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Re: [PATCH v11 01/14] machine: Deprecate "parameter=0" SMP configuration
From: |
Daniel P . Berrangé |
Subject: |
Re: [PATCH v11 01/14] machine: Deprecate "parameter=0" SMP configurations |
Date: |
Tue, 28 Sep 2021 10:58:38 +0100 |
User-agent: |
Mutt/2.0.7 (2021-05-04) |
On Tue, Sep 28, 2021 at 11:57:42AM +0800, Yanan Wang wrote:
> In the SMP configuration, we should either provide a topology
> parameter with a reasonable value (greater than zero) or just
> omit it and QEMU will compute the missing value.
>
> The users shouldn't provide a configuration with any parameter
> of it specified as zero (e.g. -smp 8,sockets=0) which could
> possibly cause unexpected results in the -smp parsing. So we
> deprecate this kind of configurations since 6.2 by adding the
> explicit sanity check.
>
> Signed-off-by: Yanan Wang <wangyanan55@huawei.com>
> Reviewed-by: Cornelia Huck <cohuck@redhat.com>
> ---
> docs/about/deprecated.rst | 15 +++++++++++++++
> hw/core/machine.c | 14 ++++++++++++++
> qapi/machine.json | 2 +-
> qemu-options.hx | 12 +++++++-----
> 4 files changed, 37 insertions(+), 6 deletions(-)
>
> diff --git a/docs/about/deprecated.rst b/docs/about/deprecated.rst
> index 3c2be84d80..97415dbecd 100644
> --- a/docs/about/deprecated.rst
> +++ b/docs/about/deprecated.rst
> @@ -160,6 +160,21 @@ Use ``-display sdl`` instead.
>
> Use ``-display curses`` instead.
>
> +``-smp`` ("parameter=0" SMP configurations) (since 6.2)
> +'''''''''''''''''''''''''''''''''''''''''''''''''''''''
> +
> +Specified CPU topology parameters must be greater than zero.
> +
> +In the SMP configuration, users should either provide a CPU topology
> +parameter with a reasonable value (greater than zero) or just omit it
> +and QEMU will compute the missing value.
> +
> +However, historically it was implicitly allowed for users to provide
> +a parameter with zero value, which is meaningless and could also possibly
> +cause unexpected results in the -smp parsing. So support for this kind of
> +configurations (e.g. -smp 8,sockets=0) is deprecated since 6.2 and will
> +be removed in the near future, users have to ensure that all the topology
> +members described with -smp are greater than zero.
>
> Plugin argument passing through ``arg=<string>`` (since 6.1)
> ''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
> diff --git a/hw/core/machine.c b/hw/core/machine.c
> index 067f42b528..711e83db54 100644
> --- a/hw/core/machine.c
> +++ b/hw/core/machine.c
> @@ -835,6 +835,20 @@ static void machine_set_smp(Object *obj, Visitor *v,
> const char *name,
> return;
> }
>
> + /*
> + * Specified CPU topology parameters must be greater than zero,
> + * explicit configuration like "cpus=0" is not allowed.
> + */
> + if ((config->has_cpus && config->cpus == 0) ||
> + (config->has_sockets && config->sockets == 0) ||
> + (config->has_dies && config->dies == 0) ||
> + (config->has_cores && config->cores == 0) ||
> + (config->has_threads && config->threads == 0) ||
> + (config->has_maxcpus && config->maxcpus == 0)) {
> + warn_report("Invalid CPU topology deprecated: "
> + "CPU topology parameters must be greater than zero");
> + }
> +
> mc->smp_parse(ms, config, errp);
> if (*errp) {
> goto out_free;
> diff --git a/qapi/machine.json b/qapi/machine.json
> index 32d47f4e35..227e75d8af 100644
> --- a/qapi/machine.json
> +++ b/qapi/machine.json
> @@ -1331,7 +1331,7 @@
> #
> # @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 change is unrelated to the rest of this commit.
It just looks like a simple bug fix and should just be
spun out into its own patch.
> diff --git a/qemu-options.hx b/qemu-options.hx
> index 8f603cc7e6..91d859aa29 100644
> --- a/qemu-options.hx
> +++ b/qemu-options.hx
> @@ -227,11 +227,13 @@ SRST
> of computing the CPU maximum count.
>
> Either the initial CPU count, or at least one of the topology parameters
> - must be specified. Values for any omitted parameters will be computed
> - from those which are given. Historically preference was given to the
> - coarsest topology parameters when computing missing values (ie sockets
> - preferred over cores, which were preferred over threads), however, this
> - behaviour is considered liable to change.
> + must be specified. The specified parameters must be greater than zero,
> + explicit configuration like "cpus=0" is not allowed. Values for any
> + omitted parameters will be computed from those which are given.
> + Historically preference was given to the coarsest topology parameters
> + when computing missing values (ie sockets preferred over cores, which
> + were preferred over threads), however, this behaviour is considered
> + liable to change.
> ERST
>
> DEF("numa", HAS_ARG, QEMU_OPTION_numa,
If you split the docs fix out into its own patch then you can add
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
to both this patch and the new patch.
Regards,
Daniel
--
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- [PATCH v11 00/14] machine: smp parsing fixes and improvement, Yanan Wang, 2021/09/27
- [PATCH v11 01/14] machine: Deprecate "parameter=0" SMP configurations, Yanan Wang, 2021/09/27
- Re: [PATCH v11 01/14] machine: Deprecate "parameter=0" SMP configurations,
Daniel P . Berrangé <=
- [PATCH v11 02/14] machine: Minor refactor/fix for the smp parsers, Yanan Wang, 2021/09/27
- [PATCH v11 05/14] machine: Improve the error reporting of smp parsing, Yanan Wang, 2021/09/27
- [PATCH v11 07/14] qtest/numa-test: Use detailed -smp CLIs in test_def_cpu_split, Yanan Wang, 2021/09/27
- [PATCH v11 08/14] machine: Prefer cores over sockets in smp parsing since 6.2, Yanan Wang, 2021/09/27