[Beowulf] cursed (and perhaps blessed) Intel microcode

Mark Hahn hahn at mcmaster.ca
Sat Mar 24 09:50:49 PDT 2018

> In message from Mark Hahn <hahn at mcmaster.ca> (Fri, 23 Mar 2018 16:02:12 -0400 
> (EDT)):
>> There *is* an updated microcode data file:
>> https://downloadcenter.intel.com/product/873/Processors
>> which seems to correspond to the document above
> How I believe, it's for correction of general defect practically for all 
> CPUs.
> Then microcode update may give also decrease of performance. May be Intel 
> have idea to improve this update and do not recommend use this version ?

I don't quite understand what you're saying.  Yes, it's expected that
the mitigations for meltdown and spectre have performance costs.
meltdown is pretty much taken care of by the way newer kernels avoid 
mapping all physical memory.  afaikt, the microcode changes are supposed
to mitigate the exfiltration risk for spectre, in combination with kernel
tweaks (retpoline, some extra patterns of fence instructions).

my appeal is for information about microcode updates that Intel claims
are now recommended for production use, and which only appeared in March.

regards, mark hahn.

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