2016-05-31 03:53-0400, Paolo Bonzini: > > 2016-05-27 17:22+0200, Radim Krčmář: > > > (I wonder why MacOS X doesn't read IA32_PERF_STATUS, though.) > > > > Oh, it maybe does ... we already emulate status and return 0x1000 in its > > bottom 16 bits. I have no idea what is that supposed to mean, but I > > think we should return 0x1000 in IA32_PERF_CTL then. > > It's 1000, not 0x1000 (instead, on real hardware the value is typically a > multiple of 256). It was added for Darwin too. Ah, thanks. (Drivers say that bottom 8 bits are not used.) > Returning different values is okay, because they are different on real > hardware too: > > (sudo dd if=/dev/cpu/0/msr skip=$((0x198)) iflag=skip_bytes bs=8 count=1; > sudo dd if=/dev/cpu/0/msr skip=$((0x199)) iflag=skip_bytes bs=8 count=1) | od -tx8 > 0000000 00001f3900001100 0000000000001300 > ^^^^^^^^^^^^^^^^ ^^^^^^^^^^^^^^^^ > PERF_STATUS PERF_CTL > > And perhaps if we returned non-zero values for PERF_CTL Darwin would try to > write to it. So returning zero is fine, I think. There is no correct answer... Yeah, 0 seems fine. PERF_CTL the target value for PERF_STATUS, but OS shouldn't put much trust in those values ... especially under KVM, where those MSRs make little sense. -- 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
