From 2d6d67e1544a8a86249a1e958e1829b41bf84cde Mon Sep 17 00:00:00 2001
From: Hiroki Narukawa <hnarukaw@yahoo-corp.jp>
Date: Thu, 9 Sep 2021 12:34:48 +0900
Subject: [PATCH] qemu: Implement virtio-blk queue-size option

The option "queue-size" in virtio-blk was added in qemu-2.12.0, and
default value increased from qemu-5.0.0.

However, increasing this value may lead to drop of random access
performance.

Signed-off-by: Hiroki Narukawa <hnarukaw@yahoo-corp.jp>
Reviewed-by: Peter Krempa <pkrempa@redhat.com>
---
 src/qemu/qemu_command.c                              |  3 +++
 src/qemu/qemu_validate.c                             |  6 ++++++
 .../disk-virtio-queues.x86_64-latest.args            | 10 ++++++++--
 tests/qemuxml2argvdata/disk-virtio-queues.xml        | 12 ++++++++++++
 4 files changed, 29 insertions(+), 2 deletions(-)

diff --git a/src/qemu/qemu_command.c b/src/qemu/qemu_command.c
index 73868ab4b7..95f0a26564 100644
--- a/src/qemu/qemu_command.c
+++ b/src/qemu/qemu_command.c
@@ -1738,6 +1738,9 @@ qemuBuildDiskDeviceStr(const virDomainDef *def,
         if (disk->queues) {
             virBufferAsprintf(&opt, ",num-queues=%u", disk->queues);
         }
+        if (disk->queue_size > 0) {
+            virBufferAsprintf(&opt, ",queue-size=%u", disk->queue_size);
+        }
 
         qemuBuildVirtioOptionsStr(&opt, disk->virtio);
 
diff --git a/src/qemu/qemu_validate.c b/src/qemu/qemu_validate.c
index 6b685881a8..6b1a0f6c02 100644
--- a/src/qemu/qemu_validate.c
+++ b/src/qemu/qemu_validate.c
@@ -2826,6 +2826,12 @@ qemuValidateDomainDeviceDefDiskFrontend(const virDomainDiskDef *disk,
                              "QEMU binary"));
             return -1;
         }
+        if (disk->queue_size > 0 &&
+            !virQEMUCapsGet(qemuCaps, QEMU_CAPS_VIRTIO_BLK_NUM_QUEUES)) {
+            virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
+                           _("queue-size property isn't supported by this QEMU binary"));
+            return -1;
+        }
         break;
 
     case VIR_DOMAIN_DISK_BUS_USB:
diff --git a/tests/qemuxml2argvdata/disk-virtio-queues.x86_64-latest.args b/tests/qemuxml2argvdata/disk-virtio-queues.x86_64-latest.args
index 6637088a35..b1ff6de857 100644
--- a/tests/qemuxml2argvdata/disk-virtio-queues.x86_64-latest.args
+++ b/tests/qemuxml2argvdata/disk-virtio-queues.x86_64-latest.args
@@ -27,9 +27,15 @@ XDG_CONFIG_HOME=/tmp/lib/domain--1-QEMUGuest1/.config \
 -no-acpi \
 -boot strict=on \
 -device piix3-usb-uhci,id=usb,bus=pci.0,addr=0x1.0x2 \
--blockdev '{"driver":"file","filename":"/tmp/data.img","node-name":"libvirt-1-storage","auto-read-only":true,"discard":"unmap"}' \
+-blockdev '{"driver":"file","filename":"/tmp/data.img","node-name":"libvirt-3-storage","auto-read-only":true,"discard":"unmap"}' \
+-blockdev '{"node-name":"libvirt-3-format","read-only":false,"driver":"raw","file":"libvirt-3-storage"}' \
+-device virtio-blk-pci,num-queues=4,bus=pci.0,addr=0x3,drive=libvirt-3-format,id=virtio-disk0,bootindex=1 \
+-blockdev '{"driver":"file","filename":"/tmp/data1.img","node-name":"libvirt-2-storage","auto-read-only":true,"discard":"unmap"}' \
+-blockdev '{"node-name":"libvirt-2-format","read-only":false,"driver":"raw","file":"libvirt-2-storage"}' \
+-device virtio-blk-pci,queue-size=256,bus=pci.0,addr=0x4,drive=libvirt-2-format,id=virtio-disk1 \
+-blockdev '{"driver":"file","filename":"/tmp/data2.img","node-name":"libvirt-1-storage","auto-read-only":true,"discard":"unmap"}' \
 -blockdev '{"node-name":"libvirt-1-format","read-only":false,"driver":"raw","file":"libvirt-1-storage"}' \
--device virtio-blk-pci,num-queues=4,bus=pci.0,addr=0x3,drive=libvirt-1-format,id=virtio-disk0,bootindex=1 \
+-device virtio-blk-pci,num-queues=4,queue-size=256,bus=pci.0,addr=0x5,drive=libvirt-1-format,id=virtio-disk2 \
 -audiodev id=audio1,driver=none \
 -sandbox on,obsolete=deny,elevateprivileges=deny,spawn=deny,resourcecontrol=deny \
 -msg timestamp=on
diff --git a/tests/qemuxml2argvdata/disk-virtio-queues.xml b/tests/qemuxml2argvdata/disk-virtio-queues.xml
index ea1001bdd4..3cfa958c97 100644
--- a/tests/qemuxml2argvdata/disk-virtio-queues.xml
+++ b/tests/qemuxml2argvdata/disk-virtio-queues.xml
@@ -23,6 +23,18 @@
       <target dev='vda' bus='virtio'/>
       <address type='pci' domain='0x0000' bus='0x00' slot='0x03' function='0x0'/>
     </disk>
+    <disk type='file' device='disk'>
+      <driver name='qemu' type='raw' queue_size='256'/>
+      <source file='/tmp/data1.img'/>
+      <target dev='vdb' bus='virtio'/>
+      <address type='pci' domain='0x0000' bus='0x00' slot='0x04' function='0x0'/>
+    </disk>
+    <disk type='file' device='disk'>
+      <driver name='qemu' type='raw' queues='4' queue_size='256'/>
+      <source file='/tmp/data2.img'/>
+      <target dev='vdc' bus='virtio'/>
+      <address type='pci' domain='0x0000' bus='0x00' slot='0x05' function='0x0'/>
+    </disk>
     <controller type='usb' index='0' model='piix3-uhci'>
       <address type='pci' domain='0x0000' bus='0x00' slot='0x01' function='0x2'/>
     </controller>