Re: [Xen-devel] [Qemu-devel] [PATCH 1/4] introduce virtqueue_unmap_sg

[Peter Maydell <peter.maydell@xxxxxxxxxx>]

On 25 November 2014 at 14:43, Stefano Stabellini
<stefano.stabellini@xxxxxxxxxxxxx> wrote:
> Introduce a function to unmap an sg previously mapped with
> virtqueue_map_sg.
>
> Signed-off-by: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>
> CC: jasowang@xxxxxxxxxx
> CC: wency@xxxxxxxxxxxxxx
> CC: mst@xxxxxxxxxx
> CC: pbonzini@xxxxxxxxxx
> ---
>  hw/virtio/virtio.c         |   22 ++++++++++++++++++++++
>  include/hw/virtio/virtio.h |    2 ++
>  2 files changed, 24 insertions(+)
>
> diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
> index 3e4b70c..2621ae6 100644
> --- a/hw/virtio/virtio.c
> +++ b/hw/virtio/virtio.c
> @@ -446,6 +446,28 @@ void virtqueue_map_sg(struct iovec *sg, hwaddr *addr,
>      }
>  }
>
> +void virtqueue_unmap_sg(const struct iovec *sg, size_t num_sg,
> +                        int is_write, unsigned int len)
> +{
> +    unsigned int i;
> +    unsigned int offset;
> +
> +    if (num_sg > VIRTQUEUE_MAX_SIZE) {
> +        error_report("virtio: unmap attempt out of bounds: %zd > %d",
> +                     num_sg, VIRTQUEUE_MAX_SIZE);
> +        exit(1);
> +    }
> +
> +    offset = 0;
> +    for (i = 0; i < num_sg; i++) {
> +        size_t size = MIN(len - offset, sg[i].iov_len);
> +
> +        cpu_physical_memory_unmap(sg[i].iov_base, sg[i].iov_len, is_write, 
> size);
> +
> +        offset += size;
> +    }
> +}

It seems rather odd that "size" and the iov_len fields in
the iovec are size_t but 'len' and 'offset' are only
unsigned int...

thanks
-- PMM

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