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| author | jkim <jkim@FreeBSD.org> | 2011-04-14 17:50:26 +0000 |
|---|---|---|
| committer | jkim <jkim@FreeBSD.org> | 2011-04-14 17:50:26 +0000 |
| commit | 38dc7c42e64b68aff5cd2f89803997efc8ba01e4 (patch) | |
| tree | 705b5be386433d0dc7fa64f2b4ef32957d3ba0f4 /sys/x86 | |
| parent | 17965a03aabd44c44fbb007f459c11fa89ba3b54 (diff) | |
| download | FreeBSD-src-38dc7c42e64b68aff5cd2f89803997efc8ba01e4.zip FreeBSD-src-38dc7c42e64b68aff5cd2f89803997efc8ba01e4.tar.gz | |
Work around an emulator problem where virtual CPU advertises TSC is P-state
invariant and APERF/MPERF MSRs exist but these MSRs never tick. When we
calculate effective frequency from cpu_est_clockrate(), it caused panic of
division-by-zero. Now we test whether these MSRs actually increase to avoid
such foot-shooting.
Reported by: dim
Tested by: dim
Diffstat (limited to 'sys/x86')
| -rw-r--r-- | sys/x86/x86/tsc.c | 14 |
1 files changed, 12 insertions, 2 deletions
diff --git a/sys/x86/x86/tsc.c b/sys/x86/x86/tsc.c index 04e936a..c08f4ad 100644 --- a/sys/x86/x86/tsc.c +++ b/sys/x86/x86/tsc.c @@ -183,8 +183,18 @@ probe_tsc_freq(void) if (cpu_high >= 6) { do_cpuid(6, regs); - if ((regs[2] & CPUID_PERF_STAT) != 0) - tsc_perf_stat = 1; + if ((regs[2] & CPUID_PERF_STAT) != 0) { + /* + * XXX Some emulators expose host CPUID without actual + * support for these MSRs. We must test whether they + * really work. + */ + wrmsr(MSR_MPERF, 0); + wrmsr(MSR_APERF, 0); + DELAY(10); + if (rdmsr(MSR_MPERF) > 0 && rdmsr(MSR_APERF) > 0) + tsc_perf_stat = 1; + } } if (tsc_skip_calibration) { |
