[linuxsh-dev] Drop-In tree updates

[NIIBE Y. <gn...@m1...>]

Jeremy Siegel wrote:
 > drivers/net/8139too.c:

Will look into.

 > mm/memory.c:
 >   There were two places where the SH code ifdef'd out cache flush calls
 >   for performance, noting in comments that a VIPT cache doesn't require
 >   them.  The second of these was in do_wp_page(), and the code changed
 >   enough that I chose NOT to ifdef out that flush call, since I wasn't
 >   sure if the conditions that made it unnecessary still applied.

VIPT: Virtually Indexed Phisically Tagged cache.

For break_cow, we don't need to flush the cache.  On some architecture
where permission informatipn is there, we need to flush it because it
was read-only before.  But it's not the case for SuperH.  If you want,
please try to enable the flushing and see how the performance going
down.

For the case of do_wp_page, I think conditions still are applied.  The
logic is same as break_cow.  On some architecture (not SuperH), it is
needed, or else, the fault occurs again and again.

 > The other places where SH tweaks common code is a few insertions of
 > cache flush calls; include/linux/highmem.h:memclear_highpage_flush() and
 > kernel/ptrace.c:access_one_page() both add flush_dcache_page(page) right
 > before flush_page_to_ram(page).  And drivers/block/rd.c:initrd_read()
 > adds flush_cache_all() right after a copy_to_user() call.  I left all
 > these alone, assuming they're still necessary (cache aliasing issue?)
 > but Niibe may want them removed if they're no longer necessary?

Those are paranoia things which can be removed.
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