Re: [Xen-devel] RE: Biweekly VMX status report. Xen: #20255 & Xen0:#b6ba0...

[Keir Fraser <keir.fraser@xxxxxxxxxxxxx>]

On 30/09/2009 02:15, "Xu, Jiajun" <jiajun.xu@xxxxxxxxx> wrote:

>> 1. Booting guest with device assigned & EPT enabled cause xen crash
>> http://bugzilla.xensource.com/bugzilla/show_bug.cgi?id=1518
> 
> For the above bug, it's a regression which does not exist in xen c/s 20187.
> Could anyone help to fix it?
> 
> It's likely that the issue is introduced by the "pod for EPT" patches
> (20191~20197).

It is caused by the addition of an assertion that p2m_is_locked_by_me in
ept_sync_domain(). This was done because that function needs to be
serialised, and we expected that anyone coming through set_p2m_entry() would
have the p2m_lock held.

So, we could 'fix' by giving ept_sync_domain() its own lock, but my
suspicion would be that any paths through the p2m code that are not holding
the p2m_lock probably need to be fixed. Adjusting p2m entries without the
lock held sounds racey to me.

 -- Keir



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