On Wed, 2023-02-01 at 14:20 +0100, Pierre Morel wrote:
> The modification of the CPU attributes are done through a monitor
> command.
>
> It allows to move the core inside the topology tree to optimise
> the cache usage in the case the host's hypervisor previously
> moved the CPU.
>
> The same command allows to modify the CPU attributes modifiers
> like polarization entitlement and the dedicated attribute to notify
> the guest if the host admin modified scheduling or dedication of a vCPU.
>
> With this knowledge the guest has the possibility to optimize the
> usage of the vCPUs.
>
> The command is made experimental for the moment.
>
> Signed-off-by: Pierre Morel <pmorel@xxxxxxxxxxxxx>
> ---
> qapi/machine-target.json | 29 +++++++++++++
> include/monitor/hmp.h | 1 +
> hw/s390x/cpu-topology.c | 88 ++++++++++++++++++++++++++++++++++++++++
> hmp-commands.hx | 16 ++++++++
> 4 files changed, 134 insertions(+)
>
> diff --git a/qapi/machine-target.json b/qapi/machine-target.json
> index 2e267fa458..58df0f5061 100644
> --- a/qapi/machine-target.json
> +++ b/qapi/machine-target.json
> @@ -342,3 +342,32 @@
> 'TARGET_S390X',
> 'TARGET_MIPS',
> 'TARGET_LOONGARCH64' ] } }
> +
> +##
> +# @x-set-cpu-topology:
> +#
> +# @core: the vCPU ID to be moved
> +# @socket: the destination socket where to move the vCPU
> +# @book: the destination book where to move the vCPU
> +# @drawer: the destination drawer where to move the vCPU
I wonder if it wouldn't be more convenient for the caller if everything is optional.
> +# @polarity: optional polarity, default is last polarity set by the guest
> +# @dedicated: optional, if the vCPU is dedicated to a real CPU
> +#
> +# Modifies the topology by moving the CPU inside the topology
> +# tree or by changing a modifier attribute of a CPU.
> +#
> +# Returns: Nothing on success, the reason on failure.
> +#
> +# Since: <next qemu stable release, eg. 1.0>
> +##
> +{ 'command': 'x-set-cpu-topology',
> + 'data': {
> + 'core': 'int',
> + 'socket': 'int',
> + 'book': 'int',
> + 'drawer': 'int',
Did you consider naming those core-id, etc.? It would be consistent with
query-cpus-fast/CpuInstanceProperties. Also all your variables end with _id.
I don't care really just wanted to point it out.
> + '*polarity': 'int',
> + '*dedicated': 'bool'
> + },
> + 'if': { 'all': [ 'TARGET_S390X', 'CONFIG_KVM' ] }
> +}
So apparently this is the old way of doing an experimental api.
> Names beginning with ``x-`` used to signify "experimental". This
> convention has been replaced by special feature "unstable".
> Feature "unstable" marks a command, event, enum value, or struct
> member as unstable. It is not supported elsewhere so far. Interfaces
> so marked may be withdrawn or changed incompatibly in future releases.
> diff --git a/include/monitor/hmp.h b/include/monitor/hmp.h
> index 1b3bdcb446..12827479cf 100644
> --- a/include/monitor/hmp.h
> +++ b/include/monitor/hmp.h
> @@ -151,5 +151,6 @@ void hmp_human_readable_text_helper(Monitor *mon,
> HumanReadableText *(*qmp_handler)(Error **));
> void hmp_info_stats(Monitor *mon, const QDict *qdict);
> void hmp_pcie_aer_inject_error(Monitor *mon, const QDict *qdict);
> +void hmp_x_set_cpu_topology(Monitor *mon, const QDict *qdict);
>
> #endif
> diff --git a/hw/s390x/cpu-topology.c b/hw/s390x/cpu-topology.c
> index c33378577b..6c50050991 100644
> --- a/hw/s390x/cpu-topology.c
> +++ b/hw/s390x/cpu-topology.c
> @@ -18,6 +18,10 @@
> #include "target/s390x/cpu.h"
> #include "hw/s390x/s390-virtio-ccw.h"
> #include "hw/s390x/cpu-topology.h"
> +#include "qapi/qapi-commands-machine-target.h"
> +#include "qapi/qmp/qdict.h"
> +#include "monitor/hmp.h"
> +#include "monitor/monitor.h"
>
> /*
> * s390_topology is used to keep the topology information.
> @@ -379,3 +383,87 @@ void s390_topology_set_cpu(MachineState *ms, S390CPU *cpu, Error **errp)
> /* topology tree is reflected in props */
> s390_update_cpu_props(ms, cpu);
> }
> +
> +/*
> + * qmp and hmp implementations
> + */
> +
> +static void s390_change_topology(int64_t core_id, int64_t socket_id,
> + int64_t book_id, int64_t drawer_id,
> + int64_t polarity, bool dedicated,
> + Error **errp)
> +{
> + MachineState *ms = current_machine;
> + S390CPU *cpu;
> + ERRP_GUARD();
> +
> + cpu = (S390CPU *)ms->possible_cpus->cpus[core_id].cpu;
> + if (!cpu) {
> + error_setg(errp, "Core-id %ld does not exist!", core_id);
> + return;
> + }
> +
> + /* Verify the new topology */
> + s390_topology_check(cpu, errp);
> + if (*errp) {
> + return;
> + }
> +
> + /* Move the CPU into its new socket */
> + s390_set_core_in_socket(cpu, drawer_id, book_id, socket_id, true, errp);
The cpu isn't being created, so that should be false instead of true, right?
> +
> + /* All checks done, report topology in environment */
> + cpu->env.drawer_id = drawer_id;
> + cpu->env.book_id = book_id;
> + cpu->env.socket_id = socket_id;
> + cpu->env.dedicated = dedicated;
> + cpu->env.entitlement = polarity;
> +
> + /* topology tree is reflected in props */
> + s390_update_cpu_props(ms, cpu);
> +
> + /* Advertise the topology change */
> + s390_cpu_topology_set_modified();
> +}
> +
> +void qmp_x_set_cpu_topology(int64_t core, int64_t socket,
> + int64_t book, int64_t drawer,
> + bool has_polarity, int64_t polarity,
> + bool has_dedicated, bool dedicated,
> + Error **errp)
> +{
> + ERRP_GUARD();
> +
> + if (!s390_has_topology()) {
> + error_setg(errp, "This machine doesn't support topology");
> + return;
> + }
> + if (!has_polarity) {
> + polarity = POLARITY_VERTICAL_MEDIUM;
> + }
> + if (!has_dedicated) {
> + dedicated = false;
> + }
> + s390_change_topology(core, socket, book, drawer, polarity, dedicated, errp);
> +}
> +
> +void hmp_x_set_cpu_topology(Monitor *mon, const QDict *qdict)
> +{
> + const int64_t core = qdict_get_int(qdict, "core");
> + const int64_t socket = qdict_get_int(qdict, "socket");
> + const int64_t book = qdict_get_int(qdict, "book");
> + const int64_t drawer = qdict_get_int(qdict, "drawer");
> + bool has_polarity = qdict_haskey(qdict, "polarity");
> + const int64_t polarity = qdict_get_try_int(qdict, "polarity", 0);
> + bool has_dedicated = qdict_haskey(qdict, "dedicated");
> + const bool dedicated = qdict_get_try_bool(qdict, "dedicated", false);
> + Error *local_err = NULL;
> +
> + qmp_x_set_cpu_topology(core, socket, book, drawer,
> + has_polarity, polarity,
> + has_dedicated, dedicated,
> + &local_err);
> + if (hmp_handle_error(mon, local_err)) {
> + return;
> + }
What is the if for? The function ends anyway.
> +}
> diff --git a/hmp-commands.hx b/hmp-commands.hx
> index 673e39a697..bb3c908356 100644
> --- a/hmp-commands.hx
> +++ b/hmp-commands.hx
> @@ -1815,3 +1815,19 @@ SRST
> Dump the FDT in dtb format to *filename*.
> ERST
> #endif
> +
> +#if defined(TARGET_S390X) && defined(CONFIG_KVM)
> + {
> + .name = "x-set-cpu-topology",
> + .args_type = "core:l,socket:l,book:l,drawer:l,polarity:l?,dedicated:b?",
> + .params = "core socket book drawer [polarity] [dedicated]",
> + .help = "Move CPU 'core' to 'socket/book/drawer' "
> + "optionaly modifies polarity and dedication",
> + .cmd = hmp_x_set_cpu_topology,
> + },
> +
> +SRST
> +``x-set-cpu-topology`` *core* *socket* *book* *drawer* *polarity* *dedicated*
> + Moves the CPU *core* to *socket* *book* *drawer* with *polarity* *dedicated*.
> +ERST
> +#endif
