[Skiboot] [PATCH v2 1/2] mbox: Harden against BMC daemon errors

[Stewart Smith]

Cyril Bur <cyril.bur at au1.ibm.com> writes:
> Bugs present in the BMC daemon mean that skiboot gets presented with
> mbox windows of size zero. These windows cannot be valid and skiboot
> already detects these conditions.
>
> Currently skiboot warns quite strongly about the occurrence of these
> problems. The problem for skiboot is that it doesn't take any action.
> Initially I wanting to avoid putting policy like this into skiboot but
> since these bugs aren't going away and skiboot barfing is leading to
> lockups and ultimately the host going down something needs to be done.
>
> I propose that when we detect the problem we fail the mbox call and punt
> the problem back up to Linux. I don't like it but at least it will cause
> errors to cascade and won't bring the host down. I'm not sure how Linux
> is supposed to detect this or what it can even do but this is better
> than a crash.
>
> Diagnosing a failure to boot if skiboot its self fails to read flash may
> be marginally more difficult with this patch. This is because skiboot
> will now only print one warning about the zero sized window rather than
> continuously spitting it out.
>
> Reported-by: Pridhiviraj Paidipeddi <ppaidipe at linux.vnet.ibm.com>
> Tested-by: Pridhiviraj Paidipeddi <ppaidipe at linux.vnet.ibm.com>
> Signed-off-by: Cyril Bur <cyril.bur at au1.ibm.com>
> ---
> V2: Added a bit about needing to update the BMC firmware.
>     I was going to take out the current prints but in having those
>     values is useful in debugging (if/when new bugs to crop up).
>
>  libflash/mbox-flash.c | 8 ++++++++
>  1 file changed, 8 insertions(+)

thanks for the series, merged to master as of 8c0224322650b69b5560828119feeb06fb487de6

-- 
Stewart Smith
OPAL Architect, IBM.