Re: [Xen-devel] [PATCH 2 of 3] Make p2m lookups fully synchronized wrt modifications

[Tim Deegan <tim@xxxxxxx>]

At 08:41 -0800 on 24 Nov (1322124101), Andres Lagar-Cavilla wrote:
> Here is one solution to consider: do not lock the p2m on lookups in shadow
> mode. Shadow mode does not support paging out and sharing of pages, which
> are primary reasons why we want synchronized p2m lookups. The hap cases
> where there is an inversion of the p2m_lock -> paging_lock order are
> reasonably simple to handle.
> 
> The other option is to invert the order and place paging_lock -> p2m_lock,
> but that will raise another set of potential inversions. I think this is a
> no go.

Is there scope for having the p2m lock split out into the overall one
(needed for allocations &c) and the per-record ones, and have them at
different levels in the lock hierarchy?

Tim.

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