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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
requested via the new DEVLINK_ATTR_REGION_DIRECT. If this attribute is set,
then perform a direct read instead of using a snapshot. Direct read is
mutually exclusive with DEVLINK_ATTR_REGION_SNAPSHOT_ID, and care is taken
to ensure that we reject commands which provide incorrect attributes.

Regions must enable support for direct read by implementing the .read()
callback function. If a region does not support such direct reads, a
suitable extended error message is reported.

Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
Reviewed-by: Jiri Pirko <jiri@nvidia.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Jacob Keller 2022-11-28 12:36:44 -08:00 committed by Jakub Kicinski
parent 2d4caf0988
commit af6397c9ee
4 changed files with 94 additions and 17 deletions
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13
Documentation/networking/devlink/devlink-region.rst
View File

@ -31,6 +31,15 @@ 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. User space can request a direct read by using the
``DEVLINK_ATTR_REGION_DIRECT`` attribute instead of specifying a snapshot
id.
example usage
-------------
@ -65,6 +74,10 @@ 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.

16
include/net/devlink.h
View File

@ -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;
};

2
include/uapi/linux/devlink.h
View File

@ -610,6 +610,8 @@ enum devlink_attr {
DEVLINK_ATTR_RATE_TX_PRIORITY, /* u32 */
DEVLINK_ATTR_RATE_TX_WEIGHT, /* u32 */
DEVLINK_ATTR_REGION_DIRECT, /* flag */
/* add new attributes above here, update the policy in devlink.c */
__DEVLINK_ATTR_MAX,

80
net/core/devlink.c
View File

@ -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 +6591,43 @@ 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 (!nla_get_flag(attrs[DEVLINK_ATTR_REGION_DIRECT])) {
NL_SET_ERR_MSG(cb->extack, "No snapshot id provided");
err = -EINVAL;
goto out_unlock;
}
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;
if (nla_get_flag(attrs[DEVLINK_ATTR_REGION_DIRECT])) {
NL_SET_ERR_MSG_ATTR(cb->extack, snapshot_attr, "Direct region read does not use snapshot");
err = -EINVAL;
goto out_unlock;
}
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 +6678,9 @@ 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;
@ -9280,6 +9325,7 @@ static const struct nla_policy devlink_nl_policy[DEVLINK_ATTR_MAX + 1] = {
[DEVLINK_ATTR_SELFTESTS] = { .type = NLA_NESTED },
[DEVLINK_ATTR_RATE_TX_PRIORITY] = { .type = NLA_U32 },
[DEVLINK_ATTR_RATE_TX_WEIGHT] = { .type = NLA_U32 },
[DEVLINK_ATTR_REGION_DIRECT] = { .type = NLA_FLAG },
};
static const struct genl_small_ops devlink_nl_ops[] = {