On Wed 22 Aug 2012 10:13:44 PM CST, Paolo Bonzini wrote:

Il 22/08/2012 15:13, Stefan Hajnoczi ha scritto:

quoted

http://lists.gnu.org/archive/html/qemu-devel/2010-12/msg01741.html

"This is a real problem in practice. IE. the USB CD-ROM on this POWER7
blade limits transfers to 0x1e000 bytes for example and the Linux "sr"
driver on the guest is going to try to give me bigger requests than that
if I don't start limiting them, which will cause all sort of errors."

It cannot be fixed for emulated SCSI HBAs in general but it can for
virtio-scsi.

For disks, this should be fixed simply by using scsi-block instead of
scsi-generic.

CD-ROMs are indeed more complicated because burning CDs cannot be done
with syscalls. :/

So, as the problem exist to CD-ROM, I will continue to get these 
patches move on.

As Paolo pointed out,  the only limit is max_sectors (the total size of 
a scatter-list),
I will drop the other 2 parameters.

Paolo, what's your opinion?

Cong

Paolo