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

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:

quoted

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