[PATCH] ARM: decompressor: ensure I-side picks up relocated code

[Russell King - ARM Linux]

On Thu, Oct 30, 2014 at 12:28:14PM -0700, Florian Fainelli wrote:
> On 10/30/2014 09:54 AM, Will Deacon wrote:
> > To speed up decompression, the decompressor sets up a flat, cacheable
> > mapping of memory. However, when there is insufficient space to hold
> > the page tables for this mapping, we don't bother to enable the caches
> > and subsequently skip all the cache maintenance hooks.
> > 
> > Skipping the cache maintenance before jumping to the relocated code
> > allows the processor to predict the branch and populate the I-cache
> > with stale data before the relocation loop has completed (since a
> > bootloader may have SCTLR.I set, which permits normal, cacheable
> > instruction fetches regardless of SCTLR.M).
> > 
> > This patch moves the cache maintenance check into the maintenance
> > routines themselves, allowing the v6/v7 versions to invalidate the
> > I-cache regardless of the MMU state.
> > 
> > Cc: Julien Grall <julien.grall at linaro.org>
> > Signed-off-by: Will Deacon <will.deacon at arm.com>
> 
> I guess we could credit Marc as well for reporting and providing early
> patches addressing this?

If we're going to start doing that, then it should also have:

Suggested-by: Russell King <rmk+kernel at arm.linux.org.uk>

since Will and myself discussed it earlier today and I suggested moving
the tst check into the cache_clean_flush methods as a way to solve this
issue.

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