On Fri, Sep 30, 2016 at 02:59:59PM +0100, Chris Wilson wrote:
> In order to keep the dmabuf alive whilst the mmap is, we need to hold a
> reference to the dmabuf and not the backing object. This is important as
> the dmabuf not only keeps the object alive, but also the device so that
>
> dmabuf = vgem_create_dmabuf();
> ptr = mmap(... dmabuf ...);
> close(dmabuf);
>
> persists across module-unload as well as device closure.
I don't see where we grab the ref to the dma-buf here instead of the
backing storage. And doesn't the exact same issue happen when you use dumb
mmap? Or maybe I'm just a bit confused about what's going on here ...
-Daniel
>
> Testcase: igt/vgem_basic/unload
> Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
> Cc: Petri Latvala <petri.latvala@xxxxxxxxx>
> ---
> drivers/gpu/drm/vgem/vgem_drv.c | 17 +++--------------
> 1 file changed, 3 insertions(+), 14 deletions(-)
>
> diff --git a/drivers/gpu/drm/vgem/vgem_drv.c b/drivers/gpu/drm/vgem/vgem_drv.c
> index f36c14729b55..74a83e41efa9 100644
> --- a/drivers/gpu/drm/vgem/vgem_drv.c
> +++ b/drivers/gpu/drm/vgem/vgem_drv.c
> @@ -198,7 +198,6 @@ static struct drm_ioctl_desc vgem_ioctls[] = {
>
> static int vgem_mmap(struct file *filp, struct vm_area_struct *vma)
> {
> - unsigned long flags = vma->vm_flags;
> int ret;
>
> ret = drm_gem_mmap(filp, vma);
> @@ -208,7 +207,7 @@ static int vgem_mmap(struct file *filp, struct vm_area_struct *vma)
> /* Keep the WC mmaping set by drm_gem_mmap() but our pages
> * are ordinary and not special.
> */
> - vma->vm_flags = flags | VM_DONTEXPAND | VM_DONTDUMP;
> + vma->vm_flags &= ~(VM_IO | VM_PFNMAP);
> return 0;
> }
>
> @@ -281,21 +280,11 @@ static int vgem_prime_mmap(struct drm_gem_object *obj,
> {
> 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);
> + ret = drm_gem_mmap_obj(obj, obj->size, 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));
> -
> + vma->vm_flags &= ~(VM_IO | VM_PFNMAP);
> return 0;
> }
>
> --
> 2.9.3
>
> _______________________________________________
> Intel-gfx mailing list
> Intel-gfx@xxxxxxxxxxxxxxxxxxxxx
> https://lists.freedesktop.org/mailman/listinfo/intel-gfx
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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