Re: [PATCH 0/5] pvSCSI (SCSI pass through) driver

[Jun Kamada <kama@jp.fujitsu.com>]

Keir-san,

On Tue, 23 Oct 2007 09:50:38 +0100
Keir Fraser <Keir.Fraser@cl.cam.ac.uk> wrote:
> Another question about the original patches: did you test that a 64-bit
> backend can communicate with 32-bit frontend (and vice versa)? Either you
> need to make sure that all the shared-memory structures defined in vscsiif.h
> compile identically for 32-bit and 64-bit mode, or you need to detect the
> frontend's 'bitness' in scsiback and optionally do 32-to-64 or 64-to-32
> conversion. I think it's obvious which is less hassle. ;-)

I suppose that the VBD uses the later method. (Is it right?) However,
the later method requires 'optimize level of frontend on compile time'
in addition to the 'bitness'. If the frontend is optimized for space,
members in structure are packed. On the other hand, if the frontend is
optimized for speed, each members are aligned on word boundary. (padding
will be inserted.)
How do you think about this?

> Handling this is really a prerequisite for putting these patches into a
> stable Xen release.

I would like to modify and post an additional patch ASAP.

-----
Jun Kamada