[PATCH] [ARM] force dcache flush if dcache_dirty bit set

[rmk+lkml@arm.linux.org.uk (Russell King)]

On Mon, Oct 12, 2009 at 05:09:53PM +0100, Hugh Dickins wrote:
> Sorry to muddy the waters on this, if you and Dave are sure that
> you have the right fix, down in your architectures, and that fix
> isn't going to hurt your performance significantly.

If I look at the issue from this point of view:

- we are using PG_arch_1 to delay cache handling for the page

- if PG_arch_1 is set on a page, we set it explicitly because we
  didn't do some flushing between the allocation of the page and
  mapping it into userspace

- if a page with PG_arch_1 set ever gets to userspace, this can
  only be because we did the lazy flushing thing

I don't see that there should have been any bearing on whether a page
has a mapping or not when we get to update_mmu_cache.  The issue here
is that > if PG_arch_1 is set on a page, then we didn't flush it at
the time when we believed it was appropriate to do so. <

Tell me I'm wrong (having only just sent it to Linus...)

-- 
Russell King
 Linux kernel    2.6 ARM Linux   - http://www.arm.linux.org.uk/
 maintainer of: