Re: [RFC PATCH 5/6] pc/machine: Disallow any configuration of dies for non-PC machines

[Daniel P . Berrangé]

On Fri, Jul 02, 2021 at 06:07:38PM +0800, Yanan Wang wrote:
> Since a machine type does not support topology parameter of dies,
> it's probably more reasonable to reject any explicit specification
> to avoid possible confuse, including "dies=0" and "dies=1" although
> they won't affect the calculation of non-PC machines.
> 
> Also a comment of struct SMPConfiguration is fixed.
> 
> Signed-off-by: Yanan Wang <wangyanan55@huawei.com>
> ---
>  hw/core/machine.c | 2 +-
>  qapi/machine.json | 2 +-
>  2 files changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/hw/core/machine.c b/hw/core/machine.c
> index 58882835be..55785feee2 100644
> --- a/hw/core/machine.c
> +++ b/hw/core/machine.c
> @@ -747,7 +747,7 @@ static void smp_parse(MachineState *ms, SMPConfiguration 
> *config, Error **errp)
>      unsigned threads = config->has_threads ? config->threads : 0;
>      unsigned maxcpus = config->has_maxcpus ? config->maxcpus : 0;
>  
> -    if (config->has_dies && config->dies != 0 && config->dies != 1) {
> +    if (config->has_dies) {
>          error_setg(errp, "dies not supported by this machine's CPU 
> topology");
>      }

This will cause a functional regression. Libvirt always specifies
dies=1 if QEMU supports it.  I don't see a need to reject it,
since conceptually it is reasonable to say that all existing
CPUs have a single die. It simply that 99% of CPUs don't support
more than 1 die.

> diff --git a/qapi/machine.json b/qapi/machine.json
> index c3210ee1fb..253f84abf6 100644
> --- a/qapi/machine.json
> +++ b/qapi/machine.json
> @@ -1297,7 +1297,7 @@
>  #
>  # @dies: number of dies per socket in the CPU topology
>  #
> -# @cores: number of cores per thread in the CPU topology
> +# @cores: number of cores per die in the CPU topology
>  #
>  # @threads: number of threads per core in the CPU topology
>  #

This is a simple docs fix and ok

Regards,
Daniel
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