Date: Wed, 4 Nov 2009 13:12:36 -0500 From: John Baldwin <jhb@freebsd.org> To: Attilio Rao <attilio@freebsd.org> Cc: svn-src-head@freebsd.org, Dag-Erling =?utf-8?q?Sm=C3=B8rgrav?= <des@des.no>, svn-src-all@freebsd.org, src-committers@freebsd.org Subject: Re: svn commit: r198868 - in head/sys: amd64/amd64 i386/i386 Message-ID: <200911041312.37676.jhb@freebsd.org> In-Reply-To: <3bbf2fe10911040815u780ea5d5h8252b46ddf0c5de7@mail.gmail.com> References: <200911040132.nA41WxtQ012750@svn.freebsd.org> <86y6mmff1a.fsf@ds4.des.no> <3bbf2fe10911040815u780ea5d5h8252b46ddf0c5de7@mail.gmail.com>
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On Wednesday 04 November 2009 11:15:28 am Attilio Rao wrote: > 2009/11/4, Dag-Erling Sm=C3=B8rgrav <des@des.no>: > > Attilio Rao <attilio@freebsd.org> writes: > > > Dag-Erling Sm=C3=B8rgrav <des@des.no> writes: > > > > According to the reference you gave, OpenSolaris has a workaround f= or > > > > this issue. Perhaps we should adopt it? > > > IIRC, based on what I readed on-line, it could be still a WARNING msg, > > > but I didn't double-check for it. > > > > Uh, apparently, it can be worked around with an additional lfence > > instruction... See the first couple of comments on that bugzilla page > > you linked to. If the cost is too high, we could make it conditional on > > "options BROKEN_OPTERON_E" or something. >=20 > Yeah but the lfence is completely impratical from the overhead POV -- > and actually I don't like the idea to add a compile time option based > on family/model. > We could maybe do a mixed approach: printout the WARNING msg only if > the BROKEN_OPTERON_E is not used otherwise be ok. > I still don't like it because it is going to dirty the atomic.h code a > bit, but it can be an acceptable compromise. We have had family/model specific hacks with an associated #ifdef in the pa= st,=20 see NO_F00F_HACK (though that is probably less invasive). Also, if it=20 affects atomic.h then you may need to leave it always enabled in userland t= o=20 be truly safe. =2D-=20 John Baldwin
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