Re: [Qemu-devel] [PATCH 7/8] [PATCH RFC v2] s390-qemu: cpu hotplug - Infrastructure for Cpu Devices

[Igor Mammedov <imammedo@redhat.com>]

On Fri,  7 Jun 2013 13:28:06 -0400
"Jason J. Herne" <jjherne@us.ibm.com> wrote:

> From: "Jason J. Herne" <jjherne@us.ibm.com>
> 
> Add infrastructure for treating cpus as devices. This patch allows cpus to be
> specified using a combination of '-smp' and '-device cpu'.  This approach
> forces a change in the way cpus are counted via smp_cpus.
> 
> Signed-off-by: Jason J. Herne <jjherne@us.ibm.com>
> ---
>  include/hw/boards.h |    3 ++
>  vl.c                |   95 +++++++++++++++++++++++++++++++++++++++++++--------
>  2 files changed, 84 insertions(+), 14 deletions(-)
> 
> diff --git a/include/hw/boards.h b/include/hw/boards.h
> index ed427a1..b0c86bf 100644
> --- a/include/hw/boards.h
> +++ b/include/hw/boards.h
> @@ -47,8 +47,11 @@ typedef struct QEMUMachine {
>      GlobalProperty *compat_props;
>      struct QEMUMachine *next;
>      const char *hw_version;
> +    const char *cpu_device_str;
>  } QEMUMachine;
>  
> +#define CPUS_ARE_DEVICES(qemu_mach)    (qemu_mach->cpu_device_str != NULL)
> +
>  int qemu_register_machine(QEMUMachine *m);
>  QEMUMachine *find_default_machine(void);
>  
> diff --git a/vl.c b/vl.c
> index 71e1e6d..873834f 100644
> --- a/vl.c
> +++ b/vl.c
> @@ -546,6 +546,46 @@ static int default_driver_check(QemuOpts *opts, void *opaque)
>      return 0;
>  }
>  
> +static void convert_smp_to_cpu_devices(QEMUMachine *machine)
> +{
> +    int i;
> +    QemuOpts *opts;
> +
> +    for (i = 0; i < smp_cpus; i++) {
> +        opts = qemu_opts_create_nofail(qemu_find_opts("device"));
> +        qemu_opt_set(opts, "driver", machine->cpu_device_str);
                                                 ^^ could be default_cpu
and probably stored in .default_machine_opts?

> +    }
> +    smp_cpus = 0;
> +}
> +
> +static int count_cpu_devices(QemuOpts *opts, void *opaque)
> +{
> +    const char *driver = qemu_opt_get(opts, "driver");
> +    QEMUMachine *machine = (QEMUMachine *)opaque;
> +
> +    /* Skip non-cpu devices*/
> +    if (!driver || strcmp(driver, machine->cpu_device_str) != 0) {
find type by driver name and dynamic cast it to common CPU, if cast is successful
it's CPU device

> +        return 0;
> +    }
> +
> +    smp_cpus += 1;
> +    return 0;
> +}
-smp smp_cpus could be treated as a number of startup cpus including CPUs
specified by -device

if number of "-device CPU" more than smp_cpus QEMU could just print error and die
at init stage asking user to correct command line.

> +static int handle_cpu_device(QemuOpts *opts, void *opaque)
> +{
> +    const char *driver = qemu_opt_get(opts, "driver");
> +    QEMUMachine *machine = (QEMUMachine *)opaque;
> +
> +    /* Skip non-cpu devices*/
> +    if (!driver || strcmp(driver, machine->cpu_device_str) != 0) {
> +        return 0;
> +    }
> +
> +    qdev_device_add(opts);
> +    return 0;
> +}
> +
>  /***********************************************************/
>  /* QEMU state */
>  
> @@ -2318,6 +2358,13 @@ static int device_help_func(QemuOpts *opts, void *opaque)
>  static int device_init_func(QemuOpts *opts, void *opaque)
>  {
>      DeviceState *dev;
> +    const char *driver = qemu_opt_get(opts, "driver");
> +    QEMUMachine *machine = (QEMUMachine *)opaque;
> +
> +    /* Skip cpu devices*/
> +    if (!driver || strcmp(driver, machine->cpu_device_str) == 0) {
> +        return 0;
> +    }
>  
>      dev = qdev_device_add(opts);
>      if (!dev)
> @@ -3630,19 +3677,6 @@ int main(int argc, char **argv, char **envp)
>                  break;
>              case QEMU_OPTION_smp:
>                  smp_parse(optarg);
> -                if (smp_cpus < 1) {
> -                    fprintf(stderr, "Invalid number of CPUs\n");
> -                    exit(1);
> -                }
> -                if (max_cpus < smp_cpus) {
> -                    fprintf(stderr, "maxcpus must be equal to or greater than "
> -                            "smp\n");
> -                    exit(1);
> -                }
> -                if (max_cpus > 255) {
> -                    fprintf(stderr, "Unsupported number of maxcpus\n");
> -                    exit(1);
> -                }
>                  break;
>  	    case QEMU_OPTION_vnc:
>  #ifdef CONFIG_VNC
> @@ -3965,6 +3999,16 @@ int main(int argc, char **argv, char **envp)
>      }
>  
>      /*
> +     * Count cpu devices. Cpu count is determied by adding -device cpu
> +     * statements to the number of cpus specified on the -smp statement.
> +     */
> +    if (CPUS_ARE_DEVICES(machine)) {
> +        convert_smp_to_cpu_devices(machine);
> +        qemu_opts_foreach(qemu_find_opts("device"), count_cpu_devices,
> +                          machine, 0);
> +    }
> +
> +    /*
>       * Default to max_cpus = smp_cpus, in case the user doesn't
>       * specify a max_cpus value.
>       */
> @@ -3979,6 +4023,20 @@ int main(int argc, char **argv, char **envp)
>          exit(1);
>      }
>  
> +    if (smp_cpus < 1) {
> +        fprintf(stderr, "Invalid number of CPUs\n");
> +        exit(1);
> +    }
> +    if (max_cpus < smp_cpus) {
> +        fprintf(stderr, "maxcpus must be equal to or greater than the number of"
> +                " cpus defined\n");
> +        exit(1);
> +    }
> +    if (max_cpus > 255) {
> +        fprintf(stderr, "Unsupported number of maxcpus\n");
> +        exit(1);
> +    }
> +
>      /*
>       * Get the default machine options from the machine if it is not already
>       * specified either by the configuration file or by the command line.
> @@ -4305,6 +4363,13 @@ int main(int argc, char **argv, char **envp)
>                                   .cpu_model = cpu_model };
>      machine->init(&args);
>  
> +    /* Create cpu devices */
> +    if (CPUS_ARE_DEVICES(machine)) {
> +        smp_cpus = 0;  /* Reset this because each cpu will count itself */
> +        qemu_opts_foreach(qemu_find_opts("device"), handle_cpu_device,
> +                          machine, 0);
> +    }
> +
>      if (machine->post_cpu_init) {
>          machine->post_cpu_init();
>      }
> @@ -4324,8 +4389,10 @@ int main(int argc, char **argv, char **envp)
>      }
>  
>      /* init generic devices */
> -    if (qemu_opts_foreach(qemu_find_opts("device"), device_init_func, NULL, 1) != 0)
> +    if (qemu_opts_foreach(qemu_find_opts("device"),
> +                          device_init_func, machine, 1) != 0) {
>          exit(1);
> +    }
>  
>      net_check_clients();
>