>>> On 18.12.14 at 19:06, <boris.ostrov...@oracle.com> wrote: > We need to make sure that last_vcpu is not pointing to VCPU whose > VPMU is being destroyed. Otherwise we may try to dereference it in > the future, when VCPU is gone. > > We have to do this via IPI since otherwise there is a (somewheat > theoretical) chance that between test and subsequent clearing > of last_vcpu the remote processor (i.e. vpmu->last_pcpu) might do > both vpmu_load() and then vpmu_save() for another VCPU. The former > will clear last_vcpu and the latter will set it to something else. > > Performing this operation via IPI will guarantee that nothing can > happen on the remote processor between testing and clearing of > last_vcpu. > > We should also check for VPMU_CONTEXT_ALLOCATED in vpmu_destroy() to > avoid unnecessary percpu tests and arch-specific destroy ops. Thus > checks in AMD and Intel routines are no longer needed. > > Signed-off-by: Boris Ostrovsky <boris.ostrov...@oracle.com>
Acked-by: Jan Beulich <jbeul...@suse.com> _______________________________________________ Xen-devel mailing list Xen-devel@lists.xen.org http://lists.xen.org/xen-devel
