On Fri, Jul 23 2021, Yanan Wang <wangyana...@huawei.com> wrote:
> In the SMP configuration, we should either specify a topology
> parameter with a reasonable value (equal to or greater than 1)
> or just leave it omitted and QEMU will calculate its value.
> Configurations which explicitly specify the topology parameters
> as zero like "sockets=0" are meaningless, so disallow them.
>
> However, the commit 1e63fe685804d
> (machine: pass QAPI struct to mc->smp_parse) has documented that
> '0' has the same semantics as omitting a parameter in the qapi
> comment for SMPConfiguration. So this patch fixes the doc and
> also adds the corresponding sanity check in the smp parsers.
>
> Reviewed-by: Andrew Jones <drjo...@redhat.com>
> Reviewed-by: Daniel P. Berrange <berra...@redhat.com>
> Tested-by: Daniel P. Berrange <berra...@redhat.com>
> Suggested-by: Andrew Jones <drjo...@redhat.com>
> Signed-off-by: Yanan Wang <wangyana...@huawei.com>
> ---
> hw/core/machine.c | 15 +++++++++++++++
> qapi/machine.json | 6 +++---
> qemu-options.hx | 12 +++++++-----
> 3 files changed, 25 insertions(+), 8 deletions(-)
>
> diff --git a/hw/core/machine.c b/hw/core/machine.c
> index 775add0795..d95e8b6903 100644
> --- a/hw/core/machine.c
> +++ b/hw/core/machine.c
> @@ -829,6 +829,21 @@ static void machine_set_smp(Object *obj, Visitor *v,
> const char *name,
> return;
> }
>
> + /*
> + * The topology parameters must be specified equal to or great than one
s/great/greater/
> + * or just omitted, 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)) {
> + error_setg(errp, "CPU topology parameters must be equal to "
> + "or greater than one if provided");
> + goto out_free;
> + }
> +
> mc->smp_parse(ms, config, errp);
> if (errp) {
> goto out_free;
> diff --git a/qapi/machine.json b/qapi/machine.json
> index c3210ee1fb..9272cb3cf8 100644
> --- a/qapi/machine.json
> +++ b/qapi/machine.json
> @@ -1288,8 +1288,8 @@
> ##
> # @SMPConfiguration:
> #
> -# Schema for CPU topology configuration. "0" or a missing value lets
> -# QEMU figure out a suitable value based on the ones that are provided.
> +# Schema for CPU topology configuration. A missing value lets QEMU
> +# figure out a suitable value based on the ones that are provided.
> #
> # @cpus: number of virtual CPUs in the virtual machine
> #
> @@ -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
> #
> diff --git a/qemu-options.hx b/qemu-options.hx
> index 99ed5ec5f1..b0168f8c48 100644
> --- a/qemu-options.hx
> +++ b/qemu-options.hx
> @@ -223,11 +223,13 @@ 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 equal to or great
s/great/greater/
> + than one, 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,
Reviewed-by: Cornelia Huck <coh...@redhat.com>
