From 1bf8a989a566b2ba41c197004ec2a02562a766a4 Mon Sep 17 00:00:00 2001 From: Denis Plotnikov Date: Fri, 20 Dec 2019 17:09:04 +0300 Subject: virtio: make seg_max virtqueue size dependent Before the patch, seg_max parameter was immutable and hardcoded to 126 (128 - 2) without respect to queue size. This has two negative effects: 1. when queue size is < 128, we have Virtio 1.1 specfication violation: (2.6.5.3.1 Driver Requirements) seq_max must be <= queue_size. This violation affects the old Linux guests (ver < 4.14). These guests crash on these queue_size setups. 2. when queue_size > 128, as was pointed out by Denis Lunev , seg_max restrics guest's block request length which affects guests' performance making them issues more block request than needed. https://lists.gnu.org/archive/html/qemu-devel/2017-12/msg03721.html To mitigate this two effects, the patch adds the property adjusting seg_max to queue size automaticaly. Since seg_max is a guest visible parameter, the property is machine type managable and allows to choose between old (seg_max = 126 always) and new (seg_max = queue_size - 2) behaviors. Not to change the behavior of the older VMs, prevent setting the default seg_max_adjust value for older machine types. Reviewed-by: Stefan Hajnoczi Signed-off-by: Denis Plotnikov Message-Id: <20191220140905.1718-2-dplotnikov@virtuozzo.com> Reviewed-by: Michael S. Tsirkin Signed-off-by: Michael S. Tsirkin --- hw/block/virtio-blk.c | 9 ++++++++- hw/core/machine.c | 3 +++ hw/scsi/vhost-scsi.c | 2 ++ hw/scsi/virtio-scsi.c | 10 +++++++++- 4 files changed, 22 insertions(+), 2 deletions(-) (limited to 'hw') diff --git a/hw/block/virtio-blk.c b/hw/block/virtio-blk.c index b12157b5eb..9bee514c4e 100644 --- a/hw/block/virtio-blk.c +++ b/hw/block/virtio-blk.c @@ -913,7 +913,8 @@ static void virtio_blk_update_config(VirtIODevice *vdev, uint8_t *config) blk_get_geometry(s->blk, &capacity); memset(&blkcfg, 0, sizeof(blkcfg)); virtio_stq_p(vdev, &blkcfg.capacity, capacity); - virtio_stl_p(vdev, &blkcfg.seg_max, 128 - 2); + virtio_stl_p(vdev, &blkcfg.seg_max, + s->conf.seg_max_adjust ? s->conf.queue_size - 2 : 128 - 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); @@ -1138,6 +1139,11 @@ static void virtio_blk_device_realize(DeviceState *dev, Error **errp) error_setg(errp, "num-queues property must be larger than 0"); return; } + if (conf->queue_size <= 2) { + error_setg(errp, "invalid queue-size property (%" PRIu16 "), " + "must be > 2", conf->queue_size); + return; + } if (!is_power_of_2(conf->queue_size) || conf->queue_size > VIRTQUEUE_MAX_SIZE) { error_setg(errp, "invalid queue-size property (%" PRIu16 "), " @@ -1267,6 +1273,7 @@ static Property virtio_blk_properties[] = { true), DEFINE_PROP_UINT16("num-queues", VirtIOBlock, conf.num_queues, 1), DEFINE_PROP_UINT16("queue-size", VirtIOBlock, conf.queue_size, 128), + DEFINE_PROP_BOOL("seg-max-adjust", VirtIOBlock, conf.seg_max_adjust, true), DEFINE_PROP_LINK("iothread", VirtIOBlock, conf.iothread, TYPE_IOTHREAD, IOThread *), DEFINE_PROP_BIT64("discard", VirtIOBlock, host_features, diff --git a/hw/core/machine.c b/hw/core/machine.c index f5e2b32b3b..ec2e3fcb61 100644 --- a/hw/core/machine.c +++ b/hw/core/machine.c @@ -29,6 +29,9 @@ GlobalProperty hw_compat_4_2[] = { { "virtio-blk-device", "x-enable-wce-if-config-wce", "off" }, + { "virtio-blk-device", "seg-max-adjust", "off"}, + { "virtio-scsi-device", "seg_max_adjust", "off"}, + { "vhost-blk-device", "seg_max_adjust", "off"}, }; const size_t hw_compat_4_2_len = G_N_ELEMENTS(hw_compat_4_2); diff --git a/hw/scsi/vhost-scsi.c b/hw/scsi/vhost-scsi.c index c693fc748a..26f710d3ec 100644 --- a/hw/scsi/vhost-scsi.c +++ b/hw/scsi/vhost-scsi.c @@ -275,6 +275,8 @@ static Property vhost_scsi_properties[] = { DEFINE_PROP_UINT32("num_queues", VirtIOSCSICommon, conf.num_queues, 1), DEFINE_PROP_UINT32("virtqueue_size", VirtIOSCSICommon, conf.virtqueue_size, 128), + DEFINE_PROP_BOOL("seg_max_adjust", VirtIOSCSICommon, conf.seg_max_adjust, + true), DEFINE_PROP_UINT32("max_sectors", VirtIOSCSICommon, conf.max_sectors, 0xFFFF), DEFINE_PROP_UINT32("cmd_per_lun", VirtIOSCSICommon, conf.cmd_per_lun, 128), diff --git a/hw/scsi/virtio-scsi.c b/hw/scsi/virtio-scsi.c index f080545f48..4bc73a370e 100644 --- a/hw/scsi/virtio-scsi.c +++ b/hw/scsi/virtio-scsi.c @@ -659,7 +659,8 @@ static void virtio_scsi_get_config(VirtIODevice *vdev, VirtIOSCSICommon *s = VIRTIO_SCSI_COMMON(vdev); virtio_stl_p(vdev, &scsiconf->num_queues, s->conf.num_queues); - virtio_stl_p(vdev, &scsiconf->seg_max, 128 - 2); + virtio_stl_p(vdev, &scsiconf->seg_max, + s->conf.seg_max_adjust ? s->conf.virtqueue_size - 2 : 128 - 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)); @@ -898,6 +899,11 @@ void virtio_scsi_common_realize(DeviceState *dev, virtio_cleanup(vdev); return; } + if (s->conf.virtqueue_size <= 2) { + error_setg(errp, "invalid virtqueue_size property (= %" PRIu32 "), " + "must be > 2", s->conf.virtqueue_size); + return; + } s->cmd_vqs = g_new0(VirtQueue *, s->conf.num_queues); s->sense_size = VIRTIO_SCSI_SENSE_DEFAULT_SIZE; s->cdb_size = VIRTIO_SCSI_CDB_DEFAULT_SIZE; @@ -954,6 +960,8 @@ 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), + 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, 0xFFFF), DEFINE_PROP_UINT32("cmd_per_lun", VirtIOSCSI, parent_obj.conf.cmd_per_lun, -- cgit v1.2.3