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Re: [Xen-devel] [PATCH MM-PART2 RESEND v2 19/19] xen/arm: Pair call to set_fixmap with call to clear_fixmap in copy_from_paddr



Hi Stefano,

On 05/06/2019 00:12, Stefano Stabellini wrote:
On Tue, 4 Jun 2019, Julien Grall wrote:
On 6/4/19 6:59 PM, Stefano Stabellini wrote:
On Tue, 14 May 2019, Julien Grall wrote:
At the moment, set_fixmap may replace a valid entry without following
the break-before-make sequence. This may result to TLB conflict abort.

Rather than dealing with Break-Before-Make in set_fixmap, every call to
set_fixmap is paired with a call to clear_fixmap.

It is not every call to set_fixmap: it is every call to
set_fixmap(FIXMAP_MISC, ...

I don't understand this request... The title explicit mention
"copy_from_paddr" and fixmap is only called with FIXMAP_MISC.

So why should I need to specify the argument?

I wasn't asking to mention FIXMAP_MISC explicitely, I don't think it is
particularly useful. I was only trying to make the wording more
specific to what the patch does.

I have to admit this wasn't clear from your answer. Anyway,...


The statement "every call to set_fixmap is paired with a call to
clear_fixmap" is too generic and I would prefer if it was limited in
scope by something like

   "in copy_from_paddr"

Like you have done in the subject. Resulting in:
every call to set_fixmap in copy_from_paddr is paired with a call to
   clear_fixmap

... thank you for your clarification. I have updated the commit message 
accordingly.

Cheers,

--
Julien Grall

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