On 2018-Jan-4, at 7:32 PM, Mark Millard <markmi at dsl-only.net> wrote:

> Darren Reed darrenr at freebsd.org wrote on
> Thu Jan 4 11:56:29 UTC 2018 :
>> Most people are only talking about meltdown which doesn't hit AMD.
>> spectre impacts *both* Intel and AMD.
>> SuSE are making available a microcode patch for AMD 17h processors that
>> disables branch prediction:
>> https://lists.opensuse.org/opensuse-security-announce/2018-01/msg00004.html
> https://www.amd.com/en/corporate/speculative-execution
> reports. . .
> For the Bounds Check Bypass Spectre variant (#1):
> Resolved by software / OS updates to be made available
> by system vendors and manufacturers. Negligible performance
> impact expected.
> For the Branch Target Injection Spectre variant (#2):
> Differences in AMD architecture mean there is a near zero
> risk of exploitation of this variant. Vulnerability to
> Variant 2 has not been demonstrated on AMD processors to
> date.
> For the Rogue Data Cache Load Meltdown variant (#3):
> Zero AMD vulnerability due to AMD architecture differences.
> How long #2 will have a "has not been demonstrated" status
> is yet to be seen.


reports that SUSE's microcode update for AMD's Zen/17h does
not disable branch prediction, despite SUSE's existing

I reached out to AMD and on Friday heard back. They wrote in an email
to Phoronix that this Zen/17h microcode update does not disable branch
prediction. They'll be working with SUSE to re-clarify this microcode
update description... But as far as what this microcode update does in
the wake of SPECTRE they have yet to clarify or why this microcode
binary has yet to make it to other Linux distributions. If/when I hear
anything more, I'll certainly post about it but doesn't appear to be
anything as dramatic as disabling branch prediction, which could have
slaughtered their CPU performance.

Mark Millard
markmi at dsl-only.net

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