[Discuss] Help needed in trying to figure out how the various Meltdown and Spectre mitigations fit together

[Alan W. Irwin]

On 2018-01-18 23:00-0800 Cy Schubert wrote:

> I suppose MB manufacturers could reflash BIOS to include firmware however
> it's simpler to let the O/S do it, distributing microcode to O/S vendors
> who can package it as patches.
>
> Depending on the CPU, a microcode update is simply writing the microcode to
> one of the machine status registers. The microcode update is erased the
> next time CPU is reset, i.e. reboot, and must be loaded again next boot.

Hi Cy:

Some of the articles I read used the term "firmware" while others
specifically mentioned BIOS changes.  But the BIOS is one kind of
firmware so I suspect the two terms mean the same in the context of
Meltdown and Spectre.  I do agree there is another kind of firmware
like you describe that can be dynamically loaded at boot time, but I
am pretty sure that is not what is being referred to in the articles
simply because some of them specifically mentioned BIOS changes.

Another twist in understanding how everything fits together (see the
later post from me) is Google came up with what they felt was a
complete fix for all 3 variants in December long before Intel and AMD
distributed the first of their "firmware" updates.  So I am fairly
sure that if no issues are spotted with the google approach, no
firmware updates will actually be required.  But I am right at the
limit of my understanding here so I might be misinterpreting what the
Google approach really was that they completed in December. Thus, if
you find an article that clearly contradicts my "no firmware updates
required" interpretation of how Google addressed the 3 issues, I would
be most interested in reading it.

Alan
__________________________
Alan W. Irwin

Astronomical research affiliation with Department of Physics and Astronomy,
University of Victoria (astrowww.phys.uvic.ca).

Programming affiliations with the FreeEOS equation-of-state
implementation for stellar interiors (freeeos.sf.net); the Time
Ephemerides project (timeephem.sf.net); PLplot scientific plotting
software package (plplot.sf.net); the libLASi project
(unifont.org/lasi); the Loads of Linux Links project (loll.sf.net);
and the Linux Brochure Project (lbproject.sf.net).
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