Since we know vq->vring.num is a power of 2, modulus is lazy (it's asserted in vring_new_virtqueue()).
Signed-off-by: Rusty Russell <[email protected]> --- drivers/virtio/virtio_ring.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-) diff --git a/arch/x86/lguest/boot.c b/arch/x86/lguest/boot.c --- a/arch/x86/lguest/boot.c +++ b/arch/x86/lguest/boot.c @@ -1420,7 +1420,7 @@ __init void lguest_init(void) add_preferred_console("hvc", 0, NULL); /* Register our very early console. */ - virtio_cons_early_init(early_put_chars); +// virtio_cons_early_init(early_put_chars); /* * Last of all, we set the power management poweroff hook to point to diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c --- a/drivers/virtio/virtio_ring.c +++ b/drivers/virtio/virtio_ring.c @@ -226,8 +226,8 @@ add_head: vq->data[head] = data; /* Put entry in available array (but don't update avail->idx until they - * do sync). FIXME: avoid modulus here? */ - avail = (vq->vring.avail->idx + vq->num_added++) % vq->vring.num; + * do sync). */ + avail = ((vq->vring.avail->idx + vq->num_added++) & (vq->vring.num-1)); vq->vring.avail->ring[avail] = head; pr_debug("Added buffer head %i to %p\n", head, vq); @@ -317,6 +317,7 @@ void *virtqueue_get_buf(struct virtqueue struct vring_virtqueue *vq = to_vvq(_vq); void *ret; unsigned int i; + u16 last_used; START_USE(vq); @@ -334,8 +335,9 @@ void *virtqueue_get_buf(struct virtqueue /* Only get used array entries after they have been exposed by host. */ virtio_rmb(); - i = vq->vring.used->ring[vq->last_used_idx%vq->vring.num].id; - *len = vq->vring.used->ring[vq->last_used_idx%vq->vring.num].len; + last_used = (vq->last_used_idx & (vq->vring.num - 1)); + i = vq->vring.used->ring[last_used].id; + *len = vq->vring.used->ring[last_used].len; if (unlikely(i >= vq->vring.num)) { BAD_RING(vq, "id %u out of range\n", i); _______________________________________________ Virtualization mailing list [email protected] https://lists.linuxfoundation.org/mailman/listinfo/virtualization
