Author: kib Date: Wed Apr 1 16:21:11 2020 New Revision: 359520 URL: https://svnweb.freebsd.org/changeset/base/359520
Log: x86 tsc: fall back to CPUID if calibration results looks unbelievable. Teested and reviewed by: scottl Sponsored by: The FreeBSD Foundation MFC after: 2 weeks Differential revision: https://reviews.freebsd.org/D24247 Modified: head/sys/x86/x86/tsc.c Modified: head/sys/x86/x86/tsc.c ============================================================================== --- head/sys/x86/x86/tsc.c Wed Apr 1 16:03:06 2020 (r359519) +++ head/sys/x86/x86/tsc.c Wed Apr 1 16:21:11 2020 (r359520) @@ -143,7 +143,7 @@ tsc_freq_vmware(void) * tsc_freq_intel(), when available. */ static bool -tsc_freq_cpuid(void) +tsc_freq_cpuid(uint64_t *res) { u_int regs[4]; @@ -151,7 +151,7 @@ tsc_freq_cpuid(void) return (false); do_cpuid(0x15, regs); if (regs[0] != 0 && regs[1] != 0 && regs[2] != 0) { - tsc_freq = (uint64_t)regs[2] * regs[1] / regs[0]; + *res = (uint64_t)regs[2] * regs[1] / regs[0]; return (true); } @@ -159,7 +159,7 @@ tsc_freq_cpuid(void) return (false); do_cpuid(0x16, regs); if (regs[0] != 0) { - tsc_freq = (uint64_t)regs[0] * 1000000; + *res = (uint64_t)regs[0] * 1000000; return (true); } @@ -228,7 +228,8 @@ tsc_freq_intel(void) static void probe_tsc_freq(void) { - uint64_t tsc1, tsc2; + uint64_t tmp_freq, tsc1, tsc2; + int no_cpuid_override; uint16_t bootflags; if (cpu_power_ecx & CPUID_PERF_STAT) { @@ -299,15 +300,15 @@ probe_tsc_freq(void) */ if (acpi_get_fadt_bootflags(&bootflags) && (bootflags & ACPI_FADT_LEGACY_DEVICES) == 0 && - tsc_freq_cpuid()) { + tsc_freq_cpuid(&tmp_freq)) { printf("Skipping TSC calibration since no legacy " "devices reported by FADT and CPUID works\n"); tsc_skip_calibration = 1; } } if (tsc_skip_calibration) { - if (tsc_freq_cpuid()) - ; + if (tsc_freq_cpuid(&tmp_freq)) + tsc_freq = tmp_freq; else if (cpu_vendor_id == CPU_VENDOR_INTEL) tsc_freq_intel(); } else { @@ -317,6 +318,32 @@ probe_tsc_freq(void) DELAY(1000000); tsc2 = rdtsc(); tsc_freq = tsc2 - tsc1; + + /* + * If the difference between calibrated frequency and + * the frequency reported by CPUID 0x15/0x16 leafs + * differ significantly, this probably means that + * calibration is bogus. It happens on machines + * without 8254 timer and with BIOS not properly + * reporting it in FADT boot flags. + */ + if (tsc_freq_cpuid(&tmp_freq) && qabs(tsc_freq - tmp_freq) > + uqmin(tsc_freq, tmp_freq)) { + no_cpuid_override = 0; + TUNABLE_INT_FETCH("machdep.disable_tsc_cpuid_override", + &no_cpuid_override); + if (!no_cpuid_override) { + if (bootverbose) { + printf( + "TSC clock: calibration freq %ju Hz, CPUID freq %ju Hz%s\n", + (uintmax_t)tsc_freq, + (uintmax_t)tmp_freq, + no_cpuid_override ? "" : + ", doing CPUID override"); + } + tsc_freq = tmp_freq; + } + } } if (bootverbose) printf("TSC clock: %ju Hz\n", (intmax_t)tsc_freq); _______________________________________________ svn-src-head@freebsd.org mailing list https://lists.freebsd.org/mailman/listinfo/svn-src-head To unsubscribe, send any mail to "svn-src-head-unsubscr...@freebsd.org"
