From 2f03e6e3d823d7381ac7c2b3d076f20d1978d5a1 Mon Sep 17 00:00:00 2001
From: root <root@localhost.guest.corp.microsoft.com>
Date: Mon, 29 Jan 2018 18:02:49 -0500
Subject: [PATCH] RH7: add optional vmbus parameter for HT when assigning CPU
 to channel

By default, in RH7 code, vmbus will assign CPUs to channels by
considering the CPU hyper-threading.
Now, add a kernel parameter to disable it: "hv_vmbus.affinity_mode=0"
---
 hv-rhel7.x/hv/channel_mgmt.c         | 34 +++++++++++++++-------------
 hv-rhel7.x/hv/hyperv_vmbus.h         |  2 ++
 hv-rhel7.x/hv/include/linux/hyperv.h |  5 ++++
 hv-rhel7.x/hv/vmbus_drv.c            |  5 ++++
 4 files changed, 30 insertions(+), 16 deletions(-)

diff --git a/hv-rhel7.x/hv/channel_mgmt.c b/hv-rhel7.x/hv/channel_mgmt.c
index 5fa49b320..a6c69d102 100644
--- a/hv-rhel7.x/hv/channel_mgmt.c
+++ b/hv-rhel7.x/hv/channel_mgmt.c
@@ -712,22 +712,24 @@ static void init_vp_index(struct vmbus_channel *channel, u16 dev_type)
 			continue;
 		}
 
-#if (RHEL_RELEASE_CODE >= RHEL_RELEASE_VERSION(7,3))  
-		cpu_sibling_mask = topology_sibling_cpumask(cur_cpu);
-		cpumask_and(cpu_thread_tmp_mask,
-			    cpu_sibling_mask,
-			    &available_mask);
-		if (!cpumask_equal(cpu_thread_tmp_mask, cpu_sibling_mask)) {
-			/*
-			 * NOTE: The thread sibling of this CPU has been
-			 * assigned to a channel.
-			 * We do not assign both Hyper-Threading CPUs of
-			 * the same physical core to vmbus channels.
-			 * So, mark this CPU as occupied too then move to
-			 * next one and try.
-			 */
-			cpumask_set_cpu(cur_cpu, alloced_mask);
-			continue;
+#if (RHEL_RELEASE_CODE >= RHEL_RELEASE_VERSION(7,3))
+		if (affinity_mode == HV_SKIP_HT_CPU) {
+			cpu_sibling_mask = topology_sibling_cpumask(cur_cpu);
+			cpumask_and(cpu_thread_tmp_mask,
+				    cpu_sibling_mask,
+				    &available_mask);
+			if (!cpumask_equal(cpu_thread_tmp_mask, cpu_sibling_mask)) {
+				/*
+				 * NOTE: The thread sibling of this CPU has been
+				 * assigned to a channel.
+				 * We do not assign both Hyper-Threading CPUs of
+				 * the same physical core to vmbus channels.
+				 * So, mark this CPU as occupied too then move to
+				 * next one and try.
+				 */
+				cpumask_set_cpu(cur_cpu, alloced_mask);
+				continue;
+			}
 		}
 #endif
 
diff --git a/hv-rhel7.x/hv/hyperv_vmbus.h b/hv-rhel7.x/hv/hyperv_vmbus.h
index a945b8194..fae02f70e 100644
--- a/hv-rhel7.x/hv/hyperv_vmbus.h
+++ b/hv-rhel7.x/hv/hyperv_vmbus.h
@@ -242,6 +242,8 @@ struct hv_context {
 
 extern struct hv_context hv_context;
 
+extern int affinity_mode;
+
 /* Hv Interface */
 
 extern int hv_init(void);
diff --git a/hv-rhel7.x/hv/include/linux/hyperv.h b/hv-rhel7.x/hv/include/linux/hyperv.h
index 79fa1c951..c00ce51b4 100644
--- a/hv-rhel7.x/hv/include/linux/hyperv.h
+++ b/hv-rhel7.x/hv/include/linux/hyperv.h
@@ -667,6 +667,11 @@ enum hv_numa_policy {
 	HV_LOCALIZED,
 };
 
+enum hv_channel_affinity_mode {
+	HV_KEEP_HT_CPU = 0,
+	HV_SKIP_HT_CPU,
+};
+
 enum vmbus_device_type {
 	HV_IDE = 0,
 	HV_SCSI,
diff --git a/hv-rhel7.x/hv/vmbus_drv.c b/hv-rhel7.x/hv/vmbus_drv.c
index e570e0626..29bf51fbd 100644
--- a/hv-rhel7.x/hv/vmbus_drv.c
+++ b/hv-rhel7.x/hv/vmbus_drv.c
@@ -48,6 +48,10 @@
 
 static struct acpi_device  *hv_acpi_dev;
 
+int affinity_mode = 1;
+module_param(affinity_mode, int, S_IRUGO);
+MODULE_PARM_DESC(affinity_mode, "vmbus channel cpu affinity mode: 0, 1");
+
 static struct completion probe_event;
 #if (RHEL_RELEASE_CODE < RHEL_RELEASE_VERSION(7,2))
 static int irq;
@@ -1838,6 +1842,7 @@ static int __init hv_acpi_init(void)
 	hv_setup_crash_handler(hv_crash_handler);
 #endif
 
+	pr_info("vmbus channel cpu affinity mode: %d\n", affinity_mode);
 	return 0;
 
 cleanup: