Patch "kvm: avoid unused variable warning for UP builds" has been added to the 4.12-stable tree

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

kvm: avoid unused variable warning for UP builds

to the 4.12-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:
kvm-avoid-unused-variable-warning-for-up-builds.patch
and it can be found in the queue-4.12 subdirectory.

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

From: Paolo Bonzini <[email protected]>
Date: Fri, 30 Jun 2017 13:25:45 +0200
Subject: kvm: avoid unused variable warning for UP builds

From: Paolo Bonzini <[email protected]>

commit b49defe83659cefbb1763d541e779da32594ab10 upstream.

The uniprocessor version of smp_call_function_many does not evaluate all of its argument, and the compiler emits a warning about "wait" being unused. This breaks the build on architectures for which "-Werror" is enabled by default.

Work around it by moving the invocation of smp_call_function_many to its own inline function.

---
 virt/kvm/kvm_main.c |   24 +++++++++++++++---------
 1 file changed, 15 insertions(+), 9 deletions(-)

@@ -187,12 +187,23 @@ static void ack_flush(void *_completed)
 {
 }
 
+static inline bool kvm_kick_many_cpus(const struct cpumask *cpus, bool wait)
+{
+	if (unlikely(!cpus))
+		cpus = cpu_online_mask;
+
+	if (cpumask_empty(cpus))
+		return false;
+
+	smp_call_function_many(cpus, ack_flush, NULL, wait);
+	return true;
+}
+
 bool kvm_make_all_cpus_request(struct kvm *kvm, unsigned int req)
 {
 	int i, cpu, me;
 	cpumask_var_t cpus;
-	bool called = true;
-	bool wait = req & KVM_REQUEST_WAIT;
+	bool called;
 	struct kvm_vcpu *vcpu;
 
 	zalloc_cpumask_var(&cpus, GFP_ATOMIC);

@@ -207,14 +218,9 @@ bool kvm_make_all_cpus_request(struct kv
 
 		if (cpus != NULL && cpu != -1 && cpu != me &&
 		    kvm_request_needs_ipi(vcpu, req))
-			cpumask_set_cpu(cpu, cpus);
+			__cpumask_set_cpu(cpu, cpus);
 	}
-	if (unlikely(cpus == NULL))
-		smp_call_function_many(cpu_online_mask, ack_flush, NULL, wait);
-	else if (!cpumask_empty(cpus))
-		smp_call_function_many(cpus, ack_flush, NULL, wait);
-	else
-		called = false;
+	called = kvm_kick_many_cpus(cpus, !!(req & KVM_REQUEST_WAIT));
 	put_cpu();
 	free_cpumask_var(cpus);
 	return called;

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

queue-4.12/kvm-avoid-unused-variable-warning-for-up-builds.patch queue-4.12/kvm-vfio-decouple-only-when-we-match-a-group.patch

Nope, this patch breaks the 4.12-stable build. If you all want it there, please provide a working backported patch.

thanks,

greg k-h