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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-changelog] [xen-unstable] x86: trust new architecturally-defined TSC Invariant bit on Intel systems
# HG changeset patch
# User Keir Fraser <keir.fraser@xxxxxxxxxx>
# Date 1255077243 -3600
# Node ID 18e80cd73366095dc50925c8a44a0774b2ca323a
# Parent 1593073ad670ba057fc854021413590167a0ae06
x86: trust new architecturally-defined TSC Invariant bit on Intel systems
Trust new architecturally-defined TSC Invariant bit (on
Intel systems only for now, AMD TBD).
Signed-off-by: Dan Magenheimer <dan.magenheimer@xxxxxxxxxx>
Signed-off-by: Keir Fraser <keir.fraser@xxxxxxxxxx>
---
xen/arch/x86/setup.c | 12 ++++++++++++
xen/arch/x86/smpboot.c | 8 ++++++++
xen/arch/x86/time.c | 31 +++++++++++++++----------------
3 files changed, 35 insertions(+), 16 deletions(-)
diff -r 1593073ad670 -r 18e80cd73366 xen/arch/x86/setup.c
--- a/xen/arch/x86/setup.c Fri Oct 09 09:33:29 2009 +0100
+++ b/xen/arch/x86/setup.c Fri Oct 09 09:34:03 2009 +0100
@@ -66,6 +66,10 @@ static int opt_watchdog = 0;
static int opt_watchdog = 0;
boolean_param("watchdog", opt_watchdog);
+/* opt_tsc_unstable: Override all tests; assume TSC is unreliable. */
+static int opt_tsc_unstable;
+boolean_param("tsc_unstable", opt_tsc_unstable);
+
/* **** Linux config option: propagated to domain0. */
/* "acpi=off": Sisables both ACPI table parsing and interpreter. */
/* "acpi=force": Override the disable blacklist. */
@@ -460,6 +464,14 @@ void __init __start_xen(unsigned long mb
while ( kextra[1] == ' ' ) kextra++;
}
cmdline_parse(cmdline);
+
+ /* If TSC is marked as unstable, clear all enhanced TSC features. */
+ if ( opt_tsc_unstable )
+ {
+ setup_clear_cpu_cap(X86_FEATURE_CONSTANT_TSC);
+ setup_clear_cpu_cap(X86_FEATURE_NONSTOP_TSC);
+ setup_clear_cpu_cap(X86_FEATURE_TSC_RELIABLE);
+ }
parse_video_info();
diff -r 1593073ad670 -r 18e80cd73366 xen/arch/x86/smpboot.c
--- a/xen/arch/x86/smpboot.c Fri Oct 09 09:33:29 2009 +0100
+++ b/xen/arch/x86/smpboot.c Fri Oct 09 09:34:03 2009 +0100
@@ -187,6 +187,11 @@ static void __init synchronize_tsc_bp (v
unsigned int one_usec;
int buggy = 0;
+ if (boot_cpu_has(X86_FEATURE_TSC_RELIABLE)) {
+ printk("TSC is reliable, synchronization unnecessary\n");
+ return;
+ }
+
printk("checking TSC synchronization across %u CPUs: ",
num_booting_cpus());
/* convert from kcyc/sec to cyc/usec */
@@ -278,6 +283,9 @@ static void __init synchronize_tsc_ap (v
static void __init synchronize_tsc_ap (void)
{
int i;
+
+ if (boot_cpu_has(X86_FEATURE_TSC_RELIABLE))
+ return;
/*
* Not every cpu is online at the time
diff -r 1593073ad670 -r 18e80cd73366 xen/arch/x86/time.c
--- a/xen/arch/x86/time.c Fri Oct 09 09:33:29 2009 +0100
+++ b/xen/arch/x86/time.c Fri Oct 09 09:34:03 2009 +0100
@@ -37,13 +37,6 @@ static char __initdata opt_clocksource[1
static char __initdata opt_clocksource[10];
string_param("clocksource", opt_clocksource);
-/*
- * opt_consistent_tscs: All TSCs tick at the exact same rate, allowing
- * simplified system time handling.
- */
-static int opt_consistent_tscs;
-boolean_param("consistent_tscs", opt_consistent_tscs);
-
unsigned long cpu_khz; /* CPU clock frequency in kHz. */
DEFINE_SPINLOCK(rtc_lock);
unsigned long pit0_ticks;
@@ -977,7 +970,7 @@ static void local_time_calibration(void)
/* The overall calibration scale multiplier. */
u32 calibration_mul_frac;
- if ( opt_consistent_tscs )
+ if ( boot_cpu_has(X86_FEATURE_CONSTANT_TSC) )
{
/* Atomically read cpu_calibration struct and write cpu_time struct. */
local_irq_disable();
@@ -1110,6 +1103,10 @@ struct calibration_rendezvous {
u64 master_tsc_stamp;
};
+/*
+ * Keep TSCs in sync when they run at the same rate, but may stop in
+ * deep-sleep C states.
+ */
static void time_calibration_tsc_rendezvous(void *_r)
{
int i;
@@ -1161,6 +1158,7 @@ static void time_calibration_tsc_rendezv
raise_softirq(TIME_CALIBRATE_SOFTIRQ);
}
+/* Ordinary rendezvous function which does not modify TSC values. */
static void time_calibration_std_rendezvous(void *_r)
{
struct cpu_calibration *c = &this_cpu(cpu_calibration);
@@ -1190,6 +1188,9 @@ static void time_calibration_std_rendezv
raise_softirq(TIME_CALIBRATE_SOFTIRQ);
}
+static void (*time_calibration_rendezvous_fn)(void *) =
+ time_calibration_std_rendezvous;
+
static void time_calibration(void *unused)
{
struct calibration_rendezvous r = {
@@ -1199,9 +1200,7 @@ static void time_calibration(void *unuse
/* @wait=1 because we must wait for all cpus before freeing @r. */
on_selected_cpus(&r.cpu_calibration_map,
- opt_consistent_tscs
- ? time_calibration_tsc_rendezvous
- : time_calibration_std_rendezvous,
+ time_calibration_rendezvous_fn,
&r, 1);
}
@@ -1229,15 +1228,15 @@ void init_percpu_time(void)
/* Late init function (after all CPUs are booted). */
int __init init_xen_time(void)
{
- if ( !boot_cpu_has(X86_FEATURE_CONSTANT_TSC) )
- opt_consistent_tscs = 0;
-
- /* If we have constant TSCs then scale factor can be shared. */
- if ( opt_consistent_tscs )
+ /* If we have constant-rate TSCs then scale factor can be shared. */
+ if ( boot_cpu_has(X86_FEATURE_CONSTANT_TSC) )
{
int cpu;
for_each_possible_cpu ( cpu )
per_cpu(cpu_time, cpu).tsc_scale = per_cpu(cpu_time, 0).tsc_scale;
+ /* If TSCs are not marked as 'reliable', re-sync during rendezvous. */
+ if ( !boot_cpu_has(X86_FEATURE_TSC_RELIABLE) )
+ time_calibration_rendezvous_fn = time_calibration_tsc_rendezvous;
}
open_softirq(TIME_CALIBRATE_SOFTIRQ, local_time_calibration);
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