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Re: [Xen-devel] [PATCH v5 7/8] xen: arm: use superpages in p2m when pages are suitably aligned





On 10/07/14 12:17, Ian Campbell wrote:
On Thu, 2014-07-10 at 11:36 +0100, Julien Grall wrote:

On 09/07/14 18:11, Ian Campbell wrote:
On Wed, 2014-07-09 at 17:28 +0100, Julien Grall wrote:
+        /*
+         * could flush up to the next boundary, but would need to be
+         * careful about preemption, so just do one page now and loop.

At the first glance I though this code didn't handle correctly superpage
flush. It took me several minutes to understand that you rely
P2M_ONE_PROGRESS{,_NOP} to do the job for you.

Can you explain this trick in the commit message?

That's what the existing comment which you've quoted is attempting to
explain. Is it not clear enough? Can you suggest an improvement?

Would "up to the next superpage boundary ... do one 4K page now and
loop" suffice?

I think the most confusing word is "loop". I was waiting for see a
"real" loop below.

I would explain that the outer function taking care of the loop.

OK.

  * could flush up to the next superpage boundary, but would need to be
  * careful about preemption, so just do one 4K page now and return
  * P2M_ONE_PROGRESS so that the caller will continue to loop over the
  * rest of the range.

?

It looks better for me.

Thanks,

--
Julien Grall

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