[libvirt] [PATCH V3] xen: check if device is assigned to guest before reattaching

[Yufang Zhang]

Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=664059

This is the version3 patch for BZ#664059. Reattaching pci device back to
host without destroying guest or detaching device from guest would cause
host to crash. This patch adds a check before doing device reattach. If
the device is being assigned to guest, libvirt refuses to reattach device
to host. The patch only works for Xen, for it just checks xenstore to get
pci device information. This version fixes some formatting problem and moves
lock-unlock out of loop so that the check is atomic.

Signed-off-by: Yufang Zhang <yuzhang at redhat.com>
---
 src/xen/xen_driver.c |   67 ++++++++++++++++++++++++++++++++++++++++++++++++++
 1 files changed, 67 insertions(+), 0 deletions(-)

diff --git a/src/xen/xen_driver.c b/src/xen/xen_driver.c
index 2a07b7b..dd94fbc 100644
--- a/src/xen/xen_driver.c
+++ b/src/xen/xen_driver.c
@@ -1927,11 +1927,70 @@ out:
 }
 
 static int
+xenUnifiedNodeDeviceAssignedDomainId (virNodeDevicePtr dev)
+{
+    int numdomains;
+    int ret = -1, i;
+    int *ids = NULL;
+    char *bdf = NULL;
+    char *xref = NULL;
+    unsigned int domain, bus, slot, function;
+    virConnectPtr conn = dev->conn;
+    xenUnifiedPrivatePtr priv = conn->privateData;
+
+    /* Get active domains */
+    numdomains = xenUnifiedNumOfDomains(conn);
+    if (numdomains < 0) {
+        return ret;
+    }
+    if (numdomains > 0){
+        if (VIR_ALLOC_N(ids, numdomains) < 0) {
+            virReportOOMError();
+            goto out;
+        }
+        if ((numdomains = xenUnifiedListDomains(conn, &ids[0], numdomains)) < 0) {
+            goto out;
+        }
+    }
+
+    /* Get pci bdf */
+    if (xenUnifiedNodeDeviceGetPciInfo(dev, &domain, &bus, &slot, &function) < 0)
+        goto out;
+
+    if (virAsprintf(&bdf, "%04x:%02x:%02x.%0x",
+                    domain, bus, slot, function) < 0) {
+        virReportOOMError();
+        goto out;
+    }
+
+    xenUnifiedLock(priv);
+    /* Check if bdf is assigned to one of active domains */
+    for (i = 0; i < numdomains; i++ ) {
+        xref = xenStoreDomainGetPCIID(conn, ids[i], bdf);
+        if (xref == NULL) {
+            continue;
+        } else {
+            ret = ids[i];
+            break;
+        }
+    }
+    xenUnifiedUnlock(priv);
+
+    VIR_FREE(xref);
+    VIR_FREE(bdf);
+out:
+    VIR_FREE(ids);
+
+    return ret;
+}
+
+static int
 xenUnifiedNodeDeviceReAttach (virNodeDevicePtr dev)
 {
     pciDevice *pci;
     unsigned domain, bus, slot, function;
     int ret = -1;
+    int domid;
 
     if (xenUnifiedNodeDeviceGetPciInfo(dev, &domain, &bus, &slot, &function) < 0)
         return -1;
@@ -1940,6 +1999,14 @@ xenUnifiedNodeDeviceReAttach (virNodeDevicePtr dev)
     if (!pci)
         return -1;
 
+    /* Check if device is assigned to an active guest */
+    if ((domid = xenUnifiedNodeDeviceAssignedDomainId(dev)) >= 0) {
+        xenUnifiedError(VIR_ERR_INTERNAL_ERROR,
+                        _("Device %s has been assigned to guest %d"),
+                        dev->name, domid);
+        goto out;
+    }
+
     if (pciReAttachDevice(pci, NULL) < 0)
         goto out;
 
-- 
1.7.4