Patch "ARM: kvm: psci: fix handling of unimplemented functions" has been added to the 4.1-stable tree

This is a note to let you know that I've just added the patch titled

ARM: kvm: psci: fix handling of unimplemented functions

to the 4.1-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
arm-kvm-psci-fix-handling-of-unimplemented-functions.patch
and it can be found in the queue-4.1 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Lorenzo Pieralisi <[email protected]>
Date: Wed, 10 Jun 2015 15:19:24 +0100
Subject: ARM: kvm: psci: fix handling of unimplemented functions

From: Lorenzo Pieralisi <[email protected]>

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.

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

@@ -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;

Patches currently in stable-queue which might be from [email protected] are

queue-4.1/arm-kvm-psci-fix-handling-of-unimplemented-functions.patch