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SubjectRe: [PATCH net-next v2 1/5] virtio: add packed ring definitions
On Mon, Sep 10, 2018 at 10:13:22AM +0800, Tiwei Bie wrote:
> On Fri, Sep 07, 2018 at 09:51:23AM -0400, Michael S. Tsirkin wrote:
> > On Wed, Jul 11, 2018 at 10:27:07AM +0800, Tiwei Bie wrote:
> > > Signed-off-by: Tiwei Bie <tiwei.bie@intel.com>
> > > ---
> > > include/uapi/linux/virtio_config.h | 3 +++
> > > include/uapi/linux/virtio_ring.h | 43 ++++++++++++++++++++++++++++++
> > > 2 files changed, 46 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..0254a2ba29cf 100644
> > > --- a/include/uapi/linux/virtio_ring.h
> > > +++ b/include/uapi/linux/virtio_ring.h
> > > @@ -44,6 +44,10 @@
> > > /* This means the buffer contains a list of buffer descriptors. */
> > > #define VRING_DESC_F_INDIRECT 4
> > >
> > > +/* Mark a descriptor as available or used. */
> > > +#define VRING_DESC_F_AVAIL (1ul << 7)
> > > +#define VRING_DESC_F_USED (1ul << 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 +57,17 @@
> > > * optimization. */
> > > #define VRING_AVAIL_F_NO_INTERRUPT 1
> > >
> > > +/* Enable events. */
> > > +#define VRING_EVENT_F_ENABLE 0x0
> > > +/* Disable events. */
> > > +#define VRING_EVENT_F_DISABLE 0x1
> > > +/*
> > > + * Enable events for a specific descriptor
> > > + * (as specified by Descriptor Ring Change Event Offset/Wrap Counter).
> > > + * Only valid if VIRTIO_RING_F_EVENT_IDX has been negotiated.
> > > + */
> > > +#define VRING_EVENT_F_DESC 0x2
> > > +
> > > /* We support indirect buffer descriptors */
> > > #define VIRTIO_RING_F_INDIRECT_DESC 28
> > >
> >
> > These are for the packed ring, right? Pls prefix accordingly.
>
> How about something like this:
>
> #define VRING_PACKED_DESC_F_AVAIL (1u << 7)
> #define VRING_PACKED_DESC_F_USED (1u << 15)

_F_ should be a bit number, not a shifted value.
Yes I know current virtio_ring.h is inconsistent in
that respect. changes welcome though we need to
maintain the old names for the sake of old apps.

>
> #define VRING_PACKED_EVENT_F_ENABLE 0x0
> #define VRING_PACKED_EVENT_F_DISABLE 0x1
> #define VRING_PACKED_EVENT_F_DESC 0x2

These are values, I think they should not have _F_.
Yes I know current virtio_ring.h is inconsistent in
that respect.


>
> > Also, you likely need macros for the wrap counters.
>
> How about something like this:
>
> #define VRING_PACKED_EVENT_WRAP_COUNTER_SHIFT 15

Given it's a single bit, maybe even
VRING_PACKED_EVENT_F_WRAP_CTR

> #define VRING_PACKED_EVENT_WRAP_COUNTER_MASK \
> (1u << VRING_PACKED_WRAP_COUNTER_SHIFT)
> #define VRING_PACKED_EVENT_OFFSET_MASK \
> ((1u << VRING_PACKED_WRAP_COUNTER_SHIFT) - 1)

I'm not sure the mask is justified.

> >
> > > @@ -171,4 +186,32 @@ 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. */
> > > + __virtio16 off_wrap;
> > > + /* Descriptor Ring Change Event Flags. */
> > > + __virtio16 flags;
> > > +};
> > > +
> > > +struct vring_packed_desc {
> > > + /* Buffer Address. */
> > > + __virtio64 addr;
> > > + /* Buffer Length. */
> > > + __virtio32 len;
> > > + /* Buffer ID. */
> > > + __virtio16 id;
> > > + /* The flags depending on descriptor type. */
> > > + __virtio16 flags;
> > > +};
> >
> > Don't use __virtioXX types, just __leXX ones.
>
> Got it, will do that.
>
> >
> > > +
> > > +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 */
> > > --
> > > 2.18.0

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