Re: [Xen-devel] [PATCH v6 05/11] pvqspinlock, x86: Allow unfair spinlock in a PV guest

[Paolo Bonzini <pbonzini@xxxxxxxxxx>]

Il 19/03/2014 04:15, Waiman Long ha scritto:
> > > You should see the same values with the PV ticketlock. It is not clear
> > > to me if this testing did include that variant of locks?
> > Yes, PV is fine.  But up to this point of the series, we are concerned
> > about spinlock performance when running on an overcommitted hypervisor
> > that doesn't support PV spinlocks.
> The unfair queue lock is designed in such a way that it will only be
> activated when running in a PV guest or it won't be mergeable upstream.
> So there must be some way to determine if it is running under a hypervisor.
Exactly.  What you want is boot_cpu_has(X86_FEATURE_HYPERVISOR).

Paolo

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