[PATCH] KVM: arm/arm64: Fix PSCI affinity info return value for non valid cores

[PATCH] KVM: arm/arm64: Fix PSCI affinity info return value for non valid cores

[Alexander Spyridakis]

If a guest requests the affinity info for a non-existing vCPU we need to
properly return an error, instead of erroneously reporting an off state.

Signed-off-by: Alexander Spyridakis <a.spyridakis@virtualopensystems.com>
Signed-off-by: Alvise Rigo <a.rigo@virtualopensystems.com>
---
 arch/arm/kvm/psci.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/arch/arm/kvm/psci.c b/arch/arm/kvm/psci.c
index 4b94b51..ad6f642 100644
--- a/arch/arm/kvm/psci.c
+++ b/arch/arm/kvm/psci.c
@@ -126,7 +126,7 @@ static unsigned long kvm_psci_vcpu_on(struct kvm_vcpu *source_vcpu)
 
 static unsigned long kvm_psci_vcpu_affinity_info(struct kvm_vcpu *vcpu)
 {
-	int i;
+	int i, matching_cpus = 0;
 	unsigned long mpidr;
 	unsigned long target_affinity;
 	unsigned long target_affinity_mask;
@@ -151,12 +151,16 @@ static unsigned long kvm_psci_vcpu_affinity_info(struct kvm_vcpu *vcpu)
 	 */
 	kvm_for_each_vcpu(i, tmp, kvm) {
 		mpidr = kvm_vcpu_get_mpidr_aff(tmp);
-		if (((mpidr & target_affinity_mask) == target_affinity) &&
-		    !tmp->arch.pause) {
-			return PSCI_0_2_AFFINITY_LEVEL_ON;
+		if ((mpidr & target_affinity_mask) == target_affinity) {
+			matching_cpus++;
+			if (!tmp->arch.pause)
+				return PSCI_0_2_AFFINITY_LEVEL_ON;
 		}
 	}
 
+	if (!matching_cpus)
+		return PSCI_RET_INVALID_PARAMS;
+
 	return PSCI_0_2_AFFINITY_LEVEL_OFF;
 }
 
-- 
2.5.1

Re: [PATCH] KVM: arm/arm64: Fix PSCI affinity info return value for non valid cores

[Marc Zyngier]

On 04/09/15 16:06, Alexander Spyridakis wrote:
> If a guest requests the affinity info for a non-existing vCPU we need to
> properly return an error, instead of erroneously reporting an off state.
> 
> Signed-off-by: Alexander Spyridakis <a.spyridakis@virtualopensystems.com>
> Signed-off-by: Alvise Rigo <a.rigo@virtualopensystems.com>

Seems sound to me. Out of curiosity, how was this found?

Reviewed-by: Marc Zyngier <marc.zyngier@arm.com>

	M.
-- 
Jazz is not dead. It just smells funny...

Re: [PATCH] KVM: arm/arm64: Fix PSCI affinity info return value for non valid cores

[Alexander Spyridakis]

On 4 September 2015 at 17:54, Marc Zyngier <marc.zyngier@arm.com> wrote:
> Seems sound to me. Out of curiosity, how was this found?

Hello Mark,

This issue came up when testing some basic bare metal tests with KVM,
which originally were meant for the multi-threading TCG effort
(https://git.virtualopensystems.com/dev/tcg_baremetal_tests.git).
While shutting down the system the test relies on PSCI to find out if
all secondary cores are powered-off by incrementally polling PSCI for
every cpu id. In the case of QEMU/TCG everything was fine, but with
KVM there was no error response for non-existing cores, and so the
system could not shut down properly.

Kind regards.

Re: [PATCH] KVM: arm/arm64: Fix PSCI affinity info return value for non valid cores

[Mark Rutland]

On Fri, Sep 04, 2015 at 04:06:24PM +0100, Alexander Spyridakis wrote:
> If a guest requests the affinity info for a non-existing vCPU we need to
> properly return an error, instead of erroneously reporting an off state.
> 
> Signed-off-by: Alexander Spyridakis <a.spyridakis@virtualopensystems.com>
> Signed-off-by: Alvise Rigo <a.rigo@virtualopensystems.com>

This looks correct to me per the PSCI 0.2 spec:

Acked-by: Mark Rutland <mark.rutland@arm.com>

Was this spotted by inspection, or do you have some client for which
this is important?

Thanks,
Mark.

> ---
>  arch/arm/kvm/psci.c | 12 ++++++++----
>  1 file changed, 8 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/arm/kvm/psci.c b/arch/arm/kvm/psci.c
> index 4b94b51..ad6f642 100644
> --- a/arch/arm/kvm/psci.c
> +++ b/arch/arm/kvm/psci.c
> @@ -126,7 +126,7 @@ static unsigned long kvm_psci_vcpu_on(struct kvm_vcpu *source_vcpu)
>  
>  static unsigned long kvm_psci_vcpu_affinity_info(struct kvm_vcpu *vcpu)
>  {
> -	int i;
> +	int i, matching_cpus = 0;
>  	unsigned long mpidr;
>  	unsigned long target_affinity;
>  	unsigned long target_affinity_mask;
> @@ -151,12 +151,16 @@ static unsigned long kvm_psci_vcpu_affinity_info(struct kvm_vcpu *vcpu)
>  	 */
>  	kvm_for_each_vcpu(i, tmp, kvm) {
>  		mpidr = kvm_vcpu_get_mpidr_aff(tmp);
> -		if (((mpidr & target_affinity_mask) == target_affinity) &&
> -		    !tmp->arch.pause) {
> -			return PSCI_0_2_AFFINITY_LEVEL_ON;
> +		if ((mpidr & target_affinity_mask) == target_affinity) {
> +			matching_cpus++;
> +			if (!tmp->arch.pause)
> +				return PSCI_0_2_AFFINITY_LEVEL_ON;
>  		}
>  	}
>  
> +	if (!matching_cpus)
> +		return PSCI_RET_INVALID_PARAMS;
> +
>  	return PSCI_0_2_AFFINITY_LEVEL_OFF;
>  }
>  
> -- 
> 2.5.1
> 
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