[PATCH 2/6] lguest tsc fix

Rusty Russell
2007-06-05T15:27:57Z

In recent -mm kernels, the TSC capability cannot be disabled,
resulting in a divide by zero error in the normal sched_clock.

The correct fix is to have a special lguest sched_clock
implementation: this is as simple as it gets.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
---
drivers/lguest/lguest.c | 10 ++++++++--
1 file changed, 8 insertions(+), 2 deletions(-)

===================================================================
--- a/drivers/lguest/lguest.c
+++ b/drivers/lguest/lguest.c
@@ -351,11 +351,18 @@ static void lguest_time_irq(unsigned int
update_process_times(user_mode_vm(get_irq_regs()));
}

+static u64 sched_clock_base;
static void lguest_time_init(void)
{
set_irq_handler(0, lguest_time_irq);
hcall(LHCALL_TIMER_READ, 0, 0, 0);
+ sched_clock_base = jiffies_64;
enable_lguest_irq(0);
+}
+
+static unsigned long long lguest_sched_clock(void)
+{
+ return (jiffies_64 - sched_clock_base) * (1000000000 / HZ);
}

static void lguest_load_esp0(struct tss_struct *tss,
@@ -494,6 +501,7 @@ __init void lguest_init(void *boot)
paravirt_ops.time_init = lguest_time_init;
paravirt_ops.set_lazy_mode = lguest_lazy_mode;
paravirt_ops.wbinvd = lguest_wbinvd;
+ paravirt_ops.sched_clock = lguest_sched_clock;

hcall(LHCALL_LGUEST_INIT, __pa(&lguest_data), 0, 0);

@@ -507,8 +515,6 @@ __init void lguest_init(void *boot)
cpu_detect(&new_cpu_data);
/* Math is always hard! */
new_cpu_data.hard_math = 1;
-
- tsc_disable = 1;

#ifdef CONFIG_X86_MCE
mce_disabled = 1;