Drivers: hv: vmbus: Improve the CPU affiliation for channels

The current code tracks the assigned CPUs within a NUMA node in the context of
the primary channel. So, if we have a VM with a single NUMA node with 8 VCPUs, we may
end up unevenly distributing the channel load. Fix the issue by tracking affiliations
globally.

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

3 files changed, 20 insertions, 5 deletions

diff --git a/drivers/hv/channel_mgmt.c b/drivers/hv/channel_mgmt.c
index 30613dfa38b3..39c5afc7970c 100644
--- a/drivers/hv/channel_mgmt.c
+++ b/drivers/hv/channel_mgmt.c
@@ -392,6 +392,7 @@ static void init_vp_index(struct vmbus_channel *channel, const uuid_le *type_gui
         struct vmbus_channel *primary = channel->primary_channel;
         int next_node;
         struct cpumask available_mask;
+        struct cpumask *alloced_mask;
 
         for (i = IDE; i < MAX_PERF_CHN; i++) {
                 if (!memcmp(type_guid->b, hp_devs[i].guid,
@@ -409,7 +410,6 @@ static void init_vp_index(struct vmbus_channel *channel, const uuid_le *type_gui
                  * channel, bind it to cpu 0.
                  */
                 channel->numa_node = 0;
-                cpumask_set_cpu(0, &channel->alloced_cpus_in_node);
                 channel->target_cpu = 0;
                 channel->target_vp = hv_context.vp_index[0];
                 return;
@@ -434,21 +434,22 @@ static void init_vp_index(struct vmbus_channel *channel, const uuid_le *type_gui
                 channel->numa_node = next_node;
                 primary = channel;
         }
+        alloced_mask = &hv_context.hv_numa_map[primary->numa_node];
 
-        if (cpumask_weight(&primary->alloced_cpus_in_node) ==
+        if (cpumask_weight(alloced_mask) ==
             cpumask_weight(cpumask_of_node(primary->numa_node))) {
                 /*
                  * We have cycled through all the CPUs in the node;
                  * reset the alloced map.
                  */
-                cpumask_clear(&primary->alloced_cpus_in_node);
+                cpumask_clear(alloced_mask);
         }
 
-        cpumask_xor(&available_mask, &primary->alloced_cpus_in_node,
+        cpumask_xor(&available_mask, alloced_mask,
                     cpumask_of_node(primary->numa_node));
 
         cur_cpu = cpumask_next(-1, &available_mask);
-        cpumask_set_cpu(cur_cpu, &primary->alloced_cpus_in_node);
+        cpumask_set_cpu(cur_cpu, alloced_mask);
 
         channel->target_cpu = cur_cpu;
         channel->target_vp = hv_context.vp_index[cur_cpu];
diff --git a/drivers/hv/hv.c b/drivers/hv/hv.c
index 41d8072d61d9..fd93cfde96d0 100644
--- a/drivers/hv/hv.c
+++ b/drivers/hv/hv.c
@@ -332,6 +332,13 @@ int hv_synic_alloc(void)
         size_t ced_size = sizeof(struct clock_event_device);
         int cpu;
 
+        hv_context.hv_numa_map = kzalloc(sizeof(struct cpumask) * nr_node_ids,
+                                         GFP_ATOMIC);
+        if (hv_context.hv_numa_map == NULL) {
+                pr_err("Unable to allocate NUMA map\n");
+                goto err;
+        }
+
         for_each_online_cpu(cpu) {
                 hv_context.event_dpc[cpu] = kmalloc(size, GFP_ATOMIC);
                 if (hv_context.event_dpc[cpu] == NULL) {
@@ -345,6 +352,7 @@ int hv_synic_alloc(void)
                         pr_err("Unable to allocate clock event device\n");
                         goto err;
                 }
+
                 hv_init_clockevent_device(hv_context.clk_evt[cpu], cpu);
 
                 hv_context.synic_message_page[cpu] =
@@ -393,6 +401,7 @@ void hv_synic_free(void)
 {
         int cpu;
 
+        kfree(hv_context.hv_numa_map);
         for_each_online_cpu(cpu)
                 hv_synic_free_cpu(cpu);
 }
diff --git a/drivers/hv/hyperv_vmbus.h b/drivers/hv/hyperv_vmbus.h
index 638370701657..6f258255ac94 100644
--- a/drivers/hv/hyperv_vmbus.h
+++ b/drivers/hv/hyperv_vmbus.h
@@ -551,6 +551,11 @@ struct hv_context {
          * Support PV clockevent device.
          */
         struct clock_event_device *clk_evt[NR_CPUS];
+        /*
+         * To manage allocations in a NUMA node.
+         * Array indexed by numa node ID.
+         */
+        struct cpumask *hv_numa_map;
 };
 
 extern struct hv_context hv_context;