Stefan Hajnoczi writes:
> 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
> ---
> qapi/virtio.json| 30 ++
> include/hw/qdev-properties-system.h | 4 +++
> hw/core/qdev-properties-system.c| 47 +
> 3 files changed, 81 insertions(+)
>
> diff --git a/qapi/virtio.json b/qapi/virtio.json
> index e6dcee7b83..cb341ae596 100644
> --- a/qapi/virtio.json
> +++ b/qapi/virtio.json
> @@ -928,3 +928,33 @@
>'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: 8.2
> +#
> +##
Please format like
##
# @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: 8.2
##
to blend in with recent commit a937b6aa739 (qapi: Reformat doc comments
to conform to current conventions).
> +
> +{ 'struct': 'IOThreadVirtQueueMapping',
> + 'data': { 'iothread': 'str', '*vqs': ['uint16'] } }
> +
> +##
> +# @IOThreadVirtQueueMappings:
> +#
> +# IOThreadVirtQueueMapping list. This struct is not actually used but the
> +# IOThreadVirtQueueMappingList type it generates is!
Two spaces between sentences for consistency, please.
Doc comments are QMP reference documentation for users. Does this
paragraph belong there?
> +#
> +# Since: 8.2
> +##
> +
> +{ 'struct': 'IOThreadVirtQueueMappings',
> + 'data': { 'mappings': ['IOThreadVirtQueueMapping'] } }
> diff --git a/include/hw/qdev-properties-system.h
> b/include/hw/qdev-properties-system.h
> index 0ac327ae60..c526e502c8 100644
> --- a/include/hw/qdev-properties-system.h
> +++ b/include/hw/qdev-properties-system.h
> @@ -22,6 +22,7 @@ extern const PropertyInfo qdev_prop_audiodev;
> 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_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)
> @@ -73,5 +74,8 @@ extern const PropertyInfo qdev_prop_pcie_link_width;
> #define DEFINE_PROP_UUID_NODEFAULT(_name, _state, _field) \
> DEFINE_PROP(_name, _state, _field, qdev_prop_uuid, QemuUUID)
>
> +#define DEFINE_PROP_IOTHREAD_VQ_MAPPING_LIST(_name, _state, _field) \
> +DEFINE_PROP(_name, _state, _field, qdev_prop_iothread_vq_mapping_list, \
> +IOThreadVirtQueueMappingList *)
>
> #endif
> diff --git a/hw/core/qdev-properties-system.c
> b/hw/core/qdev-properties-system.c
> index 6d5d43eda2..831796e106 100644
> --- a/hw/core/qdev-properties-system.c
> +++ b/hw/core/qdev-properties-system.c
> @@ -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"
> @@ -1147,3 +1148,49 @@ const PropertyInfo qdev_prop_uuid = {
> .set = set_uuid,
> .set_default_value = set_default_uuid_auto,
> };
> +
> +/* --- IOT
