Re: problem with cache flush routine for G5?

[Chris Friesen <cfriesen@nortelnetworks.com>]

Benjamin Herrenschmidt wrote:

> In fact, none of the cache flush code is
> relying on supervisor mode, you don't need to add a syscall for
> that, just copy the code you need in userland.

That's useful information.

> That's wrong. You should flush the cache over the range
> where you need it flushed. 

Yeah, I know.  I'm not sure why they want this.

 > Also, there are very few reasons
> why one would want to flush the dcache, so it would be interesting
> to know what you are really trying to do.

I'll look into it further and see what I can find out.

Assuming that I really did want to flush the whole cache, how would I go 
about doing that from userspace?  Do it like the loop in 
arch/ppc/boot/common/util.S?  How would this interact with virtual 
addresses?  Would I need to mmap an appropriately sized area of kernel 
memory to get contiguous memory?  The app is running as root, so 
permissions are not an issue.

Thanks for your help,

Chris




-- 
Chris Friesen                    | MailStop: 043/33/F10
Nortel Networks                  | work: (613) 765-0557
3500 Carling Avenue              | fax:  (613) 765-2986
Nepean, ON K2H 8E9 Canada        | email: cfriesen@nortelnetworks.com