[win-pv-devel] [PATCH] EVTCHN FIFO ABI should keep per-vcpu queue head shadow

[Paul Durrant <pdurrant@xxxxxxxxx>]

There is currently only one shadow head per priority which means that
polling event channels of the same priority on different CPUs can conflict,
leading to lost events. This patch fixes the problem.

Signed-off-by: Paul Durrant <paul.durrant@xxxxxxxxxx>
---
 src/xenbus/evtchn_fifo.c | 18 +++++++++++++-----
 1 file changed, 13 insertions(+), 5 deletions(-)

diff --git a/src/xenbus/evtchn_fifo.c b/src/xenbus/evtchn_fifo.c
index ef72fdb..e3cff7a 100644
--- a/src/xenbus/evtchn_fifo.c
+++ b/src/xenbus/evtchn_fifo.c
@@ -49,7 +49,7 @@ typedef struct _XENBUS_EVTCHN_FIFO_CONTEXT {
     PMDL                            ControlBlockMdl[MAX_HVM_VCPUS];
     PMDL                            *EventPageMdl;
     ULONG                           EventPageCount;
-    ULONG                           Head[EVTCHN_FIFO_MAX_QUEUES];
+    ULONG                           
Head[MAX_HVM_VCPUS][EVTCHN_FIFO_MAX_QUEUES];
 } XENBUS_EVTCHN_FIFO_CONTEXT, *PXENBUS_EVTCHN_FIFO_CONTEXT;
 
 #define EVENT_WORDS_PER_PAGE    (PAGE_SIZE / sizeof (event_word_t))
@@ -282,7 +282,7 @@ EvtchnFifoContract(
 static BOOLEAN
 EvtchnFifoPollPriority(
     IN  PXENBUS_EVTCHN_FIFO_CONTEXT Context,
-    IN  evtchn_fifo_control_block_t *ControlBlock,
+    IN  unsigned int                vcpu_id,
     IN  ULONG                       Priority,
     IN  PULONG                      Ready,
     IN  XENBUS_EVTCHN_ABI_EVENT     Event,
@@ -294,9 +294,17 @@ EvtchnFifoPollPriority(
     event_word_t                    *EventWord;
     BOOLEAN                         DoneSomething;
 
-    Head = Context->Head[Priority];
+    Head = Context->Head[vcpu_id][Priority];
 
     if (Head == 0) {
+        PMDL                        Mdl;
+        evtchn_fifo_control_block_t *ControlBlock;
+
+        Mdl = Context->ControlBlockMdl[vcpu_id];
+
+        ControlBlock = MmGetSystemAddressForMdlSafe(Mdl, NormalPagePriority);
+        ASSERT(ControlBlock != NULL);
+
         KeMemoryBarrier();
         Head = ControlBlock->head[Priority];
     }
@@ -315,7 +323,7 @@ EvtchnFifoPollPriority(
         __EvtchnFifoTestFlag(EventWord, EVTCHN_FIFO_PENDING))
         DoneSomething = Event(Argument, Port);
 
-    Context->Head[Priority] = Head;
+    Context->Head[vcpu_id][Priority] = Head;
 
     return DoneSomething;
 }
@@ -346,7 +354,7 @@ EvtchnFifoPoll(
 
     while (_BitScanReverse(&Priority, Ready)) {
         DoneSomething |= EvtchnFifoPollPriority(Context,
-                                                ControlBlock,
+                                                vcpu_id,
                                                 Priority,
                                                 &Ready,
                                                 Event,
-- 
2.1.1


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