IB/uverbs: Add read counters support

This patch exposes the read counters verb to user space applications. By
that verb the user can read the hardware counters which are associated
with the counters object.

The application needs to provide a sufficient memory to hold the
statistics.

Reviewed-by: Yishai Hadas <[e-mail]>
Signed-off-by: Raed Salem <[e-mail]>
Signed-off-by: Leon Romanovsky <[e-mail]>
Signed-off-by: Jason Gunthorpe <[e-mail]>

drivers/infiniband/core/uverbs_std_types_counters.c

···
 	return ret;
 }
 
+static int UVERBS_HANDLER(UVERBS_METHOD_COUNTERS_READ)(struct ib_device *ib_dev,
+						       struct ib_uverbs_file *file,
+						       struct uverbs_attr_bundle *attrs)
+{
+	struct ib_counters_read_attr read_attr = {};
+	const struct uverbs_attr *uattr;
+	struct ib_counters *counters =
+		uverbs_attr_get_obj(attrs, UVERBS_ATTR_READ_COUNTERS_HANDLE);
+	int ret;
+
+	if (!ib_dev->read_counters)
+		return -EOPNOTSUPP;
+
+	if (!atomic_read(&counters->usecnt))
+		return -EINVAL;
+
+	ret = uverbs_copy_from(&read_attr.flags, attrs,
+			       UVERBS_ATTR_READ_COUNTERS_FLAGS);
+	if (ret)
+		return ret;
+
+	uattr = uverbs_attr_get(attrs, UVERBS_ATTR_READ_COUNTERS_BUFF);
+	read_attr.ncounters = uattr->ptr_attr.len / sizeof(u64);
+	read_attr.counters_buff = kcalloc(read_attr.ncounters,
+					  sizeof(u64), GFP_KERNEL);
+	if (!read_attr.counters_buff)
+		return -ENOMEM;
+
+	ret = ib_dev->read_counters(counters,
+				    &read_attr,
+				    attrs);
+	if (ret)
+		goto err_read;
+
+	ret = uverbs_copy_to(attrs, UVERBS_ATTR_READ_COUNTERS_BUFF,
+			     read_attr.counters_buff,
+			     read_attr.ncounters * sizeof(u64));
+
+err_read:
+	kfree(read_attr.counters_buff);
+	return ret;
+}
+
 static DECLARE_UVERBS_NAMED_METHOD(UVERBS_METHOD_COUNTERS_CREATE,
 	&UVERBS_ATTR_IDR(UVERBS_ATTR_CREATE_COUNTERS_HANDLE,
 			 UVERBS_OBJECT_COUNTERS,
···
 			 UVERBS_ACCESS_DESTROY,
 			 UA_FLAGS(UVERBS_ATTR_SPEC_F_MANDATORY)));
 
+#define MAX_COUNTERS_BUFF_SIZE USHRT_MAX
+static DECLARE_UVERBS_NAMED_METHOD(UVERBS_METHOD_COUNTERS_READ,
+	&UVERBS_ATTR_IDR(UVERBS_ATTR_READ_COUNTERS_HANDLE,
+			 UVERBS_OBJECT_COUNTERS,
+			 UVERBS_ACCESS_READ,
+			 UA_FLAGS(UVERBS_ATTR_SPEC_F_MANDATORY)),
+	&UVERBS_ATTR_PTR_OUT(UVERBS_ATTR_READ_COUNTERS_BUFF,
+			     UVERBS_ATTR_SIZE(0, MAX_COUNTERS_BUFF_SIZE),
+			     UA_FLAGS(UVERBS_ATTR_SPEC_F_MANDATORY)),
+	&UVERBS_ATTR_PTR_IN(UVERBS_ATTR_READ_COUNTERS_FLAGS,
+			    UVERBS_ATTR_TYPE(__u32),
+			    UA_FLAGS(UVERBS_ATTR_SPEC_F_MANDATORY)));
+
 DECLARE_UVERBS_NAMED_OBJECT(UVERBS_OBJECT_COUNTERS,
 			    &UVERBS_TYPE_ALLOC_IDR(0, uverbs_free_counters),
 			    &UVERBS_METHOD(UVERBS_METHOD_COUNTERS_CREATE),
-			    &UVERBS_METHOD(UVERBS_METHOD_COUNTERS_DESTROY));
+			    &UVERBS_METHOD(UVERBS_METHOD_COUNTERS_DESTROY),
+			    &UVERBS_METHOD(UVERBS_METHOD_COUNTERS_READ));
 

include/uapi/rdma/ib_user_ioctl_cmds.h

···
 	UVERBS_ATTR_DESTROY_COUNTERS_HANDLE,
 };
 
+enum uverbs_attrs_read_counters_cmd_attr_ids {
+	UVERBS_ATTR_READ_COUNTERS_HANDLE,
+	UVERBS_ATTR_READ_COUNTERS_BUFF,
+	UVERBS_ATTR_READ_COUNTERS_FLAGS,
+};
+
 enum uverbs_methods_actions_counters_ops {
 	UVERBS_METHOD_COUNTERS_CREATE,
 	UVERBS_METHOD_COUNTERS_DESTROY,
+	UVERBS_METHOD_COUNTERS_READ,
 };
 
 #endif