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Date: Thu, 19 Aug 2010 22:07:39 -1000
From: Zachary Amsden <zamsden@...hat.com>
To: kvm@...r.kernel.org
Cc: Zachary Amsden <zamsden@...hat.com>, Avi Kivity <avi@...hat.com>,
Marcelo Tosatti <mtosatti@...hat.com>,
Glauber Costa <glommer@...hat.com>,
Thomas Gleixner <tglx@...utronix.de>,
John Stultz <johnstul@...ibm.com>, linux-kernel@...r.kernel.org
Subject: [KVM timekeeping 25/35] Add clock catchup mode
Make the clock update handler handle generic clock synchronization,
not just KVM clock. We add a catchup mode which keeps passthrough
TSC in line with absolute guest TSC.
Signed-off-by: Zachary Amsden <zamsden@...hat.com>
---
arch/x86/include/asm/kvm_host.h | 1 +
arch/x86/kvm/x86.c | 55 ++++++++++++++++++++++++++------------
2 files changed, 38 insertions(+), 18 deletions(-)
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 3a54cc1..ec1dc3a 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -343,6 +343,7 @@ struct kvm_vcpu_arch {
u64 last_kernel_ns;
u64 last_tsc_nsec;
u64 last_tsc_write;
+ bool tsc_rebase;
bool nmi_pending;
bool nmi_injected;
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index ac0b2d9..a4215d7 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -927,6 +927,15 @@ static void kvm_arch_set_tsc_khz(struct kvm *kvm, u32 this_tsc_khz)
kvm->arch.virtual_tsc_khz = this_tsc_khz;
}
+static u64 compute_guest_tsc(struct kvm_vcpu *vcpu, s64 kernel_ns)
+{
+ u64 tsc = pvclock_scale_delta(kernel_ns-vcpu->arch.last_tsc_nsec,
+ vcpu->kvm->arch.virtual_tsc_mult,
+ vcpu->kvm->arch.virtual_tsc_shift);
+ tsc += vcpu->arch.last_tsc_write;
+ return tsc;
+}
+
void kvm_write_tsc(struct kvm_vcpu *vcpu, u64 data)
{
struct kvm *kvm = vcpu->kvm;
@@ -984,22 +993,29 @@ static int kvm_guest_time_update(struct kvm_vcpu *v)
unsigned long this_tsc_khz;
s64 kernel_ns, max_kernel_ns;
u64 tsc_timestamp;
-
- if ((!vcpu->time_page))
- return 0;
+ bool catchup = (!vcpu->time_page);
/* Keep irq disabled to prevent changes to the clock */
local_irq_save(flags);
kvm_get_msr(v, MSR_IA32_TSC, &tsc_timestamp);
kernel_ns = getnsboottime();
this_tsc_khz = __get_cpu_var(cpu_tsc_khz);
- local_irq_restore(flags);
if (unlikely(this_tsc_khz == 0)) {
+ local_irq_restore(flags);
kvm_make_request(KVM_REQ_CLOCK_UPDATE, v);
return 1;
}
+ if (catchup) {
+ u64 tsc = compute_guest_tsc(v, kernel_ns);
+ if (tsc > tsc_timestamp)
+ kvm_x86_ops->adjust_tsc_offset(v, tsc-tsc_timestamp);
+ }
+ local_irq_restore(flags);
+ if (catchup)
+ return 0;
+
/*
* Time as measured by the TSC may go backwards when resetting the base
* tsc_timestamp. The reason for this is that the TSC resolution is
@@ -1065,14 +1081,9 @@ static int kvm_guest_time_update(struct kvm_vcpu *v)
return 0;
}
-static int kvm_request_guest_time_update(struct kvm_vcpu *v)
+static void kvm_request_clock_update(struct kvm_vcpu *v)
{
- struct kvm_vcpu_arch *vcpu = &v->arch;
-
- if (!vcpu->time_page)
- return 0;
kvm_make_request(KVM_REQ_CLOCK_UPDATE, v);
- return 1;
}
static bool msr_mtrr_valid(unsigned msr)
@@ -1398,6 +1409,7 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, u32 msr, u64 data)
}
vcpu->arch.time = data;
+ kvm_request_clock_update(vcpu);
/* we verify if the enable bit is set... */
if (!(data & 1))
@@ -1413,8 +1425,6 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, u32 msr, u64 data)
kvm_release_page_clean(vcpu->arch.time_page);
vcpu->arch.time_page = NULL;
}
-
- kvm_request_guest_time_update(vcpu);
break;
}
case MSR_IA32_MCG_CTL:
@@ -1929,16 +1939,20 @@ void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
}
kvm_x86_ops->vcpu_load(vcpu, cpu);
- if (unlikely(vcpu->cpu != cpu) || check_tsc_unstable()) {
+ if (unlikely(vcpu->cpu != cpu) || vcpu->arch.tsc_rebase) {
/* Make sure TSC doesn't go backwards */
s64 tsc_delta = !vcpu->arch.last_host_tsc ? 0 :
native_read_tsc() - vcpu->arch.last_host_tsc;
if (tsc_delta < 0)
mark_tsc_unstable("KVM discovered backwards TSC");
- if (check_tsc_unstable())
+ if (check_tsc_unstable()) {
kvm_x86_ops->adjust_tsc_offset(vcpu, -tsc_delta);
- kvm_migrate_timers(vcpu);
+ kvm_make_request(KVM_REQ_CLOCK_UPDATE, vcpu);
+ }
+ if (vcpu->cpu != cpu)
+ kvm_migrate_timers(vcpu);
vcpu->cpu = cpu;
+ vcpu->arch.tsc_rebase = 0;
}
}
@@ -1947,6 +1961,12 @@ void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu)
kvm_x86_ops->vcpu_put(vcpu);
kvm_put_guest_fpu(vcpu);
vcpu->arch.last_host_tsc = native_read_tsc();
+
+ /* For unstable TSC, force compensation and catchup on next CPU */
+ if (check_tsc_unstable()) {
+ vcpu->arch.tsc_rebase = 1;
+ kvm_make_request(KVM_REQ_CLOCK_UPDATE, vcpu);
+ }
}
static int is_efer_nx(void)
@@ -4307,8 +4327,7 @@ static int kvmclock_cpufreq_notifier(struct notifier_block *nb, unsigned long va
kvm_for_each_vcpu(i, vcpu, kvm) {
if (vcpu->cpu != freq->cpu)
continue;
- if (!kvm_request_guest_time_update(vcpu))
- continue;
+ kvm_request_clock_update(vcpu);
if (vcpu->cpu != smp_processor_id())
send_ipi = 1;
}
@@ -5597,7 +5616,7 @@ int kvm_arch_hardware_enable(void *garbage)
list_for_each_entry(kvm, &vm_list, vm_list)
kvm_for_each_vcpu(i, vcpu, kvm)
if (vcpu->cpu == smp_processor_id())
- kvm_request_guest_time_update(vcpu);
+ kvm_request_clock_update(vcpu);
return kvm_x86_ops->hardware_enable(garbage);
}
--
1.7.1
--
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