On 05.07.2017 12:35, Paolo Bonzini wrote:
> 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@xxxxxxxxxx>
> Cc: stable@xxxxxxxxxxxxxxx
> Fixes: 7a97cec26b94c909f4cbad2dc3186af3e457a522
> Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
> ---
> virt/kvm/kvm_main.c | 24 +++++++++++++++---------
> 1 file changed, 15 insertions(+), 9 deletions(-)
>
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index f0fe9d02f6bb..09368501d9cf 100644
> --- 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;
> +}
wonder if the !cpus case would be worth moving into smp_call_function_many.
smp_call_function_many() might also not kick any cpu, so we could make
it return if it actually kicked/called this on any cpu. Then you could
even get rid of the special handling of cpumask_empty(cpus) here and
simply return the result of smp_call_function_many.
> +
> 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 kvm *kvm, unsigned int req)
>
> 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));
Is the !! really needed here? I think not.
> put_cpu();
> free_cpumask_var(cpus);
> return called;
>
I like this from a cleanup point as well.
--
Thanks,
David