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

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

[gregkh]

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 <stable@vger.kernel.org> know about it.


>From b49defe83659cefbb1763d541e779da32594ab10 Mon Sep 17 00:00:00 2001
From: Paolo Bonzini <pbonzini@redhat.com>
Date: Fri, 30 Jun 2017 13:25:45 +0200
Subject: kvm: avoid unused variable warning for UP builds

From: Paolo Bonzini <pbonzini@redhat.com>

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.

Reported-by: Paul Mackerras <paulus@ozlabs.org>
Fixes: 7a97cec26b94c909f4cbad2dc3186af3e457a522
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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

--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -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 pbonzini@redhat.com 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

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

[Greg KH]

On Tue, Jul 18, 2017 at 05:16:06PM +0200, gregkh@linuxfoundation.org wrote:
> 
> 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 <stable@vger.kernel.org> know about it.
> 
> 
> >From b49defe83659cefbb1763d541e779da32594ab10 Mon Sep 17 00:00:00 2001
> From: Paolo Bonzini <pbonzini@redhat.com>
> Date: Fri, 30 Jun 2017 13:25:45 +0200
> Subject: kvm: avoid unused variable warning for UP builds
> 
> From: Paolo Bonzini <pbonzini@redhat.com>
> 
> 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.
> 
> Reported-by: Paul Mackerras <paulus@ozlabs.org>
> Fixes: 7a97cec26b94c909f4cbad2dc3186af3e457a522
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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