From: David Hildenbrand <dahi@linux.vnet.ibm.com>
Date: Thu, 5 Nov 2015 08:55:08 +0000 (+0100)
Subject: KVM: use heuristic for fast VCPU lookup by id
X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=c896939f7cff767091b5d84587cd144e5d3613b7;p=linux-beck.git

KVM: use heuristic for fast VCPU lookup by id

Usually, VCPU ids match the array index. So let's try a fast
lookup first before falling back to the slow iteration.

Suggested-by: Christian Borntraeger <borntraeger@de.ibm.com>
Reviewed-by: Dominik Dingel <dingel@linux.vnet.ibm.com>
Reviewed-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: David Hildenbrand <dahi@linux.vnet.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
---

diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 29119193a19f..a754fc08e194 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -472,6 +472,11 @@ static inline struct kvm_vcpu *kvm_get_vcpu_by_id(struct kvm *kvm, int id)
 	struct kvm_vcpu *vcpu;
 	int i;
 
+	if (id < 0 || id >= KVM_MAX_VCPUS)
+		return NULL;
+	vcpu = kvm_get_vcpu(kvm, id);
+	if (vcpu && vcpu->vcpu_id == id)
+		return vcpu;
 	kvm_for_each_vcpu(i, vcpu, kvm)
 		if (vcpu->vcpu_id == id)
 			return vcpu;