KVM: fix irq_source_id size verification

[Marcelo Tosatti <mtosatti@redhat.com>]

find_first_zero_bit works with bit numbers, not bytes.

Fixes

https://sourceforge.net/tracker/?func=detail&aid=2847560&group_id=180599&atid=893831

Reported-by: "Xu, Jiajun" <jiajun.xu@intel.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

diff --git a/virt/kvm/irq_comm.c b/virt/kvm/irq_comm.c
index 00c68d2..0d454d3 100644
--- a/virt/kvm/irq_comm.c
+++ b/virt/kvm/irq_comm.c
@@ -215,10 +215,9 @@ int kvm_request_irq_source_id(struct kvm *kvm)
 	int irq_source_id;
 
 	mutex_lock(&kvm->irq_lock);
-	irq_source_id = find_first_zero_bit(bitmap,
-				sizeof(kvm->arch.irq_sources_bitmap));
+	irq_source_id = find_first_zero_bit(bitmap, BITS_PER_LONG);
 
-	if (irq_source_id >= sizeof(kvm->arch.irq_sources_bitmap)) {
+	if (irq_source_id >= BITS_PER_LONG) {
 		printk(KERN_WARNING "kvm: exhaust allocatable IRQ sources!\n");
 		irq_source_id = -EFAULT;
 		goto unlock;
@@ -240,7 +239,7 @@ void kvm_free_irq_source_id(struct kvm *kvm, int irq_source_id)
 
 	mutex_lock(&kvm->irq_lock);
 	if (irq_source_id < 0 ||
-	    irq_source_id >= sizeof(kvm->arch.irq_sources_bitmap)) {
+	    irq_source_id >= BITS_PER_LONG) {
 		printk(KERN_ERR "kvm: IRQ source ID out of range!\n");
 		goto unlock;
 	}