Re: [Xen-devel] [for-4.7 2/2] xen/arm: p2m: Release the p2m lock before undoing the mappings

[Julien Grall <julien.grall@xxxxxxx>]

On 18/05/2016 11:10, Stefano Stabellini wrote:
> I realize that this is an unimportant case and not worth supporting. I,
> for one, would prefer not to have to think about implementation halves
> of apply_p2m_changes going forward so I would prefer a different patch.
> That said, I still retract my comment and leave it up to you. If you
> would like to change this patch, I'll be happy to review v2, otherwise,
> if you prefer to keep it as is, let me know and I'll commit this
> version.
I forgot to reply to this part. I agree that the resulting code might be 
confusing. However today, the lock is taken for a very long time (TLBs 
are flushed in the middle, memory management,...) which may result to 
starve other vCPUs on big platform.
This time would be doubled in case of failure when inserting a new mapping.

FWIW, I am planning to rework the page table code for the next release 
to get it simplified and handle break-before-make (recommended by the 
ARM ARM) more easily.
Regards,

--
Julien Grall

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