On 2013-03-13 10:03, Paolo Bonzini wrote: > Il 13/03/2013 08:39, Jan Kiszka ha scritto: >>> I think this should clear pending SIPIs, unless KVM_APIC_INIT >>> was already set in which case it should be a no-op. Something >>> like: >>> >>> e = apic->pending_events; while (!(e & KVM_APIC_INIT)) e = >>> cmpxchg(&apic->pending_events, e, (e | KVM_APIC_INIT) & >>> ~KVM_APIC_SIPI); >>> >>> If you do this, better make pending_events an atomic_t. > >> Quick question: Why atomic_t? It becomes a bit ugly to poke into >> the atomic counter for bitops, and cmpxchg is mapped on an >> interlocked version. > > It's a bit safer because it forces you to use atomic_read, and > generally points out to reviewers to think about memory barriers. But > indeed the lack of atomic_set_bit and atomic_clear_bit makes the code > uglier. And as long as there are no other bits in > apic->pending_events, the above loop is actually the same as just > > apic->pending_events = 1 << KVM_APIC_INIT; Yeah, can simplify this in the next version of the just posted patch. Jan -- Siemens AG, Corporate Technology, CT RTC ITP SDP-DE Corporate Competence Center Embedded Linux -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
