Messages in this thread | | | Date | Tue, 16 Sep 2003 09:52:56 -0400 (EDT) | From | Bill Davidsen <> | Subject | Re: [PATCH] 2.6 workaround for Athlon/Opteron prefetch errata |
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On Tue, 16 Sep 2003, Dave Jones wrote:
> On Tue, Sep 16, 2003 at 12:46:36PM +0100, Jamie Lokier wrote: > > > > The user space problem worries me more, because the expectation > > > is that if CPUID says the program can use perfetch, it could > > > and should regardless of what the kernel decided to do here. > > > > If the workaround isn't compiled in, "prefetch" should be removed from > > /proc/cpuinfo on the buggy chips. > > prefetch isn't a cpuid feature flag. The only way you could do > what you suggest is by removing '3dnow' or 'sse', which cripples > things more than necessary.
Good point, and even if it were a separate feature, any code which was clever enough to use prefetch is likely to check the CPU bits rather than the /proc anyway. That's a guess, I suspect most programs do whatever gcc/glibc choose.
If the fixup were not in place, would it be useful to emit a warning like "you have booted a non-Athlon kernel on an Athlon process, user programs may get unexpected page faults." That's in init code, hopefully there is no critical size issue there, I assume, other than how large a kernel can be booted by the boot loader.
-- bill davidsen <davidsen@tmr.com> CTO, TMR Associates, Inc Doing interesting things with little computers since 1979.
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