Re: [PATCH] use bitmap ops on a bitmap instead of bit ops

[Sheng Yang <sheng@linux.intel.com>]

On Thursday 26 February 2009 21:03:39 Gleb Natapov wrote:
> And don't zero bitmap twice. Assume that caller zeros it.
>
> Signed-off-by: Gleb Natapov <gleb@redhat.com>
> diff --git a/virt/kvm/ioapic.c b/virt/kvm/ioapic.c
> index 7c2cb2b..21627b9 100644
> --- a/virt/kvm/ioapic.c
> +++ b/virt/kvm/ioapic.c
> @@ -170,12 +170,11 @@ void kvm_ioapic_get_delivery_bitmask(struct
> kvm_ioapic *ioapic, u8 dest,
>
>  	ioapic_debug("dest %d dest_mode %d\n", dest, dest_mode);
>
Hi Gleb

> -	*mask = 0;

I think the caller should not assume anything about the output, so let 
function itself do the clean is better. (however, not in this way for "mask" 
should be KVM_MAX_VCPUS long.)

And, I found some other things are not proper after looking back code, I would 
send a patch to fix it (deliver_bitmask in kvm_get_intr_delivery_bitmask).

>  	if (dest_mode == 0) {	/* Physical mode. */
>  		if (dest == 0xFF) {	/* Broadcast. */
>  			for (i = 0; i < KVM_MAX_VCPUS; ++i)
>  				if (kvm->vcpus[i] && kvm->vcpus[i]->arch.apic)
> -					*mask |= 1 << i;
> +					__set_bit(i, *mask);

Should be __set_bit(i, mask)?

-- 
regards
Yang, Sheng

>  			return;
>  		}
>  		for (i = 0; i < KVM_MAX_VCPUS; ++i) {
> @@ -184,7 +183,7 @@ void kvm_ioapic_get_delivery_bitmask(struct kvm_ioapic
> *ioapic, u8 dest, continue;
>  			if (kvm_apic_match_physical_addr(vcpu->arch.apic, dest)) {
>  				if (vcpu->arch.apic)
> -					*mask = 1 << i;
> +					__set_bit(i, *mask);
>  				break;
>  			}
>  		}
> @@ -195,7 +194,7 @@ void kvm_ioapic_get_delivery_bitmask(struct kvm_ioapic
> *ioapic, u8 dest, continue;
>  			if (vcpu->arch.apic &&
>  			    kvm_apic_match_logical_addr(vcpu->arch.apic, dest))
> -				*mask |= 1 << vcpu->vcpu_id;
> +				__set_bit(i, *mask);
>  		}
>  	ioapic_debug("mask %x\n", *mask);
>  }
> --
> 			Gleb.