RE: [RFC] Better MCA recovery on IPF

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

> I still believe that a failed speculative read (for example 
> of poisoned data) will generate an MCA. Perhaps someone from
> Intel can confirm or deny?

It depends on exactly what you mean by "speculative read", and
even there it is not architecturally defined, so different
implementations may behave differently ("Ask not the elves for
advice for they will say both yes and no" - Tolkien).

"Speculative" reads from memory as a result of lfetch, or a code
fetch for a mispredicted branch that reference poisoned data may
not generate an MCA (since the processor can know that the poisoned
data will not be consumed.  Speculative reads from "ld.s" have
less scope to avoid the MCA

There's a new bit coming for PAL_PROC_{GET,SET}_FEATURES which
will at least tell you (and may allow you to request, if the
implementation supports it) whether the processor will respond
to poison with CMCI, or upgrade to MCA ... watch the web for a
spec update to the SDV

-Tony