[SeaBIOS] [PATCH 1/2] scsi: ensure LUN0 is added first

[Kevin O'Connor]

On Fri, Jul 07, 2017 at 04:14:01PM +0200, Paolo Bonzini wrote:
> 
> 
> On 21/06/2017 00:44, Kevin O'Connor wrote:
> > On Tue, Jun 20, 2017 at 04:05:32PM -0400, Paolo Bonzini wrote:
> >>> If virtio-scsi didn't need to allocate any space in the f-segment,
> >>> does this problem go away in practice?
> >>
> >> Yes, I think so.  I'm not sure why virtqueues are allocated
> >> in low memory.  Either cargo culting, or a remain of when
> >> virtio was a 16-bit driver, if it ever was.
> > 
> > The 'struct drive_s' storage currently must be allocated in the
> > f-segment so that the disk.c code can access some critical details of
> > mapped drives when in 16bit mode.  However, we could change the code
> > to allocate that data separately from the controller specific data and
> > then move the controller specific data to a larger memory pool.  This
> > would have two gains - there's a cap of 16 hard drives that can be
> > mapped so we'd be less likely to exceed the f-segment, and even if the
> > f-segment did run out of space it would almost certainly be on a
> > non-bootable drive.

I was hoping to be able to prototype the above, but haven't gotten a
chance to yet.  I think I should be able to get to it next week.

> Or maybe, after the first 16 hard drives, we can stop allocating from
> the fseg.

The user could select any drive to boot from, so it would be hard to
know which drives could be allocated in f-seg and which couldn't (at
least until after the user has made the boot selection).

-Kevin