Re: [PATCH] virtio_blk: add block topology support

[Alexey Zaytsev]

On Mon, Feb 1, 2010 at 04:10, Rusty Russell <rusty@xxxxxxxxxxxxxxx> wrote:
> On Sun, 31 Jan 2010 06:49:10 am Christoph Hellwig wrote:
>> On Sat, Jan 30, 2010 at 03:29:49PM +1030, Rusty Russell wrote:
>> > I bow to your expertise on that. ÂMy only query is the __u16 for min_io_size; is that likely to restrict us?
>>
>> Looks like you caught me there - I wrote the above odd format about the
>> physical_block exponent, but scsi actually does the min_io and opt_io
>> size in logical blocks, too. ÂWith that in account the u16 as in scsi
>> is perfectly fine.
>
> Thanks, applied.

Ugh, guys. I know it's already applied long ago, but this kind of
contradicts the virtio specification, doesn't it?


VIRTIO_BLK_F_SECTOR_MAX (10) Maximum total sectors in
   an I/O.
[...]

4. If the VIRTIO_BLK_F_SECTOR_MAX feature is negotiated, the sec-
   tors_max eld should be read to determine the maximum I/O size for
   the driver to use. No requests should be submitted which go beyond this
   limit.

struct virtio_blk_config        {
        u64  capacity ;
        u32  si z e_ m ax ;
        u32  seg_max ;
        struct     virtio_blk_geometry {
                    u16   cylinders ;
                    u8  heads ;
                    u8  sectors ;
        } geometry ;
        u32  blk_size ;
        u32  sectors_max ;
};
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