Re: [id]cache meaning? [Was: [parisc-linux] 2.6.10-rc1-pa11 profile data]

["Michael S. Zick" <mszick@wolfbutter.com>]

On Sun November 28 2004 15:13, Matthew Wilcox wrote:
> On Sun, Nov 28, 2004 at 09:01:42PM +0000, Joel Soete wrote:
> > 
> > include/asm-parisc/cacheflush.h:
> > [...]
> > #define flush_icache_page(vma,page)   do { 
> > flush_kernel_dcache_page(page_address(page)); 
> > flush_kernel_icache_page(page_address(page)); } while (0)
> > [...]
> 
> I see why this confuses you.  PA-RISC has writeback data caches that
> are non-coherent with the instruction cache.  So it's not enough to
> just flush the icache; if the page has been modified, we need to force
> the data in the dcache back to ram, then remove any existing cache for
> instructions in that page.  Then instruction accesses to that page will
> fetch the correct data from memory and everything will work.
> 
Matt, Joel,
Here is a, perhaps dumb, question from a non-parisc source...

I note Matt's statement: "...then remove any existing cache for
instructions in that page."

Which sounds very reasonable.

Question:
Is the:
> > flush_kernel_icache_page(page_address(page)); 
(or the hardware that receives the command)

smart enough to just mark the page 'invalid' or is it
actually an 'absolute update external storage'?

I ask because both flush commands are written the
same, BUT...
The first should be an 'absolute update external
storage'.
The second should be either just a 'mark
invalid' or 'conditional update external storage'.

Mike

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