[PATCH 4/5] KVM: arm/arm64: improve kvm_arch_vcpu_runnable

Andrew Jones
2017-09-29T11:30:41Z

Conceptually, kvm_arch_vcpu_runnable() should be "not waiting,
or waiting for interrupts and interrupts are pending",

!waiting-uninterruptable &&
(!waiting-for-interrupts || interrupts-pending)

but the implementation was only

!waiting-uninterruptable && interrupts-pending

Thanks to the context of the two callers there wasn't an issue,
however, to future-proof the function, this patch implements the
conceptual condition by applying mp_state to track waiting-
uninterruptable vs. waiting-for-interrupts.

Signed-off-by: Andrew Jones <drjones@redhat.com>
---
Documentation/virtual/kvm/api.txt | 10 ++++++----
virt/kvm/arm/arm.c | 13 +++++++++----
2 files changed, 15 insertions(+), 8 deletions(-)

diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
index e63a35fafef0..7c0bb1ae10a2 100644
--- a/Documentation/virtual/kvm/api.txt
+++ b/Documentation/virtual/kvm/api.txt
@@ -1071,7 +1071,7 @@ Possible values are:
- KVM_MP_STATE_INIT_RECEIVED: the vcpu has received an INIT signal, and is
now ready for a SIPI [x86]
- KVM_MP_STATE_HALTED: the vcpu has executed a HLT instruction and
- is waiting for an interrupt [x86]
+ is waiting for an interrupt [x86,arm/arm64]
- KVM_MP_STATE_SIPI_RECEIVED: the vcpu has just received a SIPI (vector
accessible via KVM_GET_VCPU_EVENTS) [x86]
- KVM_MP_STATE_STOPPED: the vcpu is stopped [s390,arm/arm64]
@@ -1087,8 +1087,9 @@ these architectures.

For arm/arm64:

-The only states that are valid are KVM_MP_STATE_STOPPED and
-KVM_MP_STATE_RUNNABLE which reflect if the vcpu is paused or not.
+The only states that are valid are KVM_MP_STATE_STOPPED, KVM_MP_STATE_HALTED,
+and KVM_MP_STATE_RUNNABLE which reflect if the vcpu is powered-off, waiting
+for interrupts, or powered-on and not waiting for interrupts.

4.39 KVM_SET_MP_STATE

@@ -1108,7 +1109,8 @@ these architectures.
For arm/arm64:

The only states that are valid are KVM_MP_STATE_STOPPED and
-KVM_MP_STATE_RUNNABLE which reflect if the vcpu should be paused or not.
+KVM_MP_STATE_RUNNABLE which reflect if the vcpu should be
+powered-off or not.

4.40 KVM_SET_IDENTITY_MAP_ADDR

diff --git a/virt/kvm/arm/arm.c b/virt/kvm/arm/arm.c
index 220a3dbda76c..5bc9b0d2fd0f 100644
--- a/virt/kvm/arm/arm.c
+++ b/virt/kvm/arm/arm.c
@@ -414,13 +414,16 @@ static bool vcpu_should_sleep(struct kvm_vcpu *vcpu)
* kvm_arch_vcpu_runnable - determine if the vcpu can be scheduled
* @vcpu: The VCPU pointer
*
- * If the guest CPU is not waiting for interrupts or an interrupt line is
- * asserted, the CPU is by definition runnable.
+ * If the VCPU is not waiting at all (including sleeping, which is waiting
+ * uninterruptably), or it's waiting for interrupts but interrupts are
+ * pending, then it is by definition runnable.
*/
int kvm_arch_vcpu_runnable(struct kvm_vcpu *vcpu)
{
- return (!!vcpu->arch.irq_lines || kvm_vgic_vcpu_pending_irq(vcpu))
- && !vcpu_should_sleep(vcpu);
+ return !vcpu_should_sleep(vcpu) &&
+ (vcpu->arch.mp_state != KVM_MP_STATE_HALTED ||
+ (!!vcpu->arch.irq_lines ||
+ kvm_vgic_vcpu_pending_irq(vcpu)));
}

bool kvm_arch_vcpu_in_kernel(struct kvm_vcpu *vcpu)
@@ -582,7 +585,9 @@ void kvm_arm_emulate_wfe(struct kvm_vcpu *vcpu)
void kvm_arm_emulate_wfi(struct kvm_vcpu *vcpu)
{
vcpu->stat.wfi_exit_stat++;
+ vcpu->arch.mp_state = KVM_MP_STATE_HALTED;
kvm_vcpu_block(vcpu);
+ vcpu->arch.mp_state = KVM_MP_STATE_RUNNABLE;
kvm_clear_request(KVM_REQ_UNHALT, vcpu);
}

--
2.13.5