Date: Sun, 30 Apr 2006 11:50:30 +0200 From: Marius Nuennerich <marius.nuennerich@gmx.net> To: David Xu <davidxu@freebsd.org> Cc: Igor Sysoev <is@rambler-co.ru>, freebsd-current@freebsd.org Subject: Re: FreeBSD-SA-06:14.fpu Message-ID: <20060430115030.69402983@sol> In-Reply-To: <44547C85.7040107@freebsd.org> References: <20060430115932.Y39336@is.park.rambler.ru> <44547C85.7040107@freebsd.org>
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On Sun, 30 Apr 2006 16:59:49 +0800 David Xu <davidxu@freebsd.org> wrote: > Igor Sysoev wrote: > > > > The last security advisory FreeBSD-SA-06:14.fpu > > ftp://ftp.freebsd.org/pub/FreeBSD/CERT/advisories/FreeBSD-SA-06:14.fpu.asc > > that fixes very doubtful security bug in AMD CPUs, also > > adds unnecessary penalty in FPU context switch for all other > > SSE-enabled CPUs. > > > > > > Igor Sysoev > > http://sysoev.ru/en/ > > Probably it should only be applied to AMD CPU but not Intel and others, > it is easy to check cpu vendor and put a > if (bug_fxsave) > fpu_clean_state(); > > in file npx.c. > > David Xu Shouldn't we use an existing variable which is already in L1 instead of the new dummy_variable? Or isn't this noticable in performance? btw Linux does it this way: > http://www.kernel.org/git/?p=linux/kernel/git/stable/linux-2.6.16.y.git;a=commitdiff;h=7466f9e72dac13452d871a3fb72fc7bd9c93c864 regards Marius P.S. I have no idea what variable we could use.
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