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Date:      Thu, 04 Jan 2018 07:00:02 -0800
From:      "Chris H" <bsd-lists@BSDforge.com>
To:        <freebsd-current@freebsd.org>
Subject:   Re: Intel CPU design flaw - FreeBSD affected?
Message-ID:  <39abfc53763a4a83142af49e2d56aa59@udns.ultimatedns.net>
In-Reply-To: <b735d895-342c-9a7b-4aea-acc371f48c7e@freebsd.org>

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On Thu, 4 Jan 2018 15:33:46 +0100 "Stefan Esser" <se@freebsd=2Eorg> said

> Am 04=2E01=2E18 um 12:56 schrieb Darren Reed:
> > On 4/01/2018 11:51 AM, Mark Heily wrote:
> >> On Jan 2, 2018 19:05, "Warner Losh" <imp@bsdimp=2Ecom> wrote:
> >>
> >> The register article says the specifics are under embargo still=2E That =
would
> >> make it hard for anybody working with Intel to comment publicly on the=
 flaw
> >> and any mitigations that may be underway=2E It would be unwise to assume=
 that
> >> all the details are out until the embargo lifts=2E
> >>
> >>
> >> Details of the flaws are now published at:
> >>
> >> https://meltdownattack=2Ecom
> >=20
> > The web page has both: meltdown and spectre=2E
> > Most people are only talking about meltdown which doesn't hit AMD=2E
> > spectre impacts *both* Intel and AMD=2E
> >=20
> > SuSE are making available a microcode patch for AMD 17h processors that
> > disables branch prediction:
> >=20
> > https://lists=2Eopensuse=2Eorg/opensuse-security-announce/2018-01/msg00004=2E=
html
>=20
> Disabling branch prediction will have a very noticeable effect on executi=
on
> speed in general (while split page tables only affect programs that perfo=
rm
> system calls at a high frequency)=2E
OUCH! That was the whole point of these; drop cores, and frequency, for hug=
e
cache lines, and branch prediction=2E You eliminate that branch prediction, a=
nd
these become near useless=2E :-(
Glad I waited, before getting one!

>=20
> I have not fully read the Meltdown and Spectre papers, yet, but I do assu=
me,
> that the attack at the branch prediction tries to counter KASLR, which we=
 do
> not support at all in FreeBSD=2E
>=20
> So, I guess, we do not have to bother with disabling of branch prediction=
 in
> FreeBSD for the time being?
>=20
> Regards, STefan
--Chris





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