[SeaBIOS] [PATCH] Support for booting from LSI Logic LSI53C1030, SAS1068, SAS1068e

[Kevin O'Connor]

On Wed, Jan 27, 2016 at 06:37:28PM +0100, Paolo Bonzini wrote:
> On 27/01/2016 18:30, Kevin O'Connor wrote:
> > On Wed, Jan 27, 2016 at 06:19:43PM +0100, Paolo Bonzini wrote:
> >> On 27/01/2016 18:15, Kevin O'Connor wrote:
> >>> Oh, I understand and agree that recovery isn't worth while.  My
> >>> concern is that a hardware error here will appear as a silent hang.
> >>> Breaking out of the loop eventually, calling warn_timeout(), and
> >>> returning an error code has the benefit of some debugging from seabios
> >>> and likely some strong error messages from the calling app.
> >>>
> >>> As I'm more interested in the debugging then the recovery, a simple
> >>> addition like this would be an improvement IMO:
> >>>
> >>>     u32 end = calc_timeout(30000);  // 30 second max timeout
> >>>     for (;;) {
> >>>         ...
> >>>         if (timer_check(end)) {
> >>>             warn_timeout();
> >>>             return DISK_RET_ECONTROLLER;
> >>>         }
> >>>         usleep(50);
> >>>     }
> >>
> >> I understood this to be your proposal.  The problem is that I wouldn't
> >> be able to send any further requests later, because of the way the HBA
> >> is programmed.
> > 
> > I'm a bit confused.  Without my proposal, the machine will silently
> > busy loop forever and thus also wont be able to send any further
> > requests.
> > 
> > The only difference, as I see it, is whether or not we report the
> > problem.
> 
> The difference is that with this proposal you would definitely not be
> able to recover; without it, you'll get an error (good) but you'll also
> get an error if the timeout was spurious.  In that case, if you do not
> have a timeout the behavior is a little better.
> 
> I think the best would be to handle all drivers in the same way, and
> configure the timeout at Kconfig time.  What do you think?  Are there
> drivers that do read/write timeouts?

Most of the SeaBIOS drivers do implement timeouts.  I think the only
ones that don't are lsi-scsi, pvscsi, and virtio.

The timeout should come from the hardware spec - a lot of specs do
list a maximum transaction time.  (It's also possible the SCSI
standards may specify a maximum time.)

If there is no maximum time known, then I think using 30 seconds
(which comes from the old PATA specs) is sufficient.  The transaction
size in SeaBIOS is limited to 64K, and if a drive can't read/write
that in 30 seconds then I think it's fair to assume something is
seriously broken and that the drive wont ever respond.

-Kevin