Drivers: hv: vmbus: Ignore the offers when resuming from hibernation

When the VM resumes, the host re-sends the offers. We should not add the
offers to the global vmbus_connection.chn_list again.

This patch assumes the RELIDs of the channels don't change across
hibernation. Actually this is not always true, especially in the case of
NIC SR-IOV the VF vmbus device's RELID sometimes can change. A later patch
will address this issue by mapping the new offers to the old channels and
fixing up the old channels, if necessary.

Signed-off-by: Dexuan Cui <decui@microsoft.com>
Reviewed-by: Michael Kelley <mikelley@microsoft.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/drivers/hv/channel_mgmt.c b/drivers/hv/channel_mgmt.c
index addcef5..44b92fa 100644 (file)
--- a/drivers/hv/channel_mgmt.c
+++ b/drivers/hv/channel_mgmt.c
@@ -848,18 +848,74 @@ void vmbus_initiate_unload(bool crash)
 }
 
 /*
+ * find_primary_channel_by_offer - Get the channel object given the new offer.
+ * This is only used in the resume path of hibernation.
+ */
+static struct vmbus_channel *
+find_primary_channel_by_offer(const struct vmbus_channel_offer_channel *offer)
+{
+       struct vmbus_channel *channel = NULL, *iter;
+       const guid_t *inst1, *inst2;
+
+       /* Ignore sub-channel offers. */
+       if (offer->offer.sub_channel_index != 0)
+               return NULL;
+
+       mutex_lock(&vmbus_connection.channel_mutex);
+
+       list_for_each_entry(iter, &vmbus_connection.chn_list, listentry) {
+               inst1 = &iter->offermsg.offer.if_instance;
+               inst2 = &offer->offer.if_instance;
+
+               if (guid_equal(inst1, inst2)) {
+                       channel = iter;
+                       break;
+               }
+       }
+
+       mutex_unlock(&vmbus_connection.channel_mutex);
+
+       return channel;
+}
+
+/*
  * vmbus_onoffer - Handler for channel offers from vmbus in parent partition.
  *
  */
 static void vmbus_onoffer(struct vmbus_channel_message_header *hdr)
 {
        struct vmbus_channel_offer_channel *offer;
-       struct vmbus_channel *newchannel;
+       struct vmbus_channel *oldchannel, *newchannel;
+       size_t offer_sz;
 
        offer = (struct vmbus_channel_offer_channel *)hdr;
 
        trace_vmbus_onoffer(offer);
 
+       oldchannel = find_primary_channel_by_offer(offer);
+
+       if (oldchannel != NULL) {
+               atomic_dec(&vmbus_connection.offer_in_progress);
+
+               /*
+                * We're resuming from hibernation: we expect the host to send
+                * exactly the same offers that we had before the hibernation.
+                */
+               offer_sz = sizeof(*offer);
+               if (memcmp(offer, &oldchannel->offermsg, offer_sz) == 0)
+                       return;
+
+               pr_debug("Mismatched offer from the host (relid=%d)\n",
+                        offer->child_relid);
+
+               print_hex_dump_debug("Old vmbus offer: ", DUMP_PREFIX_OFFSET,
+                                    16, 4, &oldchannel->offermsg, offer_sz,
+                                    false);
+               print_hex_dump_debug("New vmbus offer: ", DUMP_PREFIX_OFFSET,
+                                    16, 4, offer, offer_sz, false);
+               return;
+       }
+
        /* Allocate the channel object and save this offer. */
        newchannel = alloc_channel();
        if (!newchannel) {