmabuf = dma_buf->priv;
+ struct gntdev_priv *priv = hyper_dmabuf->priv;
+
+ gntdev_put_map_unlink(priv, hyper_dmabuf->u.exp.map);
+ mutex_lock(&priv->dmabuf_lock);
+ kref_put(&hyper_dmabuf->u.exp.refcount, dmabuf_exp_release);
+ mutex_unlock(&priv->dmabuf_lock);
+}
+
+static void *dmabuf_exp_ops_kmap_atomic(struct dma_buf *dma_buf,
+ unsigned long page_num)
+{
+ /* Not implemented. */
+ return NULL;
+}
+
+static void *dmabuf_exp_ops_kmap(struct dma_buf *dma_buf,
+ unsigned long page_num)
+{
+ /* Not implemented. */
+ return NULL;
+}
+
+static int dmabuf_exp_ops_mmap(struct dma_buf *dma_buf,
+ struct vm_area_struct *vma)
+{
+ /* Not implemented. */
+ return 0;
+}
+
+static const struct dma_buf_ops dmabuf_exp_ops = {
+ .attach = dmabuf_exp_ops_attach,
+ .detach = dmabuf_exp_ops_detach,
+ .map_dma_buf = dmabuf_exp_ops_map_dma_buf,
+ .unmap_dma_buf = dmabuf_exp_ops_unmap_dma_buf,
+ .release = dmabuf_exp_ops_release,
+ .kmap = dmabuf_exp_ops_kmap,
+ .kmap_atomic = dmabuf_exp_ops_kmap_atomic,
+ .mmap = dmabuf_exp_ops_mmap,
+};
+
+static int dmabuf_export(struct gntdev_priv *priv, struct grant_map *map,
+ int *fd)
+{
+ DEFINE_DMA_BUF_EXPORT_INFO(exp_info);
+ struct hyper_dmabuf *hyper_dmabuf;
+ int ret = 0;
+
+ hyper_dmabuf = kzalloc(sizeof(*hyper_dmabuf), GFP_KERNEL);
+ if (!hyper_dmabuf)
+ return -ENOMEM;
+
+ kref_init(&hyper_dmabuf->u.exp.refcount);
+
+ hyper_dmabuf->priv = priv;
+ hyper_dmabuf->nr_pages = map->count;
+ hyper_dmabuf->pages = map->pages;
+ hyper_dmabuf->u.exp.map = map;
+
+ exp_info.exp_name = KBUILD_MODNAME;
+ exp_info.ops = &dmabuf_exp_ops;
+ exp_info.size = map->count << PAGE_SHIFT;
+ exp_info.flags = O_RDWR;
+ exp_info.priv = hyper_dmabuf;
+
+ hyper_dmabuf->dmabuf = dma_buf_export(&exp_info);
+ if (IS_ERR(hyper_dmabuf->dmabuf)) {
+ ret = PTR_ERR(hyper_dmabuf->dmabuf);
+ hyper_dmabuf->dmabuf = NULL;
+ goto fail;
+ }
+
+ ret = dma_buf_fd(hyper_dmabuf->dmabuf, O_CLOEXEC);
+ if (ret < 0)
+ goto fail;
+
+ hyper_dmabuf->fd = ret;
+ *fd = ret;
+
+ pr_debug("Exporting DMA buffer with fd %d\n", ret);
+
+ mutex_lock(&priv->dmabuf_lock);
+ list_add(&hyper_dmabuf->next, &priv->dmabuf_exp_list);
+ mutex_unlock(&priv->dmabuf_lock);
+ return 0;
+
+fail:
+ if (hyper_dmabuf->dmabuf)
+ dma_buf_put(hyper_dmabuf->dmabuf);
+ kfree(hyper_dmabuf);
+ return ret;
+}
+
+static struct grant_map *
+dmabuf_exp_alloc_backing_storage(int dmabuf_flags, int count)
+{
+ struct grant_map *map;
+
+ if (unlikely(count <= 0))
+ return ERR_PTR(-EINVAL);
+
+ if ((dmabuf_flags & GNTDEV_DMABUF_FLAG_DMA_WC) &&
+ (dmabuf_flags & GNTDEV_DMABUF_FLAG_DMA_COHERENT)) {
+ pr_err("Wrong dma-buf flags: either WC or coherent, not both\n");
+ return ERR_PTR(-EINVAL);
+ }
+
+ map = gntdev_alloc_map(count, dmabuf_flags);
+ if (!map)
+ return ERR_PTR(-ENOMEM);
+
+ if (unlikely(atomic_add_return(count, &pages_mapped) > limit)) {
+ pr_err("can't map: over limit\n");
+ gntdev_put_map(NULL, map);
+ return ERR_PTR(-ENOMEM);
+ }
+ return map;
+}
+
+int gntdev_dmabuf_exp_from_refs(struct gntdev_priv *priv, int flags,
+ int count, u32 domid, u32 *refs, u32 *fd)
+{
+ struct grant_map *map;
+ int i, ret;
+
+ *fd = -1;
+
+ if (use_ptemod) {
+ pr_err("Cannot provide dma-buf: use_ptemode %d\n",
+ use_ptemod);
+ return -EINVAL;
+ }
+
+ map = dmabuf_exp_alloc_backing_storage(flags, count);
+ if (IS_ERR(map))
+ return PTR_ERR(map);
+
+ for (i = 0; i < count; i++) {
+ map->grants[i].domid = domid;
+ map->grants[i].ref = refs[i];
+ }
+
+ mutex_lock(&priv->lock);
+ gntdev_add_map(priv, map);
+ mutex_unlock(&priv->lock);
+
+ map->flags |= GNTMAP_host_map;
+#if defined(CONFIG_X86)
+ map->flags |= GNTMAP_device_map;
+#endif
+
+ ret = map_grant_pages(map);
+ if (ret < 0)
+ goto out;
+
+ ret = dmabuf_export(priv, map, fd);
+ if (ret < 0)
+ goto out;
+
+ return 0;
+
+out:
+ gntdev_put_map_unlink(priv, map);
+ return ret;
+}
+EXPORT_SYMBOL(gntdev_dmabuf_exp_from_refs);
+
+static long
+gntdev_ioctl_dmabuf_exp_from_refs(struct gntdev_priv *priv,
+ struct ioctl_gntdev_dmabuf_exp_from_refs __user *u)
+{
+ struct ioctl_gntdev_dmabuf_exp_from_refs op;
+ u32 *refs;
+ long ret;
+
+ if (copy_from_user(&op, u, sizeof(op)) != 0)
+ return -EFAULT;
+
+ refs = kcalloc(op.count, sizeof(*refs), GFP_KERNEL);
+ if (!refs)
+ return -ENOMEM;
+
+ if (copy_from_user(refs, u->refs, sizeof(*refs) * op.count) != 0) {
+ ret = -EFAULT;
+ goto out;
+ }
+
+ ret = gntdev_dmabuf_exp_from_refs(priv, op.flags, op.count,
+ op.domid, refs, &op.fd);
+ if (ret)
+ goto out;
+
+ if (copy_to_user(u, &op, sizeof(op)) != 0)
+ ret = -EFAULT;
+
+out:
+ kfree(refs);
+ return ret;
+}
+
+static long
+gntdev_ioctl_dmabuf_exp_wait_released(struct gntdev_priv *priv,
+ struct ioctl_gntdev_dmabuf_exp_wait_released __user *u)
+{
+ struct ioctl_gntdev_dmabuf_exp_wait_released op;
+
+ if (copy_from_user(&op, u, sizeof(op)) != 0)
+ return -EFAULT;
+
+ return dmabuf_exp_wait_released(priv, op.fd, op.wait_to_ms);
+}
+
+int gntdev_dmabuf_exp_wait_released(struct gntdev_priv *priv, u32 fd,
+ int wait_to_ms)
+{
+ return dmabuf_exp_wait_released(priv, fd, wait_to_ms);
+}
+EXPORT_SYMBOL(gntdev_dmabuf_exp_wait_released);
+
+/* ------------------------------------------------------------------ */
+/* DMA buffer import support. */
+/* ------------------------------------------------------------------ */
+
+static int
+dmabuf_imp_grant_foreign_access(struct page **pages, u32 *refs,
+ int count, int domid)
+{
+ grant_ref_t priv_gref_head;
+ int i, ret;
+
+ ret = gnttab_alloc_grant_references(count, &priv_gref_head);
+ if (ret < 0) {
+ pr_err("Cannot allocate grant references, ret %d\n", ret);
+ return ret;
+ }
+
+ for (i = 0; i < count; i++) {
+ int cur_ref;
+
+ cur_ref = gnttab_claim_grant_reference(&priv_gref_head);
+ if (cur_ref < 0) {
+ ret = cur_ref;
+ pr_err("Cannot claim grant reference, ret %d\n", ret);
+ goto out;
+ }
+
+ gnttab_grant_foreign_access_ref(cur_ref, domid,
+ xen_page_to_gfn(pages[i]), 0);
+ refs[i] = cur_ref;
+ }
+
+ ret = 0;
+
+out:
+ gnttab_free_grant_references(priv_gref_head);
+ return ret;
+}
+
+static void dmabuf_imp_end_foreign_access(u32 *refs, int count)
+{
+ int i;
+
+ for (i = 0; i < count; i++)
+ if (refs[i] != GRANT_INVALID_REF)
+ gnttab_end_foreign_access(refs[i], 0, 0UL);
+}
+
+static void dmabuf_imp_free_storage(struct hyper_dmabuf *hyper_dmabuf)
+{
+ kfree(hyper_dmabuf->pages);
+ kfree(hyper_dmabuf->u.imp.refs);
+ kfree(hyper_dmabuf);
+}
+
+static struct hyper_dmabuf *dmabuf_imp_alloc_storage(int count)
+{
+ struct hyper_dmabuf *hyper_dmabuf;
+ int i;
+
+ hyper_dmabuf = kzalloc(sizeof(*hyper_dmabuf), GFP_KERNEL);
+ if (!hyper_dmabuf)
+ goto fail;
+
+ hyper_dmabuf->u.imp.refs = kcalloc(count,
+ sizeof(hyper_dmabuf->u.imp.refs[0]),
+ GFP_KERNEL);
+ if (!hyper_dmabuf->u.imp.refs)
+ goto fail;
+
+ hyper_dmabuf->pages = kcalloc(count,
+ sizeof(hyper_dmabuf->pages[0]),
+ GFP_KERNEL);
+ if (!hyper_dmabuf->pages)
+ goto fail;
+
+ hyper_dmabuf->nr_pages = count;
+
+ for (i = 0; i < count; i++)
+ hyper_dmabuf->u.imp.refs[i] = GRANT_INVALID_REF;
+
+ return hyper_dmabuf;
+
+fail:
+ dmabuf_imp_free_storage(hyper_dmabuf);
+ return ERR_PTR(-ENOMEM);
+}
+
+static struct hyper_dmabuf *
+dmabuf_import(struct gntdev_priv *priv, int fd, int count, int domid)
+{
+ struct hyper_dmabuf *hyper_dmabuf, *ret;
+ struct dma_buf *dma_buf;
+ struct dma_buf_attachment *attach;
+ struct sg_table *sgt;
+ struct sg_page_iter sg_iter;
+ int i;
+
+ dma_buf = dma_buf_get(fd);
+ if (IS_ERR(dma_buf))
+ return ERR_CAST(dma_buf);
+
+ hyper_dmabuf = dmabuf_imp_alloc_storage(count);
+ if (IS_ERR(hyper_dmabuf)) {
+ ret = hyper_dmabuf;
+ goto fail_put;
+ }
+
+ hyper_dmabuf->priv = priv;
+ hyper_dmabuf->fd = fd;
+
+ attach = dma_buf_attach(dma_buf, priv->dev);
+ if (IS_ERR(attach)) {
+ ret = ERR_CAST(attach);
+ goto fail_free_obj;
+ }
+
+ hyper_dmabuf->u.imp.attach = attach;
+
+ sgt = dma_buf_map_attachment(attach, DMA_BIDIRECTIONAL);
+ if (IS_ERR(sgt)) {
+ ret = ERR_CAST(sgt);
+ goto fail_detach;
+ }
+
+ /* Check number of pages that imported buffer has. */
+ if (attach->dmabuf->size != hyper_dmabuf->nr_pages << PAGE_SHIFT) {
+ ret = ERR_PTR(-EINVAL);
+ pr_err("DMA buffer has %zu pages, user-space expects %d\n",
+ attach->dmabuf->size, hyper_dmabuf->nr_pages);
+ goto fail_unmap;
+ }
+
+ hyper_dmabuf->u.imp.sgt = sgt;
+
+ /* Now convert sgt to array of pages and check for page validity. */
+ i = 0;
+ for_each_sg_page(sgt->sgl, &sg_iter, sgt->nents, 0) {
+ struct page *page = sg_page_iter_page(&sg_iter);
+ /*
+ * Check if page is valid: this can happen if we are given
+ * a page from VRAM or other resources which are not backed
+ * by a struct page.
+ */
+ if (!pfn_valid(page_to_pfn(page))) {
+ ret = ERR_PTR(-EINVAL);
+ goto fail_unmap;
+ }
+
+ hyper_dmabuf->pages[i++] = page;
+ }
+
+ ret = ERR_PTR(dmabuf_imp_grant_foreign_access(hyper_dmabuf->pages,
+ hyper_dmabuf->u.imp.refs,
+ count, domid));
+ if (IS_ERR(ret))
+ goto fail_end_access;
+
+ pr_debug("Imported DMA buffer with fd %d\n", fd);
+
+ mutex_lock(&priv->dmabuf_lock);
+ list_add(&hyper_dmabuf->next, &priv->dmabuf_imp_list);
+ mutex_unlock(&priv->dmabuf_lock);
+
+ return hyper_dmabuf;
+
+fail_end_access:
+ dmabuf_imp_end_foreign_access(hyper_dmabuf->u.imp.refs, count);
+fail_unmap:
+ dma_buf_unmap_attachment(attach, sgt, DMA_BIDIRECTIONAL);
+fail_detach:
+ dma_buf_detach(dma_buf, attach);
+fail_free_obj:
+ dmabuf_imp_free_storage(hyper_dmabuf);
+fail_put:
+ dma_buf_put(dma_buf);
+ return ret;
+}
+
+/*
+ * Find the hyper dma-buf by its file descriptor and remove
+ * it from the buffer's list.
+ */
+static struct hyper_dmabuf *
+dmabuf_imp_find_unlink(struct gntdev_priv *priv, int fd)
+{
+ struct hyper_dmabuf *q, *hyper_dmabuf, *ret = ERR_PTR(-ENOENT);
+
+ mutex_lock(&priv->dmabuf_lock);
+ list_for_each_entry_safe(hyper_dmabuf, q, &priv->dmabuf_imp_list, next) {
+ if (hyper_dmabuf->fd == fd) {
+ pr_debug("Found hyper_dmabuf in the import list\n");
+ ret = hyper_dmabuf;
+ list_del(&hyper_dmabuf->next);
+ break;
+ }
+ }
+ mutex_unlock(&priv->dmabuf_lock);
+ return ret;
+}
+
+int gntdev_dmabuf_imp_release(struct gntdev_priv *priv, u32 fd)
+{
+ struct hyper_dmabuf *hyper_dmabuf;
+ struct dma_buf_attachment *attach;
+ struct dma_buf *dma_buf;
+
+ hyper_dmabuf = dmabuf_imp_find_unlink(priv, fd);
+ if (IS_ERR(hyper_dmabuf))
+ return PTR_ERR(hyper_dmabuf);
+
+ pr_debug("Releasing DMA buffer with fd %d\n", fd);
+
+ attach = hyper_dmabuf->u.imp.attach;
+
+ if (hyper_dmabuf->u.imp.sgt)
+ dma_buf_unmap_attachment(attach, hyper_dmabuf->u.imp.sgt,
+ DMA_BIDIRECTIONAL);
+ dma_buf = attach->dmabuf;
+ dma_buf_detach(attach->dmabuf, attach);
+ dma_buf_put(dma_buf);
+
+ dmabuf_imp_end_foreign_access(hyper_dmabuf->u.imp.refs,
+ hyper_dmabuf->nr_pages);
+ dmabuf_imp_free_storage(hyper_dmabuf);
+ return 0;
+}
+EXPORT_SYMBOL(gntdev_dmabuf_imp_release);
+
+static long
+gntdev_ioctl_dmabuf_imp_release(struct gntdev_priv *priv,
+ struct ioctl_gntdev_dmabuf_imp_release __user *u)
+{
+ struct ioctl_gntdev_dmabuf_imp_release op;
+
+ if (copy_from_user(&op, u, sizeof(op)) != 0)
+ return -EFAULT;
+
+ return gntdev_dmabuf_imp_release(priv, op.fd);
+}
+
+static long
+gntdev_ioctl_dmabuf_imp_to_refs(struct gntdev_priv *priv,
+ struct ioctl_gntdev_dmabuf_imp_to_refs __user *u)
+{
+ struct ioctl_gntdev_dmabuf_imp_to_refs op;
+ struct hyper_dmabuf *hyper_dmabuf;
+ long ret;
+
+ if (copy_from_user(&op, u, sizeof(op)) != 0)
+ return -EFAULT;
+
+ hyper_dmabuf = dmabuf_import(priv, op.fd, op.count, op.domid);
+ if (IS_ERR(hyper_dmabuf))
+ return PTR_ERR(hyper_dmabuf);
+
+ if (copy_to_user(u->refs, hyper_dmabuf->u.imp.refs,
+ sizeof(*u->refs) * op.count) != 0) {
+ ret = -EFAULT;
+ goto out_release;
+ }
+ return 0;
+
+out_release:
+ gntdev_dmabuf_imp_release(priv, op.fd);
+ return ret;
+}
+
+u32 *gntdev_dmabuf_imp_to_refs(struct gntdev_priv *priv, int fd,
+ int count, int domid, u32 **refs)
+{
+ struct hyper_dmabuf *hyper_dmabuf;
+
+ hyper_dmabuf = dmabuf_import(priv, fd, count, domid);
+ if (IS_ERR(hyper_dmabuf))
+ return ERR_CAST(hyper_dmabuf);
+
+ return hyper_dmabuf->u.imp.refs;
+}
+EXPORT_SYMBOL(gntdev_dmabuf_imp_to_refs);
+
static long gntdev_ioctl(struct file *flip,
unsigned int cmd, unsigned long arg)
{
@@ -971,6 +1889,18 @@ static long gntdev_ioctl(struct file *flip,
case IOCTL_GNTDEV_GRANT_COPY:
return gntdev_ioctl_grant_copy(priv, ptr);

+ case IOCTL_GNTDEV_DMABUF_EXP_FROM_REFS:
+ return gntdev_ioctl_dmabuf_exp_from_refs(priv, ptr);
+
+ case IOCTL_GNTDEV_DMABUF_EXP_WAIT_RELEASED:
+ return gntdev_ioctl_dmabuf_exp_wait_released(priv, ptr);
+
+ case IOCTL_GNTDEV_DMABUF_IMP_TO_REFS:
+ return gntdev_ioctl_dmabuf_imp_to_refs(priv, ptr);
+
+ case IOCTL_GNTDEV_DMABUF_IMP_RELEASE:
+ return gntdev_ioctl_dmabuf_imp_release(priv, ptr);
+
default:
pr_debug("priv %p, unknown cmd %x\n", priv, cmd);
return -ENOIOCTLCMD;
diff --git a/include/uapi/xen/gntdev.h b/include/uapi/xen/gntdev.h
index d0661977667e..7cf7ca31db21 100644
--- a/include/uapi/xen/gntdev.h
+++ b/include/uapi/xen/gntdev.h
@@ -199,4 +199,105 @@ struct ioctl_gntdev_grant_copy {
/* Send an interrupt on the indicated event channel */
#define UNMAP_NOTIFY_SEND_EVENT 0x2

+/*
+ * Create a dma-buf [1] from grant references @refs of count @count provided
+ * by the foreign domain @domid with flags @flags.
+ *
+ * By default dma-buf is backed by system memory pages, but by providing
+ * GNTDEV_DMABUF_FLAG_DMA flag it can also be created as a DMA write-combine
+ * buffer, e.g. allocated with dma_alloc_wc.
+ *
+ * Returns 0 if dma-buf was successfully created and the corresponding
+ * dma-buf's file descriptor is returned in @fd.
+ *
+ * [1] https://elixir.bootlin.com/linux/latest/source/Documentation/driver-api/dma-buf.rst
+ */
+
+/*
+ * Request dma-buf backing storage to be allocated with DMA API:
+ * the buffer is backed with memory allocated with dma_alloc_wc.
+ */
+#define GNTDEV_DMABUF_FLAG_DMA_WC (1 << 1)
+
+/*
+ * Request dma-buf backing storage to be allocated with DMA API:
+ * the buffer is backed with memory allocated with dma_alloc_coherent.
+ */
+#define GNTDEV_DMABUF_FLAG_DMA_COHERENT (1 << 2)
+
+#define IOCTL_GNTDEV_DMABUF_EXP_FROM_REFS \
+ _IOC(_IOC_NONE, 'G', 9, \
+ sizeof(struct ioctl_gntdev_dmabuf_exp_from_refs))
+struct ioctl_gntdev_dmabuf_exp_from_refs {
+ /* IN parameters. */
+ /* Specific options for this dma-buf: see GNTDEV_DMABUF_FLAG_XXX. */
+ __u32 flags;
+ /* Number of grant references in @refs array. */
+ __u32 count;
+ /* OUT parameters. */
+ /* File descriptor of the dma-buf. */
+ __u32 fd;
+ /* The domain ID of the grant references to be mapped. */
+ __u32 domid;
+ /* Variable IN parameter. */
+ /* Array of grant references of size @count. */
+ __u32 refs[1];
+};
+
+/*
+ * This will block until the dma-buf with the file descriptor @fd is
+ * released. This is only valid for buffers created with
+ * IOCTL_GNTDEV_DMABUF_EXP_FROM_REFS.
+ *
+ * If withing @wait_to_ms milliseconds the buffer is not released
+ * then -ETIMEDOUT error is returned.
+ * If the buffer with file descriptor @fd does not exist or has already
+ * been released, then -ENOENT is returned. For valid file descriptors
+ * this must not be treated as error.
+ */
+#define IOCTL_GNTDEV_DMABUF_EXP_WAIT_RELEASED \
+ _IOC(_IOC_NONE, 'G', 10, \
+ sizeof(struct ioctl_gntdev_dmabuf_exp_wait_released))
+struct ioctl_gntdev_dmabuf_exp_wait_released {
+ /* IN parameters */
+ __u32 fd;
+ __u32 wait_to_ms;
+};
+
+/*
+ * Import a dma-buf with file descriptor @fd and export granted references
+ * to the pages of that dma-buf into array @refs of size @count.
+ */
+#define IOCTL_GNTDEV_DMABUF_IMP_TO_REFS \
+ _IOC(_IOC_NONE, 'G', 11, \
+ sizeof(struct ioctl_gntdev_dmabuf_imp_to_refs))
+struct ioctl_gntdev_dmabuf_imp_to_refs {
+ /* IN parameters. */
+ /* File descriptor of the dma-buf. */
+ __u32 fd;
+ /* Number of grant references in @refs array. */
+ __u32 count;
+ /* The domain ID for which references to be granted. */
+ __u32 domid;
+ /* Reserved - must be zero. */
+ __u32 reserved;
+ /* OUT parameters. */
+ /* Array of grant references of size @count. */
+ __u32 refs[1];
+};
+
+/*
+ * This will close all references to an imported buffer, so it can be
+ * released by the owner. This is only valid for buffers created with
+ * IOCTL_GNTDEV_DMABUF_IMP_TO_REFS.
+ */
+#define IOCTL_GNTDEV_DMABUF_IMP_RELEASE \
+ _IOC(_IOC_NONE, 'G', 12, \
+ sizeof(struct ioctl_gntdev_dmabuf_imp_release))
+struct ioctl_gntdev_dmabuf_imp_release {
+ /* IN parameters */
+ __u32 fd;
+ __u32 reserved;
+};
+
#endif /* __LINUX_PUBLIC_GNTDEV_H__ */
diff --git a/include/xen/gntdev_exp.h b/include/xen/gntdev_exp.h
new file mode 100644
index 000000000000..aaf45bda30ac
--- /dev/null
+++ b/include/xen/gntdev_exp.h
@@ -0,0 +1,23 @@
+/******************************************************************************
+ * Xen grant device exported functionality
+ */
+
+#ifndef _XEN_GNTDEV_EXP_H
+#define _XEN_GNTDEV_EXP_H
+
+struct gntdev_priv *gntdev_alloc_context(struct device *dev);
+
+void gntdev_free_context(struct gntdev_priv *priv);
+
+int gntdev_dmabuf_exp_from_refs(struct gntdev_priv *priv, int flags,
+ int count, u32 domid, u32 *refs, u32 *fd);
+
+int gntdev_dmabuf_exp_wait_released(struct gntdev_priv *priv, u32 fd,
+ int wait_to_ms);
+
+int gntdev_dmabuf_imp_release(struct gntdev_priv *priv, u32 fd);
+
+u32 *gntdev_dmabuf_imp_to_refs(struct gntdev_priv *priv, int fd,
+ int count, int domid, u32 **refs);
+
+#endif
--
2.17.0
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  Last update: 2018-05-17 10:28    [W:0.142 / U:5.952 seconds]
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