Hi Yanan,
On 2022/10/31 14:56, wangyanan (Y) wrote:
> Hi Yicong,
>
> On 2022/10/27 11:26, Yicong Yang wrote:
>> From: Yicong Yang <yangyic...@hisilicon.com>
>>
>> Currently we'll always generate a cluster node no matter user has
>> specified '-smp clusters=X' or not. Cluster is an optional level
>> and will participant the building of Linux scheduling domains and
>> only appears on a few platforms. It's unncessary to always build
>> it which cannot reflect the real topology on platforms have no
>> cluster and to avoid affecting the linux scheduling domains in the
>> VM. So only generate it when user specified explicitly.
>>
>> Tested qemu-system-aarch64 with `-smp 8` and linux 6.1-rc1, without
>> this patch:
>> estuary:/sys/devices/system/cpu/cpu0/topology$ cat cluster_*
>> ff # cluster_cpus
>> 0-7 # cluster_cpus_list
>> 56 # cluster_id
>>
>> with this patch:
>> estuary:/sys/devices/system/cpu/cpu0/topology$ cat cluster_*
>> ff # cluster_cpus
>> 0-7 # cluster_cpus_list
>> 36 # cluster_id, with no cluster node kernel will make it to
>> physical package id
>>
>> Signed-off-by: Yicong Yang <yangyic...@hisilicon.com>
>> ---
>> hw/acpi/aml-build.c | 2 +-
>> hw/core/machine-smp.c | 3 +++
>> include/hw/boards.h | 2 ++
>> qemu-options.hx | 2 ++
>> 4 files changed, 8 insertions(+), 1 deletion(-)
>>
>> diff --git a/hw/acpi/aml-build.c b/hw/acpi/aml-build.c
>> index e6bfac95c7..aab73af66d 100644
>> --- a/hw/acpi/aml-build.c
>> +++ b/hw/acpi/aml-build.c
>> @@ -2030,7 +2030,7 @@ void build_pptt(GArray *table_data, BIOSLinker
>> *linker, MachineState *ms,
>> 0, socket_id, NULL, 0);
>> }
>> - if (mc->smp_props.clusters_supported) {
>> + if (mc->smp_props.clusters_supported && ms->smp.build_cluster) {
>> if (cpus->cpus[n].props.cluster_id != cluster_id) {
>> assert(cpus->cpus[n].props.cluster_id > cluster_id);
>> cluster_id = cpus->cpus[n].props.cluster_id;
>> diff --git a/hw/core/machine-smp.c b/hw/core/machine-smp.c
>> index b39ed21e65..5d37e8d07a 100644
>> --- a/hw/core/machine-smp.c
>> +++ b/hw/core/machine-smp.c
>> @@ -158,6 +158,9 @@ void machine_parse_smp_config(MachineState *ms,
>> ms->smp.threads = threads;
>> ms->smp.max_cpus = maxcpus;
>> + if (config->has_clusters)
>> + ms->smp.build_cluster = true;
>> +
>> /* sanity-check of the computed topology */
>> if (sockets * dies * clusters * cores * threads != maxcpus) {
>> g_autofree char *topo_msg = cpu_hierarchy_to_string(ms);
>> diff --git a/include/hw/boards.h b/include/hw/boards.h
>> index 311ed17e18..c53f047b90 100644
>> --- a/include/hw/boards.h
>> +++ b/include/hw/boards.h
>> @@ -305,6 +305,7 @@ typedef struct DeviceMemoryState {
>> * @cores: the number of cores in one cluster
>> * @threads: the number of threads in one core
>> * @max_cpus: the maximum number of logical processors on the machine
>> + * @build_cluster: build cluster topology or not
>> */
>> typedef struct CpuTopology {
>> unsigned int cpus;
>> @@ -314,6 +315,7 @@ typedef struct CpuTopology {
>> unsigned int cores;
>> unsigned int threads;
>> unsigned int max_cpus;
>> + bool build_cluster;
> build_cluster seems a variable defined specifically for ACPI PPTT
> generation. It may not be proper to place it in the generic struct
> CpuTopology which only holds topo members.
>
> What about a more generic variable in struct SMPCompatProps
> together with @clusters_supported. Something like below:
>
ok. will follow the suggestion. Thanks for the snippet :)
> diff --git a/include/hw/boards.h b/include/hw/boards.h
> index 1f57ee8ca2..8db0706d5d 100644
> --- a/include/hw/boards.h
> +++ b/include/hw/boards.h
> @@ -130,11 +130,14 @@ typedef struct {
> * @prefer_sockets - whether sockets are preferred over cores in smp parsing
> * @dies_supported - whether dies are supported by the machine
> * @clusters_supported - whether clusters are supported by the machine
> + * @has_clusters - whether clusters is explicitly specified in the user
> + * provided SMP configuration.
> */
> typedef struct {
> bool prefer_sockets;
> bool dies_supported;
> bool clusters_supported;
> + bool has_clusters;
> } SMPCompatProps;
>
>> } CpuTopology;
>> /**
>> diff --git a/qemu-options.hx b/qemu-options.hx
>> index eb38e5dc40..0a710e7be3 100644
>> --- a/qemu-options.hx
>> +++ b/qemu-options.hx
>> @@ -342,6 +342,8 @@ SRST
>> were preferred over threads), however, this behaviour is considered
>> liable to change. Prior to 6.2 the preference was sockets over cores
>> over threads. Since 6.2 the preference is cores over sockets over
>> threads.
>> + The cluster topology will only be generated if explicitly specified
>> + by the "-cluster" option.
> no "-cluster" option, only "-smp" :)
ok.
>> For example, the following option defines a machine board with 2
>> sockets
>> of 1 core before 6.2 and 1 socket of 2 cores after 6.2:
> Maybe better to add a note at *end* of the doc about -smp like:
>
> Note: The cluster topology will only be generated in ACPI and exposed
> to guest if it's explicitly specified in -smp.
>
will do.
Thanks.
