linux-kernel - Re: [RFC 3/3] virtio_ring: use new vring flags

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Message-ID: <20181207130822-mutt-send-email-mst@kernel.org>
Date:   Fri, 7 Dec 2018 13:10:48 -0500
From:   "Michael S. Tsirkin" <mst@...hat.com>
To:     Tiwei Bie <tiwei.bie@...el.com>
Cc:     jasowang@...hat.com, virtualization@...ts.linux-foundation.org,
        linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
        virtio-dev@...ts.oasis-open.org, wexu@...hat.com,
        jfreimann@...hat.com, maxime.coquelin@...hat.com
Subject: Re: [RFC 3/3] virtio_ring: use new vring flags

On Fri, Dec 07, 2018 at 04:48:42PM +0800, Tiwei Bie wrote:
> Switch to using the _SPLIT_ and _PACKED_ variants of vring flags
> in split ring and packed ring respectively.
> 
> Signed-off-by: Tiwei Bie <tiwei.bie@...el.com>
> ---
> @@ -502,7 +505,8 @@ static inline int virtqueue_add_split(struct virtqueue *_vq,
>  		}
>  	}
>  	/* Last one doesn't continue. */
> -	desc[prev].flags &= cpu_to_virtio16(_vq->vdev, ~VRING_DESC_F_NEXT);
> +	desc[prev].flags &= cpu_to_virtio16(_vq->vdev,
> +				(u16)~BIT(VRING_SPLIT_DESC_F_NEXT));
>  
>  	if (indirect) {
>  		/* Now that the indirect table is filled in, map it. */

I kind of dislike it that this forces use of a cast here.
Kind of makes it more fragile. Let's use a temporary instead?

> -- 
> 2.17.1