check IOMMU group devices usage when preparing device for vfio passthrough

The virsh start <domain> fails with qemu error when the hostdevices of the
same iommu group are used actively by other vms. It is not clear which
hostdev from the same iommu group is used by any of the running guests.
User has to go through every guest xml to figure out who is using the
hostdev of same iommu group.

Solution:
Iterate the iommu group of the hostdev and error our neatly in case a
device in the same iommu group is busy. Reattach code also does the same
kind of check, remove duplicate code as well.

Signed-off-by: Shivaprasad G Bhat <sbhat@linux.vnet.ibm.com>
Signed-off-by: Michal Privoznik <mprivozn@redhat.com>

src/util/virhostdev.c

@@ -54,6 +54,41 @@ static virClassPtr virHostdevManagerClass;
 static void virHostdevManagerDispose(void *obj);
 static virHostdevManagerPtr virHostdevManagerNew(void);
 
+static int virHostdevIsPCINodeDeviceUsed(virPCIDeviceAddressPtr devAddr, void *opaque)
+{
+    virPCIDevicePtr other;
+    int ret = -1;
+    virPCIDevicePtr pci = NULL;
+    virHostdevManagerPtr hostdev_mgr = opaque;
+
+    if (!(pci = virPCIDeviceNew(devAddr->domain, devAddr->bus,
+                                devAddr->slot, devAddr->function)))
+        goto cleanup;
+
+    other = virPCIDeviceListFind(hostdev_mgr->activePCIHostdevs, pci);
+    if (other) {
+        const char *other_drvname = NULL;
+        const char *other_domname = NULL;
+        virPCIDeviceGetUsedBy(other, &other_drvname, &other_domname);
+
+        if (other_drvname && other_domname)
+            virReportError(VIR_ERR_OPERATION_INVALID,
+                           _("PCI device %s is in use by "
+                             "driver %s, domain %s"),
+                           virPCIDeviceGetName(pci),
+                           other_drvname, other_domname);
+        else
+            virReportError(VIR_ERR_OPERATION_INVALID,
+                           _("PCI device %s is in use"),
+                           virPCIDeviceGetName(pci));
+        goto cleanup;
+    }
+    ret = 0;
+ cleanup:
+    virPCIDeviceFree(pci);
+    return ret;
+}
+
 static int virHostdevManagerOnceInit(void)
 {
     if (!(virHostdevManagerClass = virClassNew(virClassForObject(),
@@ -494,6 +529,7 @@ virHostdevPreparePCIDevices(virHostdevManagerPtr hostdev_mgr,
     int last_processed_hostdev_vf = -1;
     size_t i;
     int ret = -1;
+    virPCIDeviceAddressPtr devAddr = NULL;
 
     if (!nhostdevs)
         return 0;
@@ -518,7 +554,6 @@ virHostdevPreparePCIDevices(virHostdevManagerPtr hostdev_mgr,
 
     for (i = 0; i < virPCIDeviceListCount(pcidevs); i++) {
         virPCIDevicePtr dev = virPCIDeviceListGet(pcidevs, i);
-        virPCIDevicePtr other;
         bool strict_acs_check = !!(flags & VIR_HOSTDEV_STRICT_ACS_CHECK);
 
         if (!virPCIDeviceIsAssignable(dev, strict_acs_check)) {
@@ -527,24 +562,22 @@ virHostdevPreparePCIDevices(virHostdevManagerPtr hostdev_mgr,
                            virPCIDeviceGetName(dev));
             goto cleanup;
         }
-        /* The device is in use by other active domain if
-         * the dev is in list activePCIHostdevs.
-         */
-        if ((other = virPCIDeviceListFind(hostdev_mgr->activePCIHostdevs, dev))) {
-            const char *other_drvname;
-            const char *other_domname;
 
-            virPCIDeviceGetUsedBy(other, &other_drvname, &other_domname);
+        VIR_FREE(devAddr);
-            if (other_drvname && other_domname)
+        if (!(devAddr = virPCIDeviceGetAddress(dev)))
-                virReportError(VIR_ERR_OPERATION_INVALID,
+            goto cleanup;
-                               _("PCI device %s is in use by "
+
-                                 "driver %s, domain %s"),
+        /* The device is in use by other active domain if
-                               virPCIDeviceGetName(dev),
+         * the dev is in list activePCIHostdevs. VFIO devices
-                               other_drvname, other_domname);
+         * belonging to same iommu group cant be shared
-            else
+         * across guests.
-                virReportError(VIR_ERR_OPERATION_INVALID,
+         */
-                               _("PCI device %s is already in use"),
+        if (STREQ(virPCIDeviceGetStubDriver(dev), "vfio-pci")) {
-                               virPCIDeviceGetName(dev));
+            if (virPCIDeviceAddressIOMMUGroupIterate(devAddr,
+                                                     virHostdevIsPCINodeDeviceUsed,
+                                                     hostdev_mgr) < 0)
+                goto cleanup;
+        } else if (virHostdevIsPCINodeDeviceUsed(devAddr, hostdev_mgr)) {
             goto cleanup;
         }
     }
@@ -678,6 +711,7 @@ virHostdevPreparePCIDevices(virHostdevManagerPtr hostdev_mgr,
     virObjectUnlock(hostdev_mgr->activePCIHostdevs);
     virObjectUnlock(hostdev_mgr->inactivePCIHostdevs);
     virObjectUnref(pcidevs);
+    VIR_FREE(devAddr);
     return ret;
 }
 
@@ -1506,29 +1540,17 @@ int
 virHostdevPCINodeDeviceReAttach(virHostdevManagerPtr hostdev_mgr,
                                 virPCIDevicePtr pci)
 {
-    virPCIDevicePtr other;
+    virPCIDeviceAddressPtr devAddr = NULL;
     int ret = -1;
 
     virObjectLock(hostdev_mgr->activePCIHostdevs);
     virObjectLock(hostdev_mgr->inactivePCIHostdevs);
-    other = virPCIDeviceListFind(hostdev_mgr->activePCIHostdevs, pci);
-    if (other) {
-        const char *other_drvname = NULL;
-        const char *other_domname = NULL;
-        virPCIDeviceGetUsedBy(other, &other_drvname, &other_domname);
 
-        if (other_drvname && other_domname)
+    if (!(devAddr = virPCIDeviceGetAddress(pci)))
-            virReportError(VIR_ERR_OPERATION_INVALID,
+        goto out;
-                           _("PCI device %s is still in use by "
+
-                             "driver %s, domain %s"),
+    if (virHostdevIsPCINodeDeviceUsed(devAddr, hostdev_mgr))
-                           virPCIDeviceGetName(pci),
-                           other_drvname, other_domname);
-        else
-            virReportError(VIR_ERR_OPERATION_INVALID,
-                           _("PCI device %s is still in use"),
-                           virPCIDeviceGetName(pci));
         goto out;
-    }
 
     virPCIDeviceReattachInit(pci);
 
@@ -1540,6 +1562,7 @@ virHostdevPCINodeDeviceReAttach(virHostdevManagerPtr hostdev_mgr,
  out:
     virObjectUnlock(hostdev_mgr->inactivePCIHostdevs);
     virObjectUnlock(hostdev_mgr->activePCIHostdevs);
+    VIR_FREE(devAddr);
     return ret;
 }