Re: [RFC] [PATCH] cache pollution aware __copy_from_user_ll()

Hiro Yoshioka
2005-08-17T05:10:39Z

Akira,

Thanks for your suggestions.

On 8/17/05, Akira Tsukamoto <akira-t@s9.dion.ne.jp> wrote:
> Anyway, going back to copy_user topic,
> big remaining issues are
> 1)store/restore floating point register (80/64bytes) twice every time by
> surrounding with kernel_fpu_begin()/kernel_fpu_end() is big penalty

I don't know. If nobody uses MMX/XMM, then there is no need
to save and restore.

> 2)after pagefault not always come back to copy function and corrupts fp register

I'm trying to understand this mechanism but I don't
understand very well.

> 3)disabling long preemption
> Please correct me if I am wrong.
>
> I tried to implement fpsave inside pagefault handler once and here is my junk;
> http://www.suna-asobi.com/~akira-t/linux/k7-copy-user/K7-copy_47_with_fpusave_not_finished.patch
> never had a time to finish it. Hiro, does it help you?

Thanks. I'm reading your patch but could not understand very well.

I'll ask you.

Regards,
Hiro
--
Hiro Yoshioka
mailto:hyoshiok at miraclelinux.com