[libvirt] [PATCH 2/3] reattach pci device when pciBindDeviceToStub() failed

[Wen Congyang]

We should bind pci device to original driver when pciBindDeviceToStub() failed.
If the pci device is not bound to any driver before calling pciBindDeviceToStub(),
we should only unbind it from pci-stub. If it is bound to pci-stub, we should not
unbid it from pci-stub.

---
 src/util/pci.c |   90 +++++++++++++++++++++++++++++++++++++++++++++++++------
 1 files changed, 80 insertions(+), 10 deletions(-)

diff --git a/src/util/pci.c b/src/util/pci.c
index 8d2dbb0..e30f5cf 100644
--- a/src/util/pci.c
+++ b/src/util/pci.c
@@ -65,6 +65,11 @@ struct _pciDevice {
     unsigned      has_flr : 1;
     unsigned      has_pm_reset : 1;
     unsigned      managed : 1;
+
+    /* used by reattach function */
+    unsigned      unbind_from_stub : 1;
+    unsigned      remove_slot : 1;
+    unsigned      reprobe : 1;
 };
 
 struct _pciDeviceList {
@@ -834,11 +839,25 @@ recheck:
 }
 
 
+static int pciUnBindDeviceFromStub(pciDevice *dev, const char *driver);
 static int
 pciBindDeviceToStub(pciDevice *dev, const char *driver)
 {
     char drvdir[PATH_MAX];
     char path[PATH_MAX];
+    int reprobe = 0;
+    int ret = 0;
+
+    /* check whether the device is already bound to a driver */
+    pciDriverDir(drvdir, sizeof(drvdir), driver);
+    pciDeviceFile(path, sizeof(path), dev->name, "driver");
+    if (virFileExists(path)) {
+        if (virFileLinkPointsTo(path, drvdir)) {
+            /* The device is already bound to pci-stub */
+            return 0;
+        }
+        reprobe = 1;
+    }
 
     /* Add the PCI device ID to the stub's dynamic ID table;
      * this is needed to allow us to bind the device to the stub.
@@ -856,16 +875,31 @@ pciBindDeviceToStub(pciDevice *dev, const char *driver)
         return -1;
     }
 
+    /* check whether the device is bound to pci-stub when we write dev->id to
+     * new_id.
+     */
+    pciDriverDir(drvdir, sizeof(drvdir), driver);
+    pciDeviceFile(path, sizeof(path), dev->name, "driver");
+    if (virFileLinkPointsTo(path, drvdir)) {
+        dev->unbind_from_stub = 1;
+        dev->remove_slot = 1;
+        goto remove_id;
+    }
+
     /* If the device is already bound to a driver, unbind it.
      * Note, this will have rather unpleasant side effects if this
      * PCI device happens to be IDE controller for the disk hosting
      * your root filesystem.
      */
     pciDeviceFile(path, sizeof(path), dev->name, "driver/unbind");
-    if (virFileExists(path) && virFileWriteStr(path, dev->name, 0) < 0) {
-        virReportSystemError(errno,
-                             _("Failed to unbind PCI device '%s'"), dev->name);
-        return -1;
+    if (virFileExists(path)) {
+        if (virFileWriteStr(path, dev->name, 0) < 0) {
+            virReportSystemError(errno,
+                                 _("Failed to unbind PCI device '%s'"),
+                                 dev->name);
+            return -1;
+        }
+        dev->reprobe = reprobe;
     }
 
     /* If the device isn't already bound to pci-stub, try binding it now.
@@ -879,18 +913,23 @@ pciBindDeviceToStub(pciDevice *dev, const char *driver)
             virReportSystemError(errno,
                                  _("Failed to add slot for PCI device '%s' to %s"),
                                  dev->name, driver);
-            return -1;
+            ret = -1;
+            goto remove_id;
         }
+        dev->remove_slot = 1;
 
         pciDriverFile(path, sizeof(path), driver, "bind");
         if (virFileWriteStr(path, dev->name, 0) < 0) {
             virReportSystemError(errno,
                                  _("Failed to bind PCI device '%s' to %s"),
                                  dev->name, driver);
-            return -1;
+            ret = -1;
+            goto remove_id;
         }
+        dev->unbind_from_stub = 1;
     }
 
+remove_id:
     /* If 'remove_id' exists, remove the device id from pci-stub's dynamic
      * ID table so that 'drivers_probe' works below.
      */
@@ -899,10 +938,21 @@ pciBindDeviceToStub(pciDevice *dev, const char *driver)
         virReportSystemError(errno,
                              _("Failed to remove PCI ID '%s' from %s"),
                              dev->id, driver);
-        return -1;
+        ret = -1;
+
+        /* remove PCI ID from pci-stub failed, and we can not reprobe it */
+        if (dev->reprobe) {
+            VIR_WARN("Faile to remove PCI ID '%s' from %s, and the device can"
+                     "not be reprobed again.", dev->id, driver);
+        }
+        dev->reprobe = 0;
     }
 
-    return 0;
+    if (ret < 0) {
+        pciUnBindDeviceFromStub(dev, driver);
+    }
+
+    return ret;
 }
 
 int
@@ -930,6 +980,9 @@ pciUnBindDeviceFromStub(pciDevice *dev, const char *driver)
     char drvdir[PATH_MAX];
     char path[PATH_MAX];
 
+    if (!dev->unbind_from_stub)
+        goto remove_slot;
+
     /* If the device is bound to stub, unbind it.
      */
     pciDriverDir(drvdir, sizeof(drvdir), driver);
@@ -938,21 +991,36 @@ pciUnBindDeviceFromStub(pciDevice *dev, const char *driver)
         pciDriverFile(path, sizeof(path), driver, "unbind");
         if (virFileWriteStr(path, dev->name, 0) < 0) {
             virReportSystemError(errno,
-                                 _("Failed to bind PCI device '%s' to %s"),
+                                 _("Failed to unbind PCI device '%s' from %s"),
                                  dev->name, driver);
+            /* do not do it again */
+            dev->unbind_from_stub = 0;
+            dev->remove_slot = 0;
+            dev->reprobe = 0;
             return -1;
         }
     }
+    dev->unbind_from_stub = 0;
+
+remove_slot:
+    if (!dev->remove_slot)
+        goto reprobe;
 
     /* Xen's pciback.ko wants you to use remove_slot on the specific device */
     pciDriverFile(path, sizeof(path), driver, "remove_slot");
     if (virFileExists(path) && virFileWriteStr(path, dev->name, 0) < 0) {
         virReportSystemError(errno,
-                             _("Failed to remove slot for PCI device '%s' to %s"),
+                             _("Failed to remove slot for PCI device '%s' from %s"),
                              dev->name, driver);
+        dev->remove_slot = 0;
+        dev->reprobe = 0;
         return -1;
     }
+    dev->remove_slot = 0;
 
+reprobe:
+    if (!dev->reprobe)
+        return 0;
 
     /* Trigger a re-probe of the device is not in the stub's dynamic
      * ID table. If the stub is available, but 'remove_id' isn't
@@ -965,9 +1033,11 @@ pciUnBindDeviceFromStub(pciDevice *dev, const char *driver)
             virReportSystemError(errno,
                                  _("Failed to trigger a re-probe for PCI device '%s'"),
                                  dev->name);
+            dev->reprobe = 0;
             return -1;
         }
     }
+    dev->reprobe = 0;
 
     return 0;
 }
-- 
1.7.1