gen_node: add debugger support for guestfs libvirt guests

kconfigs/Kconfig.libvirt

@@ -1104,6 +1104,31 @@ config LIBVIRT_STORAGE_POOL_NAME
 	  For instance you may want to use a volume name of "data2" for a path
 	  on a partition on /data2/ or something like that.
 
+config LIBVIRT_ENABLE_GDB
+    bool "Enable GDB debugging for the guest"
+	output yaml
+	help
+	  Select this option if you want to enable debugging support for GDB.
+	  By default , it is assumed that gdb is disabled since we dont want
+	  to complicate this for the CI runs. If enabled then libvirt guest
+	  xml for each guest will be configured to use gdb on a specific
+	  tcp port.
+
+config LIBVIRT_GDB_BASEPORT
+    int
+	default $(shell, ./scripts/get_gdb_base_port.sh) if LIBVIRT
+	output yaml
+	depends on LIBVIRT_ENABLE_GDB
+	help
+	  This option defines the base port to be used for the GDB.
+	  Esentially we need to make QEMU listen for an incoming connection from
+	  gdb on a TCP port. The default port is chosen to be 1234. However we
+	  introduce variability for assigning the port to each guest by defining
+	  a base port and adding an index to it based on the number of libvrt guest
+	  nodes. Therefore the base port is extracted from the md5sum of the
+	  /scripts/get_gdb_base_port.sh file and use the last 4 digits of the md5sum
+	  of the file to assign to libvirt_gdb_baseport.
+
 source "kconfigs/Kconfig.libvirt.zns"
 source "kconfigs/Kconfig.libvirt.largeio"
 source "kconfigs/Kconfig.libvirt.cxl"

playbooks/roles/gen_nodes/defaults/main.yml

@@ -27,6 +27,9 @@ vagrant_box: "debian/testing64"
 vagrant_box_version: ""
 libvirt_vcpus_count: 8
 libvirt_mem_mb: 4096
+gdb_port_conflict: False
+libvirt_enable_gdb: False
+libvirt_gdb_baseport: 1234
 qemu_bin_path: "/usr/bin/qemu-system-x86_64"
 extra_disk_path: ".vagrant/nvme_disks"
 extra_disk_driver: "nvme"

playbooks/roles/gen_nodes/tasks/main.yml

@@ -561,13 +561,39 @@
     - kdevops_enable_guestfs|bool
     - pcie_passthrough_enable|bool
 
+- name: Find if port conflict occur
+  ansible.builtin.shell: "ss -ltn | grep ':{{ (libvirt_gdb_baseport | int) + (idx | int) }} '"
+  register: gdb_port_reg
+  failed_when: false
+  changed_when: false
+  loop: "{{ guestfs_nodes }}"
+  loop_control:
+    index_var: idx
+  when:
+    - kdevops_enable_guestfs|bool
+
+- name: Set the conflict flag on if conflict occur
+  set_fact:
+    gdb_port_conflict: True
+  when: >
+    gdb_port_reg.results is defined and
+    gdb_port_reg.results | selectattr('rc', 'equalto', 0) | list | length > 0
+
+- name: Fail bringup if gdb port conflict occur
+  fail:
+    msg: "GDB port conflict occur, please check the base port number {{ libvirt_gdb_baseport }} and try with another"
+  when: gdb_port_conflict|bool
+
 - name: Generate XML files for the libvirt guests
   vars:
     hostname: "{{ item.name }}"
+    guestidx: "{{ idx }}"
   template:
     src: "guestfs_{{ libvirt_machine_type }}.j2.xml"
     dest: "{{ topdir_path }}/guestfs/{{ hostname }}/{{ hostname }}.xml"
     force: yes
   with_items: "{{ guestfs_nodes }}"
+  loop_control:
+    index_var: idx
   when:
     - kdevops_enable_guestfs|bool

playbooks/roles/gen_nodes/templates/guestfs_q35.j2.xml

@@ -184,6 +184,10 @@
     <qemu:arg value='ICH9-LPC.disable_s4=0'/>
     <qemu:arg value='-device'/>
     <qemu:arg value='pxb-pcie,id=pcie.1,bus_nr=32,bus=pcie.0,addr=0x8'/>
+    {% if libvirt_enable_gdb %}
+      <qemu:arg value='-gdb'/>
+      <qemu:arg value='tcp::{{ libvirt_gdb_baseport + idx}}'/>
+    {% endif %}
 {% include './templates/gen_drives.j2' %}
   </qemu:commandline>
 </domain>

playbooks/roles/gen_nodes/templates/guestfs_virt.j2.xml

@@ -173,6 +173,10 @@
     <qemu:arg value='ICH9-LPC.disable_s4=0'/>
     <qemu:arg value='-device'/>
     <qemu:arg value='pxb-pcie,id=pcie.1,bus_nr=32,bus=pcie.0,addr=0x8'/>
+    {% if libvirt_enable_gdb %}
+      <qemu:arg value='-gdb'/>
+      <qemu:arg value='tcp::{{ libvirt_gdb_baseport + idx}}'/>
+    {% endif %}
 {% include './templates/gen_drives.j2' %}
   </qemu:commandline>
 </domain>

scripts/get_gdb_base_port.sh

@@ -0,0 +1,13 @@
+#!/bin/bash
+
+# This script is used to get the base port for gdbserver
+
+# get the sha1sum of the script
+
+base_md5sum=$(md5sum "$0" | awk '{print $1}')
+digits_only=$(echo $base_md5sum | tr -cd '0-9')
+
+# extract the last 4 digits from md5sum
+
+base_port=${digits_only: -4}
+echo $base_port