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[libvirt] [PATCH v2] qemu: Do not reattach PCI device used by other domain when shutdown



When failing on starting a domain, it tries to reattach all the PCI
devices defined in the domain conf, regardless of whether the devices
are still used by other domain. This will cause the devices to be deleted
from the list qemu_driver->activePciHostdevs, thus the devices will be
thought as usable even if it's not true. And following commands
nodedev-{reattach,reset} will be successful.

How to reproduce:
  1) Define two domains with same PCI device defined in the confs.
  2) # virsh start domain1
  3) # virsh start domain2
  4) # virsh nodedev-reattach $pci_device

You will see the device will be reattached to host successfully.
As pciDeviceReattach just check if the device is still used by
other domain via checking if the device is in list driver->activePciHostdevs,
however, the device is deleted from the list by step 2).

This patch is to prohibit the bug by:
  1) Prohibit a domain starting or device attachment right at
     preparation period (qemuPrepareHostdevPCIDevices) if the
     device is in list driver->activePciHostdevs, which means
     it's used by other domain.

  2) Introduces a new field for struct _pciDevice, (const char *used_by),
     it will be set as the domain name at preparation period,
     (qemuPrepareHostdevPCIDevices). Thus we can prohibit deleting
     the device from driver->activePciHostdevs if it's still used by
     other domain when stopping the domain process.

* src/pci.h (define two internal functions, pciDeviceSetUsedBy and
    pciDevceGetUsedBy)
* src/pci.c (new field "const char *used_by" for struct _pciDevice,
    implementations for the two new functions)
* src/libvirt_private.syms (Add the two new internal functions)
* src/qemu_hostdev.h (Modify the definition of functions
    qemuPrepareHostdevPCIDevices, and qemuDomainReAttachHostdevDevices)
* src/qemu_hostdev.c (Prohibit preparation and don't delete the
    device from activePciHostdevs list if it's still used by other domain)
* src/qemu_hotplug.c (Update function usage, as the definitions are
    changed)

v1 - v2:
   * char * used_by => const char *used_by, and no strdup()
   * Other nits pointed out by Eric.
---
 src/libvirt_private.syms |    2 ++
 src/qemu/qemu_hostdev.c  |   43 ++++++++++++++++++++++++++++++++++++++-----
 src/qemu/qemu_hostdev.h  |    2 ++
 src/qemu/qemu_hotplug.c  |    4 ++--
 src/util/pci.c           |   15 +++++++++++++++
 src/util/pci.h           |    3 +++
 6 files changed, 62 insertions(+), 7 deletions(-)

diff --git a/src/libvirt_private.syms b/src/libvirt_private.syms
index 4f96518..4d50d86 100644
--- a/src/libvirt_private.syms
+++ b/src/libvirt_private.syms
@@ -880,6 +880,7 @@ virNWFilterHashTableRemoveEntry;
 pciDettachDevice;
 pciDeviceFileIterate;
 pciDeviceGetManaged;
+pciDeviceGetUsedBy;
 pciDeviceIsAssignable;
 pciDeviceIsVirtualFunction;
 pciDeviceListAdd;
@@ -892,6 +893,7 @@ pciDeviceListSteal;
 pciDeviceNetName;
 pciDeviceReAttachInit;
 pciDeviceSetManaged;
+pciDeviceSetUsedBy;
 pciFreeDevice;
 pciGetDevice;
 pciGetPhysicalFunction;
diff --git a/src/qemu/qemu_hostdev.c b/src/qemu/qemu_hostdev.c
index 6f77717..f354ea8 100644
--- a/src/qemu/qemu_hostdev.c
+++ b/src/qemu/qemu_hostdev.c
@@ -101,6 +101,7 @@ cleanup:
 
 
 int qemuPrepareHostdevPCIDevices(struct qemud_driver *driver,
+                                 const char *name,
                                  virDomainHostdevDefPtr *hostdevs,
                                  int nhostdevs)
 {
@@ -111,7 +112,7 @@ int qemuPrepareHostdevPCIDevices(struct qemud_driver *driver,
     if (!(pcidevs = qemuGetPciHostDeviceList(hostdevs, nhostdevs)))
         return -1;
 
-    /* We have to use 4 loops here. *All* devices must
+    /* We have to use 6 loops here. *All* devices must
      * be detached before we reset any of them, because
      * in some cases you have to reset the whole PCI,
      * which impacts all devices on it. Also, all devices
@@ -125,9 +126,16 @@ int qemuPrepareHostdevPCIDevices(struct qemud_driver *driver,
 
     for (i = 0; i < pciDeviceListCount(pcidevs); i++) {
         pciDevice *dev = pciDeviceListGet(pcidevs, i);
-        if (!pciDeviceIsAssignable(dev, !driver->relaxedACS))
-            goto reattachdevs;
+        /* The device is in use by other active domain if
+         * the dev is in list driver->activePciHostdevs.
+         */
+        if (!pciDeviceIsAssignable(dev, !driver->relaxedACS) ||
+            pciDeviceListFind(driver->activePciHostdevs, dev))
+            goto cleanup;
+    }
 
+    for (i = 0; i < pciDeviceListCount(pcidevs); i++) {
+        pciDevice *dev = pciDeviceListGet(pcidevs, i);
         if (pciDeviceGetManaged(dev) &&
             pciDettachDevice(dev, driver->activePciHostdevs) < 0)
             goto reattachdevs;
@@ -150,6 +158,18 @@ int qemuPrepareHostdevPCIDevices(struct qemud_driver *driver,
         }
     }
 
+    /* Now set the used_by_domain of the device in driver->activePciHostdevs
+     * as domain name.
+     */
+    for (i = 0; i < pciDeviceListCount(pcidevs); i++) {
+        pciDevice *dev, *activeDev;
+
+        dev = pciDeviceListGet(pcidevs, i);
+        activeDev = pciDeviceListFind(driver->activePciHostdevs, dev);
+
+        pciDeviceSetUsedBy(activeDev, name);
+    }
+
     /* Now steal all the devices from pcidevs */
     while (pciDeviceListCount(pcidevs) > 0) {
         pciDevice *dev = pciDeviceListGet(pcidevs, 0);
@@ -183,7 +203,7 @@ static int
 qemuPrepareHostPCIDevices(struct qemud_driver *driver,
                           virDomainDefPtr def)
 {
-    return qemuPrepareHostdevPCIDevices(driver, def->hostdevs, def->nhostdevs);
+    return qemuPrepareHostdevPCIDevices(driver, def->name, def->hostdevs, def->nhostdevs);
 }
 
 
@@ -258,6 +278,7 @@ void qemuReattachPciDevice(pciDevice *dev, struct qemud_driver *driver)
 
 
 void qemuDomainReAttachHostdevDevices(struct qemud_driver *driver,
+                                      const char *name,
                                       virDomainHostdevDefPtr *hostdevs,
                                       int nhostdevs)
 {
@@ -277,6 +298,18 @@ void qemuDomainReAttachHostdevDevices(struct qemud_driver *driver,
 
     for (i = 0; i < pciDeviceListCount(pcidevs); i++) {
         pciDevice *dev = pciDeviceListGet(pcidevs, i);
+        pciDevice *activeDev = NULL;
+        const char *used_by = NULL;
+
+        /* Never delete the dev from list driver->activePciHostdevs
+         *  if it's used by other domain.
+         */
+        activeDev = pciDeviceListFind(driver->activePciHostdevs, dev);
+        if (activeDev &&
+            (used_by = pciDeviceGetUsedBy(activeDev)) &&
+            STRNEQ(name, used_by))
+            continue;
+
         pciDeviceListDel(driver->activePciHostdevs, dev);
     }
 
@@ -305,5 +338,5 @@ void qemuDomainReAttachHostDevices(struct qemud_driver *driver,
     if (!def->nhostdevs)
         return;
 
-    qemuDomainReAttachHostdevDevices(driver, def->hostdevs, def->nhostdevs);
+    qemuDomainReAttachHostdevDevices(driver, def->name, def->hostdevs, def->nhostdevs);
 }
diff --git a/src/qemu/qemu_hostdev.h b/src/qemu/qemu_hostdev.h
index 1f3d1bc..07d7de2 100644
--- a/src/qemu/qemu_hostdev.h
+++ b/src/qemu/qemu_hostdev.h
@@ -30,12 +30,14 @@
 int qemuUpdateActivePciHostdevs(struct qemud_driver *driver,
                                 virDomainDefPtr def);
 int qemuPrepareHostdevPCIDevices(struct qemud_driver *driver,
+                                 const char *name,
                                  virDomainHostdevDefPtr *hostdevs,
                                  int nhostdevs);
 int qemuPrepareHostDevices(struct qemud_driver *driver,
                            virDomainDefPtr def);
 void qemuReattachPciDevice(pciDevice *dev, struct qemud_driver *driver);
 void qemuDomainReAttachHostdevDevices(struct qemud_driver *driver,
+                                      const char *name,
                                       virDomainHostdevDefPtr *hostdevs,
                                       int nhostdevs);
 void qemuDomainReAttachHostDevices(struct qemud_driver *driver,
diff --git a/src/qemu/qemu_hotplug.c b/src/qemu/qemu_hotplug.c
index 4c1705d..bfa524b 100644
--- a/src/qemu/qemu_hotplug.c
+++ b/src/qemu/qemu_hotplug.c
@@ -893,7 +893,7 @@ int qemuDomainAttachHostPciDevice(struct qemud_driver *driver,
         return -1;
     }
 
-    if (qemuPrepareHostdevPCIDevices(driver, &hostdev, 1) < 0)
+    if (qemuPrepareHostdevPCIDevices(driver, vm->def->name, &hostdev, 1) < 0)
         return -1;
 
     if (qemuCapsGet(priv->qemuCaps, QEMU_CAPS_DEVICE)) {
@@ -959,7 +959,7 @@ error:
                                         hostdev->info.addr.pci.slot) < 0)
         VIR_WARN("Unable to release PCI address on host device");
 
-    qemuDomainReAttachHostdevDevices(driver, &hostdev, 1);
+    qemuDomainReAttachHostdevDevices(driver, vm->def->name, &hostdev, 1);
 
     VIR_FREE(devstr);
     VIR_FREE(configfd_name);
diff --git a/src/util/pci.c b/src/util/pci.c
index 8d8e157..888784a 100644
--- a/src/util/pci.c
+++ b/src/util/pci.c
@@ -62,6 +62,7 @@ struct _pciDevice {
     char          name[PCI_ADDR_LEN]; /* domain:bus:slot.function */
     char          id[PCI_ID_LEN];     /* product vendor */
     char          *path;
+    const char    *used_by;           /* The domain which uses the device */
     int           fd;
 
     unsigned      initted;
@@ -1312,6 +1313,7 @@ pciGetDevice(unsigned domain,
     dev->bus      = bus;
     dev->slot     = slot;
     dev->function = function;
+    dev->used_by  = NULL;
 
     if (snprintf(dev->name, sizeof(dev->name), "%.4x:%.2x:%.2x.%.1x",
                  dev->domain, dev->bus, dev->slot,
@@ -1374,6 +1376,7 @@ pciFreeDevice(pciDevice *dev)
     VIR_DEBUG("%s %s: freeing", dev->id, dev->name);
     pciCloseConfig(dev);
     VIR_FREE(dev->path);
+    dev->used_by = NULL;
     VIR_FREE(dev);
 }
 
@@ -1387,6 +1390,18 @@ unsigned pciDeviceGetManaged(pciDevice *dev)
     return dev->managed;
 }
 
+void
+pciDeviceSetUsedBy(pciDevice *dev, const char *name)
+{
+    dev->used_by = name;
+}
+
+const char *
+pciDeviceGetUsedBy(pciDevice *dev)
+{
+    return dev->used_by;
+}
+
 void pciDeviceReAttachInit(pciDevice *pci)
 {
     pci->unbind_from_stub = 1;
diff --git a/src/util/pci.h b/src/util/pci.h
index a1600fe..640c6af 100644
--- a/src/util/pci.h
+++ b/src/util/pci.h
@@ -47,6 +47,9 @@ int        pciResetDevice    (pciDevice     *dev,
 void      pciDeviceSetManaged(pciDevice     *dev,
                               unsigned       managed);
 unsigned  pciDeviceGetManaged(pciDevice     *dev);
+void      pciDeviceSetUsedBy(pciDevice     *dev,
+                             const char *used_by);
+const char *pciDeviceGetUsedBy(pciDevice   *dev);
 void      pciDeviceReAttachInit(pciDevice   *dev);
 
 pciDeviceList *pciDeviceListNew  (void);
-- 
1.7.6


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