linux-kernel - Re: [PATCH RFC 1/2] virtio: introduce packed ring defines

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Message-ID: <20180227085458.h5dytkwaeczrrijr@dhcp-192-241.str.redhat.com>
Date:   Tue, 27 Feb 2018 09:54:58 +0100
From:   Jens Freimann <jfreimann@...hat.com>
To:     Tiwei Bie <tiwei.bie@...el.com>
Cc:     mst@...hat.com, virtualization@...ts.linux-foundation.org,
        linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
        jasowang@...hat.com, wexu@...hat.com
Subject: Re: [PATCH RFC 1/2] virtio: introduce packed ring defines

On Fri, Feb 23, 2018 at 07:18:00PM +0800, Tiwei Bie wrote:
>Signed-off-by: Tiwei Bie <tiwei.bie@...el.com>
>---
> include/uapi/linux/virtio_config.h | 18 +++++++++-
> include/uapi/linux/virtio_ring.h   | 68 ++++++++++++++++++++++++++++++++++++++
> 2 files changed, 85 insertions(+), 1 deletion(-)
>
>diff --git a/include/uapi/linux/virtio_config.h b/include/uapi/linux/virtio_config.h
>index 308e2096291f..e3d077ef5207 100644
>--- a/include/uapi/linux/virtio_config.h
>+++ b/include/uapi/linux/virtio_config.h
>@@ -49,7 +49,7 @@
>  * transport being used (eg. virtio_ring), the rest are per-device feature
>  * bits. */
> #define VIRTIO_TRANSPORT_F_START	28
>-#define VIRTIO_TRANSPORT_F_END		34
>+#define VIRTIO_TRANSPORT_F_END		37
>
> #ifndef VIRTIO_CONFIG_NO_LEGACY
> /* Do we get callbacks when the ring is completely used, even if we've
>@@ -71,4 +71,20 @@
>  * this is for compatibility with legacy systems.
>  */
> #define VIRTIO_F_IOMMU_PLATFORM		33
>+
>+/* This feature indicates support for the packed virtqueue layout. */
>+#define VIRTIO_F_RING_PACKED		34

Spec says VIRTIO_F_PACKED_RING not RING_PACKED
>+
>+/*
>+ * This feature indicates that all buffers are used by the device
>+ * in the same order in which they have been made available.
>+ */
>+#define VIRTIO_F_IN_ORDER		35
>+
>+/*
>+ * This feature indicates that drivers pass extra data (besides
>+ * identifying the Virtqueue) in their device notifications.
>+ */
>+#define VIRTIO_F_NOTIFICATION_DATA	36
>+
> #endif /* _UAPI_LINUX_VIRTIO_CONFIG_H */
>diff --git a/include/uapi/linux/virtio_ring.h b/include/uapi/linux/virtio_ring.h
>index 6d5d5faa989b..77b1d4aeef72 100644
>--- a/include/uapi/linux/virtio_ring.h
>+++ b/include/uapi/linux/virtio_ring.h
>@@ -44,6 +44,9 @@
> /* This means the buffer contains a list of buffer descriptors. */
> #define VRING_DESC_F_INDIRECT	4
>
>+#define VRING_DESC_F_AVAIL(b)	((b) << 7)
>+#define VRING_DESC_F_USED(b)	((b) << 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. */
>@@ -104,6 +107,36 @@ struct vring {
> 	struct vring_used *used;
> };
>
>+struct vring_packed_desc_event {
>+	/* Descriptor Event Offset */
>+	__virtio16 desc_event_off   : 15,
>+	/* Descriptor Event Wrap Counter */
>+		   desc_event_wrap  : 1;
>+	/* Descriptor Event Flags */
>+	__virtio16 desc_event_flags : 2;
>+};

Where would the virtqueue number go in driver notifications?

regards,
Jens