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SubjectRe: [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 下午6:03, Tiwei Bie wrote:
> > Add types and macros for packed ring.
> >
> > Signed-off-by: Tiwei Bie <tiwei.bie@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 */

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