Re: [PATCH v16 08/11] qapi/s390x/cpu topology: set-cpu-topology monitor command

Pierre Morel
2023-02-27T10:57:57Z

On 2/24/23 18:15, Nina Schoetterl-Glausch wrote:
> On Wed, 2023-02-22 at 15:21 +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 optimize
>> 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 has a feature unstable for the moment.
>>
>> Signed-off-by: Pierre Morel <pmorel@linux.ibm.com>
>> ---
>> qapi/machine-target.json | 35 +++++++++
>> include/monitor/hmp.h | 1 +
>> hw/s390x/cpu-topology.c | 154 +++++++++++++++++++++++++++++++++++++++
>> hmp-commands.hx | 17 +++++
>> 4 files changed, 207 insertions(+)
>>
>> diff --git a/qapi/machine-target.json b/qapi/machine-target.json
>> index a52cc32f09..baa9d273cf 100644
>> --- a/qapi/machine-target.json
>> +++ b/qapi/machine-target.json
>> @@ -354,3 +354,38 @@
>> { 'enum': 'CpuS390Polarization',
>> 'prefix': 'S390_CPU_POLARIZATION',
>> 'data': [ 'horizontal', 'vertical' ] }
>> +
>> +##
>> +# @set-cpu-topology:
>> +#
>> +# @core-id: the vCPU ID to be moved
>> +# @socket-id: optional destination socket where to move the vCPU
>> +# @book-id: optional destination book where to move the vCPU
>> +# @drawer-id: optional destination drawer where to move the vCPU
>> +# @entitlement: optional entitlement
>> +# @dedicated: optional, if the vCPU is dedicated to a real CPU
>> +#
>> +# Features:
>> +# @unstable: This command may still be modified.
>> +#
>> +# Modifies the topology by moving the CPU inside the topology
>> +# tree or by changing a modifier attribute of a CPU.
>> +# Default value for optional parameter is the current value
>> +# used by the CPU.
>> +#
>> +# Returns: Nothing on success, the reason on failure.
>> +#
>> +# Since: 8.0
>> +##
>> +{ 'command': 'set-cpu-topology',
>> + 'data': {
>> + 'core-id': 'uint16',
>> + '*socket-id': 'uint16',
>> + '*book-id': 'uint16',
>> + '*drawer-id': 'uint16',
>> + '*entitlement': 'str',
> How about you add a machine-common.json and define CpuS390Entitlement there,
> and then include it from both machine.json and machine-target.json?
>
> Then you can declare it as CpuS390Entitlement and don't need to do the parsing
> manually.
>
> You could also put it in common.json, but that seems a bit too generic.
>
> Anyone have objections?

Seems Thomas has questions, I wait until every body agree or not agree.

Anyway this does not change the interface or the functionality.

>
>> + '*dedicated': 'bool'
>> + },
>> + 'features': [ 'unstable' ],
>> + 'if': { 'all': [ 'TARGET_S390X' ] }
>> +}
>> diff --git a/include/monitor/hmp.h b/include/monitor/hmp.h
>> index 2220f14fc9..4e65e6d08e 100644
>> --- a/include/monitor/hmp.h
>> +++ b/include/monitor/hmp.h
>> @@ -178,5 +178,6 @@ void hmp_ioport_read(Monitor *mon, const QDict *qdict);
>> void hmp_ioport_write(Monitor *mon, const QDict *qdict);
>> void hmp_boot_set(Monitor *mon, const QDict *qdict);
>> void hmp_info_mtree(Monitor *mon, const QDict *qdict);
>> +void hmp_set_cpu_topology(Monitor *mon, const QDict *qdict);
>>
>> #endif
>> diff --git a/hw/s390x/cpu-topology.c b/hw/s390x/cpu-topology.c
>> index ed5fc75381..3a7eb441a3 100644
>> --- a/hw/s390x/cpu-topology.c
>> +++ b/hw/s390x/cpu-topology.c
>> @@ -19,6 +19,12 @@
>> #include "hw/s390x/s390-virtio-ccw.h"
>> #include "hw/s390x/cpu-topology.h"
>> #include "qapi/qapi-types-machine-target.h"
>> +#include "qapi/qapi-types-machine.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.
>> * .cores_per_socket: tracks information on the count of cores
>> @@ -310,6 +316,26 @@ static void s390_topology_add_core_to_socket(S390CPU *cpu, int drawer_id,
>> }
>> }
>>
>> +/**
>> + * s390_topology_need_report
>> + * @cpu: Current cpu
>> + * @drawer_id: future drawer ID
>> + * @book_id: future book ID
>> + * @socket_id: future socket ID
>> + *
>> + * A modified topology change report is needed if the
>> + */
>> +static int s390_topology_need_report(S390CPU *cpu, int drawer_id,
>> + int book_id, int socket_id,
>> + uint16_t entitlement, bool dedicated)
>> +{
>> + return cpu->env.drawer_id != drawer_id ||
>> + cpu->env.book_id != book_id ||
>> + cpu->env.socket_id != socket_id ||
>> + cpu->env.entitlement != entitlement ||
>> + cpu->env.dedicated != dedicated;
>> +}
>> +
>> /**
>> * s390_update_cpu_props:
>> * @ms: the machine state
>> @@ -376,3 +402,131 @@ void s390_topology_setup_cpu(MachineState *ms, S390CPU *cpu, Error **errp)
>> /* topology tree is reflected in props */
>> s390_update_cpu_props(ms, cpu);
>> }
>> +
>> +/*
>> + * qmp and hmp implementations
>> + */
>> +
>> +#define TOPOLOGY_SET(n) do { \
>> + if (has_ ## n) { \
>> + calc_ ## n = n; \
>> + } else { \
>> + calc_ ## n = cpu->env.n; \
>> + } \
>> + } while (0)
>> +
>> +static void s390_change_topology(uint16_t core_id,
>> + bool has_socket_id, uint16_t socket_id,
>> + bool has_book_id, uint16_t book_id,
>> + bool has_drawer_id, uint16_t drawer_id,
>> + bool has_entitlement, uint16_t entitlement,
>> + bool has_dedicated, bool dedicated,
>> + Error **errp)
>> +{
>> + MachineState *ms = current_machine;
>> + uint16_t calc_dedicated, calc_entitlement;
>> + uint16_t calc_socket_id, calc_book_id, calc_drawer_id;
>> + S390CPU *cpu;
>> + int report_needed;
>> + ERRP_GUARD();
>> +
>> + if (core_id >= ms->smp.max_cpus) {
>> + error_setg(errp, "Core-id %d out of range!", core_id);
>> + return;
>> + }
>> +
>> + cpu = (S390CPU *)ms->possible_cpus->cpus[core_id].cpu;
>> + if (!cpu) {
>> + error_setg(errp, "Core-id %d does not exist!", core_id);
>> + return;
>> + }
>> +
>> + /* Get unprovided attributes from cpu and verify the new topology */
> Get attributes not provided...

Thanks, I will change this.

>
>> + TOPOLOGY_SET(entitlement);
>> + TOPOLOGY_SET(dedicated);
>> + TOPOLOGY_SET(socket_id);
>> + TOPOLOGY_SET(book_id);
>> + TOPOLOGY_SET(drawer_id);
> You could also just assign to the arguments, i.e.
>
> if (!has_socket_id)
> socket_id = cpu->env.socket_id;

Looks better

>
>> +
>> + s390_topology_check(calc_socket_id, calc_book_id, calc_drawer_id,
>> + calc_entitlement, calc_dedicated, errp);
>> + if (*errp) {
>> + return;
>> + }
>> +
>> + /* Move the CPU into its new socket */
>> + s390_topology_add_core_to_socket(cpu, calc_drawer_id, calc_book_id,
>> + calc_socket_id, false, errp);
>> + if (*errp) {
>> + return;
>> + }
>> +
>> + /* Check if we need to report the modified topology */
>> + report_needed = s390_topology_need_report(cpu, calc_drawer_id, calc_book_id,
>> + calc_socket_id, calc_entitlement,
>> + calc_dedicated);
>> +
>> + /* All checks done, report new topology into the vCPU */
>> + cpu->env.drawer_id = calc_drawer_id;
>> + cpu->env.book_id = calc_book_id;
>> + cpu->env.socket_id = calc_socket_id;
>> + cpu->env.dedicated = calc_dedicated;
>> + cpu->env.entitlement = calc_entitlement;
>> +
>> + /* topology tree is reflected in props */
>> + s390_update_cpu_props(ms, cpu);
>> +
>> + /* Advertise the topology change */
>> + if (report_needed) {
>> + s390_cpu_topology_set_changed(true);
>> + }
>> +}
>> +
>> +void qmp_set_cpu_topology(uint16_t core,
>> + bool has_socket, uint16_t socket,
>> + bool has_book, uint16_t book,
>> + bool has_drawer, uint16_t drawer,
>> + const char *entitlement_str,
>> + bool has_dedicated, bool dedicated,
>> + Error **errp)
>> +{
>> + bool has_entitlement = false;
>> + int entitlement;
>> + ERRP_GUARD();
>> +
>> + if (!s390_has_topology()) {
>> + error_setg(errp, "This machine doesn't support topology");
>> + return;
>> + }
>> +
>> + entitlement = qapi_enum_parse(&CpuS390Entitlement_lookup, entitlement_str,
>> + -1, errp);
>> + if (*errp) {
>> + return;
>> + }
>> + has_entitlement = entitlement >= 0;
> Doesn't this allow setting horizontal entitlement? Which shouldn't be possible,
> only the guest can do it.

IMHO it does not, the polarization is set by the guest through the PTF
instruction, but entitlement is set by the host.

>
>> +
>> + s390_change_topology(core, has_socket, socket, has_book, book,
>> + has_drawer, drawer, has_entitlement, entitlement,
>> + has_dedicated, dedicated, errp);
>> +}
>> +
>> +void hmp_set_cpu_topology(Monitor *mon, const QDict *qdict)
>> +{
>> + const uint16_t core = qdict_get_int(qdict, "core-id");
>> + bool has_socket = qdict_haskey(qdict, "socket-id");
>> + const uint16_t socket = qdict_get_try_int(qdict, "socket-id", 0);
>> + bool has_book = qdict_haskey(qdict, "book-id");
>> + const uint16_t book = qdict_get_try_int(qdict, "book-id", 0);
>> + bool has_drawer = qdict_haskey(qdict, "drawer-id");
>> + const uint16_t drawer = qdict_get_try_int(qdict, "drawer-id", 0);
> The names here don't match the definition below, leading to a crash,
> because core-id is a mandatory argument.

right, I should have kept the original names or change both.

>
>> + const char *entitlement = qdict_get_try_str(qdict, "entitlement");
>> + bool has_dedicated = qdict_haskey(qdict, "dedicated");
>> + const bool dedicated = qdict_get_try_bool(qdict, "dedicated", false);
>> + Error *local_err = NULL;
>> +
>> + qmp_set_cpu_topology(core, has_socket, socket, has_book, book,
>> + has_drawer, drawer, entitlement,
>> + has_dedicated, dedicated, &local_err);
>> + hmp_handle_error(mon, local_err);
>> +}
>> diff --git a/hmp-commands.hx b/hmp-commands.hx
>> index fbb5daf09b..d8c37808c7 100644
>> --- a/hmp-commands.hx
>> +++ b/hmp-commands.hx
>> @@ -1815,3 +1815,20 @@ SRST
>> Dump the FDT in dtb format to *filename*.
>> ERST
>> #endif
>> +
>> +#if defined(TARGET_S390X)
>> + {
>> + .name = "set-cpu-topology",
>> + .args_type = "core:l,socket:l?,book:l?,drawer:l?,entitlement:s?,dedicated:b?",
> Can you use ":O" for the ids? It would allow for some more flexibility.

Yes, or we can let fall the hmp interface for this series, making it
simpler, and add the hmp interface later.

I am more in favor of letting it fall for now.

Regards,

Pierre

>
>> + .params = "core [socket] [book] [drawer] [entitlement] [dedicated]",
>> + .help = "Move CPU 'core' to 'socket/book/drawer' "
>> + "optionally modifies entitlement and dedication",
>> + .cmd = hmp_set_cpu_topology,
>> + },
>> +
>> +SRST
>> +``set-cpu-topology`` *core* *socket* *book* *drawer* *entitlement* *dedicated*
>> + Modify CPU topology for the CPU *core* to move on *socket* *book* *drawer*
>> + with topology attributes *entitlement* *dedicated*.
>> +ERST
>> +#endif