[PATCH v5 0/2] virtio: make seg_max virtqueue size dependent

[PATCH v5 0/2] virtio: make seg_max virtqueue size dependent

[Denis Plotnikov]

v5:
  * rebased on the recent master [MST]
  * NOTE: the test doesn't pass because 5.0 machine type use 4.2 compat
          instead of it's own or no compat at all. The test will pass
          once the new 5.0 compat is used. 

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 | 134 ++++++++++++++++++++++
 7 files changed, 158 insertions(+), 2 deletions(-)
 create mode 100755 tests/acceptance/virtio_seg_max_adjust.py

-- 
2.17.0

[PATCH v5 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.

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

[PATCH v5 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 | 134 ++++++++++++++++++++++
 1 file changed, 134 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..5458573138
--- /dev/null
+++ b/tests/acceptance/virtio_seg_max_adjust.py
@@ -0,0 +1,134 @@
+#!/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 >= 5.0 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(".");
+
+        # versions >= 5.0 goes with seg_max_adjust enabled
+        major = int(ver[0])
+
+        if major >= 5:
+            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

[PATCH v5 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.

Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
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 v5 0/2] virtio: make seg_max virtqueue size dependent

[Denis Plotnikov]

PLEASE, IGNORE THIS PATCH SET

On 20.12.2019 17:04, Denis Plotnikov wrote:
> v5:
>    * rebased on the recent master [MST]
>    * NOTE: the test doesn't pass because 5.0 machine type use 4.2 compat
>            instead of it's own or no compat at all. The test will pass
>            once the new 5.0 compat is used.
>
> 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 | 134 ++++++++++++++++++++++
>   7 files changed, 158 insertions(+), 2 deletions(-)
>   create mode 100755 tests/acceptance/virtio_seg_max_adjust.py
>