pmap_zero_page()

[Allen Briggs <briggs%wasabisystems.com@localhost>]

arch/powerpc/powerpc/pmap.c defines pmap_zero_page() as:
void
pmap_zero_page(pa)
        paddr_t pa;
{
#if 0
        bzero((caddr_t)pa, NBPG);
#else
        int i;

        for (i = NBPG/CACHELINESIZE; i > 0; i--) {
                __asm __volatile ("dcbz 0,%0" :: "r"(pa));
                pa += CACHELINESIZE;
        }
#endif
}

When I run with this code on a new port that I'm working on (CPU is
the MPC 8240, which has a 603e core), I get an alignment exception
during boot.  The `dcbz' instruction can generate this if the memory
referenced by the EA is in caching-inhibited or write-through mode.

Shouldn't we have the alignment exception handler zero the memory if
it trips for this?  Or is pmap_zero_page() supposed to always be called
on write-back-cached pages?

-allen

-- 
 Allen Briggs                     briggs%wasabisystems.com@localhost
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