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SubjectRe: Re[2]: [PATCH] Athlon bug stomper. Pls apply.
On 19 Sep 01 at 11:43, Dan Hollis wrote:
> On Wed, 19 Sep 2001, Linus Torvalds wrote:
> > It is _probably_ an undocumented performance thing, and clearing that
> > bit may slow something down. But it might also change some behaviour,
> > and knowing _what_ the behaviour is might be very useful for figuring
> > out what it is that triggers the problem.
>
> AFAIK noone has even tested it yet to see what it does to performance! Eg
> it might slow down memory access so that athlon-optimized memcopy is now
> slower than non-athlon-optimized memcopy. And if it turns out to be the
> case, we might as well just use the non-athlon-optimized memcopy instead
> of twiddling undocumented northbridge bits...

No, we cannot. On boxes which do not work with athlon optimized kernels
any user can execute athlon's fast_page_copy from userspace, causing
corruption on completely unrelated pages, eventually leading to
kernel crash... So you cannot allow untrusted users on such machine.
Best regards,
Petr Vandrovec
vandrove@vc.cvut.cz

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