linux-kernel - [PATCH v2 2/2] Drivers: hv: vmbus: use cpu_hotplug

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Message-Id: <1432225317-31700-3-git-send-email-vkuznets@redhat.com>
Date:	Thu, 21 May 2015 18:21:57 +0200
From:	Vitaly Kuznetsov <vkuznets@...hat.com>
To:	devel@...uxdriverproject.org
Cc:	"K. Y. Srinivasan" <kys@...rosoft.com>,
	Haiyang Zhang <haiyangz@...rosoft.com>,
	linux-kernel@...r.kernel.org, Dexuan Cui <decui@...rosoft.com>,
	Ingo Molnar <mingo@...nel.org>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Radim Krčmář <rkrcmar@...hat.com>
Subject: [PATCH v2 2/2] Drivers: hv: vmbus: use cpu_hotplug_enable/disable

Commit e513229b4c38 ("Drivers: hv: vmbus: prevent cpu offlining on newer
hypervisors") was altering smp_ops.cpu_disable to prevent CPU offlining.
We can bo better by using cpu_hotplug_enable/disable functions instead of
such hard-coding.

Reported-by: Radim Krčmář <rkrcmar@...hat.com>
Signed-off-by: Vitaly Kuznetsov <vkuznets@...hat.com>
---
 drivers/hv/vmbus_drv.c | 38 ++++----------------------------------
 1 file changed, 4 insertions(+), 34 deletions(-)

diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c
index c85235e..e916ba2 100644
--- a/drivers/hv/vmbus_drv.c
+++ b/drivers/hv/vmbus_drv.c
@@ -763,38 +763,6 @@ static void vmbus_isr(void)
 	}
 }
 
-#ifdef CONFIG_HOTPLUG_CPU
-static int hyperv_cpu_disable(void)
-{
-	return -ENOSYS;
-}
-
-static void hv_cpu_hotplug_quirk(bool vmbus_loaded)
-{
-	static void *previous_cpu_disable;
-
-	/*
-	 * Offlining a CPU when running on newer hypervisors (WS2012R2, Win8,
-	 * ...) is not supported at this moment as channel interrupts are
-	 * distributed across all of them.
-	 */
-
-	if ((vmbus_proto_version == VERSION_WS2008) ||
-	    (vmbus_proto_version == VERSION_WIN7))
-		return;
-
-	if (vmbus_loaded) {
-		previous_cpu_disable = smp_ops.cpu_disable;
-		smp_ops.cpu_disable = hyperv_cpu_disable;
-		pr_notice("CPU offlining is not supported by hypervisor\n");
-	} else if (previous_cpu_disable)
-		smp_ops.cpu_disable = previous_cpu_disable;
-}
-#else
-static void hv_cpu_hotplug_quirk(bool vmbus_loaded)
-{
-}
-#endif
 
 /*
  * vmbus_bus_init -Main vmbus driver initialization routine.
@@ -836,7 +804,8 @@ static int vmbus_bus_init(int irq)
 	if (ret)
 		goto err_alloc;
 
-	hv_cpu_hotplug_quirk(true);
+	if (vmbus_proto_version > VERSION_WIN7)
+		cpu_hotplug_disable();
 
 	/*
 	 * Only register if the crash MSRs are available
@@ -1103,7 +1072,8 @@ static void __exit vmbus_exit(void)
 	for_each_online_cpu(cpu)
 		smp_call_function_single(cpu, hv_synic_cleanup, NULL, 1);
 	acpi_bus_unregister_driver(&vmbus_acpi_driver);
-	hv_cpu_hotplug_quirk(false);
+	if (vmbus_proto_version > VERSION_WIN7)
+		cpu_hotplug_enable();
 	vmbus_disconnect();
 }
 
-- 
1.9.3

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