[PATCH v4 07/11] KVM: arm/arm64: optimize VCPU RUN

Andrew Jones
2017-05-16T02:20:54Z

We can make a small optimization by not checking the state of
the power_off field on each run. This is done by treating
power_off like pause, only checking it when we get the EXIT
VCPU request. When a VCPU powers off another VCPU the EXIT
request is already made, so we just need to make sure the
request is also made on self power off. kvm_vcpu_kick() isn't
necessary for these cases, as the VCPU would just be kicking
itself, but we add it anyway as a self kick doesn't cost much,
and it makes the code more future-proof.

Signed-off-by: Andrew Jones <drjones@redhat.com>
---
virt/kvm/arm/arm.c | 19 +++++++++++--------
virt/kvm/arm/psci.c | 2 ++
2 files changed, 13 insertions(+), 8 deletions(-)

diff --git a/virt/kvm/arm/arm.c b/virt/kvm/arm/arm.c
index 21a4db90073f..9379b1d75ad3 100644
--- a/virt/kvm/arm/arm.c
+++ b/virt/kvm/arm/arm.c
@@ -368,6 +368,13 @@ void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu)
kvm_timer_vcpu_put(vcpu);
}

+static void vcpu_power_off(struct kvm_vcpu *vcpu)
+{
+ vcpu->arch.power_off = true;
+ kvm_make_request(KVM_REQ_VCPU_EXIT, vcpu);
+ kvm_vcpu_kick(vcpu);
+}
+
int kvm_arch_vcpu_ioctl_get_mpstate(struct kvm_vcpu *vcpu,
struct kvm_mp_state *mp_state)
{
@@ -387,7 +394,7 @@ int kvm_arch_vcpu_ioctl_set_mpstate(struct kvm_vcpu *vcpu,
vcpu->arch.power_off = false;
break;
case KVM_MP_STATE_STOPPED:
- vcpu->arch.power_off = true;
+ vcpu_power_off(vcpu);
break;
default:
return -EINVAL;
@@ -557,7 +564,7 @@ static void vcpu_sleep(struct kvm_vcpu *vcpu)
swait_event_interruptible(*wq, ((!vcpu->arch.power_off) &&
(!vcpu->arch.pause)));

- if (vcpu->arch.pause) {
+ if (vcpu->arch.power_off || vcpu->arch.pause) {
/* Awaken to handle a signal, request we sleep again later. */
kvm_make_request(KVM_REQ_VCPU_EXIT, vcpu);
}
@@ -623,9 +630,6 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *run)

check_vcpu_requests(vcpu);

- if (vcpu->arch.power_off)
- vcpu_sleep(vcpu);
-
/*
* Preparing the interrupts to be injected also
* involves poking the GIC, which must be done in a
@@ -662,8 +666,7 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *run)
smp_store_mb(vcpu->mode, IN_GUEST_MODE);

if (ret <= 0 || need_new_vmid_gen(vcpu->kvm) ||
- kvm_request_pending(vcpu) ||
- vcpu->arch.power_off) {
+ kvm_request_pending(vcpu)) {
vcpu->mode = OUTSIDE_GUEST_MODE;
local_irq_enable();
kvm_pmu_sync_hwstate(vcpu);
@@ -896,7 +899,7 @@ static int kvm_arch_vcpu_ioctl_vcpu_init(struct kvm_vcpu *vcpu,
* Handle the "start in power-off" case.
*/
if (test_bit(KVM_ARM_VCPU_POWER_OFF, vcpu->arch.features))
- vcpu->arch.power_off = true;
+ vcpu_power_off(vcpu);
else
vcpu->arch.power_off = false;

diff --git a/virt/kvm/arm/psci.c b/virt/kvm/arm/psci.c
index f189d0ad30d5..4a436685c552 100644
--- a/virt/kvm/arm/psci.c
+++ b/virt/kvm/arm/psci.c
@@ -65,6 +65,8 @@ static unsigned long kvm_psci_vcpu_suspend(struct kvm_vcpu *vcpu)
static void kvm_psci_vcpu_off(struct kvm_vcpu *vcpu)
{
vcpu->arch.power_off = true;
+ kvm_make_request(KVM_REQ_VCPU_EXIT, vcpu);
+ kvm_vcpu_kick(vcpu);
}

static unsigned long kvm_psci_vcpu_on(struct kvm_vcpu *source_vcpu)
--
2.9.3