From: marc.zyngier@arm.com (Marc Zyngier)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH 05/12] arm/arm64: KVM: Properly account for guest CPU time
Date: Fri, 19 Jun 2015 13:53:09 +0100 [thread overview]
Message-ID: <1434718396-13110-6-git-send-email-marc.zyngier@arm.com> (raw)
In-Reply-To: <1434718396-13110-1-git-send-email-marc.zyngier@arm.com>
From: Christoffer Dall <christoffer.dall@linaro.org>
Until now we have been calling kvm_guest_exit after re-enabling
interrupts when we come back from the guest, but this has the
unfortunate effect that CPU time accounting done in the context of timer
interrupts occurring while the guest is running doesn't properly notice
that the time since the last tick was spent in the guest.
Inspired by the comment in the x86 code, move the kvm_guest_exit() call
below the local_irq_enable() call and change __kvm_guest_exit() to
kvm_guest_exit(), because we are now calling this function with
interrupts enabled. We have to now explicitly disable preemption and
not enable preemption before we've called kvm_guest_exit(), since
otherwise we could be preempted and everything happening before we
eventually get scheduled again would be accounted for as guest time.
At the same time, move the trace_kvm_exit() call outside of the atomic
section, since there is no reason for us to do that with interrupts
disabled.
Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
---
arch/arm/kvm/arm.c | 21 +++++++++++++++++----
1 file changed, 17 insertions(+), 4 deletions(-)
diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c
index 7e82330..bc738d2 100644
--- a/arch/arm/kvm/arm.c
+++ b/arch/arm/kvm/arm.c
@@ -531,6 +531,7 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *run)
kvm_vgic_flush_hwstate(vcpu);
kvm_timer_flush_hwstate(vcpu);
+ preempt_disable();
local_irq_disable();
/*
@@ -543,6 +544,7 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *run)
if (ret <= 0 || need_new_vmid_gen(vcpu->kvm)) {
local_irq_enable();
+ preempt_enable();
kvm_timer_sync_hwstate(vcpu);
kvm_vgic_sync_hwstate(vcpu);
continue;
@@ -558,8 +560,10 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *run)
ret = kvm_call_hyp(__kvm_vcpu_run, vcpu);
vcpu->mode = OUTSIDE_GUEST_MODE;
- __kvm_guest_exit();
- trace_kvm_exit(kvm_vcpu_trap_get_class(vcpu), *vcpu_pc(vcpu));
+ /*
+ * Back from guest
+ *************************************************************/
+
/*
* We may have taken a host interrupt in HYP mode (ie
* while executing the guest). This interrupt is still
@@ -573,8 +577,17 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *run)
local_irq_enable();
/*
- * Back from guest
- *************************************************************/
+ * We do local_irq_enable() before calling kvm_guest_exit() so
+ * that if a timer interrupt hits while running the guest we
+ * account that tick as being spent in the guest. We enable
+ * preemption after calling kvm_guest_exit() so that if we get
+ * preempted we make sure ticks after that is not counted as
+ * guest time.
+ */
+ kvm_guest_exit();
+ trace_kvm_exit(kvm_vcpu_trap_get_class(vcpu), *vcpu_pc(vcpu));
+ preempt_enable();
+
kvm_timer_sync_hwstate(vcpu);
kvm_vgic_sync_hwstate(vcpu);
--
2.1.4
WARNING: multiple messages have this Message-ID (diff)
From: Marc Zyngier <marc.zyngier@arm.com>
To: Paolo Bonzini <pbonzini@redhat.com>,
Marcelo Tosatti <mtosatti@redhat.com>,
Gleb Natapov <gleb@kernel.org>
Cc: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>,
kvm@vger.kernel.org, Andre Przywara <andre.przywara@arm.com>,
linux-arm-kernel@lists.infradead.org,
Firo Yang <firogm@gmail.com>, Tiejun Chen <tiejun.chen@intel.com>,
kvmarm@lists.cs.columbia.edu
Subject: [PATCH 05/12] arm/arm64: KVM: Properly account for guest CPU time
Date: Fri, 19 Jun 2015 13:53:09 +0100 [thread overview]
Message-ID: <1434718396-13110-6-git-send-email-marc.zyngier@arm.com> (raw)
In-Reply-To: <1434718396-13110-1-git-send-email-marc.zyngier@arm.com>
From: Christoffer Dall <christoffer.dall@linaro.org>
Until now we have been calling kvm_guest_exit after re-enabling
interrupts when we come back from the guest, but this has the
unfortunate effect that CPU time accounting done in the context of timer
interrupts occurring while the guest is running doesn't properly notice
that the time since the last tick was spent in the guest.
Inspired by the comment in the x86 code, move the kvm_guest_exit() call
below the local_irq_enable() call and change __kvm_guest_exit() to
kvm_guest_exit(), because we are now calling this function with
interrupts enabled. We have to now explicitly disable preemption and
not enable preemption before we've called kvm_guest_exit(), since
otherwise we could be preempted and everything happening before we
eventually get scheduled again would be accounted for as guest time.
At the same time, move the trace_kvm_exit() call outside of the atomic
section, since there is no reason for us to do that with interrupts
disabled.
Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
---
arch/arm/kvm/arm.c | 21 +++++++++++++++++----
1 file changed, 17 insertions(+), 4 deletions(-)
diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c
index 7e82330..bc738d2 100644
--- a/arch/arm/kvm/arm.c
+++ b/arch/arm/kvm/arm.c
@@ -531,6 +531,7 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *run)
kvm_vgic_flush_hwstate(vcpu);
kvm_timer_flush_hwstate(vcpu);
+ preempt_disable();
local_irq_disable();
/*
@@ -543,6 +544,7 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *run)
if (ret <= 0 || need_new_vmid_gen(vcpu->kvm)) {
local_irq_enable();
+ preempt_enable();
kvm_timer_sync_hwstate(vcpu);
kvm_vgic_sync_hwstate(vcpu);
continue;
@@ -558,8 +560,10 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *run)
ret = kvm_call_hyp(__kvm_vcpu_run, vcpu);
vcpu->mode = OUTSIDE_GUEST_MODE;
- __kvm_guest_exit();
- trace_kvm_exit(kvm_vcpu_trap_get_class(vcpu), *vcpu_pc(vcpu));
+ /*
+ * Back from guest
+ *************************************************************/
+
/*
* We may have taken a host interrupt in HYP mode (ie
* while executing the guest). This interrupt is still
@@ -573,8 +577,17 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *run)
local_irq_enable();
/*
- * Back from guest
- *************************************************************/
+ * We do local_irq_enable() before calling kvm_guest_exit() so
+ * that if a timer interrupt hits while running the guest we
+ * account that tick as being spent in the guest. We enable
+ * preemption after calling kvm_guest_exit() so that if we get
+ * preempted we make sure ticks after that is not counted as
+ * guest time.
+ */
+ kvm_guest_exit();
+ trace_kvm_exit(kvm_vcpu_trap_get_class(vcpu), *vcpu_pc(vcpu));
+ preempt_enable();
+
kvm_timer_sync_hwstate(vcpu);
kvm_vgic_sync_hwstate(vcpu);
--
2.1.4
next prev parent reply other threads:[~2015-06-19 12:53 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-06-19 12:53 [PULL] KVM/ARM changes for 4.2 Marc Zyngier
2015-06-19 12:53 ` Marc Zyngier
2015-06-19 12:53 ` [PATCH 01/12] ARM: KVM: Remove pointless void pointer cast Marc Zyngier
2015-06-19 12:53 ` Marc Zyngier
2015-06-19 12:53 ` [PATCH 02/12] KVM: arm64: add active register handling to GICv3 emulation as well Marc Zyngier
2015-06-19 12:53 ` Marc Zyngier
2015-06-19 12:53 ` [PATCH 03/12] arm: KVM: force execution of HCPTR access on VM exit Marc Zyngier
2015-06-19 12:53 ` Marc Zyngier
2015-06-19 12:53 ` [PATCH 04/12] kvm: remove one useless check extension Marc Zyngier
2015-06-19 12:53 ` Marc Zyngier
2015-06-19 12:53 ` Marc Zyngier [this message]
2015-06-19 12:53 ` [PATCH 05/12] arm/arm64: KVM: Properly account for guest CPU time Marc Zyngier
2015-07-10 14:16 ` KVM/ARM: trap every load /store instruction hiwu
2015-11-02 18:36 ` Christopher Covington
2015-06-19 12:53 ` [PATCH 06/12] KVM: arm/arm64: Enable the KVM-VFIO device Marc Zyngier
2015-06-19 12:53 ` Marc Zyngier
2015-06-19 12:53 ` [PATCH 07/12] KVM: arm64: fix misleading comments in save/restore Marc Zyngier
2015-06-19 12:53 ` Marc Zyngier
2015-06-19 12:53 ` [PATCH 08/12] ARM: kvm: psci: fix handling of unimplemented functions Marc Zyngier
2015-06-19 12:53 ` Marc Zyngier
2015-06-19 12:53 ` [PATCH 09/12] KVM: arm: vgic: Drop useless Group0 warning Marc Zyngier
2015-06-19 12:53 ` Marc Zyngier
2015-06-19 12:53 ` [PATCH 10/12] arm/arm64: KVM: vgic: Do not save GICH_HCR / ICH_HCR_EL2 Marc Zyngier
2015-06-19 12:53 ` Marc Zyngier
2015-06-19 12:53 ` [PATCH 11/12] KVM: arm/arm64: vgic: Avoid injecting reserved IRQ numbers Marc Zyngier
2015-06-19 12:53 ` Marc Zyngier
2015-06-19 12:53 ` [PATCH 12/12] KVM: arm/arm64: vgic: Remove useless arm-gic.h #include Marc Zyngier
2015-06-19 12:53 ` Marc Zyngier
2015-06-19 15:16 ` [PULL] KVM/ARM changes for 4.2 Paolo Bonzini
2015-06-19 15:16 ` Paolo Bonzini
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