inmates: x86: Allow to bypass TSC and APIC timer calibration

Make use of the command line feature and introduce the "tsc_freq" and
"apic_freq" parameters. When provided, these values are used directly
instead of running calibrations against the PM timer.

This is particularly useful when running micro-benchmarks that are
sensitive to the inherent small variations of the calibrations.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>

diff --git a/inmates/lib/x86/timing.c b/inmates/lib/x86/timing.c
index 9dbf028e666e22e4115fcb6150e6e34e95c79784..4f3890bd1c4c1d4165dded909b8b05d04bf45ba5 100644 (file)
--- a/inmates/lib/x86/timing.c
+++ b/inmates/lib/x86/timing.c
@@ -1,7 +1,7 @@
 /*
  * Jailhouse, a Linux-based partitioning hypervisor
  *
- * Copyright (c) Siemens AG, 2013, 2014
+ * Copyright (c) Siemens AG, 2013-2016
  *
  * Authors:
  *  Jan Kiszka <jan.kiszka@siemens.com>
@@ -59,18 +59,23 @@ unsigned long tsc_init(void)
        unsigned long start_pm, end_pm;
        u64 start_tsc, end_tsc;
 
-       start_pm = pm_timer_read();
-       start_tsc = rdtsc();
-       asm volatile("mfence" : : : "memory");
+       tsc_freq = cmdline_parse_int("tsc_freq", 0);
 
-       while (pm_timer_read() - start_pm < 100 * NS_PER_MSEC)
-               cpu_relax();
+       if (tsc_freq == 0) {
+               start_pm = pm_timer_read();
+               start_tsc = rdtsc();
+               asm volatile("mfence" : : : "memory");
+
+               while (pm_timer_read() - start_pm < 100 * NS_PER_MSEC)
+                       cpu_relax();
+
+               end_pm = pm_timer_read();
+               end_tsc = rdtsc();
+               asm volatile("mfence" : : : "memory");
 
-       end_pm = pm_timer_read();
-       end_tsc = rdtsc();
-       asm volatile("mfence" : : : "memory");
+               tsc_freq = (end_tsc - start_tsc) * NS_PER_SEC / (end_pm - start_pm);
+       }
 
-       tsc_freq = (end_tsc - start_tsc) * NS_PER_SEC / (end_pm - start_pm);
        tsc_overflow = (0x100000000L * NS_PER_SEC) / tsc_freq;
 
        return tsc_freq;
@@ -99,26 +104,36 @@ void delay_us(unsigned long microsecs)
 
 unsigned long apic_timer_init(unsigned int vector)
 {
+       unsigned long long apic_freq;
        unsigned long start, end;
        unsigned long tmr;
 
-       write_msr(X2APIC_TDCR, 3);
+       apic_freq = cmdline_parse_int("apic_freq", 0);
 
-       start = pm_timer_read();
-       write_msr(X2APIC_TMICT, 0xffffffff);
+       if (apic_freq == 0) {
+               write_msr(X2APIC_TDCR, 3);
 
-       while (pm_timer_read() - start < 100 * NS_PER_MSEC)
-               cpu_relax();
+               start = pm_timer_read();
+               write_msr(X2APIC_TMICT, 0xffffffff);
+
+               while (pm_timer_read() - start < 100 * NS_PER_MSEC)
+                       cpu_relax();
+
+               end = pm_timer_read();
+               tmr = read_msr(X2APIC_TMCCT);
 
-       end = pm_timer_read();
-       tmr = read_msr(X2APIC_TMCCT);
+               write_msr(X2APIC_TMICT, 0);
 
-       divided_apic_freq = (0xffffffffULL - tmr) * NS_PER_SEC / (end - start);
+               divided_apic_freq = (0xffffffffULL - tmr) * NS_PER_SEC / (end - start);
+               apic_freq = (divided_apic_freq * 16 + 500) / 1000;
+       } else {
+               divided_apic_freq = apic_freq / 16;
+               apic_freq /= 1000;
+       }
 
-       write_msr(X2APIC_TMICT, 0);
        write_msr(X2APIC_LVTT, vector);
 
-       return (divided_apic_freq * 16 + 500) / 1000;
+       return apic_freq;
 }
 
 void apic_timer_set(unsigned long timeout_ns)