Re: [PATCH v1 1/4] virtio: introduce VIRTQUEUE_DEFUALT_SIZE instead of hardcoded constants

[Denis Plotnikov <dplotnikov@virtuozzo.com>]

On 30.01.2020 17:56, Stefan Hajnoczi wrote:
> On Wed, Jan 29, 2020 at 06:55:18PM +0100, Cornelia Huck wrote:
>> On Wed, 29 Jan 2020 17:06:59 +0300
>> Denis Plotnikov <dplotnikov@virtuozzo.com> wrote:
>>
>>> Signed-off-by: Denis Plotnikov <dplotnikov@virtuozzo.com>
>>> ---
>>>   hw/block/virtio-blk.c      | 6 ++++--
>>>   hw/scsi/virtio-scsi.c      | 5 +++--
>>>   include/hw/virtio/virtio.h | 1 +
>>>   3 files changed, 8 insertions(+), 4 deletions(-)
>>>
>>> diff --git a/hw/block/virtio-blk.c b/hw/block/virtio-blk.c
>>> index 09f46ed85f..72f935033f 100644
>>> --- a/hw/block/virtio-blk.c
>>> +++ b/hw/block/virtio-blk.c
>>> @@ -914,7 +914,8 @@ static void virtio_blk_update_config(VirtIODevice *vdev, uint8_t *config)
>>>       memset(&blkcfg, 0, sizeof(blkcfg));
>>>       virtio_stq_p(vdev, &blkcfg.capacity, capacity);
>>>       virtio_stl_p(vdev, &blkcfg.seg_max,
>>> -                 s->conf.seg_max_adjust ? s->conf.queue_size - 2 : 128 - 2);
>>> +                 s->conf.seg_max_adjust ? s->conf.queue_size - 2 :
>>> +                                          VIRTQUEUE_DEFAULT_SIZE - 2);
>>>       virtio_stw_p(vdev, &blkcfg.geometry.cylinders, conf->cyls);
>>>       virtio_stl_p(vdev, &blkcfg.blk_size, blk_size);
>>>       virtio_stw_p(vdev, &blkcfg.min_io_size, conf->min_io_size / blk_size);
>>> @@ -1272,7 +1273,8 @@ static Property virtio_blk_properties[] = {
>>>       DEFINE_PROP_BIT("request-merging", VirtIOBlock, conf.request_merging, 0,
>>>                       true),
>>>       DEFINE_PROP_UINT16("num-queues", VirtIOBlock, conf.num_queues, 1),
>>> -    DEFINE_PROP_UINT16("queue-size", VirtIOBlock, conf.queue_size, 128),
>>> +    DEFINE_PROP_UINT16("queue-size", VirtIOBlock, conf.queue_size,
>>> +                       VIRTQUEUE_DEFAULT_SIZE),
>>>       DEFINE_PROP_BOOL("seg-max-adjust", VirtIOBlock, conf.seg_max_adjust, true),
>>>       DEFINE_PROP_LINK("iothread", VirtIOBlock, conf.iothread, TYPE_IOTHREAD,
>>>                        IOThread *),
>>> diff --git a/hw/scsi/virtio-scsi.c b/hw/scsi/virtio-scsi.c
>>> index 3b61563609..36f66046ae 100644
>>> --- a/hw/scsi/virtio-scsi.c
>>> +++ b/hw/scsi/virtio-scsi.c
>>> @@ -660,7 +660,8 @@ static void virtio_scsi_get_config(VirtIODevice *vdev,
>>>   
>>>       virtio_stl_p(vdev, &scsiconf->num_queues, s->conf.num_queues);
>>>       virtio_stl_p(vdev, &scsiconf->seg_max,
>>> -                 s->conf.seg_max_adjust ? s->conf.virtqueue_size - 2 : 128 - 2);
>>> +                 s->conf.seg_max_adjust ? s->conf.virtqueue_size - 2 :
>>> +                                          VIRTQUEUE_DEFAULT_SIZE - 2);
>>>       virtio_stl_p(vdev, &scsiconf->max_sectors, s->conf.max_sectors);
>>>       virtio_stl_p(vdev, &scsiconf->cmd_per_lun, s->conf.cmd_per_lun);
>>>       virtio_stl_p(vdev, &scsiconf->event_info_size, sizeof(VirtIOSCSIEvent));
>>> @@ -965,7 +966,7 @@ static void virtio_scsi_device_unrealize(DeviceState *dev, Error **errp)
>>>   static Property virtio_scsi_properties[] = {
>>>       DEFINE_PROP_UINT32("num_queues", VirtIOSCSI, parent_obj.conf.num_queues, 1),
>>>       DEFINE_PROP_UINT32("virtqueue_size", VirtIOSCSI,
>>> -                                         parent_obj.conf.virtqueue_size, 128),
>>> +                       parent_obj.conf.virtqueue_size, VIRTQUEUE_DEFAULT_SIZE),
>>>       DEFINE_PROP_BOOL("seg_max_adjust", VirtIOSCSI,
>>>                         parent_obj.conf.seg_max_adjust, true),
>>>       DEFINE_PROP_UINT32("max_sectors", VirtIOSCSI, parent_obj.conf.max_sectors,
>>> diff --git a/include/hw/virtio/virtio.h b/include/hw/virtio/virtio.h
>>> index b69d517496..a66ea2368b 100644
>>> --- a/include/hw/virtio/virtio.h
>>> +++ b/include/hw/virtio/virtio.h
>>> @@ -48,6 +48,7 @@ size_t virtio_feature_get_config_size(VirtIOFeature *features,
>>>   typedef struct VirtQueue VirtQueue;
>>>   
>>>   #define VIRTQUEUE_MAX_SIZE 1024
>>> +#define VIRTQUEUE_DEFAULT_SIZE 128
>> Going from the header only, this looks like a value that is supposed to
>> be used for every virtqueue... but from the users, this is only for blk
>> and scsi.
>>
>> I don't think adding a default for everything makes sense, even if the
>> same value makes sense for blk and scsi.
> Agreed, this value is too general.  VIRTIO_BLK_VQ_DEFAULT_SIZE and
> VIRTIO_SCSI_VQ_DEFAULT_SIZE would make sense to me.
>
> Stefan
agree, that would be better.
Will redo and resend the series.

Denis