KVM: Steal time implementation
To implement steal time, we need the hypervisor to pass the guest
information about how much time was spent running other processes
outside the VM, while the vcpu had meaningful work to do - halt
time does not count.
This information is acquired through the run_delay field of
delayacct/schedstats infrastructure, that counts time spent in a
runqueue but not running.
Steal time is a per-cpu information, so the traditional MSR-based
infrastructure is used. A new msr, KVM_MSR_STEAL_TIME, holds the
memory area address containing information about steal time
This patch contains the hypervisor part of the steal time infrasructure,
and can be backported independently of the guest portion.
[avi, yongjie: export delayacct_on, to avoid build failures in some configs]
Signed-off-by: Glauber Costa <glommer@redhat.com>
Tested-by: Eric B Munson <emunson@mgebm.net>
CC: Rik van Riel <riel@redhat.com>
CC: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
CC: Peter Zijlstra <peterz@infradead.org>
CC: Anthony Liguori <aliguori@us.ibm.com>
Signed-off-by: Yongjie Ren <yongjie.ren@intel.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
diff --git a/arch/x86/kvm/Kconfig b/arch/x86/kvm/Kconfig
index 50f6364..99c3f05 100644
--- a/arch/x86/kvm/Kconfig
+++ b/arch/x86/kvm/Kconfig
@@ -31,6 +31,7 @@
select KVM_ASYNC_PF
select USER_RETURN_NOTIFIER
select KVM_MMIO
+ select TASK_DELAY_ACCT
---help---
Support hosting fully virtualized guest machines using hardware
virtualization extensions. You will need a fairly recent
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 0b803f0..c96cdc0 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -808,12 +808,12 @@
* kvm-specific. Those are put in the beginning of the list.
*/
-#define KVM_SAVE_MSRS_BEGIN 8
+#define KVM_SAVE_MSRS_BEGIN 9
static u32 msrs_to_save[] = {
MSR_KVM_SYSTEM_TIME, MSR_KVM_WALL_CLOCK,
MSR_KVM_SYSTEM_TIME_NEW, MSR_KVM_WALL_CLOCK_NEW,
HV_X64_MSR_GUEST_OS_ID, HV_X64_MSR_HYPERCALL,
- HV_X64_MSR_APIC_ASSIST_PAGE, MSR_KVM_ASYNC_PF_EN,
+ HV_X64_MSR_APIC_ASSIST_PAGE, MSR_KVM_ASYNC_PF_EN, MSR_KVM_STEAL_TIME,
MSR_IA32_SYSENTER_CS, MSR_IA32_SYSENTER_ESP, MSR_IA32_SYSENTER_EIP,
MSR_STAR,
#ifdef CONFIG_X86_64
@@ -1488,6 +1488,35 @@
}
}
+static void accumulate_steal_time(struct kvm_vcpu *vcpu)
+{
+ u64 delta;
+
+ if (!(vcpu->arch.st.msr_val & KVM_MSR_ENABLED))
+ return;
+
+ delta = current->sched_info.run_delay - vcpu->arch.st.last_steal;
+ vcpu->arch.st.last_steal = current->sched_info.run_delay;
+ vcpu->arch.st.accum_steal = delta;
+}
+
+static void record_steal_time(struct kvm_vcpu *vcpu)
+{
+ if (!(vcpu->arch.st.msr_val & KVM_MSR_ENABLED))
+ return;
+
+ if (unlikely(kvm_read_guest_cached(vcpu->kvm, &vcpu->arch.st.stime,
+ &vcpu->arch.st.steal, sizeof(struct kvm_steal_time))))
+ return;
+
+ vcpu->arch.st.steal.steal += vcpu->arch.st.accum_steal;
+ vcpu->arch.st.steal.version += 2;
+ vcpu->arch.st.accum_steal = 0;
+
+ kvm_write_guest_cached(vcpu->kvm, &vcpu->arch.st.stime,
+ &vcpu->arch.st.steal, sizeof(struct kvm_steal_time));
+}
+
int kvm_set_msr_common(struct kvm_vcpu *vcpu, u32 msr, u64 data)
{
switch (msr) {
@@ -1570,6 +1599,33 @@
if (kvm_pv_enable_async_pf(vcpu, data))
return 1;
break;
+ case MSR_KVM_STEAL_TIME:
+
+ if (unlikely(!sched_info_on()))
+ return 1;
+
+ if (data & KVM_STEAL_RESERVED_MASK)
+ return 1;
+
+ if (kvm_gfn_to_hva_cache_init(vcpu->kvm, &vcpu->arch.st.stime,
+ data & KVM_STEAL_VALID_BITS))
+ return 1;
+
+ vcpu->arch.st.msr_val = data;
+
+ if (!(data & KVM_MSR_ENABLED))
+ break;
+
+ vcpu->arch.st.last_steal = current->sched_info.run_delay;
+
+ preempt_disable();
+ accumulate_steal_time(vcpu);
+ preempt_enable();
+
+ kvm_make_request(KVM_REQ_STEAL_UPDATE, vcpu);
+
+ break;
+
case MSR_IA32_MCG_CTL:
case MSR_IA32_MCG_STATUS:
case MSR_IA32_MC0_CTL ... MSR_IA32_MC0_CTL + 4 * KVM_MAX_MCE_BANKS - 1:
@@ -1855,6 +1911,9 @@
case MSR_KVM_ASYNC_PF_EN:
data = vcpu->arch.apf.msr_val;
break;
+ case MSR_KVM_STEAL_TIME:
+ data = vcpu->arch.st.msr_val;
+ break;
case MSR_IA32_P5_MC_ADDR:
case MSR_IA32_P5_MC_TYPE:
case MSR_IA32_MCG_CAP:
@@ -2166,6 +2225,9 @@
kvm_migrate_timers(vcpu);
vcpu->cpu = cpu;
}
+
+ accumulate_steal_time(vcpu);
+ kvm_make_request(KVM_REQ_STEAL_UPDATE, vcpu);
}
void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu)
@@ -2487,6 +2549,10 @@
(1 << KVM_FEATURE_CLOCKSOURCE2) |
(1 << KVM_FEATURE_ASYNC_PF) |
(1 << KVM_FEATURE_CLOCKSOURCE_STABLE_BIT);
+
+ if (sched_info_on())
+ entry->eax |= (1 << KVM_FEATURE_STEAL_TIME);
+
entry->ebx = 0;
entry->ecx = 0;
entry->edx = 0;
@@ -5470,6 +5536,9 @@
r = 1;
goto out;
}
+ if (kvm_check_request(KVM_REQ_STEAL_UPDATE, vcpu))
+ record_steal_time(vcpu);
+
}
r = kvm_mmu_reload(vcpu);
@@ -6206,6 +6275,7 @@
kvm_make_request(KVM_REQ_EVENT, vcpu);
vcpu->arch.apf.msr_val = 0;
+ vcpu->arch.st.msr_val = 0;
kvmclock_reset(vcpu);