Re: [Qemu-devel] [PATCH v6 01/11] machine: Don't allow CPU toplogies with partially filled cores

[Eduardo Habkost]

On Fri, Jan 08, 2016 at 12:25:09PM +0530, Bharata B Rao wrote:
> Prevent guests from booting with CPU topologies that have partially
> filled CPU cores or can result in partially filled CPU cores after
> CPU hotplug like
> 
> -smp 15,sockets=1,cores=4,threads=4,maxcpus=16 or
> -smp 15,sockets=1,cores=4,threads=4,maxcpus=17.
> 
> This is enforced by introducing MachineClass::validate_smp_config()
> that gets called from generic SMP parsing code. Machine type versions
> that don't want to enforce this can override this method.
> 
> TODO: Only sPAPR and PC changes are done in this patch, other archs
> will be touched after there is agreement on this approach.
> 
> Signed-off-by: Bharata B Rao <address@hidden>
> ---
>  hw/core/machine.c   | 20 ++++++++++++++++++++
>  hw/i386/pc_piix.c   |  7 +++++++
>  hw/i386/pc_q35.c    |  7 +++++++
>  hw/ppc/spapr.c      |  7 +++++++
>  include/hw/boards.h |  1 +
>  vl.c                |  4 ++++
>  6 files changed, 46 insertions(+)
> 
> diff --git a/hw/core/machine.c b/hw/core/machine.c
> index c46ddc7..b66c101 100644
> --- a/hw/core/machine.c
> +++ b/hw/core/machine.c
> @@ -336,6 +336,25 @@ static void machine_init_notify(Notifier *notifier, void 
> *data)
>      foreach_dynamic_sysbus_device(error_on_sysbus_device, NULL);
>  }
>  
> +static int validate_smp_config_generic(int smp_cpus, int max_cpus,
> +                                       int smp_threads)

Please make it use a Error** parameter to return error
information, and let the caller decide what to do with the error
message. One day the mc->validate_smp_config() call may be moved
inside a function that returns error information using Error**
and needs to propagate it to the caller.

> +{
> +        if (smp_cpus % smp_threads) {
> +            error_report("cpu topology: "
> +                         "smp_cpus (%u) should be multiple of threads (%u) ",
> +                         smp_cpus, smp_threads);
> +            return 1;
> +        }
> +
> +        if (max_cpus % smp_threads) {
> +            error_report("cpu topology: "
> +                         "max_cpus (%u) should be multiple of threads (%u) ",
> +                         max_cpus, smp_threads);
> +            return 1;
> +        }
> +        return 0;
> +}
> +
[...]
> diff --git a/vl.c b/vl.c
> index 5aaea77..4b36a49 100644
> --- a/vl.c
> +++ b/vl.c
> @@ -4132,6 +4132,10 @@ int main(int argc, char **argv, char **envp)
>  
>      smp_parse(qemu_opts_find(qemu_find_opts("smp-opts"), NULL));
>  
> +    if (machine_class->validate_smp_config(smp_cpus, max_cpus, smp_threads)) 
> {
> +        exit(1);
> +    }
> +
>      machine_class->max_cpus = machine_class->max_cpus ?: 1; /* Default to UP 
> */
>      if (max_cpus > machine_class->max_cpus) {
>          error_report("Number of SMP CPUs requested (%d) exceeds max CPUs "
> -- 
> 2.1.0
> 

-- 
Eduardo