linux-kernel - [PATCH v2 5/5] KVM: optimize kvm_make_all_cpus

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Date:   Fri, 24 Feb 2017 20:50:02 +0100
From:   Radim Krčmář <rkrcmar@...hat.com>
To:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Cc:     Paolo Bonzini <pbonzini@...hat.com>,
        Andrew Jones <drjones@...hat.com>,
        Marc Zyngier <marc.zyngier@....com>,
        Christian Borntraeger <borntraeger@...ibm.com>,
        Cornelia Huck <cornelia.huck@...ibm.com>,
        James Hogan <james.hogan@...tec.com>,
        Paul Mackerras <paulus@...abs.org>,
        Christoffer Dall <christoffer.dall@...aro.org>,
        David Hildenbrand <david@...hat.com>
Subject: [PATCH v2 5/5] KVM: optimize kvm_make_all_cpus_request

Use __kvm_request_set to avoid repeated use of wmb().
kvm_make_all_cpus_request is also a candidate for renaming.

Signed-off-by: Radim Krčmář <rkrcmar@...hat.com>
---
 virt/kvm/kvm_main.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 0ee1df3bfcb8..eaab32349664 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -177,8 +177,12 @@ bool kvm_make_all_cpus_request(struct kvm *kvm, unsigned int req)
 	zalloc_cpumask_var(&cpus, GFP_ATOMIC);
 
 	me = get_cpu();
+
+	/* Paired with the smp_mb__after_atomic in kvm_request_test_and_clear. */
+	smp_wmb();
+
 	kvm_for_each_vcpu(i, vcpu, kvm) {
-		kvm_request_set(req, vcpu);
+		__kvm_request_set(req, vcpu);
 		cpu = vcpu->cpu;
 
 		/* Set ->requests bit before we read ->mode. */
-- 
2.11.1