Re: [PATCH net-next v3 01/13] virtio: add packed ring types and macros
From: Maxime Coquelin
Date: Fri Nov 30 2018 - 08:01:15 EST
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 äå6:03, Tiwei Bie wrote:
Add types and macros for packed ring.
Signed-off-by: Tiwei Bie <tiwei.bie@xxxxxxxxx>
---
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.
+ */
+#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 */