[PATCH v6 5/7] virtio-scsi-pci: default num_queues to -smp N

[Stefan Hajnoczi]

Automatically size the number of virtio-scsi-pci, vhost-scsi-pci, and
vhost-user-scsi-pci request virtqueues to match the number of vCPUs.
Other transports continue to default to 1 request virtqueue.

A 1:1 virtqueue:vCPU mapping ensures that completion interrupts are
handled on the same vCPU that submitted the request.  No IPI is
necessary to complete an I/O request and performance is improved.  The
maximum number of MSI-X vectors and virtqueues limit are respected.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
 include/hw/virtio/virtio-scsi.h |  2 ++
 hw/core/machine.c               |  3 +++
 hw/scsi/vhost-scsi.c            |  3 ++-
 hw/scsi/vhost-user-scsi.c       |  3 ++-
 hw/scsi/virtio-scsi.c           |  6 +++++-
 hw/virtio/vhost-scsi-pci.c      | 10 +++++++---
 hw/virtio/vhost-user-scsi-pci.c | 10 +++++++---
 hw/virtio/virtio-scsi-pci.c     | 10 +++++++---
 8 files changed, 35 insertions(+), 12 deletions(-)

diff --git a/include/hw/virtio/virtio-scsi.h b/include/hw/virtio/virtio-scsi.h
index 9f293bcb80..c0b8e4dd7e 100644
--- a/include/hw/virtio/virtio-scsi.h
+++ b/include/hw/virtio/virtio-scsi.h
@@ -39,6 +39,8 @@
 /* Number of virtqueues that are always present */
 #define VIRTIO_SCSI_VQ_NUM_FIXED    2
 
+#define VIRTIO_SCSI_AUTO_NUM_QUEUES UINT32_MAX
+
 typedef struct virtio_scsi_cmd_req VirtIOSCSICmdReq;
 typedef struct virtio_scsi_cmd_resp VirtIOSCSICmdResp;
 typedef struct virtio_scsi_ctrl_tmf_req VirtIOSCSICtrlTMFReq;
diff --git a/hw/core/machine.c b/hw/core/machine.c
index a6f7e4e8d7..9ee2aa0f7b 100644
--- a/hw/core/machine.c
+++ b/hw/core/machine.c
@@ -29,6 +29,9 @@
 #include "migration/vmstate.h"
 
 GlobalProperty hw_compat_5_1[] = {
+    { "vhost-scsi", "num_queues", "1"},
+    { "vhost-user-scsi", "num_queues", "1"},
+    { "virtio-scsi-device", "num_queues", "1"},
 };
 const size_t hw_compat_5_1_len = G_N_ELEMENTS(hw_compat_5_1);
 
diff --git a/hw/scsi/vhost-scsi.c b/hw/scsi/vhost-scsi.c
index 13b05af29b..a83ffeefc8 100644
--- a/hw/scsi/vhost-scsi.c
+++ b/hw/scsi/vhost-scsi.c
@@ -270,7 +270,8 @@ static Property vhost_scsi_properties[] = {
     DEFINE_PROP_STRING("vhostfd", VirtIOSCSICommon, conf.vhostfd),
     DEFINE_PROP_STRING("wwpn", VirtIOSCSICommon, conf.wwpn),
     DEFINE_PROP_UINT32("boot_tpgt", VirtIOSCSICommon, conf.boot_tpgt, 0),
-    DEFINE_PROP_UINT32("num_queues", VirtIOSCSICommon, conf.num_queues, 1),
+    DEFINE_PROP_UINT32("num_queues", VirtIOSCSICommon, conf.num_queues,
+                       VIRTIO_SCSI_AUTO_NUM_QUEUES),
     DEFINE_PROP_UINT32("virtqueue_size", VirtIOSCSICommon, conf.virtqueue_size,
                        128),
     DEFINE_PROP_BOOL("seg_max_adjust", VirtIOSCSICommon, conf.seg_max_adjust,
diff --git a/hw/scsi/vhost-user-scsi.c b/hw/scsi/vhost-user-scsi.c
index a8b821466f..7c0631656c 100644
--- a/hw/scsi/vhost-user-scsi.c
+++ b/hw/scsi/vhost-user-scsi.c
@@ -162,7 +162,8 @@ static void vhost_user_scsi_unrealize(DeviceState *dev)
 static Property vhost_user_scsi_properties[] = {
     DEFINE_PROP_CHR("chardev", VirtIOSCSICommon, conf.chardev),
     DEFINE_PROP_UINT32("boot_tpgt", VirtIOSCSICommon, conf.boot_tpgt, 0),
-    DEFINE_PROP_UINT32("num_queues", VirtIOSCSICommon, conf.num_queues, 1),
+    DEFINE_PROP_UINT32("num_queues", VirtIOSCSICommon, conf.num_queues,
+                       VIRTIO_SCSI_AUTO_NUM_QUEUES),
     DEFINE_PROP_UINT32("virtqueue_size", VirtIOSCSICommon, conf.virtqueue_size,
                        128),
     DEFINE_PROP_UINT32("max_sectors", VirtIOSCSICommon, conf.max_sectors,
diff --git a/hw/scsi/virtio-scsi.c b/hw/scsi/virtio-scsi.c
index eecdd05af5..3a71ea7097 100644
--- a/hw/scsi/virtio-scsi.c
+++ b/hw/scsi/virtio-scsi.c
@@ -891,6 +891,9 @@ void virtio_scsi_common_realize(DeviceState *dev,
     virtio_init(vdev, "virtio-scsi", VIRTIO_ID_SCSI,
                 sizeof(VirtIOSCSIConfig));
 
+    if (s->conf.num_queues == VIRTIO_SCSI_AUTO_NUM_QUEUES) {
+        s->conf.num_queues = 1;
+    }
     if (s->conf.num_queues == 0 ||
             s->conf.num_queues > VIRTIO_QUEUE_MAX - VIRTIO_SCSI_VQ_NUM_FIXED) {
         error_setg(errp, "Invalid number of queues (= %" PRIu32 "), "
@@ -964,7 +967,8 @@ static void virtio_scsi_device_unrealize(DeviceState *dev)
 }
 
 static Property virtio_scsi_properties[] = {
-    DEFINE_PROP_UINT32("num_queues", VirtIOSCSI, parent_obj.conf.num_queues, 
1),
+    DEFINE_PROP_UINT32("num_queues", VirtIOSCSI, parent_obj.conf.num_queues,
+                       VIRTIO_SCSI_AUTO_NUM_QUEUES),
     DEFINE_PROP_UINT32("virtqueue_size", VirtIOSCSI,
                                          parent_obj.conf.virtqueue_size, 256),
     DEFINE_PROP_BOOL("seg_max_adjust", VirtIOSCSI,
diff --git a/hw/virtio/vhost-scsi-pci.c b/hw/virtio/vhost-scsi-pci.c
index 06e814d30e..a6bb0dc60d 100644
--- a/hw/virtio/vhost-scsi-pci.c
+++ b/hw/virtio/vhost-scsi-pci.c
@@ -47,11 +47,15 @@ static void vhost_scsi_pci_realize(VirtIOPCIProxy 
*vpci_dev, Error **errp)
 {
     VHostSCSIPCI *dev = VHOST_SCSI_PCI(vpci_dev);
     DeviceState *vdev = DEVICE(&dev->vdev);
-    VirtIOSCSICommon *vs = VIRTIO_SCSI_COMMON(vdev);
+    VirtIOSCSIConf *conf = &dev->vdev.parent_obj.parent_obj.conf;
+
+    if (conf->num_queues == VIRTIO_SCSI_AUTO_NUM_QUEUES) {
+        conf->num_queues =
+            virtio_pci_optimal_num_queues(VIRTIO_SCSI_VQ_NUM_FIXED);
+    }
 
     if (vpci_dev->nvectors == DEV_NVECTORS_UNSPECIFIED) {
-        vpci_dev->nvectors = vs->conf.num_queues +
-                             VIRTIO_SCSI_VQ_NUM_FIXED + 1;
+        vpci_dev->nvectors = conf->num_queues + VIRTIO_SCSI_VQ_NUM_FIXED + 1;
     }
 
     qdev_realize(vdev, BUS(&vpci_dev->bus), errp);
diff --git a/hw/virtio/vhost-user-scsi-pci.c b/hw/virtio/vhost-user-scsi-pci.c
index ab6dfb71a9..25e97ca54e 100644
--- a/hw/virtio/vhost-user-scsi-pci.c
+++ b/hw/virtio/vhost-user-scsi-pci.c
@@ -53,11 +53,15 @@ static void vhost_user_scsi_pci_realize(VirtIOPCIProxy 
*vpci_dev, Error **errp)
 {
     VHostUserSCSIPCI *dev = VHOST_USER_SCSI_PCI(vpci_dev);
     DeviceState *vdev = DEVICE(&dev->vdev);
-    VirtIOSCSICommon *vs = VIRTIO_SCSI_COMMON(vdev);
+    VirtIOSCSIConf *conf = &dev->vdev.parent_obj.parent_obj.conf;
+
+    if (conf->num_queues == VIRTIO_SCSI_AUTO_NUM_QUEUES) {
+        conf->num_queues =
+            virtio_pci_optimal_num_queues(VIRTIO_SCSI_VQ_NUM_FIXED);
+    }
 
     if (vpci_dev->nvectors == DEV_NVECTORS_UNSPECIFIED) {
-        vpci_dev->nvectors = vs->conf.num_queues +
-                             VIRTIO_SCSI_VQ_NUM_FIXED + 1;
+        vpci_dev->nvectors = conf->num_queues + VIRTIO_SCSI_VQ_NUM_FIXED + 1;
     }
 
     qdev_realize(vdev, BUS(&vpci_dev->bus), errp);
diff --git a/hw/virtio/virtio-scsi-pci.c b/hw/virtio/virtio-scsi-pci.c
index 3ff9eb7ef6..fa4b3bfb50 100644
--- a/hw/virtio/virtio-scsi-pci.c
+++ b/hw/virtio/virtio-scsi-pci.c
@@ -46,13 +46,17 @@ static void virtio_scsi_pci_realize(VirtIOPCIProxy 
*vpci_dev, Error **errp)
 {
     VirtIOSCSIPCI *dev = VIRTIO_SCSI_PCI(vpci_dev);
     DeviceState *vdev = DEVICE(&dev->vdev);
-    VirtIOSCSICommon *vs = VIRTIO_SCSI_COMMON(vdev);
     DeviceState *proxy = DEVICE(vpci_dev);
+    VirtIOSCSIConf *conf = &dev->vdev.parent_obj.conf;
     char *bus_name;
 
+    if (conf->num_queues == VIRTIO_SCSI_AUTO_NUM_QUEUES) {
+        conf->num_queues =
+            virtio_pci_optimal_num_queues(VIRTIO_SCSI_VQ_NUM_FIXED);
+    }
+
     if (vpci_dev->nvectors == DEV_NVECTORS_UNSPECIFIED) {
-        vpci_dev->nvectors = vs->conf.num_queues +
-                             VIRTIO_SCSI_VQ_NUM_FIXED + 1;
+        vpci_dev->nvectors = conf->num_queues + VIRTIO_SCSI_VQ_NUM_FIXED + 1;
     }
 
     /*
-- 
2.26.2