linux-kernel - [PATCH 4.0 37/55] ARM: kvm: psci: fix handling of unimplemented functions

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Date:	Wed,  8 Jul 2015 00:35:12 -0700
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org,
	Christoffer Dall <christoffer.dall@...aro.org>,
	Sudeep Holla <sudeep.holla@....com>,
	Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
	Marc Zyngier <marc.zyngier@....com>
Subject: [PATCH 4.0 37/55] ARM: kvm: psci: fix handling of unimplemented functions

4.0-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Lorenzo Pieralisi <lorenzo.pieralisi@....com>

commit e2d997366dc5b6c9d14035867f73957f93e7578c upstream.

According to the PSCI specification and the SMC/HVC calling
convention, PSCI function_ids that are not implemented must
return NOT_SUPPORTED as return value.

Current KVM implementation takes an unhandled PSCI function_id
as an error and injects an undefined instruction into the guest
if PSCI implementation is called with a function_id that is not
handled by the resident PSCI version (ie it is not implemented),
which is not the behaviour expected by a guest when calling a
PSCI function_id that is not implemented.

This patch fixes this issue by returning NOT_SUPPORTED whenever
the kvm PSCI call is executed for a function_id that is not
implemented by the PSCI kvm layer.

Cc: Christoffer Dall <christoffer.dall@...aro.org>
Acked-by: Sudeep Holla <sudeep.holla@....com>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@....com>
Signed-off-by: Marc Zyngier <marc.zyngier@....com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 arch/arm/kvm/psci.c |   16 +++-------------
 1 file changed, 3 insertions(+), 13 deletions(-)

--- a/arch/arm/kvm/psci.c
+++ b/arch/arm/kvm/psci.c
@@ -230,10 +230,6 @@ static int kvm_psci_0_2_call(struct kvm_
 	case PSCI_0_2_FN64_AFFINITY_INFO:
 		val = kvm_psci_vcpu_affinity_info(vcpu);
 		break;
-	case PSCI_0_2_FN_MIGRATE:
-	case PSCI_0_2_FN64_MIGRATE:
-		val = PSCI_RET_NOT_SUPPORTED;
-		break;
 	case PSCI_0_2_FN_MIGRATE_INFO_TYPE:
 		/*
 		 * Trusted OS is MP hence does not require migration
@@ -242,10 +238,6 @@ static int kvm_psci_0_2_call(struct kvm_
 		 */
 		val = PSCI_0_2_TOS_MP;
 		break;
-	case PSCI_0_2_FN_MIGRATE_INFO_UP_CPU:
-	case PSCI_0_2_FN64_MIGRATE_INFO_UP_CPU:
-		val = PSCI_RET_NOT_SUPPORTED;
-		break;
 	case PSCI_0_2_FN_SYSTEM_OFF:
 		kvm_psci_system_off(vcpu);
 		/*
@@ -271,7 +263,8 @@ static int kvm_psci_0_2_call(struct kvm_
 		ret = 0;
 		break;
 	default:
-		return -EINVAL;
+		val = PSCI_RET_NOT_SUPPORTED;
+		break;
 	}
 
 	*vcpu_reg(vcpu, 0) = val;
@@ -291,12 +284,9 @@ static int kvm_psci_0_1_call(struct kvm_
 	case KVM_PSCI_FN_CPU_ON:
 		val = kvm_psci_vcpu_on(vcpu);
 		break;
-	case KVM_PSCI_FN_CPU_SUSPEND:
-	case KVM_PSCI_FN_MIGRATE:
+	default:
 		val = PSCI_RET_NOT_SUPPORTED;
 		break;
-	default:
-		return -EINVAL;
 	}
 
 	*vcpu_reg(vcpu, 0) = val;


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