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.
3. Make gntdev's common code and structures available to dma-buf.
Signed-off-by: Oleksandr Andrushchenko oleksandr_andrushchenko@epam.com --- drivers/xen/gntdev-dmabuf.c | 470 +++++++++++++++++++++++++++++++++++- 1 file changed, 467 insertions(+), 3 deletions(-)
diff --git a/drivers/xen/gntdev-dmabuf.c b/drivers/xen/gntdev-dmabuf.c index af782c0a8a19..07a98aa52cab 100644 --- a/drivers/xen/gntdev-dmabuf.c +++ b/drivers/xen/gntdev-dmabuf.c @@ -3,11 +3,14 @@ /* * Xen dma-buf functionality for gntdev. * + * DMA buffer implementation is based on drivers/gpu/drm/drm_prime.c. + * * Copyright (c) 2018 Oleksandr Andrushchenko, EPAM Systems Inc. */
#include <linux/kernel.h> #include <linux/errno.h> +#include <linux/dma-buf.h> #include <linux/slab.h> #include <linux/types.h> #include <linux/uaccess.h> @@ -18,6 +21,39 @@ #include "gntdev-common.h" #include "gntdev-dmabuf.h"
+struct gntdev_dmabuf { + struct gntdev_dmabuf_priv *priv; + struct dma_buf *dmabuf; + struct list_head next; + int fd; + + union { + struct { + /* Exported buffers are reference counted. */ + struct kref refcount; + + struct gntdev_priv *priv; + struct gntdev_grant_map *map; + } exp; + } u; + + /* Number of pages this buffer has. */ + int nr_pages; + /* Pages of this buffer. */ + struct page **pages; +}; + +struct gntdev_dmabuf_wait_obj { + struct list_head next; + struct gntdev_dmabuf *gntdev_dmabuf; + struct completion completion; +}; + +struct gntdev_dmabuf_attachment { + struct sg_table *sgt; + enum dma_data_direction dir; +}; + struct gntdev_dmabuf_priv { /* List of exported DMA buffers. */ struct list_head exp_list; @@ -31,17 +67,441 @@ struct gntdev_dmabuf_priv {
/* Implementation of wait for exported DMA buffer to be released. */
+static void dmabuf_exp_release(struct kref *kref); + +static struct gntdev_dmabuf_wait_obj * +dmabuf_exp_wait_obj_new(struct gntdev_dmabuf_priv *priv, + struct gntdev_dmabuf *gntdev_dmabuf) +{ + struct gntdev_dmabuf_wait_obj *obj; + + obj = kzalloc(sizeof(*obj), GFP_KERNEL); + if (!obj) + return ERR_PTR(-ENOMEM); + + init_completion(&obj->completion); + obj->gntdev_dmabuf = gntdev_dmabuf; + + mutex_lock(&priv->lock); + list_add(&obj->next, &priv->exp_wait_list); + /* Put our reference and wait for gntdev_dmabuf's release to fire. */ + kref_put(&gntdev_dmabuf->u.exp.refcount, dmabuf_exp_release); + mutex_unlock(&priv->lock); + return obj; +} + +static void dmabuf_exp_wait_obj_free(struct gntdev_dmabuf_priv *priv, + struct gntdev_dmabuf_wait_obj *obj) +{ + mutex_lock(&priv->lock); + list_del(&obj->next); + mutex_unlock(&priv->lock); + kfree(obj); +} + +static int dmabuf_exp_wait_obj_wait(struct gntdev_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_dmabuf_priv *priv, + struct gntdev_dmabuf *gntdev_dmabuf) +{ + struct gntdev_dmabuf_wait_obj *obj; + + list_for_each_entry(obj, &priv->exp_wait_list, next) + if (obj->gntdev_dmabuf == gntdev_dmabuf) { + pr_debug("Found gntdev_dmabuf in the wait list, wake\n"); + complete_all(&obj->completion); + break; + } +} + +static struct gntdev_dmabuf * +dmabuf_exp_wait_obj_get_dmabuf(struct gntdev_dmabuf_priv *priv, int fd) +{ + struct gntdev_dmabuf *gntdev_dmabuf, *ret = ERR_PTR(-ENOENT); + + mutex_lock(&priv->lock); + list_for_each_entry(gntdev_dmabuf, &priv->exp_list, next) + if (gntdev_dmabuf->fd == fd) { + pr_debug("Found gntdev_dmabuf in the wait list\n"); + kref_get(&gntdev_dmabuf->u.exp.refcount); + ret = gntdev_dmabuf; + break; + } + mutex_unlock(&priv->lock); + return ret; +} + static int dmabuf_exp_wait_released(struct gntdev_dmabuf_priv *priv, int fd, int wait_to_ms) { - return -EINVAL; + struct gntdev_dmabuf *gntdev_dmabuf; + struct gntdev_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. + */ + gntdev_dmabuf = dmabuf_exp_wait_obj_get_dmabuf(priv, fd); + if (IS_ERR(gntdev_dmabuf)) + return PTR_ERR(gntdev_dmabuf); + + /* + * gntdev_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, gntdev_dmabuf); + if (IS_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 gntdev_dmabuf_attachment *gntdev_dmabuf_attach; + + gntdev_dmabuf_attach = kzalloc(sizeof(*gntdev_dmabuf_attach), + GFP_KERNEL); + if (!gntdev_dmabuf_attach) + return -ENOMEM; + + gntdev_dmabuf_attach->dir = DMA_NONE; + attach->priv = gntdev_dmabuf_attach; + return 0; +} + +static void dmabuf_exp_ops_detach(struct dma_buf *dma_buf, + struct dma_buf_attachment *attach) +{ + struct gntdev_dmabuf_attachment *gntdev_dmabuf_attach = attach->priv; + + if (gntdev_dmabuf_attach) { + struct sg_table *sgt = gntdev_dmabuf_attach->sgt; + + if (sgt) { + if (gntdev_dmabuf_attach->dir != DMA_NONE) + dma_unmap_sg_attrs(attach->dev, sgt->sgl, + sgt->nents, + gntdev_dmabuf_attach->dir, + DMA_ATTR_SKIP_CPU_SYNC); + sg_free_table(sgt); + } + + kfree(sgt); + kfree(gntdev_dmabuf_attach); + attach->priv = NULL; + } +} + +static struct sg_table * +dmabuf_exp_ops_map_dma_buf(struct dma_buf_attachment *attach, + enum dma_data_direction dir) +{ + struct gntdev_dmabuf_attachment *gntdev_dmabuf_attach = attach->priv; + struct gntdev_dmabuf *gntdev_dmabuf = attach->dmabuf->priv; + struct sg_table *sgt; + + pr_debug("Mapping %d pages for dev %p\n", gntdev_dmabuf->nr_pages, + attach->dev); + + if (dir == DMA_NONE || !gntdev_dmabuf_attach) + return ERR_PTR(-EINVAL); + + /* Return the cached mapping when possible. */ + if (gntdev_dmabuf_attach->dir == dir) + return gntdev_dmabuf_attach->sgt; + + /* + * Two mappings with different directions for the same attachment are + * not allowed. + */ + if (gntdev_dmabuf_attach->dir != DMA_NONE) + return ERR_PTR(-EBUSY); + + sgt = dmabuf_pages_to_sgt(gntdev_dmabuf->pages, + gntdev_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 { + gntdev_dmabuf_attach->sgt = sgt; + gntdev_dmabuf_attach->dir = dir; + } + } + if (IS_ERR(sgt)) + pr_debug("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 gntdev_dmabuf *gntdev_dmabuf = + container_of(kref, struct gntdev_dmabuf, u.exp.refcount); + + dmabuf_exp_wait_obj_signal(gntdev_dmabuf->priv, gntdev_dmabuf); + list_del(&gntdev_dmabuf->next); + kfree(gntdev_dmabuf); +} + +static void dmabuf_exp_remove_map(struct gntdev_priv *priv, + struct gntdev_grant_map *map) +{ + mutex_lock(&priv->lock); + list_del(&map->next); + gntdev_put_map(NULL /* already removed */, map); + mutex_unlock(&priv->lock); +} + +static void dmabuf_exp_ops_release(struct dma_buf *dma_buf) +{ + struct gntdev_dmabuf *gntdev_dmabuf = dma_buf->priv; + struct gntdev_dmabuf_priv *priv = gntdev_dmabuf->priv; + + dmabuf_exp_remove_map(gntdev_dmabuf->u.exp.priv, + gntdev_dmabuf->u.exp.map); + mutex_lock(&priv->lock); + kref_put(&gntdev_dmabuf->u.exp.refcount, dmabuf_exp_release); + mutex_unlock(&priv->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, +}; + +struct gntdev_dmabuf_export_args { + struct gntdev_priv *priv; + struct gntdev_grant_map *map; + struct gntdev_dmabuf_priv *dmabuf_priv; + struct device *dev; + int count; + struct page **pages; + u32 fd; +}; + +static int dmabuf_exp_from_pages(struct gntdev_dmabuf_export_args *args) +{ + DEFINE_DMA_BUF_EXPORT_INFO(exp_info); + struct gntdev_dmabuf *gntdev_dmabuf; + int ret; + + gntdev_dmabuf = kzalloc(sizeof(*gntdev_dmabuf), GFP_KERNEL); + if (!gntdev_dmabuf) + return -ENOMEM; + + kref_init(&gntdev_dmabuf->u.exp.refcount); + + gntdev_dmabuf->priv = args->dmabuf_priv; + gntdev_dmabuf->nr_pages = args->count; + gntdev_dmabuf->pages = args->pages; + gntdev_dmabuf->u.exp.priv = args->priv; + gntdev_dmabuf->u.exp.map = args->map; + + exp_info.exp_name = KBUILD_MODNAME; + if (args->dev->driver && args->dev->driver->owner) + exp_info.owner = args->dev->driver->owner; + else + exp_info.owner = THIS_MODULE; + exp_info.ops = &dmabuf_exp_ops; + exp_info.size = args->count << PAGE_SHIFT; + exp_info.flags = O_RDWR; + exp_info.priv = gntdev_dmabuf; + + gntdev_dmabuf->dmabuf = dma_buf_export(&exp_info); + if (IS_ERR(gntdev_dmabuf->dmabuf)) { + ret = PTR_ERR(gntdev_dmabuf->dmabuf); + gntdev_dmabuf->dmabuf = NULL; + goto fail; + } + + ret = dma_buf_fd(gntdev_dmabuf->dmabuf, O_CLOEXEC); + if (ret < 0) + goto fail; + + gntdev_dmabuf->fd = ret; + args->fd = ret; + + pr_debug("Exporting DMA buffer with fd %d\n", ret); + + mutex_lock(&args->dmabuf_priv->lock); + list_add(&gntdev_dmabuf->next, &args->dmabuf_priv->exp_list); + mutex_unlock(&args->dmabuf_priv->lock); + return 0; + +fail: + if (gntdev_dmabuf->dmabuf) + dma_buf_put(gntdev_dmabuf->dmabuf); + kfree(gntdev_dmabuf); + return ret; +} + +static struct gntdev_grant_map * +dmabuf_exp_alloc_backing_storage(struct gntdev_priv *priv, int dmabuf_flags, + int count) +{ + struct gntdev_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_debug("Wrong dma-buf flags: 0x%x\n", dmabuf_flags); + return ERR_PTR(-EINVAL); + } + + map = gntdev_alloc_map(priv, count, dmabuf_flags); + if (!map) + return ERR_PTR(-ENOMEM); + + if (unlikely(gntdev_account_mapped_pages(count))) { + pr_debug("can't map %d pages: over limit\n", count); + 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) { - *fd = -1; - return -EINVAL; + struct gntdev_grant_map *map; + struct gntdev_dmabuf_export_args args; + int i, ret; + + 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 = gntdev_map_grant_pages(map); + if (ret < 0) + goto out; + + args.priv = priv; + args.map = map; + args.dev = priv->dma_dev; + args.dmabuf_priv = priv->dmabuf_priv; + args.count = map->count; + args.pages = map->pages; + + ret = dmabuf_exp_from_pages(&args); + if (ret < 0) + goto out; + + *fd = args.fd; + return 0; + +out: + dmabuf_exp_remove_map(priv, map); + return ret; }
/* DMA buffer import support. */ @@ -168,6 +628,10 @@ struct gntdev_dmabuf_priv *gntdev_dmabuf_init(void) if (!priv) return ERR_PTR(-ENOMEM);
+ mutex_init(&priv->lock); + INIT_LIST_HEAD(&priv->exp_list); + INIT_LIST_HEAD(&priv->exp_wait_list); + return priv; }