Re: [Xen-devel] [PATCH v3] x86/VPMU: Clear last_vcpu when destroying VPMU

["Jan Beulich" <jbeulich@xxxxxxxx>]

>>> Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx> 12/17/14 4:10 PM >>>
>+    /* Need to clear last_vcpu in case it points to v */
>+    (void)cmpxchg(last, v, NULL);
 
In a (later) reply to v2 I had indicated that it doesn't seem safe to so here 
but
rely on an IPI in the other path altering that value. Can you explain why you
think this is safe without changing the others to CPU-atomic accesses too?

Jan


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