[PATCH] Skip uninitialized CPUs

[Owen Smith <owen.smith@xxxxxxxxx>]

From: Owen Smith <owen.smith@xxxxxxxxxx>

EvtchnFifoAcquire will loop through all CPUs to call EVTCHNOP_init_control.
Skip any CPUs that are not initialized, which is indicated by
SystemProcessorVcpuId failing, instead of failing the Acquire operation.

This is primarily an issue when KeQueryMaximumProcessorCountEx returns
a different value to KeQueryActiveProcessorCountEx, or the system
processor callback has not been called with KeProcessorAddCompleteNotify
for that CPU.

Signed-off-by: Owen Smith <owen.smith@xxxxxxxxxx>
---
 src/xenbus/evtchn_fifo.c | 19 +++++++++----------
 1 file changed, 9 insertions(+), 10 deletions(-)

diff --git a/src/xenbus/evtchn_fifo.c b/src/xenbus/evtchn_fifo.c
index a8dab8c..7a74af7 100644
--- a/src/xenbus/evtchn_fifo.c
+++ b/src/xenbus/evtchn_fifo.c
@@ -501,20 +501,21 @@ EvtchnFifoAcquire(
 
     ProcessorCount = KeQueryMaximumProcessorCountEx(ALL_PROCESSOR_GROUPS);
 
-    Index = 0;
-    while (Index < ProcessorCount) {
+    for (Index = 0; Index < ProcessorCount; ++Index) {
         unsigned int        vcpu_id;
         PFN_NUMBER          Pfn;
         PHYSICAL_ADDRESS    Address;
 
+        status = SystemProcessorVcpuId(Index, &vcpu_id);
+        if (status == STATUS_NOT_SUPPORTED)
+            continue;
+        if (!NT_SUCCESS(status))
+            goto fail1;
+
         Mdl = __AllocatePage();
 
         status = STATUS_NO_MEMORY;
         if (Mdl == NULL)
-            goto fail1;
-
-        status = SystemProcessorVcpuId(Index, &vcpu_id);
-        if (!NT_SUCCESS(status))
             goto fail2;
 
         Pfn = MmGetMdlPfnArray(Mdl)[0];
@@ -532,8 +533,6 @@ EvtchnFifoAcquire(
                   Address.LowPart);
 
         Context->ControlBlockMdl[vcpu_id] = Mdl;
-
-        Index++;
     }
 
     Trace("<====\n");
@@ -546,11 +545,11 @@ done:
 fail3:
     Error("fail3\n");
 
+    __FreePage(Mdl);
+
 fail2:
     Error("fail2\n");
 
-    __FreePage(Mdl);
-
 fail1:
     Error("fail1 (%08x)\n", status);
 
-- 
2.39.0.windows.1