Re: [Qemu-devel] [PATCH for-2.8 v2 3/3] pc: fix FW_CFG_NB_CPUS to account for -device added CPUs

[Eduardo Habkost]

On Tue, Nov 15, 2016 at 01:17:16PM +0100, Igor Mammedov wrote:
[...]
> @@ -1265,6 +1267,8 @@ void pc_machine_done(Notifier *notifier, void *data)
>      if (pcms->fw_cfg) {
>          pc_build_smbios(pcms->fw_cfg);
>          pc_build_feature_control_file(pcms);
> +        /* update FW_CFG_NB_CPUS to account for -device added CPUs */
> +        fw_cfg_modify_i16(pcms->fw_cfg, FW_CFG_NB_CPUS, pcms->boot_cpus);
>      }
>  
>      if (pcms->apic_id_limit > 255) {
> @@ -1342,7 +1346,7 @@ void xen_load_linux(PCMachineState *pcms)
>      assert(MACHINE(pcms)->kernel_filename != NULL);
>  
>      fw_cfg = fw_cfg_init_io(FW_CFG_IO_BASE);
> -    fw_cfg_add_i16(fw_cfg, FW_CFG_NB_CPUS, (uint16_t)smp_cpus);
> +    fw_cfg_add_i16(fw_cfg, FW_CFG_NB_CPUS, pcms->boot_cpus);
>      rom_set_fw(fw_cfg);
>  
>      load_linux(pcms, fw_cfg);
> @@ -1824,9 +1828,10 @@ static void pc_cpu_plug(HotplugHandler *hotplug_dev,
>          }
>      }
>  
> +    /* increment the number of CPUs */
> +    pcms->boot_cpus++;
>      if (dev->hotplugged) {
> -        /* increment the number of CPUs */
> -        rtc_set_memory(pcms->rtc, 0x5f, rtc_get_memory(pcms->rtc, 0x5f) + 1);
> +        rtc_set_cpus_count(pcms->rtc, pcms->boot_cpus);
>      }
>  
>      found_cpu = pc_find_cpu_slot(pcms, CPU(dev), NULL);
> @@ -1880,7 +1885,10 @@ static void pc_cpu_unplug_cb(HotplugHandler 
> *hotplug_dev,
>      found_cpu->cpu = NULL;
>      object_unparent(OBJECT(dev));
>  
> -    rtc_set_memory(pcms->rtc, 0x5f, rtc_get_memory(pcms->rtc, 0x5f) - 1);
> +    /* decrement the number of CPUs */
> +    pcms->boot_cpus--;
> +    /* Update the number of CPUs in CMOS */
> +    rtc_set_cpus_count(pcms->rtc, pcms->boot_cpus);

Don't we need to call fw_cfg_modify_i16() on hotplug/hot-unplug,
too?

-- 
Eduardo