[PATCH 5/5] qmp: Added find-ebpf-rss-helper command.

[Andrew Melnychenko]

New qmp command to query ebpf helper.
It's crucial that QEMU and helper are in sync.
Technically helper should pass eBPF fds that QEMU may accept.
And different QEMU's builds may have different eBPF programs.
QEMU returns helper that should "fit" to virtio-net.
QEMU would check the stamp of the helper to make sure
that eBPF program is valid.

Signed-off-by: Andrew Melnychenko <andrew@daynix.com>
---
 monitor/qmp-cmds.c | 28 ++++++++++++++++++++++++++++
 qapi/misc.json     | 42 ++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 70 insertions(+)

diff --git a/monitor/qmp-cmds.c b/monitor/qmp-cmds.c
index 859012aef4..2f91c34bbb 100644
--- a/monitor/qmp-cmds.c
+++ b/monitor/qmp-cmds.c
@@ -31,6 +31,7 @@
 #include "hw/mem/memory-device.h"
 #include "hw/intc/intc.h"
 #include "hw/rdma/rdma.h"
+#include "qemu-ebpf-rss-helper-stamp-utils.h"
 
 NameInfo *qmp_query_name(Error **errp)
 {
@@ -202,3 +203,30 @@ static void __attribute__((__constructor__)) 
monitor_init_qmp_commands(void)
                          qmp_marshal_qmp_capabilities,
                          QCO_ALLOW_PRECONFIG, 0);
 }
+
+HelperPath *qmp_find_ebpf_rss_helper(bool has_path,
+                                     strList *path, Error **errp)
+{
+    HelperPath *ret = NULL;
+    char *helperbin = NULL;
+
+    /* Look for helper in the suggested pathes */
+    if (has_path) {
+        strList *str_list = NULL;
+        for (str_list = path;
+             str_list && !helperbin;
+             str_list = str_list->next) {
+            helperbin = qemu_check_suggested_ebpf_rss_helper(str_list->value);
+        }
+    }
+
+    if (helperbin == NULL) {
+        helperbin = qemu_find_default_ebpf_rss_helper();
+    }
+
+    if (helperbin) {
+        ret = g_new0(HelperPath, 1);
+        ret->path = helperbin;
+    }
+    return ret;
+}
diff --git a/qapi/misc.json b/qapi/misc.json
index 27ef5a2b20..1dfb3c132e 100644
--- a/qapi/misc.json
+++ b/qapi/misc.json
@@ -584,3 +584,45 @@
 { 'event': 'VFU_CLIENT_HANGUP',
   'data': { 'vfu-id': 'str', 'vfu-qom-path': 'str',
             'dev-id': 'str', 'dev-qom-path': 'str' } }
+
+##
+# @HelperPath:
+#
+# Name of the helper and binary location.
+##
+{ 'struct': 'HelperPath',
+  'data': {'path': 'str'} }
+
+##
+# @find-ebpf-rss-helper:
+#
+# Query helper paths to find qemu-ebpf-rss-helper.
+# The qemu would check "the stamp" and
+# returns the proper helper.
+# It's possible to provide paths where to look for a helper.
+# If the path is provided to a file - qemu would check the file for the stamp.
+# If the path is provided to a directory - qemu would look for
+# a file "qemu-ebpf-rss-helper" and check its stamp.
+#
+# Returns: path to the helper with a valid stamp.
+#
+# Note: Provided path arguments have the highest priority where to look
+#       for a helper. Then, default "helper directory" and then
+#       near the qemu binary.
+#
+# Since: 7.2
+#
+# Example:
+#
+# -> { "execute": "find-ebpf-rss-helper", "arguments": { "path": 
"/opt/qemu_helpers/" } }
+# <- { "return": [
+#        {
+#          "path": "/usr/local/libexec/qemu-ebpf-rss-helper"
+#        }
+#      ]
+#    }
+#
+##
+{ 'command': 'find-ebpf-rss-helper',
+  'data': {'*path': ['str']},
+  'returns': 'HelperPath' }
-- 
2.39.1