On Tue, Jan 15, 2019 at 02:22:57PM +0100, Joerg Roedel wrote:
> From: Joerg Roedel <jroe...@suse.de>
> 
> Segments can't be larger than the maximum DMA mapping size
> supported on the platform. Take that into account when
> setting the maximum segment size for a block device.
> 
> Signed-off-by: Joerg Roedel <jroe...@suse.de>
> ---
>  drivers/block/virtio_blk.c | 10 ++++++----
>  1 file changed, 6 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
> index b16a887bbd02..6193962a7fec 100644
> --- a/drivers/block/virtio_blk.c
> +++ b/drivers/block/virtio_blk.c
> @@ -723,7 +723,7 @@ static int virtblk_probe(struct virtio_device *vdev)
>       struct request_queue *q;
>       int err, index;
>  
> -     u32 v, blk_size, sg_elems, opt_io_size;
> +     u32 v, blk_size, max_size, sg_elems, opt_io_size;
>       u16 min_io_size;
>       u8 physical_block_exp, alignment_offset;
>  
> @@ -826,14 +826,16 @@ static int virtblk_probe(struct virtio_device *vdev)
>       /* No real sector limit. */
>       blk_queue_max_hw_sectors(q, -1U);
>  
> +     max_size = dma_max_mapping_size(&vdev->dev);
> +


Should this be limited to ACCESS_PLATFORM?

I see no reason to limit this without as guest can
access any memory.


I'd like a bit of time to consider this point.

>       /* Host can optionally specify maximum segment size and number of
>        * segments. */
>       err = virtio_cread_feature(vdev, VIRTIO_BLK_F_SIZE_MAX,
>                                  struct virtio_blk_config, size_max, &v);
>       if (!err)
> -             blk_queue_max_segment_size(q, v);
> -     else
> -             blk_queue_max_segment_size(q, -1U);
> +             max_size = min(max_size, v);
> +
> +     blk_queue_max_segment_size(q, max_size);
>  
>       /* Host can optionally specify the block size of the device */
>       err = virtio_cread_feature(vdev, VIRTIO_BLK_F_BLK_SIZE,
> -- 
> 2.17.1
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