[PATCH 7/7] KVM-GST: KVM Steal time registration

Glauber Costa
2011-06-13T23:31:37Z

Register steal time within KVM. Everytime we sample the steal time
information, we update a local variable that tells what was the
last time read. We then account the difference.

Signed-off-by: Glauber Costa <glommer@redhat.com>
CC: Rik van Riel <riel@redhat.com>
CC: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
CC: Peter Zijlstra <peterz@infradead.org>
CC: Avi Kivity <avi@redhat.com>
CC: Anthony Liguori <aliguori@us.ibm.com>
CC: Eric B Munson <emunson@mgebm.net>
---
Documentation/kernel-parameters.txt | 4 ++
arch/x86/include/asm/kvm_para.h | 1 +
arch/x86/kernel/kvm.c | 72 +++++++++++++++++++++++++++++++++++
arch/x86/kernel/kvmclock.c | 2 +
4 files changed, 79 insertions(+), 0 deletions(-)

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index fd248a31..a722574 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -1737,6 +1737,10 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
fault handling.

+ no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
+ steal time is computed, but won't influence scheduler
+ behaviour
+
nolapic [X86-32,APIC] Do not enable or use the local APIC.

nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
diff --git a/arch/x86/include/asm/kvm_para.h b/arch/x86/include/asm/kvm_para.h
index 0341e61..2a8f2a5 100644
--- a/arch/x86/include/asm/kvm_para.h
+++ b/arch/x86/include/asm/kvm_para.h
@@ -94,6 +94,7 @@ struct kvm_vcpu_pv_apf_data {

extern void kvmclock_init(void);
extern int kvm_register_clock(char *txt);
+extern void kvm_disable_steal_time(void);

/* This instruction is vmcall. On non-VT architectures, it will generate a
diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
index 33c07b0..5a5ac19 100644
--- a/arch/x86/kernel/kvm.c
+++ b/arch/x86/kernel/kvm.c
@@ -51,6 +51,15 @@ static int parse_no_kvmapf(char *arg)

early_param("no-kvmapf", parse_no_kvmapf);

+static int steal_acc = 1;
+static int parse_no_stealacc(char *arg)
+{
+ steal_acc = 0;
+ return 0;
+}
+
+early_param("no-steal-acc", parse_no_stealacc);
+
struct kvm_para_state {
u8 mmu_queue[MMU_QUEUE_SIZE];
int mmu_queue_len;
@@ -58,6 +67,8 @@ struct kvm_para_state {

static DEFINE_PER_CPU(struct kvm_para_state, para_state);
static DEFINE_PER_CPU(struct kvm_vcpu_pv_apf_data, apf_reason) __aligned(64);
+static DEFINE_PER_CPU(struct kvm_steal_time, steal_time) __aligned(64);
+static int has_steal_clock = 0;

static struct kvm_para_state *kvm_para_state(void)
{
@@ -483,23 +494,66 @@ static struct notifier_block kvm_pv_reboot_nb = {
.notifier_call = kvm_pv_reboot_notify,
};

+static void kvm_register_steal_time(void)
+{
+ int cpu = smp_processor_id();
+ struct kvm_steal_time *st = &per_cpu(steal_time, cpu);
+
+ if (!has_steal_clock)
+ return;
+
+ memset(st, 0, sizeof(*st));
+
+ wrmsrl(MSR_KVM_STEAL_TIME, (__pa(st) | KVM_MSR_ENABLED));
+ printk(KERN_INFO "kvm-stealtime: cpu %d, msr %lx\n",
+ cpu, __pa(st));
+}
+
+static u64 kvm_steal_clock(int cpu)
+{
+ u64 steal;
+ struct kvm_steal_time *src;
+ int version;
+
+ src = &per_cpu(steal_time, cpu);
+ do {
+ version = src->version;
+ rmb();
+ steal = src->steal;
+ rmb();
+ } while ((version & 1) || (version != src->version));
+
+ return steal;
+}
+
#ifdef CONFIG_SMP
static void __init kvm_smp_prepare_boot_cpu(void)
{
#ifdef CONFIG_KVM_CLOCK
WARN_ON(kvm_register_clock("primary cpu clock"));
#endif
+ kvm_register_steal_time();
kvm_guest_cpu_init();
native_smp_prepare_boot_cpu();
}

static void __cpuinit kvm_guest_cpu_online(void *dummy)
{
+ kvm_register_steal_time();
kvm_guest_cpu_init();
}

+void kvm_disable_steal_time(void)
+{
+ if (!has_steal_clock)
+ return;
+
+ wrmsr(MSR_KVM_STEAL_TIME, 0, 0);
+}
+
static void kvm_guest_cpu_offline(void *dummy)
{
+ kvm_disable_steal_time();
kvm_pv_disable_apf(NULL);
apf_task_wake_all();
}
@@ -548,6 +602,11 @@ void __init kvm_guest_init(void)
if (kvm_para_has_feature(KVM_FEATURE_ASYNC_PF))
x86_init.irqs.trap_init = kvm_apf_trap_init;

+ if (kvm_para_has_feature(KVM_FEATURE_STEAL_TIME)) {
+ has_steal_clock = 1;
+ pv_time_ops.steal_clock = kvm_steal_clock;
+ }
+
#ifdef CONFIG_SMP
smp_ops.smp_prepare_boot_cpu = kvm_smp_prepare_boot_cpu;
register_cpu_notifier(&kvm_cpu_notifier);
@@ -555,3 +614,16 @@ void __init kvm_guest_init(void)
kvm_guest_cpu_init();
#endif
}
+
+static __init int activate_jump_labels(void)
+{
+ if (has_steal_clock) {
+ jump_label_inc(&paravirt_steal_enabled);
+ if (steal_acc)
+ jump_label_inc(&paravirt_steal_rq_enabled);
+ }
+
+ return 0;
+}
+arch_initcall(activate_jump_labels);
+
diff --git a/arch/x86/kernel/kvmclock.c b/arch/x86/kernel/kvmclock.c
index 6389a6b..c1a0188 100644
--- a/arch/x86/kernel/kvmclock.c
+++ b/arch/x86/kernel/kvmclock.c
@@ -160,6 +160,7 @@ static void __cpuinit kvm_setup_secondary_clock(void)
static void kvm_crash_shutdown(struct pt_regs *regs)
{
native_write_msr(msr_kvm_system_time, 0, 0);
+ kvm_disable_steal_time();
native_machine_crash_shutdown(regs);
}
#endif
@@ -167,6 +168,7 @@ static void kvm_crash_shutdown(struct pt_regs *regs)
static void kvm_shutdown(void)
{
native_write_msr(msr_kvm_system_time, 0, 0);
+ kvm_disable_steal_time();
native_machine_shutdown();
}

--
1.7.3.4