Drivers: hv: vmbus: don't loose HVMSG_TIMER_EXPIRED messages

We must handle HVMSG_TIMER_EXPIRED messages in the interrupt context
and we offload all the rest to vmbus_on_msg_dpc() tasklet. This functions
loops to see if there are new messages pending. In case we'll ever see
HVMSG_TIMER_EXPIRED message there we're going to lose it as we can't
handle it from there. Avoid looping in vmbus_on_msg_dpc(), we're OK
with handling one message per interrupt.

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Reviewed-by: Radim Kr.má<rkrcmar@redhat.com>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 33 insertions, 35 deletions

diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c
index 063e5f53ca78..30ea8ad902e2 100644
--- a/drivers/hv/vmbus_drv.c
+++ b/drivers/hv/vmbus_drv.c
@@ -740,51 +740,49 @@ static void vmbus_on_msg_dpc(unsigned long data)
         struct vmbus_channel_message_table_entry *entry;
         struct onmessage_work_context *ctx;
 
-        while (1) {
-                if (msg->header.message_type == HVMSG_NONE)
-                        /* no msg */
-                        break;
+        if (msg->header.message_type == HVMSG_NONE)
+                /* no msg */
+                return;
 
-                hdr = (struct vmbus_channel_message_header *)msg->u.payload;
+        hdr = (struct vmbus_channel_message_header *)msg->u.payload;
 
-                if (hdr->msgtype >= CHANNELMSG_COUNT) {
-                        WARN_ONCE(1, "unknown msgtype=%d\n", hdr->msgtype);
-                        goto msg_handled;
-                }
+        if (hdr->msgtype >= CHANNELMSG_COUNT) {
+                WARN_ONCE(1, "unknown msgtype=%d\n", hdr->msgtype);
+                goto msg_handled;
+        }
 
-                entry = &channel_message_table[hdr->msgtype];
-                if (entry->handler_type == VMHT_BLOCKING) {
-                        ctx = kmalloc(sizeof(*ctx), GFP_ATOMIC);
-                        if (ctx == NULL)
-                                continue;
+        entry = &channel_message_table[hdr->msgtype];
+        if (entry->handler_type == VMHT_BLOCKING) {
+                ctx = kmalloc(sizeof(*ctx), GFP_ATOMIC);
+                if (ctx == NULL)
+                        return;
 
-                        INIT_WORK(&ctx->work, vmbus_onmessage_work);
-                        memcpy(&ctx->msg, msg, sizeof(*msg));
+                INIT_WORK(&ctx->work, vmbus_onmessage_work);
+                memcpy(&ctx->msg, msg, sizeof(*msg));
 
-                        queue_work(vmbus_connection.work_queue, &ctx->work);
-                } else
-                        entry->message_handler(hdr);
+                queue_work(vmbus_connection.work_queue, &ctx->work);
+        } else
+                entry->message_handler(hdr);
 
 msg_handled:
-                msg->header.message_type = HVMSG_NONE;
+        msg->header.message_type = HVMSG_NONE;
+
+        /*
+         * Make sure the write to MessageType (ie set to
+         * HVMSG_NONE) happens before we read the
+         * MessagePending and EOMing. Otherwise, the EOMing
+         * will not deliver any more messages since there is
+         * no empty slot
+         */
+        mb();
 
+        if (msg->header.message_flags.msg_pending) {
                 /*
-                 * Make sure the write to MessageType (ie set to
-                 * HVMSG_NONE) happens before we read the
-                 * MessagePending and EOMing. Otherwise, the EOMing
-                 * will not deliver any more messages since there is
-                 * no empty slot
+                 * This will cause message queue rescan to
+                 * possibly deliver another msg from the
+                 * hypervisor
                  */
-                mb();
-
-                if (msg->header.message_flags.msg_pending) {
-                        /*
-                         * This will cause message queue rescan to
-                         * possibly deliver another msg from the
-                         * hypervisor
-                         */
-                        wrmsrl(HV_X64_MSR_EOM, 0);
-                }
+                wrmsrl(HV_X64_MSR_EOM, 0);
         }
 }