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

On Fri, 2011-03-11 at 19:24 +0000, Russell King - ARM Linux wrote:

On Fri, Mar 11, 2011 at 05:32:58PM +0000, Catalin Marinas wrote:

quoted

On Wed, 2011-03-09 at 18:35 +0000, Russell King - ARM Linux wrote:

quoted

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.

If we're removing pte entries then tlb->vma is non-NULL.  Please look at
the comments - I've documented the three modes of use there along with
how things are setup for each of those modes, and what we do with each.

Yes, I read them (they are useful) and I was only referring to point 3
in the comments, shift_arg_pages(). In this case tlb->vma is NULL and we
flush the full mm in tlb_flush(). Can we have a smaller address range
since we can get the from pte_free_tlb()?

This would mean removing the !tlb->vma check in tlb_flush() and change
tlb_add_flush() to take a range rather than just an address.

-- 
Catalin