Patch "arm64: KVM: Fix SMCCC handling of unimplemented SMC/HVC calls" has been added to the 4.4-stable tree

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

arm64: KVM: Fix SMCCC handling of unimplemented SMC/HVC calls

to the 4.4-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:
arm64-kvm-fix-smccc-handling-of-unimplemented-smc-hvc-calls.patch
and it can be found in the queue-4.4 subdirectory.

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

From: Marc Zyngier <[email protected]>
Date: Tue, 16 Jan 2018 10:23:47 +0000
Subject: arm64: KVM: Fix SMCCC handling of unimplemented SMC/HVC calls

From: Marc Zyngier <[email protected]>

commit acfb3b883f6d6a4b5d27ad7fdded11f6a09ae6dd upstream.

KVM doesn't follow the SMCCC when it comes to unimplemented calls, and inject an UNDEF instead of returning an error. Since firmware calls are now used for security mitigation, they are becoming more common, and the undef is counter productive.

Instead, let's follow the SMCCC which states that -1 must be returned to the caller when getting an unknown function number.

---
 arch/arm64/kvm/handle_exit.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

@@ -42,7 +42,7 @@ static int handle_hvc(struct kvm_vcpu *v
 
 	ret = kvm_psci_call(vcpu);
 	if (ret < 0) {
-		kvm_inject_undefined(vcpu);
+		vcpu_set_reg(vcpu, 0, ~0UL);
 		return 1;
 	}
 

@@ -51,7 +51,7 @@ static int handle_hvc(struct kvm_vcpu *v
 
 static int handle_smc(struct kvm_vcpu *vcpu, struct kvm_run *run)
 {
-	kvm_inject_undefined(vcpu);
+	vcpu_set_reg(vcpu, 0, ~0UL);
 	return 1;
 }
 

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

queue-4.4/arm64-kvm-fix-smccc-handling-of-unimplemented-smc-hvc-calls.patch