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x86 tsc: fall back to CPUID if calibration results looks unbelievable.

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Teested and reviewed by:	scottl
Sponsored by:	The FreeBSD Foundation
MFC after:	2 weeks
Differential revision:	https://reviews.freebsd.org/D24247
This commit is contained in:
Konstantin Belousov 2020-04-01 16:21:11 +00:00
parent af5319f92c
commit bd8a359f81
1 changed files with 34 additions and 7 deletions
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41
sys/x86/x86/tsc.c
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@ -143,7 +143,7 @@ tsc_freq_vmware(void)
* tsc_freq_intel(), when available. * tsc_freq_intel(), when available.
*/ */
static bool static bool
tsc_freq_cpuid(void) tsc_freq_cpuid(uint64_t *res)
{ {
u_int regs[4]; u_int regs[4];
@ -151,7 +151,7 @@ tsc_freq_cpuid(void)
return (false); return (false);
do_cpuid(0x15, regs); do_cpuid(0x15, regs);
if (regs[0] != 0 && regs[1] != 0 && regs[2] != 0) { 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); return (true);
} }
@ -159,7 +159,7 @@ tsc_freq_cpuid(void)
return (false); return (false);
do_cpuid(0x16, regs); do_cpuid(0x16, regs);
if (regs[0] != 0) { if (regs[0] != 0) {
tsc_freq = (uint64_t)regs[0] * 1000000; *res = (uint64_t)regs[0] * 1000000;
return (true); return (true);
} }
@ -228,7 +228,8 @@ tsc_freq_intel(void)
static void static void
probe_tsc_freq(void) probe_tsc_freq(void)
{ {
uint64_t tsc1, tsc2; uint64_t tmp_freq, tsc1, tsc2;
int no_cpuid_override;
uint16_t bootflags; uint16_t bootflags;
if (cpu_power_ecx & CPUID_PERF_STAT) { if (cpu_power_ecx & CPUID_PERF_STAT) {
@ -299,15 +300,15 @@ probe_tsc_freq(void)
*/ */
if (acpi_get_fadt_bootflags(&bootflags) && if (acpi_get_fadt_bootflags(&bootflags) &&
(bootflags & ACPI_FADT_LEGACY_DEVICES) == 0 && (bootflags & ACPI_FADT_LEGACY_DEVICES) == 0 &&
tsc_freq_cpuid()) { tsc_freq_cpuid(&tmp_freq)) {
printf("Skipping TSC calibration since no legacy " printf("Skipping TSC calibration since no legacy "
"devices reported by FADT and CPUID works\n"); "devices reported by FADT and CPUID works\n");
tsc_skip_calibration = 1; tsc_skip_calibration = 1;
} }
} }
if (tsc_skip_calibration) { 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) else if (cpu_vendor_id == CPU_VENDOR_INTEL)
tsc_freq_intel(); tsc_freq_intel();
} else { } else {
@ -317,6 +318,32 @@ probe_tsc_freq(void)
DELAY(1000000); DELAY(1000000);
tsc2 = rdtsc(); tsc2 = rdtsc();
tsc_freq = tsc2 - tsc1; 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) if (bootverbose)
printf("TSC clock: %ju Hz\n", (intmax_t)tsc_freq); printf("TSC clock: %ju Hz\n", (intmax_t)tsc_freq);