qdev: add IOThreadVirtQueueMappingList property type

virtio-blk and virtio-scsi devices will need a way to specify the
mapping between IOThreads and virtqueues. At the moment all virtqueues
are assigned to a single IOThread or the main loop. This single thread
can be a CPU bottleneck, so it is necessary to allow finer-grained
assignment to spread the load.

Introduce DEFINE_PROP_IOTHREAD_VQ_MAPPING_LIST() so devices can take a
parameter that maps virtqueues to IOThreads. The command-line syntax for
this new property is as follows:

  --device '{"driver":"foo","iothread-vq-mapping":[{"iothread":"iothread0","vqs":[0,1,2]},...]}'

IOThreads are specified by name and virtqueues are specified by 0-based
index.

It will be common to simply assign virtqueues round-robin across a set
of IOThreads. A convenient syntax that does not require specifying
individual virtqueue indices is available:

  --device '{"driver":"foo","iothread-vq-mapping":[{"iothread":"iothread0"},{"iothread":"iothread1"},...]}'

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-ID: <20231220134755.814917-4-stefanha@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Stefan Hajnoczi 2023-12-20 08:47:54 -05:00 committed by Kevin Wolf
parent 350147a871
commit cf03a152c5
3 changed files with 80 additions and 0 deletions

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@ -18,6 +18,7 @@
#include "qapi/qapi-types-block.h"
#include "qapi/qapi-types-machine.h"
#include "qapi/qapi-types-migration.h"
#include "qapi/qapi-visit-virtio.h"
#include "qapi/qmp/qerror.h"
#include "qemu/ctype.h"
#include "qemu/cutils.h"
@ -1160,3 +1161,48 @@ const PropertyInfo qdev_prop_cpus390entitlement = {
.set = qdev_propinfo_set_enum,
.set_default_value = qdev_propinfo_set_default_value_enum,
};
/* --- IOThreadVirtQueueMappingList --- */
static void get_iothread_vq_mapping_list(Object *obj, Visitor *v,
const char *name, void *opaque, Error **errp)
{
IOThreadVirtQueueMappingList **prop_ptr =
object_field_prop_ptr(obj, opaque);
visit_type_IOThreadVirtQueueMappingList(v, name, prop_ptr, errp);
}
static void set_iothread_vq_mapping_list(Object *obj, Visitor *v,
const char *name, void *opaque, Error **errp)
{
IOThreadVirtQueueMappingList **prop_ptr =
object_field_prop_ptr(obj, opaque);
IOThreadVirtQueueMappingList *list;
if (!visit_type_IOThreadVirtQueueMappingList(v, name, &list, errp)) {
return;
}
qapi_free_IOThreadVirtQueueMappingList(*prop_ptr);
*prop_ptr = list;
}
static void release_iothread_vq_mapping_list(Object *obj,
const char *name, void *opaque)
{
IOThreadVirtQueueMappingList **prop_ptr =
object_field_prop_ptr(obj, opaque);
qapi_free_IOThreadVirtQueueMappingList(*prop_ptr);
*prop_ptr = NULL;
}
const PropertyInfo qdev_prop_iothread_vq_mapping_list = {
.name = "IOThreadVirtQueueMappingList",
.description = "IOThread virtqueue mapping list [{\"iothread\":\"<id>\", "
"\"vqs\":[1,2,3,...]},...]",
.get = get_iothread_vq_mapping_list,
.set = set_iothread_vq_mapping_list,
.release = release_iothread_vq_mapping_list,
};

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@ -24,6 +24,7 @@ extern const PropertyInfo qdev_prop_off_auto_pcibar;
extern const PropertyInfo qdev_prop_pcie_link_speed;
extern const PropertyInfo qdev_prop_pcie_link_width;
extern const PropertyInfo qdev_prop_cpus390entitlement;
extern const PropertyInfo qdev_prop_iothread_vq_mapping_list;
#define DEFINE_PROP_PCI_DEVFN(_n, _s, _f, _d) \
DEFINE_PROP_SIGNED(_n, _s, _f, _d, qdev_prop_pci_devfn, int32_t)
@ -82,4 +83,8 @@ extern const PropertyInfo qdev_prop_cpus390entitlement;
DEFINE_PROP_SIGNED(_n, _s, _f, _d, qdev_prop_cpus390entitlement, \
CpuS390Entitlement)
#define DEFINE_PROP_IOTHREAD_VQ_MAPPING_LIST(_name, _state, _field) \
DEFINE_PROP(_name, _state, _field, qdev_prop_iothread_vq_mapping_list, \
IOThreadVirtQueueMappingList *)
#endif

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@ -928,3 +928,32 @@
'data': { 'path': 'str', 'queue': 'uint16', '*index': 'uint16' },
'returns': 'VirtioQueueElement',
'features': [ 'unstable' ] }
##
# @IOThreadVirtQueueMapping:
#
# Describes the subset of virtqueues assigned to an IOThread.
#
# @iothread: the id of IOThread object
#
# @vqs: an optional array of virtqueue indices that will be handled by this
# IOThread. When absent, virtqueues are assigned round-robin across all
# IOThreadVirtQueueMappings provided. Either all IOThreadVirtQueueMappings
# must have @vqs or none of them must have it.
#
# Since: 9.0
##
{ 'struct': 'IOThreadVirtQueueMapping',
'data': { 'iothread': 'str', '*vqs': ['uint16'] } }
##
# @DummyVirtioForceArrays:
#
# Not used by QMP; hack to let us use IOThreadVirtQueueMappingList internally
#
# Since: 9.0
##
{ 'struct': 'DummyVirtioForceArrays',
'data': { 'unused-iothread-vq-mapping': ['IOThreadVirtQueueMapping'] } }