[win-pv-devel] [PATCH 1/2] Avoid holding a reference to the UNLPLUG interface

[Paul Durrant <pdurrant@xxxxxxxxx>]

If the system goes into S3 or S4 then currently the reference will still be
held. This is not problematic for this interface but it is not desirable to
hold references in this circumstance and for other interfaces it can lead
to bugchecks.

This patch adds a function, PdoRequestUnplug(), which only acquires the
interface as needed and then makes use of that.

Signed-off-by: Paul Durrant <paul.durrant@xxxxxxxxxx>
---
 src/xenvif/pdo.c | 90 ++++++++++++++++++++++++++++----------------------------
 1 file changed, 45 insertions(+), 45 deletions(-)

diff --git a/src/xenvif/pdo.c b/src/xenvif/pdo.c
index 77fee31..53bed7a 100644
--- a/src/xenvif/pdo.c
+++ b/src/xenvif/pdo.c
@@ -1008,11 +1008,6 @@ PdoD3ToD0(
 
     KeLowerIrql(Irql);
 
-    XENBUS_UNPLUG(Request,
-                  &Pdo->UnplugInterface,
-                  XENBUS_UNPLUG_DEVICE_TYPE_NICS,
-                  TRUE);
-
     return STATUS_SUCCESS;
 
 fail3:
@@ -1043,11 +1038,6 @@ PdoD0ToD3(
 
     ASSERT3U(KeGetCurrentIrql(), ==, PASSIVE_LEVEL);
 
-    XENBUS_UNPLUG(Request,
-                  &Pdo->UnplugInterface,
-                  XENBUS_UNPLUG_DEVICE_TYPE_NICS,
-                  FALSE);
-
     KeRaiseIrql(DISPATCH_LEVEL, &Irql);
 
     XENBUS_SUSPEND(Deregister,
@@ -1144,6 +1134,26 @@ fail1:
     return status;
 }
 
+static VOID
+PdoUnplugRequest(
+    IN  PXENVIF_PDO Pdo,
+    IN  BOOLEAN     Make
+    )
+{
+    NTSTATUS        status;
+
+    status = XENBUS_UNPLUG(Acquire, &Pdo->UnplugInterface);
+    if (!NT_SUCCESS(status))
+        return;
+
+    XENBUS_UNPLUG(Request,
+                  &Pdo->UnplugInterface,
+                  XENBUS_UNPLUG_DEVICE_TYPE_NICS,
+                  Make);
+
+    XENBUS_UNPLUG(Release, &Pdo->UnplugInterface);
+}
+
 static DECLSPEC_NOINLINE NTSTATUS
 PdoStartDevice(
     IN  PXENVIF_PDO     Pdo,
@@ -1165,21 +1175,19 @@ PdoStartDevice(
     if (DriverIsRebootRequested())
         goto fail1;
 
-    status = XENBUS_UNPLUG(Acquire, &Pdo->UnplugInterface);
-    if (!NT_SUCCESS(status))
-        goto fail2;
+    PdoUnplugRequest(Pdo, TRUE);
 
     status = RegistryOpenSoftwareKey(__PdoGetDeviceObject(Pdo),
                                      KEY_ALL_ACCESS,
                                      &SoftwareKey);
     if (!NT_SUCCESS(status))
-        goto fail3;
+        goto fail2;
 
     status = RegistryOpenHardwareKey(__PdoGetDeviceObject(Pdo),
                                      KEY_ALL_ACCESS,
                                      &HardwareKey);
     if (!NT_SUCCESS(status))
-        goto fail4;
+        goto fail3;
 
     (VOID) PdoSetFriendlyName(Pdo,
                               SoftwareKey,
@@ -1187,23 +1195,23 @@ PdoStartDevice(
 
     status = __PdoSetCurrentAddress(Pdo, SoftwareKey);
     if (!NT_SUCCESS(status))
-        goto fail5;
+        goto fail4;
 
     status = LinkGetRoutineAddress("netio.sys",
                                    "GetIfTable2",
                                    (PVOID *)&__GetIfTable2);
     if (!NT_SUCCESS(status))
-        goto fail6;
+        goto fail5;
 
     status = LinkGetRoutineAddress("netio.sys",
                                    "FreeMibTable",
                                    (PVOID *)&__FreeMibTable);
     if (!NT_SUCCESS(status))
-        goto fail7;
+        goto fail6;
 
     status = __GetIfTable2(&Table);
     if (!NT_SUCCESS(status))
-        goto fail8;
+        goto fail7;
 
     //
     // Look for a network interface with the same permanent address
@@ -1229,7 +1237,7 @@ PdoStartDevice(
             continue;
 
         status = STATUS_UNSUCCESSFUL;
-        goto fail9;
+        goto fail8;
     }
 
     //
@@ -1257,7 +1265,7 @@ PdoStartDevice(
 
     status = PdoD3ToD0(Pdo);
     if (!NT_SUCCESS(status))
-        goto fail10;
+        goto fail9;
 
     __PdoSetDevicePnpState(Pdo, Started);
 
@@ -1270,15 +1278,15 @@ PdoStartDevice(
 
     return STATUS_SUCCESS;
 
-fail10:
-    Error("fail10\n");
+fail9:
+    Error("fail9\n");
 
     __FreeMibTable(Table);
 
-    goto fail7;
+    goto fail6;
 
-fail9:
-    Error("fail9\n");
+fail8:
+    Error("fail8\n");
 
     (VOID) SettingsSave(SoftwareKey,
                         Row->Alias,
@@ -1286,39 +1294,29 @@ fail9:
                         &Row->InterfaceGuid,
                         &Row->InterfaceLuid);
 
-    XENBUS_UNPLUG(Request,
-                  &Pdo->UnplugInterface,
-                  XENBUS_UNPLUG_DEVICE_TYPE_NICS,
-                  TRUE);
-
     DriverRequestReboot();
     __FreeMibTable(Table);
 
-fail8:
-    Error("fail8\n");
-
 fail7:
     Error("fail7\n");
 
 fail6:
     Error("fail6\n");
 
-    RtlZeroMemory(&Pdo->CurrentAddress, sizeof (ETHERNET_ADDRESS));
-
 fail5:
     Error("fail5\n");
 
-    RegistryCloseKey(HardwareKey);
+    RtlZeroMemory(&Pdo->CurrentAddress, sizeof (ETHERNET_ADDRESS));
 
 fail4:
     Error("fail4\n");
 
-    RegistryCloseKey(SoftwareKey);
+    RegistryCloseKey(HardwareKey);
 
 fail3:
     Error("fail3\n");
 
-    XENBUS_UNPLUG(Release, &Pdo->UnplugInterface);
+    RegistryCloseKey(SoftwareKey);
 
 fail2:
     Error("fail2\n");
@@ -1358,7 +1356,6 @@ PdoCancelStopDevice(
     NTSTATUS        status;
 
     __PdoRestoreDevicePnpState(Pdo, StopPending);
-
     status = STATUS_SUCCESS;
 
     Irp->IoStatus.Status = status;
@@ -1375,12 +1372,16 @@ PdoStopDevice(
 {
     NTSTATUS            status;
 
+    if (__PdoGetDevicePowerState(Pdo) != PowerDeviceD0)
+        goto done;
+
+    PdoUnplugRequest(Pdo, FALSE);
+
     PdoD0ToD3(Pdo);
 
+done:
     RtlZeroMemory(&Pdo->CurrentAddress, sizeof (ETHERNET_ADDRESS));
 
-    XENBUS_UNPLUG(Release, &Pdo->UnplugInterface);
-
     __PdoSetDevicePnpState(Pdo, Stopped);
     status = STATUS_SUCCESS;
 
@@ -1419,7 +1420,6 @@ PdoCancelRemoveDevice(
         FrontendEjectFailed(__PdoGetFrontend(Pdo));
 
     __PdoRestoreDevicePnpState(Pdo, RemovePending);
-
     status = STATUS_SUCCESS;
 
     Irp->IoStatus.Status = status;
@@ -1462,11 +1462,11 @@ PdoRemoveDevice(
 
     PdoD0ToD3(Pdo);
 
+    PdoUnplugRequest(Pdo, FALSE);
+
 done:
     RtlZeroMemory(&Pdo->CurrentAddress, sizeof (ETHERNET_ADDRESS));
 
-    XENBUS_UNPLUG(Release, &Pdo->UnplugInterface);
-
     NeedInvalidate = FALSE;
 
     FdoAcquireMutex(Fdo);
-- 
2.1.1


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