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Date: Wed, 23 Nov 2022 12:38:31 -0800
From: Jacob Keller <jacob.e.keller@...el.com>
To: netdev@...r.kernel.org
Cc: Jacob Keller <jacob.e.keller@...el.com>,
Jiri Pirko <jiri@...dia.com>, Jakub Kicinski <kuba@...nel.org>
Subject: [PATCH net-next v2 6/9] devlink: support directly reading from region memory
To read from a region, user space must currently request a new snapshot of
the region and then read from that snapshot. This can sometimes be overkill
if user space only reads a tiny portion. They first create the snapshot,
then request a read, then destroy the snapshot.
For regions which have a single underlying "contents", it makes sense to
allow supporting direct reading of the region data.
Extend the DEVLINK_CMD_REGION_READ to allow direct reading from a region if
supported. Instead of reporting a missing snapshot id as invalid, check if
the region supports direct read and if so switch to the direct access
method for reading the region data.
Signed-off-by: Jacob Keller <jacob.e.keller@...el.com>
---
Changes since v1:
* Update documentation to explain that direct reads are not atomic
.../networking/devlink/devlink-region.rst | 11 ++++
include/net/devlink.h | 16 +++++
net/core/devlink.c | 66 ++++++++++++++-----
3 files changed, 76 insertions(+), 17 deletions(-)
diff --git a/Documentation/networking/devlink/devlink-region.rst b/Documentation/networking/devlink/devlink-region.rst
index f06dca9a1eb6..6525a9120a4e 100644
--- a/Documentation/networking/devlink/devlink-region.rst
+++ b/Documentation/networking/devlink/devlink-region.rst
@@ -31,6 +31,13 @@ in its ``devlink_region_ops`` structure. If snapshot id is not set in
the ``DEVLINK_CMD_REGION_NEW`` request kernel will allocate one and send
the snapshot information to user space.
+Regions may optionally allow directly reading from their contents without a
+snapshot. Direct read requests are not atomic. In particular a read request
+of size 256 bytes or larger will be split into multiple chunks. If atomic
+access is required, use a snapshot. A driver wishing to enable this for a
+region should implement the ``.read`` callback in the ``devlink_region_ops``
+structure.
+
example usage
-------------
@@ -65,6 +72,10 @@ example usage
$ devlink region read pci/0000:00:05.0/fw-health snapshot 1 address 0 length 16
0000000000000000 0014 95dc 0014 9514 0035 1670 0034 db30
+ # Read from the region without a snapshot
+ $ devlink region read pci/0000:00:05.0/fw-health address 16 length 16
+ 0000000000000010 0000 0000 ffff ff04 0029 8c00 0028 8cc8
+
As regions are likely very device or driver specific, no generic regions are
defined. See the driver-specific documentation files for information on the
specific regions a driver supports.
diff --git a/include/net/devlink.h b/include/net/devlink.h
index 074a79b8933f..02528f736f65 100644
--- a/include/net/devlink.h
+++ b/include/net/devlink.h
@@ -650,6 +650,10 @@ struct devlink_info_req;
* the data variable must be updated to point to the snapshot data.
* The function will be called while the devlink instance lock is
* held.
+ * @read: callback to directly read a portion of the region. On success,
+ * the data pointer will be updated with the contents of the
+ * requested portion of the region. The function will be called
+ * while the devlink instance lock is held.
* @priv: Pointer to driver private data for the region operation
*/
struct devlink_region_ops {
@@ -659,6 +663,10 @@ struct devlink_region_ops {
const struct devlink_region_ops *ops,
struct netlink_ext_ack *extack,
u8 **data);
+ int (*read)(struct devlink *devlink,
+ const struct devlink_region_ops *ops,
+ struct netlink_ext_ack *extack,
+ u64 offset, u32 size, u8 *data);
void *priv;
};
@@ -670,6 +678,10 @@ struct devlink_region_ops {
* the data variable must be updated to point to the snapshot data.
* The function will be called while the devlink instance lock is
* held.
+ * @read: callback to directly read a portion of the region. On success,
+ * the data pointer will be updated with the contents of the
+ * requested portion of the region. The function will be called
+ * while the devlink instance lock is held.
* @priv: Pointer to driver private data for the region operation
*/
struct devlink_port_region_ops {
@@ -679,6 +691,10 @@ struct devlink_port_region_ops {
const struct devlink_port_region_ops *ops,
struct netlink_ext_ack *extack,
u8 **data);
+ int (*read)(struct devlink_port *port,
+ const struct devlink_port_region_ops *ops,
+ struct netlink_ext_ack *extack,
+ u64 offset, u32 size, u8 *data);
void *priv;
};
diff --git a/net/core/devlink.c b/net/core/devlink.c
index 729e2162a4db..f249b5b57677 100644
--- a/net/core/devlink.c
+++ b/net/core/devlink.c
@@ -6515,6 +6515,26 @@ devlink_region_snapshot_fill(void *cb_priv, u8 *chunk, u32 chunk_size,
return 0;
}
+static int
+devlink_region_port_direct_fill(void *cb_priv, u8 *chunk, u32 chunk_size,
+ u64 curr_offset, struct netlink_ext_ack *extack)
+{
+ struct devlink_region *region = cb_priv;
+
+ return region->port_ops->read(region->port, region->port_ops, extack,
+ curr_offset, chunk_size, chunk);
+}
+
+static int
+devlink_region_direct_fill(void *cb_priv, u8 *chunk, u32 chunk_size,
+ u64 curr_offset, struct netlink_ext_ack *extack)
+{
+ struct devlink_region *region = cb_priv;
+
+ return region->ops->read(region->devlink, region->ops, extack,
+ curr_offset, chunk_size, chunk);
+}
+
static int devlink_nl_cmd_region_read_dumpit(struct sk_buff *skb,
struct netlink_callback *cb)
{
@@ -6523,12 +6543,12 @@ static int devlink_nl_cmd_region_read_dumpit(struct sk_buff *skb,
u64 ret_offset, start_offset, end_offset = U64_MAX;
struct nlattr **attrs = info->attrs;
struct devlink_port *port = NULL;
- struct devlink_snapshot *snapshot;
+ devlink_chunk_fill_t *region_cb;
struct devlink_region *region;
const char *region_name;
struct devlink *devlink;
unsigned int index;
- u32 snapshot_id;
+ void *region_cb_priv;
void *hdr;
int err;
@@ -6546,12 +6566,6 @@ static int devlink_nl_cmd_region_read_dumpit(struct sk_buff *skb,
goto out_unlock;
}
- if (!attrs[DEVLINK_ATTR_REGION_SNAPSHOT_ID]) {
- NL_SET_ERR_MSG(cb->extack, "No snapshot id provided");
- err = -EINVAL;
- goto out_unlock;
- }
-
if (info->attrs[DEVLINK_ATTR_PORT_INDEX]) {
index = nla_get_u32(info->attrs[DEVLINK_ATTR_PORT_INDEX]);
@@ -6577,12 +6591,30 @@ static int devlink_nl_cmd_region_read_dumpit(struct sk_buff *skb,
}
snapshot_attr = attrs[DEVLINK_ATTR_REGION_SNAPSHOT_ID];
- snapshot_id = nla_get_u32(snapshot_attr);
- snapshot = devlink_region_snapshot_get_by_id(region, snapshot_id);
- if (!snapshot) {
- NL_SET_ERR_MSG_ATTR(cb->extack, snapshot_attr, "requested snapshot does not exist");
- err = -EINVAL;
- goto out_unlock;
+ if (!snapshot_attr) {
+ if (!region->ops->read) {
+ NL_SET_ERR_MSG(cb->extack, "requested region does not support direct read");
+ err = -EOPNOTSUPP;
+ goto out_unlock;
+ }
+ if (port)
+ region_cb = &devlink_region_port_direct_fill;
+ else
+ region_cb = &devlink_region_direct_fill;
+ region_cb_priv = region;
+ } else {
+ struct devlink_snapshot *snapshot;
+ u32 snapshot_id;
+
+ snapshot_id = nla_get_u32(snapshot_attr);
+ snapshot = devlink_region_snapshot_get_by_id(region, snapshot_id);
+ if (!snapshot) {
+ NL_SET_ERR_MSG_ATTR(cb->extack, snapshot_attr, "requested snapshot does not exist");
+ err = -EINVAL;
+ goto out_unlock;
+ }
+ region_cb = &devlink_region_snapshot_fill;
+ region_cb_priv = snapshot;
}
if (attrs[DEVLINK_ATTR_REGION_CHUNK_ADDR] &&
@@ -6633,9 +6665,9 @@ static int devlink_nl_cmd_region_read_dumpit(struct sk_buff *skb,
goto nla_put_failure;
}
- err = devlink_nl_region_read_fill(skb, &devlink_region_snapshot_fill,
- snapshot, start_offset, end_offset,
- &ret_offset, cb->extack);
+ err = devlink_nl_region_read_fill(skb, region_cb, region_cb_priv,
+ start_offset, end_offset, &ret_offset,
+ cb->extack);
if (err && err != -EMSGSIZE)
goto nla_put_failure;
--
2.38.1.420.g319605f8f00e
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