linux-kernel - [PATCH] Drivers: hv: vmbus: Adding isolated cpu support for channel interrupts mapping

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Date:   Thu, 26 May 2022 11:55:14 -0700
From:   Saurabh Sengar <ssengar@...ux.microsoft.com>
To:     kys@...rosoft.com, haiyangz@...rosoft.com, sthemmin@...rosoft.com,
        wei.liu@...nel.org, decui@...rosoft.com,
        linux-hyperv@...r.kernel.org, linux-kernel@...r.kernel.org,
        ssengar@...rosoft.com, mikelley@...rosoft.com
Subject: [PATCH] Drivers: hv: vmbus: Adding isolated cpu support for channel interrupts mapping

Adding support for vmbus channels to take isolated cpu in consideration
while assigning interrupt to different cpus. This also prevents user from
setting any isolated cpu to vmbus channel interrupt assignment by sysfs
entry. Isolated cpu can be configured by kernel command line parameter
'isolcpus=managed_irq,<#cpu>'.

Signed-off-by: Saurabh Sengar <ssengar@...ux.microsoft.com>
---
 drivers/hv/channel_mgmt.c | 18 ++++++++++++------
 drivers/hv/vmbus_drv.c    |  6 ++++++
 2 files changed, 18 insertions(+), 6 deletions(-)

diff --git a/drivers/hv/channel_mgmt.c b/drivers/hv/channel_mgmt.c
index 97d8f56..e1fe029 100644
--- a/drivers/hv/channel_mgmt.c
+++ b/drivers/hv/channel_mgmt.c
@@ -21,6 +21,7 @@
 #include <linux/cpu.h>
 #include <linux/hyperv.h>
 #include <asm/mshyperv.h>
+#include <linux/sched/isolation.h>
 
 #include "hyperv_vmbus.h"
 
@@ -728,16 +729,20 @@ static void init_vp_index(struct vmbus_channel *channel)
 	u32 i, ncpu = num_online_cpus();
 	cpumask_var_t available_mask;
 	struct cpumask *allocated_mask;
+	const struct cpumask *hk_mask = housekeeping_cpumask(HK_TYPE_MANAGED_IRQ);
 	u32 target_cpu;
 	int numa_node;
 
 	if (!perf_chn ||
-	    !alloc_cpumask_var(&available_mask, GFP_KERNEL)) {
+	    !alloc_cpumask_var(&available_mask, GFP_KERNEL) ||
+	    cpumask_empty(hk_mask)) {
 		/*
 		 * If the channel is not a performance critical
 		 * channel, bind it to VMBUS_CONNECT_CPU.
 		 * In case alloc_cpumask_var() fails, bind it to
 		 * VMBUS_CONNECT_CPU.
+		 * If all the cpus are isolated, bind it to
+		 * VMBUS_CONNECT_CPU.
 		 */
 		channel->target_cpu = VMBUS_CONNECT_CPU;
 		if (perf_chn)
@@ -758,17 +763,19 @@ static void init_vp_index(struct vmbus_channel *channel)
 		}
 		allocated_mask = &hv_context.hv_numa_map[numa_node];
 
-		if (cpumask_equal(allocated_mask, cpumask_of_node(numa_node))) {
+retry:
+		cpumask_xor(available_mask, allocated_mask, cpumask_of_node(numa_node));
+		cpumask_and(available_mask, available_mask, hk_mask);
+
+		if (cpumask_empty(available_mask)) {
 			/*
 			 * We have cycled through all the CPUs in the node;
 			 * reset the allocated map.
 			 */
 			cpumask_clear(allocated_mask);
+			goto retry;
 		}
 
-		cpumask_xor(available_mask, allocated_mask,
-			    cpumask_of_node(numa_node));
-
 		target_cpu = cpumask_first(available_mask);
 		cpumask_set_cpu(target_cpu, allocated_mask);
 
@@ -778,7 +785,6 @@ static void init_vp_index(struct vmbus_channel *channel)
 	}
 
 	channel->target_cpu = target_cpu;
-
 	free_cpumask_var(available_mask);
 }
 
diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c
index 714d549..23660a8 100644
--- a/drivers/hv/vmbus_drv.c
+++ b/drivers/hv/vmbus_drv.c
@@ -21,6 +21,7 @@
 #include <linux/kernel_stat.h>
 #include <linux/clockchips.h>
 #include <linux/cpu.h>
+#include <linux/sched/isolation.h>
 #include <linux/sched/task_stack.h>
 
 #include <linux/delay.h>
@@ -1770,6 +1771,11 @@ static ssize_t target_cpu_store(struct vmbus_channel *channel,
 	if (target_cpu >= nr_cpumask_bits)
 		return -EINVAL;
 
+	if (!cpumask_test_cpu(target_cpu, housekeeping_cpumask(HK_TYPE_MANAGED_IRQ))) {
+		dev_err(&channel->device_obj->device,
+			"cpu (%d) is isolated, can't be assigned\n", target_cpu);
+		return -EINVAL;
+	}
 	/* No CPUs should come up or down during this. */
 	cpus_read_lock();
 
-- 
1.8.3.1