[PATCH v4 0/2] virtio: make seg_max virtqueue size dependent

[PATCH v4 0/2] virtio: make seg_max virtqueue size dependent

[Denis Plotnikov]

v4:
  * rebased on 4.2 [MST]

v3:
  * add property to set in machine type [MST]
  * add min queue size check [Stefan]
  * add avocado based test [Max, Stefan, Eduardo, Cleber]

v2:
  * the standalone patch to make seg_max virtqueue size dependent
  * other patches are postponed

v1:
  the initial series

Denis Plotnikov (2):
  virtio: make seg_max virtqueue size dependent
  tests: add virtio-scsi and virtio-blk seg_max_adjust test

 hw/block/virtio-blk.c                     |   9 +-
 hw/core/machine.c                         |   3 +
 hw/scsi/vhost-scsi.c                      |   2 +
 hw/scsi/virtio-scsi.c                     |  10 +-
 include/hw/virtio/virtio-blk.h            |   1 +
 include/hw/virtio/virtio-scsi.h           |   1 +
 tests/acceptance/virtio_seg_max_adjust.py | 135 ++++++++++++++++++++++
 7 files changed, 159 insertions(+), 2 deletions(-)
 create mode 100755 tests/acceptance/virtio_seg_max_adjust.py

-- 
2.17.0

[PATCH v4 1/2] virtio: make seg_max virtqueue size dependent

[Denis Plotnikov]

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 <den@virtuozzo.com>,
   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.

Signed-off-by: Denis Plotnikov <dplotnikov@virtuozzo.com>
---
 hw/block/virtio-blk.c           |  9 ++++++++-
 hw/core/machine.c               |  3 +++
 hw/scsi/vhost-scsi.c            |  2 ++
 hw/scsi/virtio-scsi.c           | 10 +++++++++-
 include/hw/virtio/virtio-blk.h  |  1 +
 include/hw/virtio/virtio-scsi.h |  1 +
 6 files changed, 24 insertions(+), 2 deletions(-)

diff --git a/hw/block/virtio-blk.c b/hw/block/virtio-blk.c
index d62e6377c2..0f6f8113b7 100644
--- a/hw/block/virtio-blk.c
+++ b/hw/block/virtio-blk.c
@@ -908,7 +908,8 @@ 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);
@@ -1133,6 +1134,11 @@ 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 "), "
@@ -1262,6 +1268,7 @@ 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 023548b4f3..bfa320387e 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 e8b2b64d09..405cb6c953 100644
--- a/hw/scsi/virtio-scsi.c
+++ b/hw/scsi/virtio-scsi.c
@@ -654,7 +654,8 @@ 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));
@@ -893,6 +894,11 @@ void virtio_scsi_common_realize(DeviceState *dev,
         virtio_cleanup(vdev);
         return;
     }
+    if (s->conf.virtqueue_size <= 2) {
+        error_setg(errp, "invalid virtqueue_size property (= %" PRIu16 "), "
+                   "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;
@@ -949,6 +955,8 @@ 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,
diff --git a/include/hw/virtio/virtio-blk.h b/include/hw/virtio/virtio-blk.h
index 9c19f5b634..1e62f869b2 100644
--- a/include/hw/virtio/virtio-blk.h
+++ b/include/hw/virtio/virtio-blk.h
@@ -38,6 +38,7 @@ struct VirtIOBlkConf
     uint32_t request_merging;
     uint16_t num_queues;
     uint16_t queue_size;
+    bool seg_max_adjust;
     uint32_t max_discard_sectors;
     uint32_t max_write_zeroes_sectors;
     bool x_enable_wce_if_config_wce;
diff --git a/include/hw/virtio/virtio-scsi.h b/include/hw/virtio/virtio-scsi.h
index 122f7c4b6f..24e768909d 100644
--- a/include/hw/virtio/virtio-scsi.h
+++ b/include/hw/virtio/virtio-scsi.h
@@ -48,6 +48,7 @@ typedef struct virtio_scsi_config VirtIOSCSIConfig;
 struct VirtIOSCSIConf {
     uint32_t num_queues;
     uint32_t virtqueue_size;
+    bool seg_max_adjust;
     uint32_t max_sectors;
     uint32_t cmd_per_lun;
 #ifdef CONFIG_VHOST_SCSI
-- 
2.17.0

Re: [PATCH v4 1/2] virtio: make seg_max virtqueue size dependent

[Michael S. Tsirkin]

On Mon, Dec 16, 2019 at 01:04:50PM +0300, Denis Plotnikov wrote:
> 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 <den@virtuozzo.com>,
>    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.
> 
> Signed-off-by: Denis Plotnikov <dplotnikov@virtuozzo.com>

Stefan I think you acked this already? Could you ack?

Denis could you rebase on latest master pls so I can apply?

Thanks!

> ---
>  hw/block/virtio-blk.c           |  9 ++++++++-
>  hw/core/machine.c               |  3 +++
>  hw/scsi/vhost-scsi.c            |  2 ++
>  hw/scsi/virtio-scsi.c           | 10 +++++++++-
>  include/hw/virtio/virtio-blk.h  |  1 +
>  include/hw/virtio/virtio-scsi.h |  1 +
>  6 files changed, 24 insertions(+), 2 deletions(-)
> 
> diff --git a/hw/block/virtio-blk.c b/hw/block/virtio-blk.c
> index d62e6377c2..0f6f8113b7 100644
> --- a/hw/block/virtio-blk.c
> +++ b/hw/block/virtio-blk.c
> @@ -908,7 +908,8 @@ 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);
> @@ -1133,6 +1134,11 @@ 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 "), "
> @@ -1262,6 +1268,7 @@ 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 023548b4f3..bfa320387e 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 e8b2b64d09..405cb6c953 100644
> --- a/hw/scsi/virtio-scsi.c
> +++ b/hw/scsi/virtio-scsi.c
> @@ -654,7 +654,8 @@ 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));
> @@ -893,6 +894,11 @@ void virtio_scsi_common_realize(DeviceState *dev,
>          virtio_cleanup(vdev);
>          return;
>      }
> +    if (s->conf.virtqueue_size <= 2) {
> +        error_setg(errp, "invalid virtqueue_size property (= %" PRIu16 "), "
> +                   "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;
> @@ -949,6 +955,8 @@ 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,
> diff --git a/include/hw/virtio/virtio-blk.h b/include/hw/virtio/virtio-blk.h
> index 9c19f5b634..1e62f869b2 100644
> --- a/include/hw/virtio/virtio-blk.h
> +++ b/include/hw/virtio/virtio-blk.h
> @@ -38,6 +38,7 @@ struct VirtIOBlkConf
>      uint32_t request_merging;
>      uint16_t num_queues;
>      uint16_t queue_size;
> +    bool seg_max_adjust;
>      uint32_t max_discard_sectors;
>      uint32_t max_write_zeroes_sectors;
>      bool x_enable_wce_if_config_wce;
> diff --git a/include/hw/virtio/virtio-scsi.h b/include/hw/virtio/virtio-scsi.h
> index 122f7c4b6f..24e768909d 100644
> --- a/include/hw/virtio/virtio-scsi.h
> +++ b/include/hw/virtio/virtio-scsi.h
> @@ -48,6 +48,7 @@ typedef struct virtio_scsi_config VirtIOSCSIConfig;
>  struct VirtIOSCSIConf {
>      uint32_t num_queues;
>      uint32_t virtqueue_size;
> +    bool seg_max_adjust;
>      uint32_t max_sectors;
>      uint32_t cmd_per_lun;
>  #ifdef CONFIG_VHOST_SCSI
> -- 
> 2.17.0

[PATCH v4 2/2] tests: add virtio-scsi and virtio-blk seg_max_adjust test

[Denis Plotnikov]

It tests proper seg_max_adjust settings for all machine types except
'none', 'isapc', 'microvm'

Signed-off-by: Denis Plotnikov <dplotnikov@virtuozzo.com>
---
 tests/acceptance/virtio_seg_max_adjust.py | 135 ++++++++++++++++++++++
 1 file changed, 135 insertions(+)
 create mode 100755 tests/acceptance/virtio_seg_max_adjust.py

diff --git a/tests/acceptance/virtio_seg_max_adjust.py b/tests/acceptance/virtio_seg_max_adjust.py
new file mode 100755
index 0000000000..00cf2565d9
--- /dev/null
+++ b/tests/acceptance/virtio_seg_max_adjust.py
@@ -0,0 +1,135 @@
+#!/usr/bin/env python
+#
+# Test virtio-scsi and virtio-blk queue settings for all machine types
+#
+# Copyright (c) 2019 Virtuozzo International GmbH
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 2 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+#
+
+import sys
+import os
+import re
+
+sys.path.append(os.path.join(os.path.dirname(__file__), '..', '..', 'python'))
+from qemu.machine import QEMUMachine
+from avocado_qemu import Test
+
+#list of machine types and virtqueue properties to test
+VIRTIO_SCSI_PROPS = {'seg_max_adjust': 'seg_max_adjust'}
+VIRTIO_BLK_PROPS = {'seg_max_adjust': 'seg-max-adjust'}
+
+DEV_TYPES = {'virtio-scsi-pci': VIRTIO_SCSI_PROPS,
+             'virtio-blk-pci': VIRTIO_BLK_PROPS}
+
+VM_DEV_PARAMS = {'virtio-scsi-pci': ['-device', 'virtio-scsi-pci,id=scsi0'],
+                 'virtio-blk-pci': ['-device',
+                                    'virtio-blk-pci,id=scsi0,drive=drive0',
+                                    '-drive',
+                                    'driver=null-co,id=drive0,if=none']}
+
+
+class VirtioMaxSegSettingsCheck(Test):
+    @staticmethod
+    def make_pattern(props):
+        pattern_items = ['{0} = \w+'.format(prop) for prop in props]
+        return '|'.join(pattern_items)
+
+    def query_virtqueue(self, vm, dev_type_name):
+        query_ok = False
+        error = None
+        props = None
+
+        output = vm.command('human-monitor-command',
+                            command_line = 'info qtree')
+        props_list = DEV_TYPES[dev_type_name].values();
+        pattern = self.make_pattern(props_list)
+        res = re.findall(pattern, output)
+
+        if len(res) != len(props_list):
+            props_list = set(props_list)
+            res = set(res)
+            not_found = props_list.difference(res)
+            not_found = ', '.join(not_found)
+            error = '({0}): The following properties not found: {1}'\
+                     .format(dev_type_name, not_found)
+        else:
+            query_ok = True
+            props = dict()
+            for prop in res:
+                p = prop.split(' = ')
+                props[p[0]] = p[1]
+        return query_ok, props, error
+
+    def check_mt(self, mt, dev_type_name):
+        with QEMUMachine(self.qemu_bin) as vm:
+            vm.set_machine(mt["name"])
+            for s in VM_DEV_PARAMS[dev_type_name]:
+                vm.add_args(s)
+            vm.launch()
+            query_ok, props, error = self.query_virtqueue(vm, dev_type_name)
+
+        if not query_ok:
+            self.fail('machine type {0}: {1}'.format(mt['name'], error))
+
+        for prop_name, prop_val in props.items():
+            expected_val = mt[prop_name]
+            self.assertEqual(expected_val, prop_val)
+
+    @staticmethod
+    def seg_max_adjust_enabled(mt):
+        # machine types > 4.2 should have seg_max_adjust = true
+        # others seg_max_adjust = false
+        mt = mt.split("-")
+
+        # machine types with one line name and name like pc-x.x
+        if len(mt) <= 2:
+            return False
+
+        # machine types like pc-<chip_name>-x.x[.x]
+        ver = mt[2]
+        ver = ver.split(".");
+
+        # all versions greater than 4.2 goes with seg_max_adjust enabled
+        major = int(ver[0])
+        minor = int(ver[1])
+
+        if major > 4 or (major == 4 and minor > 2):
+            return True
+        return False
+
+    def test_machine_types(self):
+        # collect all machine types except 'none', 'isapc', 'microvm'
+        with QEMUMachine(self.qemu_bin) as vm:
+            vm.launch()
+            machines = [m['name'] for m in vm.command('query-machines')]
+            vm.shutdown()
+        machines.remove('none')
+        machines.remove('isapc')
+        machines.remove('microvm')
+
+        for dev_type in DEV_TYPES:
+            # create the list of machine types and their parameters.
+            mtypes = list()
+            for m in machines:
+                if self.seg_max_adjust_enabled(m):
+                    enabled = 'true'
+                else:
+                    enabled = 'false'
+                mtypes.append({'name': m,
+                               DEV_TYPES[dev_type]['seg_max_adjust']: enabled})
+
+            # test each machine type for a device type
+            for mt in mtypes:
+                self.check_mt(mt, dev_type)
-- 
2.17.0

Re: [PATCH v4 0/2] virtio: make seg_max virtqueue size dependent

[Michael S. Tsirkin]

On Mon, Dec 16, 2019 at 01:04:49PM +0300, Denis Plotnikov wrote:
> v4:
>   * rebased on 4.2 [MST]


Looks good. Can I get some acks from storage guys pls?

> v3:
>   * add property to set in machine type [MST]
>   * add min queue size check [Stefan]
>   * add avocado based test [Max, Stefan, Eduardo, Cleber]
> 
> v2:
>   * the standalone patch to make seg_max virtqueue size dependent
>   * other patches are postponed
> 
> v1:
>   the initial series
> 
> Denis Plotnikov (2):
>   virtio: make seg_max virtqueue size dependent
>   tests: add virtio-scsi and virtio-blk seg_max_adjust test
> 
>  hw/block/virtio-blk.c                     |   9 +-
>  hw/core/machine.c                         |   3 +
>  hw/scsi/vhost-scsi.c                      |   2 +
>  hw/scsi/virtio-scsi.c                     |  10 +-
>  include/hw/virtio/virtio-blk.h            |   1 +
>  include/hw/virtio/virtio-scsi.h           |   1 +
>  tests/acceptance/virtio_seg_max_adjust.py | 135 ++++++++++++++++++++++
>  7 files changed, 159 insertions(+), 2 deletions(-)
>  create mode 100755 tests/acceptance/virtio_seg_max_adjust.py
> 
> -- 
> 2.17.0

Re: [PATCH v4 0/2] virtio: make seg_max virtqueue size dependent

[Stefan Hajnoczi]

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On Mon, Dec 16, 2019 at 06:04:21AM -0500, Michael S. Tsirkin wrote:
> On Mon, Dec 16, 2019 at 01:04:49PM +0300, Denis Plotnikov wrote:
> > v4:
> >   * rebased on 4.2 [MST]
> 
> 
> Looks good. Can I get some acks from storage guys pls?

Looks good to me.

Stefan

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Re: [PATCH v4 0/2] virtio: make seg_max virtqueue size dependent

[Stefan Hajnoczi]

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On Mon, Dec 16, 2019 at 01:04:49PM +0300, Denis Plotnikov wrote:
> v4:
>   * rebased on 4.2 [MST]
> 
> v3:
>   * add property to set in machine type [MST]
>   * add min queue size check [Stefan]
>   * add avocado based test [Max, Stefan, Eduardo, Cleber]
> 
> v2:
>   * the standalone patch to make seg_max virtqueue size dependent
>   * other patches are postponed
> 
> v1:
>   the initial series
> 
> Denis Plotnikov (2):
>   virtio: make seg_max virtqueue size dependent
>   tests: add virtio-scsi and virtio-blk seg_max_adjust test
> 
>  hw/block/virtio-blk.c                     |   9 +-
>  hw/core/machine.c                         |   3 +
>  hw/scsi/vhost-scsi.c                      |   2 +
>  hw/scsi/virtio-scsi.c                     |  10 +-
>  include/hw/virtio/virtio-blk.h            |   1 +
>  include/hw/virtio/virtio-scsi.h           |   1 +
>  tests/acceptance/virtio_seg_max_adjust.py | 135 ++++++++++++++++++++++
>  7 files changed, 159 insertions(+), 2 deletions(-)
>  create mode 100755 tests/acceptance/virtio_seg_max_adjust.py

Bellissimo!  Thanks for doing this :)

Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>

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