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

[Christoph Egger <Christoph.Egger@xxxxxxx>]

On 04/14/11 12:28, Keir Fraser wrote:
> On 14/04/2011 10:26, "Christoph Egger"<Christoph.Egger@xxxxxxx>  wrote:
>
> > > What if nv_n2asid wast last assigned on a previous generation, but nv_n1asid
> > > was assigned from the current generation? Then you'd have next_asid>
> > > nv_n2asid, but nv_n2asid is stale.
> > When the generation changes, next_asid is set back to 1 and the hw TLB
> > flushed.
> >
> > If next_asid is larger than nv_n2asid then it is reused and this is ok
> > since the hw TLB got flushed. It is just important that nv_n1asid never
> > gets the same hw ASID assigned and that is what the do { } while loop
> > ensures.
> 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.
Christoph

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