This effectively reverts
commit 54c4ea8f3a
Author: Zhao Liu <zhao1.liu@intel.com>
Date: Sat Mar 9 00:01:37 2024 +0800
hw/core/machine-smp: Deprecate unsupported "parameter=1" SMP configurations
but is not done as a 'git revert' since the part of the changes to the
file hw/core/machine-smp.c which add 'has_XXX' checks remain desirable.
Furthermore, we have to tweak the subsequently added unit test to
account for differing warning message.
The rationale for the original deprecation was:
"Currently, it was allowed for users to specify the unsupported
topology parameter as "1". For example, x86 PC machine doesn't
support drawer/book/cluster topology levels, but user could specify
"-smp drawers=1,books=1,clusters=1".
This is meaningless and confusing, so that the support for this kind
of configurations is marked deprecated since 9.0."
There are varying POVs on the topic of 'unsupported' topology levels.
It is common to say that on a system without hyperthreading, that there
is always 1 thread. Likewise when new CPUs introduced a concept of
multiple "dies', it was reasonable to say that all historical CPUs
before that implicitly had 1 'die'. Likewise for the more recently
introduced 'modules' and 'clusters' parameter'. From this POV, it is
valid to set 'parameter=1' on the -smp command line for any machine,
only a value > 1 is strictly an error condition.
It doesn't cause any functional difficulty for QEMU, because internally
the QEMU code is itself assuming that all "unsupported" parameters
implicitly have a value of '1'.
At the libvirt level, we've allowed applications to set 'parameter=1'
when configuring a guest, and pass that through to QEMU.
Deprecating this creates extra difficulty for because there's no info
exposed from QEMU about which machine types "support" which parameters.
Thus, libvirt can't know whether it is valid to pass 'parameter=1' for
a given machine type, or whether it will trigger deprecation messages.
Since there's no apparent functional benefit to deleting this deprecated
behaviour from QEMU, and it creates problems for consumers of QEMU,
remove this deprecation.
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: Zhao Liu <zhao1.liu@intel.com>
Reviewed-by: Ján Tomko <jtomko@redhat.com>
Message-ID: <20240513123358.612355-2-berrange@redhat.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Add "modules" parameter parsing support in -smp.
Suggested-by: Xiaoyao Li <xiaoyao.li@intel.com>
Tested-by: Yongwei Ma <yongwei.ma@intel.com>
Signed-off-by: Zhao Liu <zhao1.liu@intel.com>
Tested-by: Babu Moger <babu.moger@amd.com>
Acked-by: Markus Armbruster <armbru@redhat.com>
Message-ID: <20240424154929.1487382-3-zhao1.liu@intel.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
In x86, module is the topology level above core, which contains a set
of cores that share certain resources (in current products, the resource
usually includes L2 cache, as well as module scoped features and MSRs).
Though smp.clusters could also share the L2 cache resource [1], there
are following reasons that drive us to introduce the new smp.modules:
* As the CPU topology abstraction in device tree [2], cluster supports
nesting (though currently QEMU hasn't support that). In contrast,
(x86) module does not support nesting.
* Due to nesting, there is great flexibility in sharing resources
on cluster, rather than narrowing cluster down to sharing L2 (and
L3 tags) as the lowest topology level that contains cores.
* Flexible nesting of cluster allows it to correspond to any level
between the x86 package and core.
* In Linux kernel, x86's cluster only represents the L2 cache domain
but QEMU's smp.clusters is the CPU topology level. Linux kernel will
also expose module level topology information in sysfs for x86. To
avoid cluster ambiguity and keep a consistent CPU topology naming
style with the Linux kernel, we introduce module level for x86.
The module is, in existing hardware practice, the lowest layer that
contains the core, while the cluster is able to have a higher
topological scope than the module due to its nesting.
Therefore, place the module between the cluster and the core:
drawer/book/socket/die/cluster/module/core/thread
With the above topological hierarchy order, introduce module level
support in MachineState and MachineClass.
[1]: https://lore.kernel.org/qemu-devel/c3d68005-54e0-b8fe-8dc1-5989fe3c7e69@huawei.com/
[2]: https://www.kernel.org/doc/Documentation/devicetree/bindings/cpu/cpu-topology.txt
Suggested-by: Xiaoyao Li <xiaoyao.li@intel.com>
Tested-by: Yongwei Ma <yongwei.ma@intel.com>
Signed-off-by: Zhao Liu <zhao1.liu@intel.com>
Tested-by: Babu Moger <babu.moger@amd.com>
Message-ID: <20240424154929.1487382-2-zhao1.liu@intel.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
In machine_parse_smp_config(), the number of total CPUs is calculated
by:
drawers * books * sockets * dies * clusters * cores * threads
To avoid missing the future new topology level, use a local variable to
cache the calculation result so that total CPUs are only calculated
once.
Signed-off-by: Zhao Liu <zhao1.liu@intel.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-ID: <20240308160148.3130837-4-zhao1.liu@linux.intel.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Currently, it was allowed for users to specify the unsupported
topology parameter as "1". For example, x86 PC machine doesn't
support drawer/book/cluster topology levels, but user could specify
"-smp drawers=1,books=1,clusters=1".
This is meaningless and confusing, so that the support for this kind of
configurations is marked deprecated since 9.0. And report warning
message for such case like:
qemu-system-x86_64: warning: Deprecated CPU topology (considered invalid):
Unsupported clusters parameter mustn't be specified as 1
qemu-system-x86_64: warning: Deprecated CPU topology (considered invalid):
Unsupported books parameter mustn't be specified as 1
qemu-system-x86_64: warning: Deprecated CPU topology (considered invalid):
Unsupported drawers parameter mustn't be specified as 1
Users have to ensure that all the topology members described with -smp
are supported by the target machine.
Signed-off-by: Zhao Liu <zhao1.liu@intel.com>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Message-ID: <20240308160148.3130837-3-zhao1.liu@linux.intel.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
The "parameter=0" SMP configurations have been marked as deprecated
since v6.2.
For these cases, -smp currently returns the warning and adjusts the
zeroed parameters to 1 by default.
Remove the above compatibility logic in v9.0, and return error directly
if any -smp parameter is set as 0.
Signed-off-by: Zhao Liu <zhao1.liu@intel.com>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Reviewed-by: Prasad Pandit <pjp@fedoraproject.org>
Message-ID: <20240308160148.3130837-2-zhao1.liu@linux.intel.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
S390 adds two new SMP levels, drawers and books to the CPU
topology.
S390 CPUs have specific topology features like dedication and
entitlement. These indicate to the guest information on host
vCPU scheduling and help the guest make better scheduling decisions.
Add the new levels to the relevant QAPI structs.
Add all the supported topology levels, dedication and entitlement
as properties to S390 CPUs.
Create machine-common.json so we can later include it in
machine-target.json also.
Signed-off-by: Pierre Morel <pmorel@linux.ibm.com>
Reviewed-by: Nina Schoetterl-Glausch <nsg@linux.ibm.com>
Co-developed-by: Nina Schoetterl-Glausch <nsg@linux.ibm.com>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Signed-off-by: Nina Schoetterl-Glausch <nsg@linux.ibm.com>
Message-ID: <20231016183925.2384704-3-nsg@linux.ibm.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>
The number of cores/threads per socket are needed for smbios, and are
also useful for other modules.
Provide the helpers to wrap the calculation of cores/threads per socket
so that we can avoid calculation errors caused by other modules miss
topology changes.
Suggested-by: Igor Mammedov <imammedo@redhat.com>
Signed-off-by: Zhao Liu <zhao1.liu@intel.com>
Message-Id: <20230628135437.1145805-2-zhao1.liu@linux.intel.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
This had been pulled in via qemu/plugin.h from hw/core/cpu.h,
but that will be removed.
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-Id: <20230310195252.210956-5-richard.henderson@linaro.org>
[AJB: add various additional cases shown by CI]
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <20230315174331.2959-15-alex.bennee@linaro.org>
Reviewed-by: Emilio Cota <cota@braap.org>
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 when it cannot reflect the real topology on platforms having no
cluster implementation and to avoid affecting the linux scheduling
domains in the VM. So only generate the cluster topology in ACPI
PPTT when the user has specified it explicitly in -smp.
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
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Yanan Wang <wangyanan55@huawei.com>
Tested-by: Yanan Wang <wangyanan55@huawei.com>
Signed-off-by: Yicong Yang <yangyicong@hisilicon.com>
Message-Id: <20221229065513.55652-3-yangyicong@huawei.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
The new Cluster-Aware Scheduling support has landed in Linux 5.16,
which has been proved to benefit the scheduling performance (e.g.
load balance and wake_affine strategy) on both x86_64 and AArch64.
So now in Linux 5.16 we have four-level arch-neutral CPU topology
definition like below and a new scheduler level for clusters.
struct cpu_topology {
int thread_id;
int core_id;
int cluster_id;
int package_id;
int llc_id;
cpumask_t thread_sibling;
cpumask_t core_sibling;
cpumask_t cluster_sibling;
cpumask_t llc_sibling;
}
A cluster generally means a group of CPU cores which share L2 cache
or other mid-level resources, and it is the shared resources that
is used to improve scheduler's behavior. From the point of view of
the size range, it's between CPU die and CPU core. For example, on
some ARM64 Kunpeng servers, we have 6 clusters in each NUMA node,
and 4 CPU cores in each cluster. The 4 CPU cores share a separate
L2 cache and a L3 cache tag, which brings cache affinity advantage.
In virtualization, on the Hosts which have pClusters (physical
clusters), if we can design a vCPU topology with cluster level for
guest kernel and have a dedicated vCPU pinning. A Cluster-Aware
Guest kernel can also make use of the cache affinity of CPU clusters
to gain similar scheduling performance.
This patch adds infrastructure for CPU cluster level topology
configuration and parsing, so that the user can specify cluster
parameter if their machines support it.
Signed-off-by: Yanan Wang <wangyanan55@huawei.com>
Message-Id: <20211228092221.21068-3-wangyanan55@huawei.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
[PMD: Added '(since 7.0)' to @clusters in qapi/machine.json]
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
All methods related to MachineState are prefixed with "machine_".
smp_parse() does not need to be an exception. Rename it and
const'ify the SMPConfiguration argument, since it doesn't need
to be modified.
Reviewed-by: Andrew Jones <drjones@redhat.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Yanan Wang <wangyanan55@huawei.com>
Tested-by: Yanan Wang <wangyanan55@huawei.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Message-Id: <20211216132015.815493-9-philmd@redhat.com>
We are going to introduce an unit test for the parser smp_parse()
in hw/core/machine.c, but now machine.c is only built in softmmu.
In order to solve the build dependency on the smp parsing code and
avoid building unrelated stuff for the unit tests, move the tested
code from machine.c into a separate file, i.e., machine-smp.c and
build it in common field.
Signed-off-by: Yanan Wang <wangyanan55@huawei.com>
Reviewed-by: Andrew Jones <drjones@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Tested-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Message-Id: <20211026034659.22040-2-wangyanan55@huawei.com>
Acked-by: Eduardo Habkost <ehabkost@redhat.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
