Yury Norov <yury.norov@xxxxxxxxx> writes:
> In some places kvm/hyperv.c code calls bitmap_weight() to check if any bit
> of a given bitmap is set. It's better to use bitmap_empty() in that case
> because bitmap_empty() stops traversing the bitmap as soon as it finds
> first set bit, while bitmap_weight() counts all bits unconditionally.
>
> Signed-off-by: Yury Norov <yury.norov@xxxxxxxxx>
> ---
> arch/x86/kvm/hyperv.c | 8 ++++----
> 1 file changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
> index 6e38a7d22e97..2c3400dea4b3 100644
> --- a/arch/x86/kvm/hyperv.c
> +++ b/arch/x86/kvm/hyperv.c
> @@ -90,7 +90,7 @@ static void synic_update_vector(struct kvm_vcpu_hv_synic *synic,
> {
> struct kvm_vcpu *vcpu = hv_synic_to_vcpu(synic);
> struct kvm_hv *hv = to_kvm_hv(vcpu->kvm);
> - int auto_eoi_old, auto_eoi_new;
> + bool auto_eoi_old, auto_eoi_new;
>
> if (vector < HV_SYNIC_FIRST_VALID_VECTOR)
> return;
> @@ -100,16 +100,16 @@ static void synic_update_vector(struct kvm_vcpu_hv_synic *synic,
> else
> __clear_bit(vector, synic->vec_bitmap);
>
> - auto_eoi_old = bitmap_weight(synic->auto_eoi_bitmap, 256);
> + auto_eoi_old = bitmap_empty(synic->auto_eoi_bitmap, 256);
I would've preferred this written as
auto_eoi_old = !bitmap_empty(synic->auto_eoi_bitmap, 256);
so the variable would indicate wether AutoEOI was previosly enabled, not
disabled.
>
> if (synic_has_vector_auto_eoi(synic, vector))
> __set_bit(vector, synic->auto_eoi_bitmap);
> else
> __clear_bit(vector, synic->auto_eoi_bitmap);
>
> - auto_eoi_new = bitmap_weight(synic->auto_eoi_bitmap, 256);
> + auto_eoi_new = bitmap_empty(synic->auto_eoi_bitmap, 256);
Same here, of course. "auto_eoi_new = true" sounds like "AutoEOI is now
enabled".
>
> - if (!!auto_eoi_old == !!auto_eoi_new)
> + if (auto_eoi_old == auto_eoi_new)
> return;
>
> down_write(&vcpu->kvm->arch.apicv_update_lock);
The change look good to me otherwise, feel free to add
Reviewed-by: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>
--
Vitaly
