[libvirt] [PATCH v2 3/5] qemu: Add vhost-scsi string for -device parameter

[Eric Farman]

Open /dev/vhost-scsi, and record the resulting file descriptor, so that
the guest has access to the host device outside of the libvirt daemon.
Pass this information, along with data parsed from the XML file, to build
a device string for the qemu command line.  That device string will be
for either a vhost-scsi-ccw device in the case of an s390 machine, or
vhost-scsi-pci for any others.

Signed-off-by: Eric Farman <farman at linux.vnet.ibm.com>
---
 src/libvirt_private.syms |  1 +
 src/qemu/qemu_command.c  | 80 ++++++++++++++++++++++++++++++++++++++++++++++++
 src/qemu/qemu_command.h  |  6 ++++
 src/util/virscsi.c       | 26 ++++++++++++++++
 src/util/virscsi.h       |  1 +
 5 files changed, 114 insertions(+)

diff --git a/src/libvirt_private.syms b/src/libvirt_private.syms
index a32ce1c..68f0b26 100644
--- a/src/libvirt_private.syms
+++ b/src/libvirt_private.syms
@@ -2262,6 +2262,7 @@ virSCSIDeviceListNew;
 virSCSIDeviceListSteal;
 virSCSIDeviceNew;
 virSCSIDeviceSetUsedBy;
+virSCSIOpenVhost;
 
 
 # util/virseclabel.h
diff --git a/src/qemu/qemu_command.c b/src/qemu/qemu_command.c
index a6dea6a..0af98ac 100644
--- a/src/qemu/qemu_command.c
+++ b/src/qemu/qemu_command.c
@@ -4711,6 +4711,52 @@ qemuBuildSCSIiSCSIHostdevDrvStr(virDomainHostdevDefPtr dev)
 }
 
 char *
+qemuBuildHostHostdevDevStr(const virDomainDef *def,
+                           virDomainHostdevDefPtr dev,
+                           virQEMUCapsPtr qemuCaps,
+                           char *vhostfdName,
+                           size_t vhostfdSize)
+{
+    virBuffer buf = VIR_BUFFER_INITIALIZER;
+    virDomainHostdevSubsysHostPtr hostsrc = &dev->source.subsys.u.host;
+
+    if (!virQEMUCapsGet(qemuCaps, QEMU_CAPS_DEVICE_VHOST_SCSI)) {
+        virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
+                       _("This QEMU doesn't support vhost-scsi devices"));
+        goto cleanup;
+    }
+
+    if (ARCH_IS_S390(def->os.arch))
+        virBufferAddLit(&buf, "vhost-scsi-ccw");
+    else
+        virBufferAddLit(&buf, "vhost-scsi-pci");
+
+    virBufferAsprintf(&buf, ",wwpn=%s", hostsrc->wwpn);
+
+    if (vhostfdSize == 1) {
+        virBufferAsprintf(&buf, ",vhostfd=%s", vhostfdName);
+    } else {
+        virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
+                       _("QEMU supports a single vhost-scsi file descriptor"));
+        goto cleanup;
+    }
+
+    virBufferAsprintf(&buf, ",id=%s", dev->info->alias);
+
+    if (qemuBuildDeviceAddressStr(&buf, def, dev->info, qemuCaps) < 0)
+        goto cleanup;
+
+    if (virBufferCheckError(&buf) < 0)
+        goto cleanup;
+
+    return virBufferContentAndReset(&buf);
+
+ cleanup:
+    virBufferFreeAndReset(&buf);
+    return NULL;
+}
+
+char *
 qemuBuildSCSIHostdevDrvStr(virDomainHostdevDefPtr dev)
 {
     virBuffer buf = VIR_BUFFER_INITIALIZER;
@@ -5156,6 +5202,40 @@ qemuBuildHostdevCommandLine(virCommandPtr cmd,
                 return -1;
             }
         }
+
+        /* SCSI_host */
+        if (hostdev->mode == VIR_DOMAIN_HOSTDEV_MODE_SUBSYS &&
+            subsys->type == VIR_DOMAIN_HOSTDEV_SUBSYS_TYPE_HOST) {
+            if (virQEMUCapsGet(qemuCaps, QEMU_CAPS_DEVICE_SCSI_GENERIC)) {
+                if (hostdev->source.subsys.u.host.protocol == VIR_DOMAIN_HOSTDEV_HOST_PROTOCOL_TYPE_VHOST) {
+                    char *vhostfdName = NULL;
+                    int vhostfd = -1;
+                    size_t vhostfdSize = 1;
+
+                    if (virSCSIOpenVhost(&vhostfd, &vhostfdSize) < 0)
+                        return -1;
+
+                    if (virAsprintf(&vhostfdName, "%d", vhostfd) < 0) {
+                        VIR_FORCE_CLOSE(vhostfd);
+                        return -1;
+                    }
+
+                    virCommandPassFD(cmd, vhostfd, VIR_COMMAND_PASS_FD_CLOSE_PARENT);
+
+                    virCommandAddArg(cmd, "-device");
+                    if (!(devstr = qemuBuildHostHostdevDevStr(def, hostdev, qemuCaps, vhostfdName, vhostfdSize)))
+                        return -1;
+                    virCommandAddArg(cmd, devstr);
+
+                    VIR_FREE(vhostfdName);
+                    VIR_FREE(devstr);
+                }
+            } else {
+                virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
+                               _("SCSI passthrough is not supported by this version of qemu"));
+                return -1;
+            }
+        }
     }
 
     return 0;
diff --git a/src/qemu/qemu_command.h b/src/qemu/qemu_command.h
index dcf9ba6..323b470 100644
--- a/src/qemu/qemu_command.h
+++ b/src/qemu/qemu_command.h
@@ -158,6 +158,12 @@ char *qemuBuildSCSIHostdevDrvStr(virDomainHostdevDefPtr dev);
 char *qemuBuildSCSIHostdevDevStr(const virDomainDef *def,
                                  virDomainHostdevDefPtr dev,
                                  virQEMUCapsPtr qemuCaps);
+char *
+qemuBuildHostHostdevDevStr(const virDomainDef *def,
+                           virDomainHostdevDefPtr dev,
+                           virQEMUCapsPtr qemuCaps,
+                           char *vhostfdName,
+                           size_t vhostfdSize);
 
 char *qemuBuildRedirdevDevStr(const virDomainDef *def,
                               virDomainRedirdevDefPtr dev,
diff --git a/src/util/virscsi.c b/src/util/virscsi.c
index 4843367..290b692 100644
--- a/src/util/virscsi.c
+++ b/src/util/virscsi.c
@@ -105,6 +105,32 @@ virSCSIDeviceGetAdapterId(const char *adapter,
     return -1;
 }
 
+int
+virSCSIOpenVhost(int *vhostfd,
+                 size_t *vhostfdSize)
+{
+    size_t i;
+
+    for (i = 0; i < *vhostfdSize; i++) {
+        vhostfd[i] = open("/dev/vhost-scsi", O_RDWR);
+
+        if (vhostfd[i] < 0) {
+            virReportSystemError(errno, "%s",
+                                 _("vhost-scsi was requested for an interface, "
+                                   "but is unavailable"));
+            goto error;
+        }
+    }
+
+    return 0;
+
+ error:
+    while (i--)
+        VIR_FORCE_CLOSE(vhostfd[i]);
+
+    return -1;
+}
+
 char *
 virSCSIDeviceGetSgName(const char *sysfs_prefix,
                        const char *adapter,
diff --git a/src/util/virscsi.h b/src/util/virscsi.h
index df40d7f..cb37da8 100644
--- a/src/util/virscsi.h
+++ b/src/util/virscsi.h
@@ -33,6 +33,7 @@ typedef virSCSIDevice *virSCSIDevicePtr;
 typedef struct _virSCSIDeviceList virSCSIDeviceList;
 typedef virSCSIDeviceList *virSCSIDeviceListPtr;
 
+int virSCSIOpenVhost(int *vhostfd, size_t *vhostfdSize);
 char *virSCSIDeviceGetSgName(const char *sysfs_prefix,
                              const char *adapter,
                              unsigned int bus,
-- 
1.9.1