From: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx> Tuesday, November 27, 2018 5:11 AM > > I personally tend to prefer masks over bitfields, so I'd rather do the > > consolidation in the opposite direction: use the definitions in > > hyperv-tlfs.h and replace those unions/bitfields elsewhere. (I vaguely > > remember posting such a patchset a couple of years ago but I lacked the > > motivation to complete it). > > Are there any known advantages of using masks over bitfields or the > resulting binary code is the same? Assuming there are no I'd personally > prefer bitfields - not sure why but to me e.g. > (stimer->config.enabled && !stimer->config.direct_mode) > looks nicer than > (stimer->config & HV_STIMER_ENABLED && !(stimer->config & HV_STIMER_DIRECT)) > > + there's no need to do shifts, e.g. > > vector = stimer->config.apic_vector > > looks cleaner that > > vector = (stimer->config & HV_STIMER_APICVECTOR_MASK) >> > HV_STIMER_APICVECTOR_SHIFT > > ... and we already use a few in hyperv-tlfs.h. I'm, however, flexible :-) > > K. Y., Michael, Haiyang, Stephen - would you prefer to get rid of all > bitfields from hyperv-tlfs.h? If so I can work on a patchset. As to this > series, my understanding is that Paolo already queued it so in any case > this is going to be a separate effort (unless there are strong > objections of course). > I prefer to keep the bit fields. I concur think it makes the code more readable. Even if there is a modest performance benefit, at least within a Linux guest most of the manipulation of the fields is during initialization when performance doesn't matter. But I can't speak to KVM's implementation of the hypervisor side. Michael
