[PATCH V2] arm64: mm: Optimise tlb flush logic where we have >4K granule

[Steve Capper]

On Fri, May 02, 2014 at 12:26:18PM +0100, Will Deacon wrote:
> On Fri, May 02, 2014 at 11:37:14AM +0100, Steve Capper wrote:
> > The tlb maintainence functions: __cpu_flush_user_tlb_range and
> > __cpu_flush_kern_tlb_range do not take into consideration the page
> > granule when looping through the address range, and repeatedly flush
> > tlb entries for the same page when operating with 64K pages.
> > 
> > This patch re-works the logic s.t. we instead advance the loop by
> >  1 << (PAGE_SHIFT - 12), so avoid repeating ourselves.
> > 
> > Also the routines have been converted from assembler to static inline
> > functions to aid with legibility and potential compiler optimisations.
> > 
> > Signed-off-by: Steve Capper <steve.capper at linaro.org>
> > Acked-by: Will Deacon <will.deacon at arm.com>
> > ---
> > Changed in V2: added the missing isb(.) to the kernel tlb flush.
> 
> Hold your horses ;)

:-)

> 
> You mentioned remapping kernel text rw/ro, but if you think about it, it's
> still executable for both of these, so the isb() isn't needed. Do we have a
> case for changing whether or not something is executable?

I think module loading and unloading in future would likely need this.
i.e. if we get stuff like set_memory_nx and friends for ARM64.

We've just had this added to ARM:
 75374ad ARM: mm: Define set_memory_* functions for ARM

Cheers,
-- 
Steve

> 
> Will