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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-changelog] [xen-unstable] X86: Prefer TSC-deadline timer in Xen
# HG changeset patch
# User Keir Fraser <keir@xxxxxxx>
# Date 1288345214 -3600
# Node ID fb34514bf76bf575164ff83130b1cf9c8e3fea5a
# Parent b48d8f27fca251c2df0222d195ffcb772d6a1128
X86: Prefer TSC-deadline timer in Xen
The new TSC Deadline Timer offers system software a low overhead
per-logical-thread deadline timer in TSC units.
The timer is implemented via a new architectural 64-bit register,
IA32_TSC_DEADLINE_MSR. Reads and writes of this MSR occur in program
order, but are non-serializing.
The support for this feature is indicated by
CPUID.01H:ECX.TSC_Deadline[bit 24] =3D 1 as documented in the Intel
Architecture Software Developer's Manual.
The LOCAL APIC on new processors has a mode where its underlying
hardware timer can now be accessed via the non-serializing
IA32_TSC_DEADLINE_MSR in TSC tick units.
If this mode is present, prefer it over the traditional LAPIC timer
mode. KERN_DEBUG dmesg will print "TSC deadline timer enabled" when
TDT is used.
Bootparam "tdt=off" is available to revert to LAPIC timer mode.
This patch is based on original work by Len Brown for Linux kernel.
cc: Len Brown <len.brown@xxxxxxxxx>
Signed-off-by: Wei Gang <gang.wei@xxxxxxxxx>
Signed-off-by: Keir Fraser <keir@xxxxxxx>
---
xen/arch/x86/apic.c | 28 ++++++++++++++++++++++++++++
xen/arch/x86/time.c | 28 +++++++++++++++-------------
xen/include/asm-x86/cpufeature.h | 1 +
xen/include/asm-x86/msr-index.h | 2 ++
xen/include/asm-x86/time.h | 2 ++
xen/include/xen/time.h | 4 +++-
6 files changed, 51 insertions(+), 14 deletions(-)
diff -r b48d8f27fca2 -r fb34514bf76b xen/arch/x86/apic.c
--- a/xen/arch/x86/apic.c Fri Oct 29 10:29:14 2010 +0100
+++ b/xen/arch/x86/apic.c Fri Oct 29 10:40:14 2010 +0100
@@ -37,6 +37,15 @@
#include <asm/asm_defns.h> /* for BUILD_SMP_INTERRUPT */
#include <mach_apic.h>
#include <io_ports.h>
+
+#define APIC_TIMER_MODE_ONESHOT (0 << 17)
+#define APIC_TIMER_MODE_PERIODIC (1 << 17)
+#define APIC_TIMER_MODE_TSC_DEADLINE (2 << 17)
+#define APIC_TIMER_MODE_MASK (3 << 17)
+
+static int tdt_enabled __read_mostly;
+static int tdt_enable __initdata = 1;
+boolean_param("tdt", tdt_enable);
static struct {
int active;
@@ -1198,6 +1207,13 @@ static void __setup_APIC_LVTT(unsigned i
lvtt_value = /*APIC_LVT_TIMER_PERIODIC |*/ LOCAL_TIMER_VECTOR;
if (!APIC_INTEGRATED(ver))
lvtt_value |= SET_APIC_TIMER_BASE(APIC_TIMER_BASE_DIV);
+
+ if ( tdt_enabled )
+ {
+ lvtt_value &= (~APIC_TIMER_MODE_MASK);
+ lvtt_value |= APIC_TIMER_MODE_TSC_DEADLINE;
+ }
+
apic_write_around(APIC_LVTT, lvtt_value);
tmp_value = apic_read(APIC_TDCR);
@@ -1311,6 +1327,12 @@ void __init setup_boot_APIC_clock(void)
calibrate_APIC_clock();
+ if ( tdt_enable && boot_cpu_has(X86_FEATURE_TSC_DEADLINE) )
+ {
+ printk(KERN_DEBUG "TSC deadline timer enabled\n");
+ tdt_enabled = 1;
+ }
+
setup_APIC_timer();
local_irq_restore(flags);
@@ -1359,6 +1381,12 @@ int reprogram_timer(s_time_t timeout)
/* No local APIC: timer list is polled via the PIT interrupt. */
if ( !cpu_has_apic )
return 1;
+
+ if ( tdt_enabled )
+ {
+ wrmsrl(MSR_IA32_TSC_DEADLINE, timeout ? stime2tsc(timeout) : 0);
+ return 1;
+ }
if ( timeout && ((expire = timeout - NOW()) > 0) )
apic_tmict = min_t(u64, (bus_scale * expire) >> 18, UINT_MAX);
diff -r b48d8f27fca2 -r fb34514bf76b xen/arch/x86/time.c
--- a/xen/arch/x86/time.c Fri Oct 29 10:29:14 2010 +0100
+++ b/xen/arch/x86/time.c Fri Oct 29 10:40:14 2010 +0100
@@ -662,26 +662,28 @@ static void __init init_platform_timer(v
freq_string(pts->frequency), pts->name);
}
-void cstate_restore_tsc(void)
+u64 stime2tsc(s_time_t stime)
{
struct cpu_time *t;
struct time_scale sys_to_tsc;
s_time_t stime_delta;
- u64 new_tsc;
-
+
+ t = &this_cpu(cpu_time);
+ sys_to_tsc = scale_reciprocal(t->tsc_scale);
+
+ stime_delta = stime - t->stime_local_stamp;
+ if ( stime_delta < 0 )
+ stime_delta = 0;
+
+ return t->local_tsc_stamp + scale_delta(stime_delta, &sys_to_tsc);
+}
+
+void cstate_restore_tsc(void)
+{
if ( boot_cpu_has(X86_FEATURE_NONSTOP_TSC) )
return;
- t = &this_cpu(cpu_time);
- sys_to_tsc = scale_reciprocal(t->tsc_scale);
-
- stime_delta = read_platform_stime() - t->stime_master_stamp;
- if ( stime_delta < 0 )
- stime_delta = 0;
-
- new_tsc = t->local_tsc_stamp + scale_delta(stime_delta, &sys_to_tsc);
-
- write_tsc(new_tsc);
+ write_tsc(stime2tsc(read_platform_stime()));
}
/***************************************************************************
diff -r b48d8f27fca2 -r fb34514bf76b xen/include/asm-x86/cpufeature.h
--- a/xen/include/asm-x86/cpufeature.h Fri Oct 29 10:29:14 2010 +0100
+++ b/xen/include/asm-x86/cpufeature.h Fri Oct 29 10:40:14 2010 +0100
@@ -99,6 +99,7 @@
#define X86_FEATURE_SSE4_2 (4*32+20) /* Streaming SIMD Extensions 4.2 */
#define X86_FEATURE_X2APIC (4*32+21) /* Extended xAPIC */
#define X86_FEATURE_POPCNT (4*32+23) /* POPCNT instruction */
+#define X86_FEATURE_TSC_DEADLINE (4*32+24) /* "tdt" TSC Deadline Timer */
#define X86_FEATURE_XSAVE (4*32+26) /* XSAVE/XRSTOR/XSETBV/XGETBV */
#define X86_FEATURE_OSXSAVE (4*32+27) /* OSXSAVE */
#define X86_FEATURE_HYPERVISOR (4*32+31) /* Running under some hypervisor */
diff -r b48d8f27fca2 -r fb34514bf76b xen/include/asm-x86/msr-index.h
--- a/xen/include/asm-x86/msr-index.h Fri Oct 29 10:29:14 2010 +0100
+++ b/xen/include/asm-x86/msr-index.h Fri Oct 29 10:40:14 2010 +0100
@@ -327,6 +327,8 @@
#define MSR_IA32_MISC_ENABLE_MONITOR_ENABLE (1<<18)
#define MSR_IA32_MISC_ENABLE_LIMIT_CPUID (1<<22)
#define MSR_IA32_MISC_ENABLE_XTPR_DISABLE (1<<23)
+
+#define MSR_IA32_TSC_DEADLINE 0x000006E0
/* Intel Model 6 */
#define MSR_P6_EVNTSEL0 0x00000186
diff -r b48d8f27fca2 -r fb34514bf76b xen/include/asm-x86/time.h
--- a/xen/include/asm-x86/time.h Fri Oct 29 10:29:14 2010 +0100
+++ b/xen/include/asm-x86/time.h Fri Oct 29 10:40:14 2010 +0100
@@ -74,4 +74,6 @@ void cpuid_time_leaf(uint32_t sub_idx, u
void cpuid_time_leaf(uint32_t sub_idx, unsigned int *eax, unsigned int *ebx,
unsigned int *ecx, unsigned int *edx);
+u64 stime2tsc(s_time_t stime);
+
#endif /* __X86_TIME_H__ */
diff -r b48d8f27fca2 -r fb34514bf76b xen/include/xen/time.h
--- a/xen/include/xen/time.h Fri Oct 29 10:29:14 2010 +0100
+++ b/xen/include/xen/time.h Fri Oct 29 10:40:14 2010 +0100
@@ -10,7 +10,6 @@
#include <xen/types.h>
#include <public/xen.h>
-#include <asm/time.h>
extern int init_xen_time(void);
extern void cstate_restore_tsc(void);
@@ -18,6 +17,7 @@ extern unsigned long cpu_khz;
extern unsigned long cpu_khz;
struct domain;
+struct vcpu;
/*
* System Time
@@ -63,6 +63,8 @@ extern void send_timer_event(struct vcpu
void domain_set_time_offset(struct domain *d, int32_t time_offset_seconds);
+#include <asm/time.h>
+
#endif /* __XEN_TIME_H__ */
/*
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