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Index: head/sys/x86/x86/tsc.c
===================================================================
--- head/sys/x86/x86/tsc.c
+++ head/sys/x86/x86/tsc.c
@@ -143,7 +143,7 @@
* 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 @@
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 @@
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 @@
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 @@
*/
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 @@
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);

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