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From:   David Laight <David.Laight@ACULAB.COM>
To:     'Tiwei Bie' <tiwei.bie@intel.com>,
        "mst@redhat.com" <mst@redhat.com>,
        "virtualization@lists.linux-foundation.org" 
        <virtualization@lists.linux-foundation.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "netdev@vger.kernel.org" <netdev@vger.kernel.org>
CC:     "jasowang@redhat.com" <jasowang@redhat.com>,
        "wexu@redhat.com" <wexu@redhat.com>,
        "jfreimann@redhat.com" <jfreimann@redhat.com>
Subject: RE: [PATCH RFC 1/2] virtio: introduce packed ring defines
Thread-Topic: [PATCH RFC 1/2] virtio: introduce packed ring defines
Thread-Index: AQHTrJhawi/1jB/uq0q3lsGi4wUZ3aO4ADyQ
Date:   Tue, 27 Feb 2018 09:26:27 +0000
Message-ID: <e7a7f045b87a420a8863030b9378cb38@AcuMS.aculab.com>
References: <20180223111801.15240-1-tiwei.bie@intel.com>
 <20180223111801.15240-2-tiwei.bie@intel.com>
In-Reply-To: <20180223111801.15240-2-tiwei.bie@intel.com>
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From: Tiwei Bie
> Sent: 23 February 2018 11:18
...
> +struct vring_packed_desc_event {
> +	/* Descriptor Event Offset */
> +	__virtio16 desc_event_off   : 15,
> +	/* Descriptor Event Wrap Counter */
> +		   desc_event_wrap  : 1;
> +	/* Descriptor Event Flags */
> +	__virtio16 desc_event_flags : 2;
> +};

This looks like you are assuming that a bit-field has a defined
layout and can be used to map a 'hardware' structure.
The don't, don't use them like that.

	David