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Subject[PATCH 6/7] xen: Enable PV clocksource for HVM
Date
PV clocksource can provide a reliable clocksource for HVM running on Xen.

To enable it, put following line to the HVM configure file:

cpuid = [ '0x40000002:edx=0x3' ]
It would set bit 0 and bit 1 in 0x40000002:edx, which enable PV extension
framework and PV clocksource.
Signed-off-by: Sheng Yang <sheng@linux.intel.com>
---
arch/x86/xen/hvmpv.c | 24 ++++++++++++++++++++++++
arch/x86/xen/time.c | 12 +++++++++++-
arch/x86/xen/xen-ops.h | 1 +
3 files changed, 36 insertions(+), 1 deletions(-)
diff --git a/arch/x86/xen/hvmpv.c b/arch/x86/xen/hvmpv.c
index 540eef4..e944caf 100644
--- a/arch/x86/xen/hvmpv.c
+++ b/arch/x86/xen/hvmpv.c
@@ -43,6 +43,8 @@ static void __init xen_hvm_pv_banner(void)
pv_info.name);
printk(KERN_INFO "Xen version: %d.%d%s\n",
version >> 16, version & 0xffff, extra.extraversion);
+ if (xen_hvm_pv_clock_enabled())
+ printk(KERN_INFO "PV feature: PV clocksource enabled\n");
}

static int __init xen_para_available(void)
@@ -82,6 +84,9 @@ static int __init init_hvm_pv_info(void)
if (!(edx & XEN_CPUID_FEAT2_HVM_PV))
return -ENODEV;

+ if (edx & XEN_CPUID_FEAT2_HVM_PV_CLOCK)
+ xen_hvm_pv_features |= XEN_HVM_PV_CLOCK_ENABLED;
+
if (pages < 1)
return -ENODEV;

@@ -112,6 +117,23 @@ static int __init init_shared_info(void)
return 0;
}

+static void __init init_pv_clocksource(void)
+{
+ if (!xen_hvm_pv_clock_enabled())
+ return;
+
+ if (enable_hvm_pv(HVM_PV_CLOCK))
+ BUG();
+
+ pv_time_ops.sched_clock = xen_sched_clock;
+
+ x86_platform.calibrate_tsc = xen_tsc_khz;
+ x86_platform.get_wallclock = xen_get_wallclock;
+ x86_platform.set_wallclock = xen_set_wallclock;
+
+ xen_register_clocksource();
+}
+
void __init xen_guest_init(void)
{
int r;
@@ -134,4 +156,6 @@ void __init xen_guest_init(void)
pv_info = xen_hvm_pv_info;

xen_domain_type = XEN_HVM_DOMAIN;
+
+ init_pv_clocksource();
}
diff --git a/arch/x86/xen/time.c b/arch/x86/xen/time.c
index 0d3f07c..06b3e72 100644
--- a/arch/x86/xen/time.c
+++ b/arch/x86/xen/time.c
@@ -472,11 +472,21 @@ void xen_timer_resume(void)
}
}

+static bool xen_clocksource_enabled;
+
+void xen_register_clocksource(void)
+{
+ if (!xen_clocksource_enabled) {
+ clocksource_register(&xen_clocksource);
+ xen_clocksource_enabled = 1;
+ }
+}
+
__init void xen_time_init(void)
{
int cpu = smp_processor_id();

- clocksource_register(&xen_clocksource);
+ xen_register_clocksource();

if (HYPERVISOR_vcpu_op(VCPUOP_stop_periodic_timer, cpu, NULL) == 0) {
/* Successfully turned off 100Hz tick, so we have the
diff --git a/arch/x86/xen/xen-ops.h b/arch/x86/xen/xen-ops.h
index f9153a3..d56b660 100644
--- a/arch/x86/xen/xen-ops.h
+++ b/arch/x86/xen/xen-ops.h
@@ -48,6 +48,7 @@ cycle_t xen_clocksource_read(void);
void xen_setup_cpu_clockevents(void);
unsigned long xen_tsc_khz(void);
void __init xen_time_init(void);
+void xen_register_clocksource(void);
unsigned long xen_get_wallclock(void);
int xen_set_wallclock(unsigned long time);
unsigned long long xen_sched_clock(void);
--
1.5.4.5


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