RE: [RFC] How drivers notice a MCA on I/O read? [1/3]

["Luck, Tony" <tony.luck@intel.com>]

> This would not only be useful for the occasional device failure, but
> also for accessing memory spaces which by definition may or may not
> respond to PIO requets, like legacy I/O bus and memory regions.  Upon
> entering readb_check(), you could set a global telling the MCA handler
> to potentially expect a failure from the address or range that was
> passed in.  This would allow the MCA handler describe in simple terms
> what went wrong in case of failure and/or take appropriate action.

As Zoltan mentioned in his mail you'd have to do some heavy fencing
around the internals of readb_check() to make this safe ... which
might make readb_check() too expensive to use for the 99.999999% of
the cases where the I/O board isn't broken.  But I don't actually know
how much overhead would be involved ... I/O reads are already horrendously
slow, so you may be able to add some sizeable overhead without affecting
macro benchmarks more than a few percent.

-Tony