Re: [PATCH 3/3] virtio-blk: Consider dma_max_mapping_size() for maximum segment size
From: "Michael S. Tsirkin" <mst@redhat.com>
Date: 2019-01-16 14:05:40
On Tue, Jan 15, 2019 at 02:22:57PM +0100, Joerg Roedel wrote:
quoted hunk
From: Joerg Roedel <redacted> 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 <redacted> --- 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