Improved copy_page() function, about 30% speed up for mpc860!

Daniel Jacobowitz drow at
Tue Mar 4 11:54:05 EST 2003

On Mon, Mar 03, 2003 at 07:43:08PM -0500, Dan Malek wrote:
> Joakim Tjernlund wrote:
> >OK so this is not it then, but what is it then? Are you 100% that
> >the bug(whatever this may be) is present for mpc860, rev D4 or later?
> >How can I make it bite me on kernel space memory?
> >I can't find that info in the archives, if it's there please give me a
> >hint.
> I guess once again I don't understand the questions or failed to express
> my responses properly.
> In the previous message, you included a link that indicated a problem
> setting the DAR, cache instructions, and asked if this was a problem.
> In this case, due to the way we map kernel space and use the cache
> instructions,
> we have "fixed" this bug.  I believe it was found because of the way we
> copy instructions in the C library, and it affected user applications.
> The specific problem described in this link is not a problem with Linux.

That is, in fact, incorrect.  It's fatal from userland.  I experimented
with it just a couple of months ago.

Only way to sort it out would be to do instruction decoding on the
faulting address, which is hideous beyond words.

Daniel Jacobowitz
MontaVista Software                         Debian GNU/Linux Developer

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