diff mbox series

[4/5] KVM: arm/arm64: Implement PSCI ON_PENDING when turning on VCPUs

Message ID 20190125094656.5026-5-christoffer.dall@arm.com (mailing list archive)
State New, archived
Headers show
Series KVM: arm/arm64: Fix VCPU power management problems | expand

Commit Message

Christoffer Dall Jan. 25, 2019, 9:46 a.m. UTC 
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@arm.com>
Acked-by: Marc Zyngier <marc.zyngier@arm.com>
---
 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(-)

Comments

Andrew Jones Jan. 29, 2019, 4:27 p.m. UTC | #1 
On Fri, Jan 25, 2019 at 10:46:55AM +0100, Christoffer Dall wrote:
> 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@arm.com>
> Acked-by: Marc Zyngier <marc.zyngier@arm.com>
> ---
>  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
>

Reviewed-by: Andrew Jones <drjones@redhat.com>
diff mbox series

Patch

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;
 		}
 	}