[PATCH v3] drm/vgem: Enable dmabuf interface for export

[Zach Reizner]

On Mon, Jun 20, 2016 at 1:07 PM Chris Wilson <chris at chris-wilson.co.uk>
wrote:

> Enable the standard GEM dma-buf interface provided by the DRM core, but
> only for exporting the VGEM object. This allows passing around the VGEM
> objects created from the dumb interface and using them as sources
> elsewhere. Creating a VGEM object for a foriegn handle is not supported.
>
> v2: With additional completeness.
> v3: Need to clear the CPU cache upon exporting the dma-addresses.
>
> Testcase: igt/vgem_basic/dmabuf-*
> Testcase: igt/prime_vgem
> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> Cc: Sean Paul <seanpaul at chromium.org>
> Cc: Zach Reizner <zachr at google.com>
> ---
>  drivers/gpu/drm/vgem/vgem_drv.c | 112
> +++++++++++++++++++++++++++++++++++++++-
>  1 file changed, 111 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/vgem/vgem_drv.c
> b/drivers/gpu/drm/vgem/vgem_drv.c
> index e1a697d0662f..db48e837992d 100644
> --- a/drivers/gpu/drm/vgem/vgem_drv.c
> +++ b/drivers/gpu/drm/vgem/vgem_drv.c
> @@ -193,14 +193,124 @@ static const struct file_operations
> vgem_driver_fops = {
>         .release        = drm_release,
>  };
>
> +static void __put_pages(struct page **pages, long n_pages)
> +{
> +       while (n_pages--)
> +               put_page(pages[n_pages]);
> +       drm_free_large(pages);
> +}
> +
> +static int vgem_prime_pin(struct drm_gem_object *obj)
> +{
> +       long n_pages = obj->size >> PAGE_SHIFT;
> +       struct page **pages;
> +
> +       /* Flush the object from the CPU cache so that importers
> +        * can rely on coherent indirect access via access the
> +        * exported dma-address.
> +        */
> +       pages = drm_gem_get_pages(obj);
> +       if (IS_ERR(pages))
> +               return PTR_ERR(pages);
> +
> +       drm_clflush_pages(pages, n_pages);
> +       __put_pages(pages, n_pages);
> +
> +       return 0;
> +}
> +
> +static struct sg_table *vgem_prime_get_sg_table(struct drm_gem_object
> *obj)
> +{
> +       long n_pages = obj->size >> PAGE_SHIFT;
> +       struct sg_table *st;
> +       struct page **pages;
> +       int ret;
> +
> +       st = kmalloc(sizeof(struct sg_table), GFP_KERNEL);
> +       if (st == NULL)
> +               return ERR_PTR(-ENOMEM);
> +
> +       pages = drm_gem_get_pages(obj);
> +       if (IS_ERR(pages)) {
> +               ret = PTR_ERR(pages);
> +               goto err;
> +       }
> +
> +       ret = sg_alloc_table_from_pages(st, pages, n_pages,
> +                                       0, obj->size, GFP_KERNEL);
> +       __put_pages(pages, n_pages);
> +       if (ret)
> +               goto err;
> +
> +       return st;
> +
> +err:
> +       kfree(st);
> +       return ERR_PTR(ret);
> +}
> +
> +static void *vgem_prime_vmap(struct drm_gem_object *obj)
> +{
> +       long n_pages = obj->size >> PAGE_SHIFT;
> +       struct page **pages;
> +       void *addr;
> +
> +       pages = drm_gem_get_pages(obj);
> +       if (IS_ERR(pages))
> +               return NULL;
> +
> +       addr = vmap(pages, n_pages, 0,
> pgprot_writecombine(PAGE_KERNEL_IO));
> +       __put_pages(pages, n_pages);
> +
> +       return addr;
> +}
> +
> +static void vgem_prime_vunmap(struct drm_gem_object *obj, void *vaddr)
> +{
> +       vunmap(vaddr);
> +}
> +
> +static int vgem_prime_mmap(struct drm_gem_object *obj,
> +                          struct vm_area_struct *vma)
> +{
> +       int ret;
> +
> +       if (obj->size < vma->vm_end - vma->vm_start)
> +               return -EINVAL;
> +
> +       if (!obj->filp)
> +               return -ENODEV;
> +
> +       ret = obj->filp->f_op->mmap(obj->filp, vma);
> +       if (ret)
> +               return ret;
> +
> +       fput(vma->vm_file);
> +       vma->vm_file = get_file(obj->filp);
> +       vma->vm_flags |= VM_DONTEXPAND | VM_DONTDUMP;
> +       vma->vm_page_prot =
> pgprot_writecombine(vm_get_page_prot(vma->vm_flags));
> +
> +       return 0;
> +}
> +
>  static struct drm_driver vgem_driver = {
> -       .driver_features                = DRIVER_GEM,
> +       .driver_features                = DRIVER_GEM | DRIVER_PRIME,
>         .gem_free_object_unlocked       = vgem_gem_free_object,
>         .gem_vm_ops                     = &vgem_gem_vm_ops,
>         .ioctls                         = vgem_ioctls,
>         .fops                           = &vgem_driver_fops,
> +
>         .dumb_create                    = vgem_gem_dumb_create,
>         .dumb_map_offset                = vgem_gem_dumb_map,
> +
> +       .prime_handle_to_fd = drm_gem_prime_handle_to_fd,
> +       .gem_prime_pin = vgem_prime_pin,
> +       .gem_prime_export = drm_gem_prime_export,
> +       .gem_prime_get_sg_table = vgem_prime_get_sg_table,
> +       .gem_prime_vmap = vgem_prime_vmap,
> +       .gem_prime_vunmap = vgem_prime_vunmap,
> +       .gem_prime_mmap = vgem_prime_mmap,
> +
>         .name   = DRIVER_NAME,
>         .desc   = DRIVER_DESC,
>         .date   = DRIVER_DATE,
> --
> 2.8.1
>
>
Acked-by: Zach Reizner <zachr at google.com>
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