Drivers: hv: vmbus: fix init_vp_index() for reloading hv_netvsc

This fixes the recent commit 3b71107d73b16074afa7658f3f0fcf837aabfe24:
Drivers: hv: vmbus: Further improve CPU affiliation logic

Without the fix, reloading hv_netvsc hangs the guest.

Signed-off-by: Dexuan Cui <decui@microsoft.com>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 17 insertions, 0 deletions

diff --git a/drivers/hv/channel_mgmt.c b/drivers/hv/channel_mgmt.c
index 2f9aead4ecfc..652afd11a9ef 100644
--- a/drivers/hv/channel_mgmt.c
+++ b/drivers/hv/channel_mgmt.c
@@ -204,6 +204,8 @@ void hv_process_channel_removal(struct vmbus_channel *channel, u32 relid)
                 spin_lock_irqsave(&vmbus_connection.channel_lock, flags);
                 list_del(&channel->listentry);
                 spin_unlock_irqrestore(&vmbus_connection.channel_lock, flags);
+
+                primary_channel = channel;
         } else {
                 primary_channel = channel->primary_channel;
                 spin_lock_irqsave(&primary_channel->lock, flags);
@@ -211,6 +213,14 @@ void hv_process_channel_removal(struct vmbus_channel *channel, u32 relid)
                 primary_channel->num_sc--;
                 spin_unlock_irqrestore(&primary_channel->lock, flags);
         }
+
+        /*
+         * We need to free the bit for init_vp_index() to work in the case
+         * of sub-channel, when we reload drivers like hv_netvsc.
+         */
+        cpumask_clear_cpu(channel->target_cpu,
+                          &primary_channel->alloced_cpus_in_node);
+
         free_channel(channel);
 }
 
@@ -458,6 +468,13 @@ static void init_vp_index(struct vmbus_channel *channel, const uuid_le *type_gui
                         continue;
                 }
 
+                /*
+                 * NOTE: in the case of sub-channel, we clear the sub-channel
+                 * related bit(s) in primary->alloced_cpus_in_node in
+                 * hv_process_channel_removal(), so when we reload drivers
+                 * like hv_netvsc in SMP guest, here we're able to re-allocate
+                 * bit from primary->alloced_cpus_in_node.
+                 */
                 if (!cpumask_test_cpu(cur_cpu,
                                 &primary->alloced_cpus_in_node)) {
                         cpumask_set_cpu(cur_cpu,