[RFC,2/3] virtio_ring: add VIRTIO_RING_NO_LEGACY
diff mbox series

Message ID 20181207084842.13133-3-tiwei.bie@intel.com
State New
Headers show
Series
  • virtio_ring: define flags as shifts consistently
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Commit Message

Tiwei Bie Dec. 7, 2018, 8:48 a.m. UTC
Introduce VIRTIO_RING_NO_LEGACY to support disabling legacy
macros and layout definitions.

Suggested-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Tiwei Bie <tiwei.bie@intel.com>
---
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.

 include/uapi/linux/virtio_ring.h | 4 ++++
 1 file changed, 4 insertions(+)

Comments

Michael S. Tsirkin Dec. 7, 2018, 6:05 p.m. UTC | #1
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 <mst@redhat.com>
> Signed-off-by: Tiwei Bie <tiwei.bie@intel.com>
> ---
> 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 <linux/types.h>
>  #include <linux/virtio_types.h>
>  
> +#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
Tiwei Bie Dec. 8, 2018, 1:33 p.m. UTC | #2
On Fri, Dec 07, 2018 at 01:05:35PM -0500, Michael S. Tsirkin wrote:
> 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 <mst@redhat.com>
> > Signed-off-by: Tiwei Bie <tiwei.bie@intel.com>
> > ---
> > 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.

Make sense. Thanks!

> 
> > 
> >  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 <linux/types.h>
> >  #include <linux/virtio_types.h>
> >  
> > +#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

Patch
diff mbox series

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 <linux/types.h>
 #include <linux/virtio_types.h>
 
+#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