On Thu, 4 Jan 2018 15:33:46 +0100 "Stefan Esser" <s...@freebsd.org> said

Am 04.01.18 um 12:56 schrieb Darren Reed:
> On 4/01/2018 11:51 AM, Mark Heily wrote:
>> On Jan 2, 2018 19:05, "Warner Losh" <i...@bsdimp.com> wrote:
>> The register article says the specifics are under embargo still. That would
>> make it hard for anybody working with Intel to comment publicly on the flaw
>> and any mitigations that may be underway. It would be unwise to assume that
>> all the details are out until the embargo lifts.
>> Details of the flaws are now published at:
>> https://meltdownattack.com
> > The web page has both: meltdown and spectre.
> 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

Disabling branch prediction will have a very noticeable effect on execution
speed in general (while split page tables only affect programs that perform
system calls at a high frequency).
OUCH! That was the whole point of these; drop cores, and frequency, for huge
cache lines, and branch prediction. You eliminate that branch prediction, and
these become near useless. :-(
Glad I waited, before getting one!

I have not fully read the Meltdown and Spectre papers, yet, but I do assume,
that the attack at the branch prediction tries to counter KASLR, which we do
not support at all in FreeBSD.

So, I guess, we do not have to bother with disabling of branch prediction in
FreeBSD for the time being?

Regards, STefan

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