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

Il 19/03/2014 17:58, Waiman Long ha scritto:
Exactly.  What you want is boot_cpu_has(X86_FEATURE_HYPERVISOR).

The unfair lock is to be enabled by boot time check, not just by the
presence of a configuration macro during the build process in order to
avoid using unfair lock on bare metal. Of course, Linux distros can
modify this if that suits their need.

"boot_cpu_has" is a run-time check. You can use it after setup_arch has called init_hypervisor_platform and kvm_guest_init. Can you just just check if the PV path has been enabled and, if not, do a static_key_inc to enable the unfair path?


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