Re: [Qemu-devel] [PATCH v2] scsi-disk: Don't enlarge min_io_size to max_io_size

[Paolo Bonzini <pbonzini@redhat.com>]

On 27/03/2018 18:41, Fam Zheng wrote:
> Some backends report big max_io_sectors. Making min_io_size the same
> value in this case will make it impossible for guest to align memory,
> therefore the disk may not be usable at all.
> 
> Do not enlarge them when they are zero.
> 
> Reported-by: David Gibson <dgibson@redhat.com>
> Signed-off-by: Fam Zheng <famz@redhat.com>
> 
> ---
> 
> v2: Leave the values alone if zero. [Paolo]
>     At least we can consult block layer for a slightly more sensible
>     opt_io_size, but that's for another patch.
> ---
>  hw/scsi/scsi-disk.c | 10 ++++++----
>  1 file changed, 6 insertions(+), 4 deletions(-)
> 
> diff --git a/hw/scsi/scsi-disk.c b/hw/scsi/scsi-disk.c
> index f5ab767ab5..f8ed8cf2b4 100644
> --- a/hw/scsi/scsi-disk.c
> +++ b/hw/scsi/scsi-disk.c
> @@ -714,10 +714,12 @@ static int scsi_disk_emulate_inquiry(SCSIRequest *req, uint8_t *outbuf)
>  
>                  /* min_io_size and opt_io_size can't be greater than
>                   * max_io_sectors */
> -                min_io_size =
> -                    MIN_NON_ZERO(min_io_size, max_io_sectors);
> -                opt_io_size =
> -                    MIN_NON_ZERO(opt_io_size, max_io_sectors);
> +                if (min_io_size) {
> +                    min_io_size = MIN(min_io_size, max_io_sectors);
> +                }
> +                if (opt_io_size) {
> +                    opt_io_size = MIN(opt_io_size, max_io_sectors);
> +                }
>              }
>              /* required VPD size with unmap support */
>              buflen = 0x40;
> 

Queued, thanks.

Paolo