From: Oleksandr Andrushchenko oleksandr_andrushchenko@epam.com
1. Create a dma-buf from grant references provided by the foreign domain. By default dma-buf is backed by system memory pages, but by providing GNTDEV_DMA_FLAG_XXX flags it can also be created as a DMA write-combine/coherent buffer, e.g. allocated with corresponding dma_alloc_xxx API. Export the resulting buffer as a new dma-buf.
2. Implement waiting for the dma-buf to be released: block until the dma-buf with the file descriptor provided is released. If within the time-out provided the buffer is not released then -ETIMEDOUT error is returned. If the buffer with the file descriptor does not exist or has already been released, then -ENOENT is returned. For valid file descriptors this must not be treated as error.
Signed-off-by: Oleksandr Andrushchenko oleksandr_andrushchenko@epam.com --- drivers/xen/gntdev.c | 478 ++++++++++++++++++++++++++++++++++++++++++- 1 file changed, 476 insertions(+), 2 deletions(-)
diff --git a/drivers/xen/gntdev.c b/drivers/xen/gntdev.c index 9e450622af1a..52abc6cd5846 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 * (c) 2018 Oleksandr Andrushchenko, EPAM Systems Inc. @@ -41,6 +43,9 @@ #ifdef CONFIG_XEN_GRANT_DMA_ALLOC #include <linux/of_device.h> #endif +#ifdef CONFIG_XEN_GNTDEV_DMABUF +#include <linux/dma-buf.h> +#endif
#include <xen/xen.h> #include <xen/grant_table.h> @@ -81,6 +86,17 @@ struct gntdev_priv { /* Device for which DMA memory is allocated. */ struct device *dma_dev; #endif + +#ifdef CONFIG_XEN_GNTDEV_DMABUF + /* Private data of the hyper DMA buffers. */ + + /* List of exported DMA buffers. */ + struct list_head dmabuf_exp_list; + /* List of wait objects. */ + struct list_head dmabuf_exp_wait_list; + /* This is the lock which protects dma_buf_xxx lists. */ + struct mutex dmabuf_lock; +#endif };
struct unmap_notify { @@ -125,12 +141,38 @@ struct grant_map {
#ifdef CONFIG_XEN_GNTDEV_DMABUF struct xen_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; } imp; } u; + + /* Number of pages this buffer has. */ + int nr_pages; + /* Pages of this buffer. */ + struct page **pages; +}; + +struct xen_dmabuf_wait_obj { + struct list_head next; + struct xen_dmabuf *xen_dmabuf; + struct completion completion; +}; + +struct xen_dmabuf_attachment { + struct sg_table *sgt; + enum dma_data_direction dir; }; #endif
@@ -320,6 +362,16 @@ static void gntdev_put_map(struct gntdev_priv *priv, struct grant_map *map) gntdev_free_map(map); }
+#ifdef CONFIG_XEN_GNTDEV_DMABUF +static void gntdev_remove_map(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); +} +#endif + /* ------------------------------------------------------------------ */
static int find_grant_ptes(pte_t *pte, pgtable_t token, @@ -628,6 +680,12 @@ static int gntdev_open(struct inode *inode, struct file *flip) INIT_LIST_HEAD(&priv->freeable_maps); mutex_init(&priv->lock);
+#ifdef CONFIG_XEN_GNTDEV_DMABUF + mutex_init(&priv->dmabuf_lock); + INIT_LIST_HEAD(&priv->dmabuf_exp_list); + INIT_LIST_HEAD(&priv->dmabuf_exp_wait_list); +#endif + if (use_ptemod) { priv->mm = get_task_mm(current); if (!priv->mm) { @@ -1053,17 +1111,433 @@ static long gntdev_ioctl_grant_copy(struct gntdev_priv *priv, void __user *u) /* DMA buffer export support. */ /* ------------------------------------------------------------------ */
+/* ------------------------------------------------------------------ */ +/* Implementation of wait for exported DMA buffer to be released. */ +/* ------------------------------------------------------------------ */ + +static void dmabuf_exp_release(struct kref *kref); + +static struct xen_dmabuf_wait_obj * +dmabuf_exp_wait_obj_new(struct gntdev_priv *priv, + struct xen_dmabuf *xen_dmabuf) +{ + struct xen_dmabuf_wait_obj *obj; + + obj = kzalloc(sizeof(*obj), GFP_KERNEL); + if (!obj) + return ERR_PTR(-ENOMEM); + + init_completion(&obj->completion); + obj->xen_dmabuf = xen_dmabuf; + + mutex_lock(&priv->dmabuf_lock); + list_add(&obj->next, &priv->dmabuf_exp_wait_list); + /* Put our reference and wait for xen_dmabuf's release to fire. */ + kref_put(&xen_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 xen_dmabuf_wait_obj *obj) +{ + struct xen_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 xen_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 xen_dmabuf *xen_dmabuf) +{ + struct xen_dmabuf_wait_obj *obj, *q; + + list_for_each_entry_safe(obj, q, &priv->dmabuf_exp_wait_list, next) + if (obj->xen_dmabuf == xen_dmabuf) { + pr_debug("Found xen_dmabuf in the wait list, wake\n"); + complete_all(&obj->completion); + } +} + +static struct xen_dmabuf * +dmabuf_exp_wait_obj_get_by_fd(struct gntdev_priv *priv, int fd) +{ + struct xen_dmabuf *q, *xen_dmabuf, *ret = ERR_PTR(-ENOENT); + + mutex_lock(&priv->dmabuf_lock); + list_for_each_entry_safe(xen_dmabuf, q, &priv->dmabuf_exp_list, next) + if (xen_dmabuf->fd == fd) { + pr_debug("Found xen_dmabuf in the wait list\n"); + kref_get(&xen_dmabuf->u.exp.refcount); + ret = xen_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) { - return -ETIMEDOUT; + struct xen_dmabuf *xen_dmabuf; + struct xen_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. + */ + xen_dmabuf = dmabuf_exp_wait_obj_get_by_fd(priv, fd); + if (IS_ERR(xen_dmabuf)) + return PTR_ERR(xen_dmabuf); + + /* + * xen_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, xen_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(*sgt), 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 xen_dmabuf_attachment *xen_dmabuf_attach; + + xen_dmabuf_attach = kzalloc(sizeof(*xen_dmabuf_attach), GFP_KERNEL); + if (!xen_dmabuf_attach) + return -ENOMEM; + + xen_dmabuf_attach->dir = DMA_NONE; + attach->priv = xen_dmabuf_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 xen_dmabuf_attachment *xen_dmabuf_attach = attach->priv; + + if (xen_dmabuf_attach) { + struct sg_table *sgt = xen_dmabuf_attach->sgt; + + if (sgt) { + if (xen_dmabuf_attach->dir != DMA_NONE) + dma_unmap_sg_attrs(attach->dev, sgt->sgl, + sgt->nents, + xen_dmabuf_attach->dir, + DMA_ATTR_SKIP_CPU_SYNC); + sg_free_table(sgt); + } + + kfree(sgt); + kfree(xen_dmabuf_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 xen_dmabuf_attachment *xen_dmabuf_attach = attach->priv; + struct xen_dmabuf *xen_dmabuf = attach->dmabuf->priv; + struct sg_table *sgt; + + pr_debug("Mapping %d pages for dev %p\n", xen_dmabuf->nr_pages, + attach->dev); + + if (WARN_ON(dir == DMA_NONE || !xen_dmabuf_attach)) + return ERR_PTR(-EINVAL); + + /* Return the cached mapping when possible. */ + if (xen_dmabuf_attach->dir == dir) + return xen_dmabuf_attach->sgt; + + /* + * Two mappings with different directions for the same attachment are + * not allowed. + */ + if (WARN_ON(xen_dmabuf_attach->dir != DMA_NONE)) + return ERR_PTR(-EBUSY); + + sgt = dmabuf_pages_to_sgt(xen_dmabuf->pages, xen_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 { + xen_dmabuf_attach->sgt = sgt; + xen_dmabuf_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 xen_dmabuf *xen_dmabuf = + container_of(kref, struct xen_dmabuf, u.exp.refcount); + + dmabuf_exp_wait_obj_signal(xen_dmabuf->priv, xen_dmabuf); + list_del(&xen_dmabuf->next); + kfree(xen_dmabuf); +} + +static void dmabuf_exp_ops_release(struct dma_buf *dma_buf) +{ + struct xen_dmabuf *xen_dmabuf = dma_buf->priv; + struct gntdev_priv *priv = xen_dmabuf->priv; + + gntdev_remove_map(priv, xen_dmabuf->u.exp.map); + mutex_lock(&priv->dmabuf_lock); + kref_put(&xen_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_kunmap_atomic(struct dma_buf *dma_buf, + unsigned long page_num, void *addr) +{ + /* Not implemented. */ +} + +static void *dmabuf_exp_ops_kmap(struct dma_buf *dma_buf, + unsigned long page_num) +{ + /* Not implemented. */ + return NULL; +} + +static void dmabuf_exp_ops_kunmap(struct dma_buf *dma_buf, + unsigned long page_num, void *addr) +{ + /* Not implemented. */ +} + +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, + .map = dmabuf_exp_ops_kmap, + .map_atomic = dmabuf_exp_ops_kmap_atomic, + .unmap = dmabuf_exp_ops_kunmap, + .unmap_atomic = dmabuf_exp_ops_kunmap_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 xen_dmabuf *xen_dmabuf; + int ret = 0; + + xen_dmabuf = kzalloc(sizeof(*xen_dmabuf), GFP_KERNEL); + if (!xen_dmabuf) + return -ENOMEM; + + kref_init(&xen_dmabuf->u.exp.refcount); + + xen_dmabuf->priv = priv; + xen_dmabuf->nr_pages = map->count; + xen_dmabuf->pages = map->pages; + xen_dmabuf->u.exp.map = map; + + exp_info.exp_name = KBUILD_MODNAME; + if (map->dma_dev->driver && map->dma_dev->driver->owner) + exp_info.owner = map->dma_dev->driver->owner; + else + exp_info.owner = THIS_MODULE; + exp_info.ops = &dmabuf_exp_ops; + exp_info.size = map->count << PAGE_SHIFT; + exp_info.flags = O_RDWR; + exp_info.priv = xen_dmabuf; + + xen_dmabuf->dmabuf = dma_buf_export(&exp_info); + if (IS_ERR(xen_dmabuf->dmabuf)) { + ret = PTR_ERR(xen_dmabuf->dmabuf); + xen_dmabuf->dmabuf = NULL; + goto fail; + } + + ret = dma_buf_fd(xen_dmabuf->dmabuf, O_CLOEXEC); + if (ret < 0) + goto fail; + + xen_dmabuf->fd = ret; + *fd = ret; + + pr_debug("Exporting DMA buffer with fd %d\n", ret); + + mutex_lock(&priv->dmabuf_lock); + list_add(&xen_dmabuf->next, &priv->dmabuf_exp_list); + mutex_unlock(&priv->dmabuf_lock); + return 0; + +fail: + if (xen_dmabuf->dmabuf) + dma_buf_put(xen_dmabuf->dmabuf); + kfree(xen_dmabuf); + return ret; +} + +static struct grant_map * +dmabuf_exp_alloc_backing_storage(struct gntdev_priv *priv, int dmabuf_flags, + int count) +{ + struct grant_map *map; + + if (unlikely(count <= 0)) + return ERR_PTR(-EINVAL); + + if ((dmabuf_flags & GNTDEV_DMA_FLAG_WC) && + (dmabuf_flags & GNTDEV_DMA_FLAG_COHERENT)) { + pr_err("Wrong dma-buf flags: either WC or coherent, not both\n"); + return ERR_PTR(-EINVAL); + } + + map = gntdev_alloc_map(priv, 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; }
static int 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; - return -EINVAL; + + if (use_ptemod) { + pr_err("Cannot provide dma-buf: use_ptemode %d\n", + use_ptemod); + return -EINVAL; + } + + map = dmabuf_exp_alloc_backing_storage(priv, 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_remove_map(priv, map); + return ret; }
/* ------------------------------------------------------------------ */