virtio-scsi-pci: default num_queues to -smp N

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>
Message-Id: <20200818143348.310613-6-stefanha@redhat.com>
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Reviewed-by: Raphael Norwitz <raphael.norwitz@nutanix.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

hw/core/machine.c

@@ -28,7 +28,11 @@
 #include "hw/mem/nvdimm.h"
 #include "migration/vmstate.h"
 
-GlobalProperty hw_compat_5_1[] = {};
+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);
 
 GlobalProperty hw_compat_5_0[] = {

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,

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,

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,

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 +
+        vpci_dev->nvectors = conf->num_queues + VIRTIO_SCSI_VQ_NUM_FIXED + 1;
-                             VIRTIO_SCSI_VQ_NUM_FIXED + 1;
     }
 
     qdev_realize(vdev, BUS(&vpci_dev->bus), errp);

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 +
+        vpci_dev->nvectors = conf->num_queues + VIRTIO_SCSI_VQ_NUM_FIXED + 1;
-                             VIRTIO_SCSI_VQ_NUM_FIXED + 1;
     }
 
     qdev_realize(vdev, BUS(&vpci_dev->bus), errp);

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 +
+        vpci_dev->nvectors = conf->num_queues + VIRTIO_SCSI_VQ_NUM_FIXED + 1;
-                             VIRTIO_SCSI_VQ_NUM_FIXED + 1;
     }
 
     /*

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;