[PATCH 3/3] Avoid unnecessary check for non-NULL Processor->Interrupt in EvtchnRelease()

[Paul Durrant <paul@xxxxxxx>]

From: Paul Durrant <pdurrant@xxxxxxxxxx>

If EvtchnIsProcessorEnabled() is TRUE then Processor->Interrupt should be
valid. Hence use an ASSERTion instead. Also replicate the check of
EvtchnIsProcessorEnabled() in the error path in EvtchnAcquire().
While we're at it, let's also use EvtchnIsProcessorEnabled() in
EvtchnInterruptEnable() and EvtchnInterruptDisable().

Signed-off-by: Paul Durrant <pdurrant@xxxxxxxxxx>
---
 src/xenbus/evtchn.c | 64 +++++++++++++++++++++++----------------------
 1 file changed, 33 insertions(+), 31 deletions(-)

diff --git a/src/xenbus/evtchn.c b/src/xenbus/evtchn.c
index 9f7026db8dde..123f4a3a75e5 100644
--- a/src/xenbus/evtchn.c
+++ b/src/xenbus/evtchn.c
@@ -1271,6 +1271,22 @@ EvtchnAbiRelease(
     RtlZeroMemory(&Context->EvtchnAbi, sizeof (XENBUS_EVTCHN_ABI));
 }
 
+static BOOLEAN
+EvtchnIsProcessorEnabled(
+    IN  PXENBUS_EVTCHN_CONTEXT      Context,
+    IN  ULONG                       Cpu
+    )
+{
+    if (!XENBUS_SHARED_INFO(UpcallSupported,
+                            &Context->SharedInfoInterface,
+                            Cpu))
+        return FALSE;
+
+    return XENBUS_EVTCHN_ABI(IsProcessorEnabled,
+                             &Context->EvtchnAbi,
+                             Cpu);
+}
+
 static VOID
 EvtchnInterruptEnable(
     IN  PXENBUS_EVTCHN_CONTEXT  Context
@@ -1297,15 +1313,15 @@ EvtchnInterruptEnable(
 
         Processor = &Context->Processor[Cpu];
 
-        if (Processor->Interrupt == NULL)
-            continue;
-
-        status = SystemProcessorVcpuId(Cpu, &vcpu_id);
-        if (!NT_SUCCESS(status))
+        if (!EvtchnIsProcessorEnabled(Context, Cpu))
             continue;
 
+        ASSERT(Processor->Interrupt != NULL);
         Vector = FdoGetInterruptVector(Context->Fdo, Processor->Interrupt);
 
+        status = SystemProcessorVcpuId(Cpu, &vcpu_id);
+        ASSERT(NT_SUCCESS(status));
+
         status = HvmSetEvtchnUpcallVector(vcpu_id, Vector);
         if (!NT_SUCCESS(status)) {
             if (status != STATUS_NOT_IMPLEMENTED )
@@ -1368,9 +1384,10 @@ EvtchnInterruptDisable(
         if (!Processor->UpcallEnabled)
             continue;
 
+        ASSERT(EvtchnIsProcessorEnabled(Context, Cpu));
+
         status = SystemProcessorVcpuId(Cpu, &vcpu_id);
-        if (!NT_SUCCESS(status))
-            continue;
+        ASSERT(NT_SUCCESS(status));
 
         (VOID) HvmSetEvtchnUpcallVector(vcpu_id, 0);
         Processor->UpcallEnabled = FALSE;
@@ -1517,22 +1534,6 @@ EvtchnDebugCallback(
     }
 }
 
-static BOOLEAN
-EvtchnIsProcessorEnabled(
-    IN  PXENBUS_EVTCHN_CONTEXT      Context,
-    IN  ULONG                       Cpu
-    )
-{
-    if (!XENBUS_SHARED_INFO(UpcallSupported,
-                            &Context->SharedInfoInterface,
-                            Cpu))
-        return FALSE;
-
-    return XENBUS_EVTCHN_ABI(IsProcessorEnabled,
-                             &Context->EvtchnAbi,
-                             Cpu);
-}
-
 static NTSTATUS
 EvtchnAcquire(
     IN  PINTERFACE          Interface
@@ -1657,16 +1658,18 @@ fail9:
     for (Cpu = 0; Cpu < Context->ProcessorCount; Cpu++) {
         PXENBUS_EVTCHN_PROCESSOR Processor;
 
+        if (!EvtchnIsProcessorEnabled(Context, Cpu))
+            continue;
+
         ASSERT(Context->Processor != NULL);
         Processor = &Context->Processor[Cpu];
 
         RtlZeroMemory(&Processor->Dpc, sizeof (KDPC));
         RtlZeroMemory(&Processor->PendingList, sizeof (LIST_ENTRY));
 
-        if (Processor->Interrupt != NULL) {
-            FdoFreeInterrupt(Fdo, Processor->Interrupt);
-            Processor->Interrupt = NULL;
-        }
+        ASSERT(Processor->Interrupt != NULL);
+        FdoFreeInterrupt(Fdo, Processor->Interrupt);
+        Processor->Interrupt = NULL;
 
         Processor->Cpu = 0;
         Processor->Context = NULL;
@@ -1765,10 +1768,9 @@ EvtchnRelease(
         RtlZeroMemory(&Processor->Dpc, sizeof (KDPC));
         RtlZeroMemory(&Processor->PendingList, sizeof (LIST_ENTRY));
 
-        if (Processor->Interrupt != NULL) {
-            FdoFreeInterrupt(Fdo, Processor->Interrupt);
-            Processor->Interrupt = NULL;
-        }
+        ASSERT(Processor->Interrupt != NULL);
+        FdoFreeInterrupt(Fdo, Processor->Interrupt);
+        Processor->Interrupt = NULL;
 
         Processor->Cpu = 0;
         Processor->Context = NULL;
-- 
2.25.1