Re: [PATCH] drm/virtio: Use vmalloc for command buffer allocations.

From
Chia-I Wu <olvaffe@gmail.com>
Date
2019-08-30 16:24:37
On Fri, Aug 30, 2019 at 4:16 AM Gerd Hoffmann [off-list ref] wrote:
  Hi,
quoted
quoted
quoted
-     kfree(vbuf->data_buf);
+     kvfree(vbuf->data_buf);
if (is_vmalloc_addr(vbuf->data_buf)) ...

needed here I gues?
kvfree() handles vmalloc/kmalloc/kvmalloc internally by doing that check.
Ok.
quoted
- videobuf_vmalloc_to_sg in drivers/media/v4l2-core/videobuf-dma-sg.c,
assumes contiguous array of scatterlist and that the buffer being converted
is page aligned
Well, vmalloc memory _is_ page aligned.

sg_alloc_table_from_pages() does alot of what you need, you just need a
small loop around vmalloc_to_page() create a struct page array
beforehand.

Completely different approach: use get_user_pages() and don't copy the
execbuffer at all.
It would be really nice if execbuffer does not copy.

The user space owns the buffer and may overwrite the contents
immediately after the ioctl.  We also need a flag to indicate that the
ownership of the buffer is transferred to the kernel.



cheers,
  Gerd

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Thread (1 message) 1 message, 1 author, last reply 2019-08-30
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