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Re: [Xen-devel] [PATCH] nestedhvm: ASID emulation

To: Keir Fraser <keir@xxxxxxx>
Subject: Re: [Xen-devel] [PATCH] nestedhvm: ASID emulation
From: Christoph Egger <Christoph.Egger@xxxxxxx>
Date: Fri, 15 Apr 2011 10:20:22 +0200
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On 04/14/11 16:43, Keir Fraser wrote:
On 14/04/2011 15:01, "Christoph Egger"<Christoph.Egger@xxxxxxx>  wrote:

What if some other vcpu's nv_n1asid or nv_n2asid got assigned the same HW
asid in this generation as this vcpu's (now stale, as it's from a previous
generation's) nv_n2asid? This PCPU can be interleaving execution of other
HVM VCPUs after all.

I am not sure if I got you right. You mean what if two vcpus run on one
physical cpu? In this case svm_do_resume() calls hvm_asid_flush_vcpu()
before so that asid_generation and core_asid_generation do not match and
a new asid is always assigned.

No, it only does that if a given VCPU gets scheduled onto a *different* PCPU
than last time it ran.

I've attached a mostly rewritten version of your patch that is about half
the size and I believe has a fighting chance of being correct (however it is
only build tested). Give it a look and a spin.

Yes, it is correct. I like the idea to maintain a generation per asid.
Please apply it. Thanks for this work.

Christoph


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