Re: [PATCH 0 of 7] Synchronized p2m lookups v2

[Tim Deegan <tim@xen.org>]

At 00:45 -0500 on 09 Feb (1328748345), Andres Lagar-Cavilla wrote:
> Up until now, p2m lookups (get_gfn*) in the x86 architecture were not
> synchronized against concurrent updates. With the addition of sharing and
> paging subsystems that can dynamically modify the p2m, the need for
> synchronized lookups becomes more pressing.
> 
> Without synchronized lookups, we've encountered host crashes triggered by race
> conditions, particularly when exercising the sharing subsystem.
> 
> In this patch series we make p2m lookups fully synchronized. We still use a
> single per-domain p2m lock (profiling work tbd may or may not indicate the need
> for fine-grained locking).
> 
> We only enforce locking of p2m queries for hap-assisted domains. These are the
> domains (in the case of EPT) that can exercise the paging and sharing
> subsystems and thus most in need of synchronized lookups.
> 
> While the code *should* work for domains relying on shadow paging, it has not
> been tested, hence we do not enable this at the moment.
> 
> Finally, the locking discipline in the PoD subsystem has been updated, since
> PoD relied on some assumptions about the way the p2m lock is used.
> 
> Signed-off-by: Andres Lagar-Cavilla <andres@lagarcavilla.org>
> Signed-off-by: Adin Scannell <adin@scannell.ca>

Applied, thanks.

Tim.