Drivers: hv: vmbus: Resume after fixing up old primary channels

When the host re-offers the primary channels upon resume, the host only
guarantees the Instance GUID  doesn't change, so vmbus_bus_suspend()
should invalidate channel->offermsg.child_relid and figure out the
number of primary channels that need to be fixed up upon resume.

Upon resume, vmbus_onoffer() finds the old channel structs, and maps
the new offers to the old channels, and fixes up the old structs,
and finally the resume callbacks of the VSC drivers will re-open
the channels.

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

1 files changed, 65 insertions, 20 deletions

diff --git a/drivers/hv/channel_mgmt.c b/drivers/hv/channel_mgmt.c
index 5518d031f62a..8eb167540b4f 100644
--- a/drivers/hv/channel_mgmt.c
+++ b/drivers/hv/channel_mgmt.c
@@ -407,7 +407,15 @@ void hv_process_channel_removal(struct vmbus_channel *channel)
 		cpumask_clear_cpu(channel->target_cpu,
 				  &primary_channel->alloced_cpus_in_node);
 
-	vmbus_release_relid(channel->offermsg.child_relid);
+	/*
+	 * Upon suspend, an in-use hv_sock channel is marked as "rescinded" and
+	 * the relid is invalidated; after hibernation, when the user-space app
+	 * destroys the channel, the relid is INVALID_RELID, and in this case
+	 * it's unnecessary and unsafe to release the old relid, since the same
+	 * relid can refer to a completely different channel now.
+	 */
+	if (channel->offermsg.child_relid != INVALID_RELID)
+		vmbus_release_relid(channel->offermsg.child_relid);
 
 	free_channel(channel);
 }
@@ -851,6 +859,36 @@ void vmbus_initiate_unload(bool crash)
 		vmbus_wait_for_unload();
 }
 
+static void check_ready_for_resume_event(void)
+{
+	/*
+	 * If all the old primary channels have been fixed up, then it's safe
+	 * to resume.
+	 */
+	if (atomic_dec_and_test(&vmbus_connection.nr_chan_fixup_on_resume))
+		complete(&vmbus_connection.ready_for_resume_event);
+}
+
+static void vmbus_setup_channel_state(struct vmbus_channel *channel,
+				      struct vmbus_channel_offer_channel *offer)
+{
+	/*
+	 * Setup state for signalling the host.
+	 */
+	channel->sig_event = VMBUS_EVENT_CONNECTION_ID;
+
+	if (vmbus_proto_version != VERSION_WS2008) {
+		channel->is_dedicated_interrupt =
+				(offer->is_dedicated_interrupt != 0);
+		channel->sig_event = offer->connection_id;
+	}
+
+	memcpy(&channel->offermsg, offer,
+	       sizeof(struct vmbus_channel_offer_channel));
+	channel->monitor_grp = (u8)offer->monitorid / 32;
+	channel->monitor_bit = (u8)offer->monitorid % 32;
+}
+
 /*
  * find_primary_channel_by_offer - Get the channel object given the new offer.
  * This is only used in the resume path of hibernation.
@@ -902,14 +940,29 @@ static void vmbus_onoffer(struct vmbus_channel_message_header *hdr)
 		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.
+		 * We're resuming from hibernation: all the sub-channel and
+		 * hv_sock channels we had before the hibernation should have
+		 * been cleaned up, and now we must be seeing a re-offered
+		 * primary channel that we had before the hibernation.
 		 */
+
+		WARN_ON(oldchannel->offermsg.child_relid != INVALID_RELID);
+		/* Fix up the relid. */
+		oldchannel->offermsg.child_relid = offer->child_relid;
+
 		offer_sz = sizeof(*offer);
-		if (memcmp(offer, &oldchannel->offermsg, offer_sz) == 0)
+		if (memcmp(offer, &oldchannel->offermsg, offer_sz) == 0) {
+			check_ready_for_resume_event();
 			return;
+		}
 
-		pr_debug("Mismatched offer from the host (relid=%d)\n",
+		/*
+		 * This is not an error, since the host can also change the
+		 * other field(s) of the offer, e.g. on WS RS5 (Build 17763),
+		 * the offer->connection_id of the Mellanox VF vmbus device
+		 * can change when the host reoffers the device upon resume.
+		 */
+		pr_debug("vmbus offer changed: relid=%d\n",
 			 offer->child_relid);
 
 		print_hex_dump_debug("Old vmbus offer: ", DUMP_PREFIX_OFFSET,
@@ -917,6 +970,12 @@ static void vmbus_onoffer(struct vmbus_channel_message_header *hdr)
 				     false);
 		print_hex_dump_debug("New vmbus offer: ", DUMP_PREFIX_OFFSET,
 				     16, 4, offer, offer_sz, false);
+
+		/* Fix up the old channel. */
+		vmbus_setup_channel_state(oldchannel, offer);
+
+		check_ready_for_resume_event();
+
 		return;
 	}
 
@@ -929,21 +988,7 @@ static void vmbus_onoffer(struct vmbus_channel_message_header *hdr)
 		return;
 	}
 
-	/*
-	 * Setup state for signalling the host.
-	 */
-	newchannel->sig_event = VMBUS_EVENT_CONNECTION_ID;
-
-	if (vmbus_proto_version != VERSION_WS2008) {
-		newchannel->is_dedicated_interrupt =
-				(offer->is_dedicated_interrupt != 0);
-		newchannel->sig_event = offer->connection_id;
-	}
-
-	memcpy(&newchannel->offermsg, offer,
-	       sizeof(struct vmbus_channel_offer_channel));
-	newchannel->monitor_grp = (u8)offer->monitorid / 32;
-	newchannel->monitor_bit = (u8)offer->monitorid % 32;
+	vmbus_setup_channel_state(newchannel, offer);
 
 	vmbus_process_offer(newchannel);
 }