[RFC PATCH 2/2] ARMv7: Invalidate the TLB before freeing page tables

[Catalin Marinas]

On Wed, 2011-03-09 at 18:35 +0000, Russell King - ARM Linux wrote:
> On Wed, Mar 09, 2011 at 03:40:05PM +0000, Catalin Marinas wrote:
> > The above call to tlb_add_flush() would only add a PAGE_SIZE. But
> > since we free an entire PTE, shouldn't the range cover addr ..
> > addr+PTRS_PER_PTE*PAGE_SIZE?
> 
> Why do we need to?  We're not flushing away the individual PTE entries
> when we remove an entire page table - we will have already walked the
> page table removing those entries, which will already have been added.

Ah, I missed the fact that tlb_flush() invalidates the whole TLB when
there is no tlb->vma (the shift_arg_pages case). We could optimise this
to add the range covered by the PTE page and avoid the !tlb->vma check
(and a flush_tlb_mm), though not sure it's worth.

> This code is to cover the case with LPAE where we need to flush out the
> L1 entries.  It's nothing to do with the TLB itself.

This would happen even with the classic page tables on Cortex-A15, L1
entries are cached.

-- 
Catalin