It's not necessarily safe to access interfaces when device is not in D0

The Scan, Suspend and Balloon threads should not try to access interfaces
such as STORE when the device is not in D0 as the interfaces are not there
if the system is at S4 or higher.

Signed-off-by: Paul Durrant <paul.durrant@citrix.com>

diff --git a/src/xenbus/fdo.c b/src/xenbus/fdo.c
index 694e6c2e8abd760c6fa9f703e2d7db0f44fffa98..f4a599160a85dc2624722db24f532892f080e859 100644 (file)
--- a/src/xenbus/fdo.c
+++ b/src/xenbus/fdo.c
@@ -877,7 +877,7 @@ FdoScan(
     HANDLE              ParametersKey;
     NTSTATUS            status;
 
-    Trace("====>\n");
+    Info("====>\n");
 
     Event = ThreadGetEvent(Self);
 
@@ -906,10 +906,13 @@ FdoScan(
         if (ThreadIsAlerted(Self))
             break;
 
-        STORE(Acquire, &Fdo->StoreInterface);
+        // It is not safe to use interfaces before this point
+        if (__FdoGetDevicePnpState(Fdo) != Started) {
+            KeSetEvent(&Fdo->ScanEvent, IO_NO_INCREMENT, FALSE);
+            continue;
+        }
 
-        if (__FdoGetDevicePnpState(Fdo) != Started)
-            goto loop;
+        STORE(Acquire, &Fdo->StoreInterface);
 
         status = STORE(Directory,
                        &Fdo->StoreInterface,
@@ -1003,7 +1006,7 @@ loop:
 
     KeSetEvent(&Fdo->ScanEvent, IO_NO_INCREMENT, FALSE);
 
-    Trace("<====\n");
+    Info("<====\n");
     return STATUS_SUCCESS;
 }
 
@@ -1049,7 +1052,7 @@ FdoSuspend(
     PXENBUS_FDO         Fdo = Context;
     PKEVENT             Event;
 
-    Trace("====>\n");
+    Info("====>\n");
 
     // We really want to know what CPU this thread will run on
     KeSetSystemAffinityThread((KAFFINITY)1);
@@ -1075,10 +1078,13 @@ FdoSuspend(
         if (ThreadIsAlerted(Self))
             break;
 
-        STORE(Acquire, &Fdo->StoreInterface);
+        // It is not safe to use interfaces before this point
+        if (__FdoGetDevicePowerState(Fdo) != PowerDeviceD0) {
+            KeSetEvent(&Fdo->SuspendEvent, IO_NO_INCREMENT, FALSE);
+            continue;
+        }
 
-        if (__FdoGetDevicePowerState(Fdo) != PowerDeviceD0)
-            goto loop;
+        STORE(Acquire, &Fdo->StoreInterface);
 
         status = STORE(Read,
                        &Fdo->StoreInterface,
@@ -1123,7 +1129,7 @@ loop:
 
     KeSetEvent(&Fdo->SuspendEvent, IO_NO_INCREMENT, FALSE);
 
-    Trace("<====\n");
+    Info("<====\n");
     return STATUS_SUCCESS;
 }
 
@@ -1189,59 +1195,23 @@ FdoBalloon(
     PXENBUS_FDO         Fdo = Context;
     PKEVENT             Event;
     LARGE_INTEGER       Timeout;
-    PCHAR               Buffer;
-    ULONGLONG           VideoRAM;
     ULONGLONG           StaticMax;
+    BOOLEAN             Initialized;
     BOOLEAN             Active;
     NTSTATUS            status;
 
-    Trace("====>\n");
+    Info("====>\n");
 
     Event = ThreadGetEvent(Self);
 
     Timeout.QuadPart = TIME_RELATIVE(TIME_S(1));
 
-    STORE(Acquire, &Fdo->StoreInterface);
-
-    status = STORE(Read,
-                   &Fdo->StoreInterface,
-                   NULL,
-                   "memory",
-                   "static-max",
-                   &Buffer);
-    if (!NT_SUCCESS(status))
-        goto fail1;
-
-    StaticMax = _strtoui64(Buffer, NULL, 10);
-
-    STORE(Free,
-          &Fdo->StoreInterface,
-          Buffer);
-
-    status = STORE(Read,
-                   &Fdo->StoreInterface,
-                   NULL,
-                   "memory",
-                   "videoram",
-                   &Buffer);
-    if (NT_SUCCESS(status)) {
-        VideoRAM = _strtoui64(Buffer, NULL, 10);
-
-        STORE(Free,
-              &Fdo->StoreInterface,
-              Buffer);
-    } else {
-        VideoRAM = 0;
-    }
-
-    StaticMax -= VideoRAM;
-    StaticMax /= 4;   // We need the value in pages
-
-    STORE(Release, &Fdo->StoreInterface);
-
+    StaticMax = 0;
+    Initialized = FALSE;
     Active = FALSE;
 
     for (;;) {
+        PCHAR       Buffer;
         ULONGLONG   Target;
         ULONGLONG   Size;
         BOOLEAN     AllowInflation;
@@ -1263,10 +1233,69 @@ FdoBalloon(
         if (ThreadIsAlerted(Self))
             break;
 
+        // It is not safe to use interfaces before this point
+        if (__FdoGetDevicePowerState(Fdo) != PowerDeviceD0) {
+            if (Active) {
+                Active = FALSE;
+
+                __FdoBalloonClearActive(Fdo);
+            }
+
+            KeSetEvent(&Fdo->BalloonEvent, IO_NO_INCREMENT, FALSE);
+            continue;
+        }
+
         STORE(Acquire, &Fdo->StoreInterface);
 
-        if (__FdoGetDevicePowerState(Fdo) != PowerDeviceD0)
-            goto loop;
+        if (!Initialized) {
+            ULONGLONG   VideoRAM;
+
+            ASSERT(!Active);
+
+            status = STORE(Read,
+                           &Fdo->StoreInterface,
+                           NULL,
+                           "memory",
+                           "static-max",
+                           &Buffer);
+            if (!NT_SUCCESS(status))
+                goto loop;
+
+            StaticMax = _strtoui64(Buffer, NULL, 10);
+
+            STORE(Free,
+                  &Fdo->StoreInterface,
+                  Buffer);
+
+            if (StaticMax == 0)
+                goto loop;
+
+            status = STORE(Read,
+                           &Fdo->StoreInterface,
+                           NULL,
+                           "memory",
+                           "videoram",
+                           &Buffer);
+            if (NT_SUCCESS(status)) {
+                VideoRAM = _strtoui64(Buffer, NULL, 10);
+
+                STORE(Free,
+                      &Fdo->StoreInterface,
+                      Buffer);
+            } else {
+                VideoRAM = 0;
+            }
+
+            if (StaticMax < VideoRAM)
+                goto loop;
+
+            StaticMax -= VideoRAM;
+            StaticMax /= 4;   // We need the value in pages
+
+            Initialized = TRUE;
+        }
+
+        ASSERT(Initialized);
 
         status = STORE(Read,
                        &Fdo->StoreInterface,
@@ -1362,13 +1391,8 @@ loop:
 
     KeSetEvent(&Fdo->BalloonEvent, IO_NO_INCREMENT, FALSE);
 
-    Trace("<====\n");
+    Info("<====\n");
     return STATUS_SUCCESS;
-
-fail1:
-    Error("fail1 (%08x)\n", status);
-
-    return status;
 }
 
 static DECLSPEC_NOINLINE VOID