thr3ads.net - Virtualization - [PATCH net-next v3 01/13] virtio: add packed ring types and macros [Nov 2018]

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Jason Wang

2018-Nov-30 08:10 UTC

[PATCH net-next v3 01/13] virtio: add packed ring types and macros

On 2018/11/21 ??6:03, Tiwei Bie wrote:> Add types and macros for packed ring.
>
> Signed-off-by: Tiwei Bie <tiwei.bie at intel.com>
> ---
>   include/uapi/linux/virtio_config.h |  3 +++
>   include/uapi/linux/virtio_ring.h   | 52
++++++++++++++++++++++++++++++++++++++
>   2 files changed, 55 insertions(+)
>
> diff --git a/include/uapi/linux/virtio_config.h
b/include/uapi/linux/virtio_config.h
> index 449132c76b1c..1196e1c1d4f6 100644
> --- a/include/uapi/linux/virtio_config.h
> +++ b/include/uapi/linux/virtio_config.h
> @@ -75,6 +75,9 @@
>    */
>   #define VIRTIO_F_IOMMU_PLATFORM		33
>   
> +/* This feature indicates support for the packed virtqueue layout. */
> +#define VIRTIO_F_RING_PACKED		34
> +
>   /*
>    * Does the device support Single Root I/O Virtualization?
>    */
> diff --git a/include/uapi/linux/virtio_ring.h
b/include/uapi/linux/virtio_ring.h
> index 6d5d5faa989b..2414f8af26b3 100644
> --- a/include/uapi/linux/virtio_ring.h
> +++ b/include/uapi/linux/virtio_ring.h
> @@ -44,6 +44,13 @@
>   /* This means the buffer contains a list of buffer descriptors. */
>   #define VRING_DESC_F_INDIRECT	4
>   
> +/*
> + * Mark a descriptor as available or used in packed ring.
> + * Notice: they are defined as shifts instead of shifted values.

This looks inconsistent to previous flags, any reason for using shifts?

> + */
> +#define VRING_PACKED_DESC_F_AVAIL	7
> +#define VRING_PACKED_DESC_F_USED	15
> +
>   /* The Host uses this in used->flags to advise the Guest: don't
kick me when
>    * you add a buffer.  It's unreliable, so it's simply an
optimization.  Guest
>    * will still kick if it's out of buffers. */
> @@ -53,6 +60,23 @@
>    * optimization.  */
>   #define VRING_AVAIL_F_NO_INTERRUPT	1
>   
> +/* Enable events in packed ring. */
> +#define VRING_PACKED_EVENT_FLAG_ENABLE	0x0
> +/* Disable events in packed ring. */
> +#define VRING_PACKED_EVENT_FLAG_DISABLE	0x1
> +/*
> + * Enable events for a specific descriptor in packed ring.
> + * (as specified by Descriptor Ring Change Event Offset/Wrap Counter).
> + * Only valid if VIRTIO_RING_F_EVENT_IDX has been negotiated.
> + */
> +#define VRING_PACKED_EVENT_FLAG_DESC	0x2

Any reason for using _FLAG_ instead of _F_?

Thanks

> +
> +/*
> + * Wrap counter bit shift in event suppression structure
> + * of packed ring.
> + */
> +#define VRING_PACKED_EVENT_F_WRAP_CTR	15
> +
>   /* We support indirect buffer descriptors */
>   #define VIRTIO_RING_F_INDIRECT_DESC	28
>   
> @@ -171,4 +195,32 @@ static inline int vring_need_event(__u16 event_idx,
__u16 new_idx, __u16 old)
>   	return (__u16)(new_idx - event_idx - 1) < (__u16)(new_idx - old);
>   }
>   
> +struct vring_packed_desc_event {
> +	/* Descriptor Ring Change Event Offset/Wrap Counter. */
> +	__le16 off_wrap;
> +	/* Descriptor Ring Change Event Flags. */
> +	__le16 flags;
> +};
> +
> +struct vring_packed_desc {
> +	/* Buffer Address. */
> +	__le64 addr;
> +	/* Buffer Length. */
> +	__le32 len;
> +	/* Buffer ID. */
> +	__le16 id;
> +	/* The flags depending on descriptor type. */
> +	__le16 flags;
> +};
> +
> +struct vring_packed {
> +	unsigned int num;
> +
> +	struct vring_packed_desc *desc;
> +
> +	struct vring_packed_desc_event *driver;
> +
> +	struct vring_packed_desc_event *device;
> +};
> +
>   #endif /* _UAPI_LINUX_VIRTIO_RING_H */

Tiwei Bie

2018-Nov-30 09:53 UTC

head link

[PATCH net-next v3 01/13] virtio: add packed ring types and macros

On Fri, Nov 30, 2018 at 04:10:55PM +0800, Jason Wang
wrote:> 
> On 2018/11/21 ??6:03, Tiwei Bie wrote:
> > Add types and macros for packed ring.
> > 
> > Signed-off-by: Tiwei Bie <tiwei.bie at intel.com>
> > ---
> >   include/uapi/linux/virtio_config.h |  3 +++
> >   include/uapi/linux/virtio_ring.h   | 52
++++++++++++++++++++++++++++++++++++++
> >   2 files changed, 55 insertions(+)
> > 
> > diff --git a/include/uapi/linux/virtio_config.h
b/include/uapi/linux/virtio_config.h
> > index 449132c76b1c..1196e1c1d4f6 100644
> > --- a/include/uapi/linux/virtio_config.h
> > +++ b/include/uapi/linux/virtio_config.h
> > @@ -75,6 +75,9 @@
> >    */
> >   #define VIRTIO_F_IOMMU_PLATFORM		33
> > +/* This feature indicates support for the packed virtqueue layout. */
> > +#define VIRTIO_F_RING_PACKED		34
> > +
> >   /*
> >    * Does the device support Single Root I/O Virtualization?
> >    */
> > diff --git a/include/uapi/linux/virtio_ring.h
b/include/uapi/linux/virtio_ring.h
> > index 6d5d5faa989b..2414f8af26b3 100644
> > --- a/include/uapi/linux/virtio_ring.h
> > +++ b/include/uapi/linux/virtio_ring.h
> > @@ -44,6 +44,13 @@
> >   /* This means the buffer contains a list of buffer descriptors. */
> >   #define VRING_DESC_F_INDIRECT	4
> > +/*
> > + * Mark a descriptor as available or used in packed ring.
> > + * Notice: they are defined as shifts instead of shifted values.
> 
> 
> This looks inconsistent to previous flags, any reason for using shifts?
Yeah, it was suggested to use shifts, as _F_ should be a bit
number, not a shifted value:

https://patchwork.ozlabs.org/patch/942296/#1989390
> 
> 
> > + */
> > +#define VRING_PACKED_DESC_F_AVAIL	7
> > +#define VRING_PACKED_DESC_F_USED	15
> > +
> >   /* The Host uses this in used->flags to advise the Guest:
don't kick me when
> >    * you add a buffer.  It's unreliable, so it's simply an
optimization.  Guest
> >    * will still kick if it's out of buffers. */
> > @@ -53,6 +60,23 @@
> >    * optimization.  */
> >   #define VRING_AVAIL_F_NO_INTERRUPT	1
> > +/* Enable events in packed ring. */
> > +#define VRING_PACKED_EVENT_FLAG_ENABLE	0x0
> > +/* Disable events in packed ring. */
> > +#define VRING_PACKED_EVENT_FLAG_DISABLE	0x1
> > +/*
> > + * Enable events for a specific descriptor in packed ring.
> > + * (as specified by Descriptor Ring Change Event Offset/Wrap
Counter).
> > + * Only valid if VIRTIO_RING_F_EVENT_IDX has been negotiated.
> > + */
> > +#define VRING_PACKED_EVENT_FLAG_DESC	0x2
> 
> 
> Any reason for using _FLAG_ instead of _F_?
Yeah, it was suggested to not use _F_, as these are values,
should not have _F_:

https://patchwork.ozlabs.org/patch/942296/#1989390

Regards,
Tiwei
> 
> Thanks
> 
> 
> > +
> > +/*
> > + * Wrap counter bit shift in event suppression structure
> > + * of packed ring.
> > + */
> > +#define VRING_PACKED_EVENT_F_WRAP_CTR	15
> > +
> >   /* We support indirect buffer descriptors */
> >   #define VIRTIO_RING_F_INDIRECT_DESC	28
> > @@ -171,4 +195,32 @@ static inline int vring_need_event(__u16
event_idx, __u16 new_idx, __u16 old)
> >   	return (__u16)(new_idx - event_idx - 1) < (__u16)(new_idx -
old);
> >   }
> > +struct vring_packed_desc_event {
> > +	/* Descriptor Ring Change Event Offset/Wrap Counter. */
> > +	__le16 off_wrap;
> > +	/* Descriptor Ring Change Event Flags. */
> > +	__le16 flags;
> > +};
> > +
> > +struct vring_packed_desc {
> > +	/* Buffer Address. */
> > +	__le64 addr;
> > +	/* Buffer Length. */
> > +	__le32 len;
> > +	/* Buffer ID. */
> > +	__le16 id;
> > +	/* The flags depending on descriptor type. */
> > +	__le16 flags;
> > +};
> > +
> > +struct vring_packed {
> > +	unsigned int num;
> > +
> > +	struct vring_packed_desc *desc;
> > +
> > +	struct vring_packed_desc_event *driver;
> > +
> > +	struct vring_packed_desc_event *device;
> > +};
> > +
> >   #endif /* _UAPI_LINUX_VIRTIO_RING_H */

Michael S. Tsirkin

2018-Nov-30 12:47 UTC

head link

[PATCH net-next v3 01/13] virtio: add packed ring types and macros

On Fri, Nov 30, 2018 at 05:53:40PM +0800, Tiwei Bie
wrote:> On Fri, Nov 30, 2018 at 04:10:55PM +0800, Jason Wang wrote:
> > 
> > On 2018/11/21 ??6:03, Tiwei Bie wrote:
> > > Add types and macros for packed ring.
> > > 
> > > Signed-off-by: Tiwei Bie <tiwei.bie at intel.com>
> > > ---
> > >   include/uapi/linux/virtio_config.h |  3 +++
> > >   include/uapi/linux/virtio_ring.h   | 52
++++++++++++++++++++++++++++++++++++++
> > >   2 files changed, 55 insertions(+)
> > > 
> > > diff --git a/include/uapi/linux/virtio_config.h
b/include/uapi/linux/virtio_config.h
> > > index 449132c76b1c..1196e1c1d4f6 100644
> > > --- a/include/uapi/linux/virtio_config.h
> > > +++ b/include/uapi/linux/virtio_config.h
> > > @@ -75,6 +75,9 @@
> > >    */
> > >   #define VIRTIO_F_IOMMU_PLATFORM		33
> > > +/* This feature indicates support for the packed virtqueue
layout. */
> > > +#define VIRTIO_F_RING_PACKED		34
> > > +
> > >   /*
> > >    * Does the device support Single Root I/O Virtualization?
> > >    */
> > > diff --git a/include/uapi/linux/virtio_ring.h
b/include/uapi/linux/virtio_ring.h
> > > index 6d5d5faa989b..2414f8af26b3 100644
> > > --- a/include/uapi/linux/virtio_ring.h
> > > +++ b/include/uapi/linux/virtio_ring.h
> > > @@ -44,6 +44,13 @@
> > >   /* This means the buffer contains a list of buffer descriptors.
*/
> > >   #define VRING_DESC_F_INDIRECT	4
> > > +/*
> > > + * Mark a descriptor as available or used in packed ring.
> > > + * Notice: they are defined as shifts instead of shifted values.
> > 
> > 
> > This looks inconsistent to previous flags, any reason for using
shifts?
> 
> Yeah, it was suggested to use shifts, as _F_ should be a bit
> number, not a shifted value:
> 
> https://patchwork.ozlabs.org/patch/942296/#1989390
But let's add a _SPLIT_ variant that uses shifts consistently.

> > 
> > 
> > > + */
> > > +#define VRING_PACKED_DESC_F_AVAIL	7
> > > +#define VRING_PACKED_DESC_F_USED	15
> > > +
> > >   /* The Host uses this in used->flags to advise the Guest:
don't kick me when
> > >    * you add a buffer.  It's unreliable, so it's simply
an optimization.  Guest
> > >    * will still kick if it's out of buffers. */
> > > @@ -53,6 +60,23 @@
> > >    * optimization.  */
> > >   #define VRING_AVAIL_F_NO_INTERRUPT	1
> > > +/* Enable events in packed ring. */
> > > +#define VRING_PACKED_EVENT_FLAG_ENABLE	0x0
> > > +/* Disable events in packed ring. */
> > > +#define VRING_PACKED_EVENT_FLAG_DISABLE	0x1
> > > +/*
> > > + * Enable events for a specific descriptor in packed ring.
> > > + * (as specified by Descriptor Ring Change Event Offset/Wrap
Counter).
> > > + * Only valid if VIRTIO_RING_F_EVENT_IDX has been negotiated.
> > > + */
> > > +#define VRING_PACKED_EVENT_FLAG_DESC	0x2
> > 
> > 
> > Any reason for using _FLAG_ instead of _F_?
> 
> Yeah, it was suggested to not use _F_, as these are values,
> should not have _F_:
> 
> https://patchwork.ozlabs.org/patch/942296/#1989390
> 
> Regards,
> Tiwei
> 
> > 
> > Thanks
> > 
> > 
> > > +
> > > +/*
> > > + * Wrap counter bit shift in event suppression structure
> > > + * of packed ring.
> > > + */
> > > +#define VRING_PACKED_EVENT_F_WRAP_CTR	15
> > > +
> > >   /* We support indirect buffer descriptors */
> > >   #define VIRTIO_RING_F_INDIRECT_DESC	28
> > > @@ -171,4 +195,32 @@ static inline int vring_need_event(__u16
event_idx, __u16 new_idx, __u16 old)
> > >   	return (__u16)(new_idx - event_idx - 1) < (__u16)(new_idx -
old);
> > >   }
> > > +struct vring_packed_desc_event {
> > > +	/* Descriptor Ring Change Event Offset/Wrap Counter. */
> > > +	__le16 off_wrap;
> > > +	/* Descriptor Ring Change Event Flags. */
> > > +	__le16 flags;
> > > +};
> > > +
> > > +struct vring_packed_desc {
> > > +	/* Buffer Address. */
> > > +	__le64 addr;
> > > +	/* Buffer Length. */
> > > +	__le32 len;
> > > +	/* Buffer ID. */
> > > +	__le16 id;
> > > +	/* The flags depending on descriptor type. */
> > > +	__le16 flags;
> > > +};
> > > +
> > > +struct vring_packed {
> > > +	unsigned int num;
> > > +
> > > +	struct vring_packed_desc *desc;
> > > +
> > > +	struct vring_packed_desc_event *driver;
> > > +
> > > +	struct vring_packed_desc_event *device;
> > > +};
> > > +
> > >   #endif /* _UAPI_LINUX_VIRTIO_RING_H */

Michael S. Tsirkin

2018-Nov-30 13:52 UTC

head link

[PATCH net-next v3 01/13] virtio: add packed ring types and macros

On Fri, Nov 30, 2018 at 02:01:06PM +0100, Maxime Coquelin
wrote:> 
> 
> On 11/30/18 1:47 PM, Michael S. Tsirkin wrote:
> > On Fri, Nov 30, 2018 at 05:53:40PM +0800, Tiwei Bie wrote:
> > > On Fri, Nov 30, 2018 at 04:10:55PM +0800, Jason Wang wrote:
> > > > 
> > > > On 2018/11/21 ??6:03, Tiwei Bie wrote:
> > > > > Add types and macros for packed ring.
> > > > > 
> > > > > Signed-off-by: Tiwei Bie <tiwei.bie at intel.com>
> > > > > ---
> > > > >    include/uapi/linux/virtio_config.h |  3 +++
> > > > >    include/uapi/linux/virtio_ring.h   | 52
++++++++++++++++++++++++++++++++++++++
> > > > >    2 files changed, 55 insertions(+)
> > > > > 
> > > > > diff --git a/include/uapi/linux/virtio_config.h
b/include/uapi/linux/virtio_config.h
> > > > > index 449132c76b1c..1196e1c1d4f6 100644
> > > > > --- a/include/uapi/linux/virtio_config.h
> > > > > +++ b/include/uapi/linux/virtio_config.h
> > > > > @@ -75,6 +75,9 @@
> > > > >     */
> > > > >    #define VIRTIO_F_IOMMU_PLATFORM		33
> > > > > +/* This feature indicates support for the packed
virtqueue layout. */
> > > > > +#define VIRTIO_F_RING_PACKED		34
> > > > > +
> > > > >    /*
> > > > >     * Does the device support Single Root I/O
Virtualization?
> > > > >     */
> > > > > diff --git a/include/uapi/linux/virtio_ring.h
b/include/uapi/linux/virtio_ring.h
> > > > > index 6d5d5faa989b..2414f8af26b3 100644
> > > > > --- a/include/uapi/linux/virtio_ring.h
> > > > > +++ b/include/uapi/linux/virtio_ring.h
> > > > > @@ -44,6 +44,13 @@
> > > > >    /* This means the buffer contains a list of buffer
descriptors. */
> > > > >    #define VRING_DESC_F_INDIRECT	4
> > > > > +/*
> > > > > + * Mark a descriptor as available or used in packed
ring.
> > > > > + * Notice: they are defined as shifts instead of
shifted values.
> > > > 
> > > > 
> > > > This looks inconsistent to previous flags, any reason for
using shifts?
> > > 
> > > Yeah, it was suggested to use shifts, as _F_ should be a bit
> > > number, not a shifted value:
> > > 
> > > https://patchwork.ozlabs.org/patch/942296/#1989390
> > 
> > But let's add a _SPLIT_ variant that uses shifts consistently.
> 
> Maybe we could avoid adding SPLIT and PACKED, but define as follow:
> 
> #define VRING_DESC_F_INDIRECT_SHIFT 2
> #define VRING_DESC_F_INDIRECT (1ull <<  VRING_DESC_F_INDIRECT_SHIFT)
> 
> #define VRING_DESC_F_AVAIL_SHIFT 7
> #define VRING_DESC_F_AVAIL (1ull << VRING_DESC_F_AVAIL_SHIFT)
> 
> I think it would be better for consistency.
I don't think that will help. the problem is that
most of the existing virtio code consistently uses _F_ as shifts.
So we just need to do something about these 5 being inconsistent:

include/uapi/linux/virtio_ring.h:#define VRING_DESC_F_NEXT      1
include/uapi/linux/virtio_ring.h:#define VRING_DESC_F_WRITE     2
include/uapi/linux/virtio_ring.h:#define VRING_DESC_F_INDIRECT  4
include/uapi/linux/virtio_ring.h:#define VRING_USED_F_NO_NOTIFY 1
include/uapi/linux/virtio_ring.h:#define VRING_AVAIL_F_NO_INTERRUPT     1

I do not want all of virtio to become verbose with _SHIFT, ergo
we need to change the above 5 to have names which are with _F_ and
have the bit number.


> > 
> > 
> > > > 
> > > > 
> > > > > + */
> > > > > +#define VRING_PACKED_DESC_F_AVAIL	7
> > > > > +#define VRING_PACKED_DESC_F_USED	15
> > > > > +
> > > > >    /* The Host uses this in used->flags to advise
the Guest: don't kick me when
> > > > >     * you add a buffer.  It's unreliable, so
it's simply an optimization.  Guest
> > > > >     * will still kick if it's out of buffers. */
> > > > > @@ -53,6 +60,23 @@
> > > > >     * optimization.  */
> > > > >    #define VRING_AVAIL_F_NO_INTERRUPT	1
> > > > > +/* Enable events in packed ring. */
> > > > > +#define VRING_PACKED_EVENT_FLAG_ENABLE	0x0
> > > > > +/* Disable events in packed ring. */
> > > > > +#define VRING_PACKED_EVENT_FLAG_DISABLE	0x1
> > > > > +/*
> > > > > + * Enable events for a specific descriptor in packed
ring.
> > > > > + * (as specified by Descriptor Ring Change Event
Offset/Wrap Counter).
> > > > > + * Only valid if VIRTIO_RING_F_EVENT_IDX has been
negotiated.
> > > > > + */
> > > > > +#define VRING_PACKED_EVENT_FLAG_DESC	0x2
> > > > 
> > > > 
> > > > Any reason for using _FLAG_ instead of _F_?
> > > 
> > > Yeah, it was suggested to not use _F_, as these are values,
> > > should not have _F_:
> > > 
> > > https://patchwork.ozlabs.org/patch/942296/#1989390
> > > 
> > > Regards,
> > > Tiwei
> > > 
> > > > 
> > > > Thanks
> > > > 
> > > > 
> > > > > +
> > > > > +/*
> > > > > + * Wrap counter bit shift in event suppression
structure
> > > > > + * of packed ring.
> > > > > + */
> > > > > +#define VRING_PACKED_EVENT_F_WRAP_CTR	15
> > > > > +
> > > > >    /* We support indirect buffer descriptors */
> > > > >    #define VIRTIO_RING_F_INDIRECT_DESC	28
> > > > > @@ -171,4 +195,32 @@ static inline int
vring_need_event(__u16 event_idx, __u16 new_idx, __u16 old)
> > > > >    	return (__u16)(new_idx - event_idx - 1) <
(__u16)(new_idx - old);
> > > > >    }
> > > > > +struct vring_packed_desc_event {
> > > > > +	/* Descriptor Ring Change Event Offset/Wrap Counter.
*/
> > > > > +	__le16 off_wrap;
> > > > > +	/* Descriptor Ring Change Event Flags. */
> > > > > +	__le16 flags;
> > > > > +};
> > > > > +
> > > > > +struct vring_packed_desc {
> > > > > +	/* Buffer Address. */
> > > > > +	__le64 addr;
> > > > > +	/* Buffer Length. */
> > > > > +	__le32 len;
> > > > > +	/* Buffer ID. */
> > > > > +	__le16 id;
> > > > > +	/* The flags depending on descriptor type. */
> > > > > +	__le16 flags;
> > > > > +};
> > > > > +
> > > > > +struct vring_packed {
> > > > > +	unsigned int num;
> > > > > +
> > > > > +	struct vring_packed_desc *desc;
> > > > > +
> > > > > +	struct vring_packed_desc_event *driver;
> > > > > +
> > > > > +	struct vring_packed_desc_event *device;
> > > > > +};
> > > > > +
> > > > >    #endif /* _UAPI_LINUX_VIRTIO_RING_H */

Tiwei Bie

2018-Nov-30 15:37 UTC

head link

[PATCH net-next v3 01/13] virtio: add packed ring types and macros

On Fri, Nov 30, 2018 at 08:52:42AM -0500, Michael S. Tsirkin
wrote:> On Fri, Nov 30, 2018 at 02:01:06PM +0100, Maxime Coquelin wrote:
> > On 11/30/18 1:47 PM, Michael S. Tsirkin wrote:
> > > On Fri, Nov 30, 2018 at 05:53:40PM +0800, Tiwei Bie wrote:
> > > > On Fri, Nov 30, 2018 at 04:10:55PM +0800, Jason Wang wrote:
> > > > > 
> > > > > On 2018/11/21 ??6:03, Tiwei Bie wrote:
> > > > > > Add types and macros for packed ring.
> > > > > > 
> > > > > > Signed-off-by: Tiwei Bie <tiwei.bie at
intel.com>
> > > > > > ---
> > > > > >    include/uapi/linux/virtio_config.h |  3 +++
> > > > > >    include/uapi/linux/virtio_ring.h   | 52
++++++++++++++++++++++++++++++++++++++
> > > > > >    2 files changed, 55 insertions(+)
> > > > > > 
> > > > > > diff --git a/include/uapi/linux/virtio_config.h
b/include/uapi/linux/virtio_config.h
> > > > > > index 449132c76b1c..1196e1c1d4f6 100644
> > > > > > --- a/include/uapi/linux/virtio_config.h
> > > > > > +++ b/include/uapi/linux/virtio_config.h
> > > > > > @@ -75,6 +75,9 @@
> > > > > >     */
> > > > > >    #define VIRTIO_F_IOMMU_PLATFORM		33
> > > > > > +/* This feature indicates support for the packed
virtqueue layout. */
> > > > > > +#define VIRTIO_F_RING_PACKED		34
> > > > > > +
> > > > > >    /*
> > > > > >     * Does the device support Single Root I/O
Virtualization?
> > > > > >     */
> > > > > > diff --git a/include/uapi/linux/virtio_ring.h
b/include/uapi/linux/virtio_ring.h
> > > > > > index 6d5d5faa989b..2414f8af26b3 100644
> > > > > > --- a/include/uapi/linux/virtio_ring.h
> > > > > > +++ b/include/uapi/linux/virtio_ring.h
> > > > > > @@ -44,6 +44,13 @@
> > > > > >    /* This means the buffer contains a list of
buffer descriptors. */
> > > > > >    #define VRING_DESC_F_INDIRECT	4
> > > > > > +/*
> > > > > > + * Mark a descriptor as available or used in
packed ring.
> > > > > > + * Notice: they are defined as shifts instead of
shifted values.
> > > > > 
> > > > > 
> > > > > This looks inconsistent to previous flags, any reason
for using shifts?
> > > > 
> > > > Yeah, it was suggested to use shifts, as _F_ should be a bit
> > > > number, not a shifted value:
> > > > 
> > > > https://patchwork.ozlabs.org/patch/942296/#1989390
> > > 
> > > But let's add a _SPLIT_ variant that uses shifts
consistently.
> > 
> > Maybe we could avoid adding SPLIT and PACKED, but define as follow:
> > 
> > #define VRING_DESC_F_INDIRECT_SHIFT 2
> > #define VRING_DESC_F_INDIRECT (1ull << 
VRING_DESC_F_INDIRECT_SHIFT)
> > 
> > #define VRING_DESC_F_AVAIL_SHIFT 7
> > #define VRING_DESC_F_AVAIL (1ull << VRING_DESC_F_AVAIL_SHIFT)
> > 
> > I think it would be better for consistency.
> 
> I don't think that will help. the problem is that
> most of the existing virtio code consistently uses _F_ as shifts.
> So we just need to do something about these 5 being inconsistent:
> 
> include/uapi/linux/virtio_ring.h:#define VRING_DESC_F_NEXT      1
> include/uapi/linux/virtio_ring.h:#define VRING_DESC_F_WRITE     2
> include/uapi/linux/virtio_ring.h:#define VRING_DESC_F_INDIRECT  4
> include/uapi/linux/virtio_ring.h:#define VRING_USED_F_NO_NOTIFY 1
> include/uapi/linux/virtio_ring.h:#define VRING_AVAIL_F_NO_INTERRUPT     1
> 
> I do not want all of virtio to become verbose with _SHIFT, ergo
> we need to change the above 5 to have names which are with _F_ and
> have the bit number.
How about something like this:

#define VRING_COMM_DESC_F_NEXT			0
#define VRING_COMM_DESC_F_WRITE			1
#define VRING_COMM_DESC_F_INDIRECT		2

#define VRING_SPLIT_USED_F_NO_NOTIFY		0
#define VRING_SPLIT_AVAIL_F_NO_INTERRUPT	0

or

#define VRING_SPLIT_DESC_F_NEXT			0
#define VRING_SPLIT_DESC_F_WRITE		1
#define VRING_SPLIT_DESC_F_INDIRECT		2

#define VRING_SPLIT_USED_F_NO_NOTIFY		0
#define VRING_SPLIT_AVAIL_F_NO_INTERRUPT	0

#define VRING_PACKED_DESC_F_NEXT		0
#define VRING_PACKED_DESC_F_WRITE		1
#define VRING_PACKED_DESC_F_INDIRECT		2
> 
> 
> 
> > > 
> > > 
> > > > > 
> > > > > 
> > > > > > + */
> > > > > > +#define VRING_PACKED_DESC_F_AVAIL	7
> > > > > > +#define VRING_PACKED_DESC_F_USED	15
> > > > > > +
> > > > > >    /* The Host uses this in used->flags to
advise the Guest: don't kick me when
> > > > > >     * you add a buffer.  It's unreliable, so
it's simply an optimization.  Guest
> > > > > >     * will still kick if it's out of buffers.
*/
> > > > > > @@ -53,6 +60,23 @@
> > > > > >     * optimization.  */
> > > > > >    #define VRING_AVAIL_F_NO_INTERRUPT	1
> > > > > > +/* Enable events in packed ring. */
> > > > > > +#define VRING_PACKED_EVENT_FLAG_ENABLE	0x0
> > > > > > +/* Disable events in packed ring. */
> > > > > > +#define VRING_PACKED_EVENT_FLAG_DISABLE	0x1
> > > > > > +/*
> > > > > > + * Enable events for a specific descriptor in
packed ring.
> > > > > > + * (as specified by Descriptor Ring Change Event
Offset/Wrap Counter).
> > > > > > + * Only valid if VIRTIO_RING_F_EVENT_IDX has been
negotiated.
> > > > > > + */
> > > > > > +#define VRING_PACKED_EVENT_FLAG_DESC	0x2
> > > > > 
> > > > > 
> > > > > Any reason for using _FLAG_ instead of _F_?
> > > > 
> > > > Yeah, it was suggested to not use _F_, as these are values,
> > > > should not have _F_:
> > > > 
> > > > https://patchwork.ozlabs.org/patch/942296/#1989390
> > > > 
> > > > Regards,
> > > > Tiwei
> > > > 
> > > > > 
> > > > > Thanks
> > > > > 
> > > > > 
> > > > > > +
> > > > > > +/*
> > > > > > + * Wrap counter bit shift in event suppression
structure
> > > > > > + * of packed ring.
> > > > > > + */
> > > > > > +#define VRING_PACKED_EVENT_F_WRAP_CTR	15
> > > > > > +
> > > > > >    /* We support indirect buffer descriptors */
> > > > > >    #define VIRTIO_RING_F_INDIRECT_DESC	28
> > > > > > @@ -171,4 +195,32 @@ static inline int
vring_need_event(__u16 event_idx, __u16 new_idx, __u16 old)
> > > > > >    	return (__u16)(new_idx - event_idx - 1) <
(__u16)(new_idx - old);
> > > > > >    }
> > > > > > +struct vring_packed_desc_event {
> > > > > > +	/* Descriptor Ring Change Event Offset/Wrap
Counter. */
> > > > > > +	__le16 off_wrap;
> > > > > > +	/* Descriptor Ring Change Event Flags. */
> > > > > > +	__le16 flags;
> > > > > > +};
> > > > > > +
> > > > > > +struct vring_packed_desc {
> > > > > > +	/* Buffer Address. */
> > > > > > +	__le64 addr;
> > > > > > +	/* Buffer Length. */
> > > > > > +	__le32 len;
> > > > > > +	/* Buffer ID. */
> > > > > > +	__le16 id;
> > > > > > +	/* The flags depending on descriptor type. */
> > > > > > +	__le16 flags;
> > > > > > +};
> > > > > > +
> > > > > > +struct vring_packed {
> > > > > > +	unsigned int num;
> > > > > > +
> > > > > > +	struct vring_packed_desc *desc;
> > > > > > +
> > > > > > +	struct vring_packed_desc_event *driver;
> > > > > > +
> > > > > > +	struct vring_packed_desc_event *device;
> > > > > > +};
> > > > > > +
> > > > > >    #endif /* _UAPI_LINUX_VIRTIO_RING_H */

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