Updates the firmware config with the next boot cpus information and also
registers the reset callback to be called when guest reboots to reset the cpu.

Co-developed-by: Keqian Zhu <zhukeqian1@huawei.com>
Signed-off-by: Keqian Zhu <zhukeqian1@huawei.com>
Signed-off-by: Salil Mehta <salil.mehta@huawei.com>
---
 hw/arm/boot.c         |  2 +-
 hw/arm/virt.c         | 18 +++++++++++++++---
 include/hw/arm/boot.h |  2 ++
 include/hw/arm/virt.h |  1 +
 4 files changed, 19 insertions(+), 4 deletions(-)

diff --git a/hw/arm/boot.c b/hw/arm/boot.c
index 5301d8d318..8bf8d003eb 100644
--- a/hw/arm/boot.c
+++ b/hw/arm/boot.c
@@ -682,7 +682,7 @@ fail:
     return -1;
 }
 
-static void do_cpu_reset(void *opaque)
+void do_cpu_reset(void *opaque)
 {
     ARMCPU *cpu = opaque;
     CPUState *cs = CPU(cpu);
diff --git a/hw/arm/virt.c b/hw/arm/virt.c
index 9634011ae7..8cb66c11a1 100644
--- a/hw/arm/virt.c
+++ b/hw/arm/virt.c
@@ -45,6 +45,8 @@
 #include "sysemu/device_tree.h"
 #include "sysemu/numa.h"
 #include "sysemu/runstate.h"
+#include "sysemu/reset.h"
+#include "sysemu/sysemu.h"
 #include "sysemu/tpm.h"
 #include "sysemu/tcg.h"
 #include "sysemu/kvm.h"
@@ -1427,7 +1429,7 @@ static FWCfgState *create_fw_cfg(const VirtMachineState *vms, AddressSpace *as)
     char *nodename;
 
     fw_cfg = fw_cfg_init_mem_wide(base + 8, base, 8, base + 16, as);
-    fw_cfg_add_i16(fw_cfg, FW_CFG_NB_CPUS, (uint16_t)ms->smp.cpus);
+    fw_cfg_add_i16(fw_cfg, FW_CFG_NB_CPUS, vms->boot_cpus);
 
     nodename = g_strdup_printf("/fw-cfg@%" PRIx64, base);
     qemu_fdt_add_subnode(ms->fdt, nodename);
@@ -3197,7 +3199,13 @@ static void virt_cpu_plug(HotplugHandler *hotplug_dev, DeviceState *dev,
     }
 
     if (vms->acpi_dev) {
-        /* TODO: register cpu for reset & update F/W info for the next boot */
+        qemu_register_reset(do_cpu_reset, ARM_CPU(cs));
+    }
+
+    /* update the firmware information for the next boot. */
+    vms->boot_cpus++;
+    if (vms->fw_cfg) {
+        fw_cfg_modify_i16(vms->fw_cfg, FW_CFG_NB_CPUS, vms->boot_cpus);
     }
 
     /*
@@ -3263,7 +3271,11 @@ static void virt_cpu_unplug(HotplugHandler *hotplug_dev, DeviceState *dev,
     unwire_gic_cpu_irqs(vms, cs);
     virt_update_gic(vms, cs, false);
 
-    /* TODO: unregister cpu for reset & update F/W info for the next boot */
+    qemu_unregister_reset(do_cpu_reset, ARM_CPU(cs));
+    vms->boot_cpus--;
+    if (vms->fw_cfg) {
+        fw_cfg_modify_i16(vms->fw_cfg, FW_CFG_NB_CPUS, vms->boot_cpus);
+    }
 
     qobject_unref(dev->opts);
     dev->opts = NULL;
diff --git a/include/hw/arm/boot.h b/include/hw/arm/boot.h
index 80c492d742..f81326a1dc 100644
--- a/include/hw/arm/boot.h
+++ b/include/hw/arm/boot.h
@@ -178,6 +178,8 @@ AddressSpace *arm_boot_address_space(ARMCPU *cpu,
 int arm_load_dtb(hwaddr addr, const struct arm_boot_info *binfo,
                  hwaddr addr_limit, AddressSpace *as, MachineState *ms);
 
+void do_cpu_reset(void *opaque);
+
 /* Write a secure board setup routine with a dummy handler for SMCs */
 void arm_write_secure_board_setup_dummy_smc(ARMCPU *cpu,
                                             const struct arm_boot_info *info,
diff --git a/include/hw/arm/virt.h b/include/hw/arm/virt.h
index 0202f0252c..073d18281e 100644
--- a/include/hw/arm/virt.h
+++ b/include/hw/arm/virt.h
@@ -172,6 +172,7 @@ struct VirtMachineState {
     MemMapEntry *memmap;
     char *pciehb_nodename;
     const int *irqmap;
+    uint16_t boot_cpus;
     int fdt_size;
     uint32_t clock_phandle;
     uint32_t gic_phandle;
-- 
2.34.1