From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Michael S. Tsirkin" Subject: Re: [RFC 2/3] virtio_ring: add VIRTIO_RING_NO_LEGACY Date: Fri, 7 Dec 2018 13:05:35 -0500 Message-ID: <20181207130336-mutt-send-email-mst@kernel.org> References: <20181207084842.13133-1-tiwei.bie@intel.com> <20181207084842.13133-3-tiwei.bie@intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: jasowang@redhat.com, virtualization@lists.linux-foundation.org, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, virtio-dev@lists.oasis-open.org, wexu@redhat.com, jfreimann@redhat.com, maxime.coquelin@redhat.com To: Tiwei Bie Return-path: Sender: List-Post: List-Help: List-Unsubscribe: List-Subscribe: Content-Disposition: inline In-Reply-To: <20181207084842.13133-3-tiwei.bie@intel.com> List-Id: netdev.vger.kernel.org On Fri, Dec 07, 2018 at 04:48:41PM +0800, Tiwei Bie wrote: > Introduce VIRTIO_RING_NO_LEGACY to support disabling legacy > macros and layout definitions. > > Suggested-by: Michael S. Tsirkin > Signed-off-by: Tiwei Bie > --- > VRING_AVAIL_ALIGN_SIZE, VRING_USED_ALIGN_SIZE and VRING_DESC_ALIGN_SIZE > are not pre-virtio 1.0, but can also be disabled by VIRTIO_RING_NO_LEGACY > in this patch, because their names are not consistent with other names. > Not sure whether this is a good idea. If we want this, we may also want > to define _SPLIT_ version for them. I don't think it's a good idea to have alignment in there - the point of NO_LEGACY is to help catch bugs not to sanitize coding style IMHO. And spec calls "legacy" the 0.X interfaces, let's not muddy the waters. > > include/uapi/linux/virtio_ring.h | 4 ++++ > 1 file changed, 4 insertions(+) > > diff --git a/include/uapi/linux/virtio_ring.h b/include/uapi/linux/virtio_ring.h > index 9b0c0d92ab62..192573827850 100644 > --- a/include/uapi/linux/virtio_ring.h > +++ b/include/uapi/linux/virtio_ring.h > @@ -37,6 +37,7 @@ > #include > #include > > +#ifndef VIRTIO_RING_NO_LEGACY > /* > * Notice: unlike other _F_ flags, below flags are defined as shifted > * values instead of shifts for compatibility. > @@ -51,6 +52,7 @@ > #define VRING_USED_F_NO_NOTIFY 1 > /* Same as VRING_SPLIT_AVAIL_F_NO_INTERRUPT. */ > #define VRING_AVAIL_F_NO_INTERRUPT 1 > +#endif /* VIRTIO_RING_NO_LEGACY */ > > /* Mark a buffer as continuing via the next field in split ring. */ > #define VRING_SPLIT_DESC_F_NEXT 0 > @@ -151,6 +153,7 @@ struct vring { > struct vring_used *used; > }; > > +#ifndef VIRTIO_RING_NO_LEGACY > /* Alignment requirements for vring elements. > * When using pre-virtio 1.0 layout, these fall out naturally. > */ > @@ -203,6 +206,7 @@ static inline unsigned vring_size(unsigned int num, unsigned long align) > + align - 1) & ~(align - 1)) > + sizeof(__virtio16) * 3 + sizeof(struct vring_used_elem) * num; > } > +#endif /* VIRTIO_RING_NO_LEGACY */ > > /* The following is used with USED_EVENT_IDX and AVAIL_EVENT_IDX */ > /* Assuming a given event_idx value from the other side, if > -- > 2.17.1