# HG changeset patch
# User Keir Fraser <keir.fraser@xxxxxxxxxx>
# Date 1257240802 0
# Node ID 450f2ddd2dc6688bb3c5be3636944b33b3b1bb9c
# Parent 7d7631b57d1966ba2fe7ccf4333f87d8a77d2fb4
x86: Clean up APIC local timer handling.
1. Writing TMICT=0 disables the timer. Use this fact to simplify and
improve reprogram_timer(). In particular, we always write TMICT, and
write zero when we do not need a timer interrupt.
2. In HPET broadcast timer handler, set TMICT=0 when we mask the APIC
local timer. May as well do this early, before entering deep sleep.
3. In HVM-guest APIC emulation, disable the emulated local timer when
the guest sets TMICT=0. Previously we would issue an immediate
one-shot interrupt.
Signed-off-by: Keir Fraser <keir.fraser@xxxxxxxxxx>
---
xen/arch/x86/apic.c | 62 ++++++++--------------------------------------
xen/arch/x86/hpet.c | 7 ++---
xen/arch/x86/hvm/vlapic.c | 11 ++++++--
3 files changed, 23 insertions(+), 57 deletions(-)
diff -r 7d7631b57d19 -r 450f2ddd2dc6 xen/arch/x86/apic.c
--- a/xen/arch/x86/apic.c Tue Nov 03 08:40:40 2009 +0000
+++ b/xen/arch/x86/apic.c Tue Nov 03 09:33:22 2009 +0000
@@ -1178,65 +1178,25 @@ void enable_APIC_timer(void)
#undef APIC_DIVISOR
/*
- * reprogram the APIC timer. Timeoutvalue is in ns from start of boot
- * returns 1 on success
- * returns 0 if the timeout value is too small or in the past.
+ * reprogram_timer: Reprogram the APIC timer.
+ * Timeout is a Xen system time (nanoseconds since boot); 0 disables the timer.
+ * Returns 1 on success; 0 if the timeout is too soon or is in the past.
*/
int reprogram_timer(s_time_t timeout)
{
- s_time_t now;
- s_time_t expire;
- u64 apic_tmict;
-
- /*
- * If we don't have local APIC then we just poll the timer list off the
- * PIT interrupt.
- */
+ s_time_t expire;
+ u32 apic_tmict = 0;
+
+ /* No local APIC: timer list is polled via the PIT interrupt. */
if ( !cpu_has_apic )
return 1;
- /*
- * We use this value because we don't trust zero (we think it may just
- * cause an immediate interrupt). At least this is guaranteed to hold it
- * off for ages (esp. since the clock ticks on bus clock, not cpu clock!).
- */
- if ( timeout == 0 )
- {
- apic_tmict = 0xffffffff;
- goto reprogram;
- }
-
- now = NOW();
- expire = timeout - now; /* value from now */
-
- if ( expire <= 0 )
- {
- Dprintk("APICT[%02d] Timeout in the past 0x%08X%08X > 0x%08X%08X\n",
- smp_processor_id(), (u32)(now>>32),
- (u32)now, (u32)(timeout>>32),(u32)timeout);
- return 0;
- }
-
- /* conversion to bus units */
- apic_tmict = (((u64)bus_scale) * expire)>>18;
-
- if ( apic_tmict >= 0xffffffff )
- {
- Dprintk("APICT[%02d] Timeout value too large\n", smp_processor_id());
- apic_tmict = 0xffffffff;
- }
-
- if ( apic_tmict == 0 )
- {
- Dprintk("APICT[%02d] timeout value too small\n", smp_processor_id());
- return 0;
- }
-
- reprogram:
- /* Program the timer. */
+ if ( timeout && ((expire = timeout - NOW()) > 0) )
+ apic_tmict = min_t(u64, (bus_scale * expire) >> 18, UINT_MAX);
+
apic_write(APIC_TMICT, (unsigned long)apic_tmict);
- return 1;
+ return apic_tmict || !timeout;
}
fastcall void smp_apic_timer_interrupt(struct cpu_user_regs * regs)
diff -r 7d7631b57d19 -r 450f2ddd2dc6 xen/arch/x86/hpet.c
--- a/xen/arch/x86/hpet.c Tue Nov 03 08:40:40 2009 +0000
+++ b/xen/arch/x86/hpet.c Tue Nov 03 09:33:22 2009 +0000
@@ -642,6 +642,8 @@ void hpet_broadcast_enter(void)
if ( hpet_attach_channel )
hpet_attach_channel(cpu, ch);
+ /* Cancel any outstanding LAPIC timer event and disable interrupts. */
+ reprogram_timer(0);
disable_APIC_timer();
cpu_set(cpu, ch->cpumask);
@@ -664,11 +666,8 @@ void hpet_broadcast_exit(void)
if ( cpu_test_and_clear(cpu, ch->cpumask) )
{
- /* Cancel any outstanding LAPIC event and re-enable interrupts. */
- reprogram_timer(0);
+ /* Reprogram the deadline; trigger timer work now if it has passed. */
enable_APIC_timer();
-
- /* Reprogram the deadline; trigger timer work now if it has passed. */
if ( !reprogram_timer(per_cpu(timer_deadline, cpu)) )
raise_softirq(TIMER_SOFTIRQ);
diff -r 7d7631b57d19 -r 450f2ddd2dc6 xen/arch/x86/hvm/vlapic.c
--- a/xen/arch/x86/hvm/vlapic.c Tue Nov 03 08:40:40 2009 +0000
+++ b/xen/arch/x86/hvm/vlapic.c Tue Nov 03 09:33:22 2009 +0000
@@ -667,10 +667,17 @@ static int vlapic_write(struct vcpu *v,
case APIC_TMICT:
{
- uint64_t period = (uint64_t)APIC_BUS_CYCLE_NS *
- (uint32_t)val * vlapic->hw.timer_divisor;
+ uint64_t period;
vlapic_set_reg(vlapic, APIC_TMICT, val);
+ if ( val == 0 )
+ {
+ destroy_periodic_time(&vlapic->pt);
+ break;
+ }
+
+ period = ((uint64_t)APIC_BUS_CYCLE_NS *
+ (uint32_t)val * vlapic->hw.timer_divisor);
create_periodic_time(current, &vlapic->pt, period,
vlapic_lvtt_period(vlapic) ? period : 0,
vlapic->pt.irq, vlapic_pt_cb,
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