We are currently not implementing the PSCI spec completely, as we do not
take handle the situation where two VCPUs are attempting to turn on a
third VCPU at the same time. The PSCI implementation should make sure
that only one requesting VCPU wins the race and that the other receives
PSCI_RET_ON_PENDING.
Implement this by changing the VCPU power state to a tristate enum and
ensure only a single VCPU can turn on another VCPU at a given time using
a cmpxchg operation.
Signed-off-by: Christoffer Dall <christoffer.dall@xxxxxxx>
Acked-by: Marc Zyngier <marc.zyngier@xxxxxxx>
---
arch/arm/include/asm/kvm_host.h | 10 ++++++++--
arch/arm64/include/asm/kvm_host.h | 10 ++++++++--
virt/kvm/arm/arm.c | 24 +++++++++++++++---------
virt/kvm/arm/psci.c | 21 ++++++++++++++-------
4 files changed, 45 insertions(+), 20 deletions(-)
diff --git a/arch/arm/include/asm/kvm_host.h b/arch/arm/include/asm/kvm_host.h
index b1cfae222441..4dc47fea1ac8 100644
--- a/arch/arm/include/asm/kvm_host.h
+++ b/arch/arm/include/asm/kvm_host.h
@@ -157,6 +157,12 @@ struct vcpu_reset_state {
bool reset;
};
+enum vcpu_power_state {
+ KVM_ARM_VCPU_OFF,
+ KVM_ARM_VCPU_ON_PENDING,
+ KVM_ARM_VCPU_ON,
+};
+
struct kvm_vcpu_arch {
struct kvm_cpu_context ctxt;
@@ -184,8 +190,8 @@ struct kvm_vcpu_arch {
* here.
*/
- /* vcpu power-off state */
- bool power_off;
+ /* vcpu power state */
+ enum vcpu_power_state power_state;
/* Don't run the guest (internal implementation need) */
bool pause;
diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index d43b13421987..0647a409657b 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -218,6 +218,12 @@ struct vcpu_reset_state {
bool reset;
};
+enum vcpu_power_state {
+ KVM_ARM_VCPU_OFF,
+ KVM_ARM_VCPU_ON_PENDING,
+ KVM_ARM_VCPU_ON,
+};
+
struct kvm_vcpu_arch {
struct kvm_cpu_context ctxt;
@@ -285,8 +291,8 @@ struct kvm_vcpu_arch {
u32 mdscr_el1;
} guest_debug_preserved;
- /* vcpu power-off state */
- bool power_off;
+ /* vcpu power state */
+ enum vcpu_power_state power_state;
/* Don't run the guest (internal implementation need) */
bool pause;
diff --git a/virt/kvm/arm/arm.c b/virt/kvm/arm/arm.c
index 785076176814..1e3195155860 100644
--- a/virt/kvm/arm/arm.c
+++ b/virt/kvm/arm/arm.c
@@ -411,7 +411,7 @@ static void vcpu_power_off(struct kvm_vcpu *vcpu)
int kvm_arch_vcpu_ioctl_get_mpstate(struct kvm_vcpu *vcpu,
struct kvm_mp_state *mp_state)
{
- if (vcpu->arch.power_off)
+ if (vcpu->arch.power_state != KVM_ARM_VCPU_ON)
mp_state->mp_state = KVM_MP_STATE_STOPPED;
else
mp_state->mp_state = KVM_MP_STATE_RUNNABLE;
@@ -426,7 +426,7 @@ int kvm_arch_vcpu_ioctl_set_mpstate(struct kvm_vcpu *vcpu,
switch (mp_state->mp_state) {
case KVM_MP_STATE_RUNNABLE:
- vcpu->arch.power_off = false;
+ vcpu->arch.power_state = KVM_ARM_VCPU_ON;
break;
case KVM_MP_STATE_STOPPED:
vcpu_power_off(vcpu);
@@ -448,8 +448,9 @@ int kvm_arch_vcpu_ioctl_set_mpstate(struct kvm_vcpu *vcpu,
int kvm_arch_vcpu_runnable(struct kvm_vcpu *v)
{
bool irq_lines = *vcpu_hcr(v) & (HCR_VI | HCR_VF);
- return ((irq_lines || kvm_vgic_vcpu_pending_irq(v))
- && !v->arch.power_off && !v->arch.pause);
+ return (irq_lines || kvm_vgic_vcpu_pending_irq(v)) &&
+ v->arch.power_state == KVM_ARM_VCPU_ON &&
+ !v->arch.pause;
}
bool kvm_arch_vcpu_in_kernel(struct kvm_vcpu *vcpu)
@@ -614,14 +615,19 @@ void kvm_arm_resume_guest(struct kvm *kvm)
}
}
+static bool vcpu_sleeping(struct kvm_vcpu *vcpu)
+{
+ return vcpu->arch.power_state != KVM_ARM_VCPU_ON ||
+ vcpu->arch.pause;
+}
+
static void vcpu_req_sleep(struct kvm_vcpu *vcpu)
{
struct swait_queue_head *wq = kvm_arch_vcpu_wq(vcpu);
- swait_event_interruptible_exclusive(*wq, ((!vcpu->arch.power_off) &&
- (!vcpu->arch.pause)));
+ swait_event_interruptible_exclusive(*wq, !vcpu_sleeping(vcpu));
- if (vcpu->arch.power_off || vcpu->arch.pause) {
+ if (vcpu_sleeping(vcpu)) {
/* Awaken to handle a signal, request we sleep again later. */
kvm_make_request(KVM_REQ_SLEEP, vcpu);
}
@@ -646,7 +652,7 @@ static void check_vcpu_requests(struct kvm_vcpu *vcpu)
vcpu_req_sleep(vcpu);
if (kvm_check_request(KVM_REQ_VCPU_OFF, vcpu)) {
- vcpu->arch.power_off = true;
+ vcpu->arch.power_state = KVM_ARM_VCPU_OFF;
vcpu_req_sleep(vcpu);
}
@@ -1016,7 +1022,7 @@ static int kvm_arch_vcpu_ioctl_vcpu_init(struct kvm_vcpu *vcpu,
if (test_bit(KVM_ARM_VCPU_POWER_OFF, vcpu->arch.features))
vcpu_power_off(vcpu);
else
- vcpu->arch.power_off = false;
+ vcpu->arch.power_state = KVM_ARM_VCPU_ON;
return 0;
}
diff --git a/virt/kvm/arm/psci.c b/virt/kvm/arm/psci.c
index 20255319e193..5c2d9eeb810c 100644
--- a/virt/kvm/arm/psci.c
+++ b/virt/kvm/arm/psci.c
@@ -106,6 +106,7 @@ static unsigned long kvm_psci_vcpu_on(struct kvm_vcpu *source_vcpu)
struct kvm *kvm = source_vcpu->kvm;
struct kvm_vcpu *vcpu = NULL;
unsigned long cpu_id;
+ enum vcpu_power_state old_power_state;
cpu_id = smccc_get_arg1(source_vcpu) & MPIDR_HWID_BITMASK;
if (vcpu_mode_is_32bit(source_vcpu))
@@ -119,12 +120,18 @@ static unsigned long kvm_psci_vcpu_on(struct kvm_vcpu *source_vcpu)
*/
if (!vcpu)
return PSCI_RET_INVALID_PARAMS;
- if (!vcpu->arch.power_off) {
- if (kvm_psci_version(source_vcpu, kvm) != KVM_ARM_PSCI_0_1)
- return PSCI_RET_ALREADY_ON;
- else
+ old_power_state = cmpxchg(&vcpu->arch.power_state,
+ KVM_ARM_VCPU_OFF,
+ KVM_ARM_VCPU_ON_PENDING);
+
+ if (old_power_state != KVM_ARM_VCPU_OFF &&
+ kvm_psci_version(source_vcpu, kvm) == KVM_ARM_PSCI_0_1)
return PSCI_RET_INVALID_PARAMS;
- }
+
+ if (old_power_state == KVM_ARM_VCPU_ON_PENDING)
+ return PSCI_RET_ON_PENDING;
+ else if (old_power_state == KVM_ARM_VCPU_ON)
+ return PSCI_RET_ALREADY_ON;
reset_state = &vcpu->arch.reset_state;
@@ -148,7 +155,7 @@ static unsigned long kvm_psci_vcpu_on(struct kvm_vcpu *source_vcpu)
*/
smp_wmb();
- vcpu->arch.power_off = false;
+ vcpu->arch.power_state = KVM_ARM_VCPU_ON;
kvm_vcpu_wake_up(vcpu);
return PSCI_RET_SUCCESS;
@@ -183,7 +190,7 @@ static unsigned long kvm_psci_vcpu_affinity_info(struct kvm_vcpu *vcpu)
mpidr = kvm_vcpu_get_mpidr_aff(tmp);
if ((mpidr & target_affinity_mask) == target_affinity) {
matching_cpus++;
- if (!tmp->arch.power_off)
+ if (tmp->arch.power_state == KVM_ARM_VCPU_ON)
return PSCI_0_2_AFFINITY_LEVEL_ON;
}
}
--
2.18.0
_______________________________________________
kvmarm mailing list
kvmarm@xxxxxxxxxxxxxxxxxxxxx
https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
