[PATCH] Invalidate FDOs when no devices are present

[Paul Durrant <paul@xxxxxxx>]

From: Tu Dinh <ngoc-tu.dinh@xxxxxxxxxx>

In cases where the entire xenstore device key is removed, FdoScan()
currently skips reenumeration entirely. This causes it to not pass the
removal event to xennet. Fix the issue by reenumerating devices even if
xenstore key does not exist.

Signed-off-by: Tu Dinh <ngoc-tu.dinh@xxxxxxxxxx>

Ported from XENVIF.

Signed-off-by: Paul Durrant <pdurrant@xxxxxxxxxx>
---
 src/xenvkbd/fdo.c | 86 ++++++++++++++++++++++++++---------------------
 1 file changed, 48 insertions(+), 38 deletions(-)

diff --git a/src/xenvkbd/fdo.c b/src/xenvkbd/fdo.c
index 7a87ead0801a..98297fc1a1a1 100644
--- a/src/xenvkbd/fdo.c
+++ b/src/xenvkbd/fdo.c
@@ -756,36 +756,38 @@ __FdoEnumerate(
             Name = PdoGetName(Pdo);
             Missing = TRUE;
 
-            // If the PDO already exists and its name is in the device list
-            // then we don't want to remove it.
-            for (Index = 0; Devices[Index].Buffer != NULL; Index++) {
-                PANSI_STRING Device = &Devices[Index];
-
-                if (Device->Length == 0)
-                    continue;
-
-                if (strcmp(Name, Device->Buffer) == 0) {
-                    Missing = FALSE;
-                    Device->Length = 0;  // avoid duplication
-                    break;
+            if (Devices != NULL) {
+                // If the PDO already exists and its name is in the device list
+                // then we don't want to remove it.
+                for (Index = 0; Devices[Index].Buffer != NULL; Index++) {
+                    PANSI_STRING Device = &Devices[Index];
+
+                    if (Device->Length == 0)
+                        continue;
+
+                    if (strcmp(Name, Device->Buffer) == 0) {
+                        Missing = FALSE;
+                        Device->Length = 0;  // avoid duplication
+                        break;
+                    }
                 }
-            }
 
-            if (!PdoIsMissing(Pdo)) {
-                if (PdoIsEjectRequested(Pdo)) {
-                    IoRequestDeviceEject(PdoGetDeviceObject(Pdo));
-                } else if (Missing) {
-                    PdoSetMissing(Pdo, "device disappeared");
-
-                    // If the PDO has not yet been enumerated then we can
-                    // go ahead and mark it as deleted, otherwise we need
-                    // to notify PnP manager and wait for the REMOVE_DEVICE
-                    // IRP.
-                    if (PdoGetDevicePnpState(Pdo) == Present) {
-                        PdoSetDevicePnpState(Pdo, Deleted);
-                        PdoDestroy(Pdo);
-                    } else {
-                        NeedInvalidate = TRUE;
+                if (!PdoIsMissing(Pdo)) {
+                    if (PdoIsEjectRequested(Pdo)) {
+                        IoRequestDeviceEject(PdoGetDeviceObject(Pdo));
+                    } else if (Missing) {
+                        PdoSetMissing(Pdo, "device disappeared");
+
+                        // If the PDO has not yet been enumerated then we can
+                        // go ahead and mark it as deleted, otherwise we need
+                        // to notify PnP manager and wait for the REMOVE_DEVICE
+                        // IRP.
+                        if (PdoGetDevicePnpState(Pdo) == Present) {
+                            PdoSetDevicePnpState(Pdo, Deleted);
+                            PdoDestroy(Pdo);
+                        } else {
+                            NeedInvalidate = TRUE;
+                        }
                     }
                 }
             }
@@ -795,15 +797,17 @@ __FdoEnumerate(
     }
 
     // Walk the class list and create PDOs for any new device
-    for (Index = 0; Devices[Index].Buffer != NULL; Index++) {
-        PANSI_STRING Device = &Devices[Index];
+    if (Devices != NULL) {
+        for (Index = 0; Devices[Index].Buffer != NULL; Index++) {
+            PANSI_STRING Device = &Devices[Index];
 
-        if (Device->Length == 0)
-            continue;
+            if (Device->Length == 0)
+                continue;
 
-        status = PdoCreate(Fdo, Device);
-        if (NT_SUCCESS(status))
-            NeedInvalidate = TRUE;
+            status = PdoCreate(Fdo, Device);
+            if (NT_SUCCESS(status))
+                NeedInvalidate = TRUE;
+        }
     }
 
     __FdoReleaseMutex(Fdo);
@@ -950,8 +954,12 @@ FdoScan(
             Devices = NULL;
         }
 
-        if (Devices == NULL)
-            goto loop;
+        if (Devices == NULL) {
+            if (status == STATUS_OBJECT_PATH_NOT_FOUND)
+                goto invalidate;
+            else
+                goto loop;
+        }
 
         if (ParametersKey != NULL) {
             status = RegistryQuerySzValue(ParametersKey,
@@ -991,9 +999,11 @@ FdoScan(
         if (UnsupportedDevices != NULL)
             RegistryFreeSzValue(UnsupportedDevices);
 
+invalidate:
         NeedInvalidate = __FdoEnumerate(Fdo, Devices);
 
-        __FdoFreeAnsi(Devices);
+        if (Devices != NULL)
+            __FdoFreeAnsi(Devices);
 
         if (NeedInvalidate) {
             NeedInvalidate = FALSE;
-- 
2.25.1