Patch "[PATCH 097/135] Drivers: hv: vmbus: avoid infinite loop in" has been added to the 4.4-stable tree

Patch "[PATCH 097/135] Drivers: hv: vmbus: avoid infinite loop in" has been added to the 4.4-stable tree

[gregkh]

This is a note to let you know that I've just added the patch titled

    [PATCH 097/135] Drivers: hv: vmbus: avoid infinite loop in

to the 4.4-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     0097-Drivers-hv-vmbus-avoid-infinite-loop-in-init_vp_inde.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From 864900991b27198b2006f7e8abc50599ea923968 Mon Sep 17 00:00:00 2001
From: Vitaly Kuznetsov <vkuznets@redhat.com>
Date: Wed, 27 Jan 2016 22:29:34 -0800
Subject: [PATCH 097/135] Drivers: hv: vmbus: avoid infinite loop in
 init_vp_index()

[ Upstream commit 79fd8e706637a5c7c41f9498fe0fbfb437abfdc8 ]

When we pick a CPU to use for a new subchannel we try find a non-used one
on the appropriate NUMA node, we keep track of them with the
primary->alloced_cpus_in_node mask. Under normal circumstances we don't run
out of available CPUs but it is possible when we we don't initialize some
cpus in Linux, e.g. when we boot with 'nr_cpus=' limitation.

Avoid the infinite loop in init_vp_index() by checking that we still have
non-used CPUs in the alloced_cpus_in_node mask and resetting it in case
we don't.

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <alexander.levin@verizon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/hv/channel_mgmt.c |   11 +++++++++++
 1 file changed, 11 insertions(+)

--- a/drivers/hv/channel_mgmt.c
+++ b/drivers/hv/channel_mgmt.c
@@ -459,6 +459,17 @@ static void init_vp_index(struct vmbus_c
 		    cpumask_of_node(primary->numa_node));
 
 	cur_cpu = -1;
+
+	/*
+	 * Normally Hyper-V host doesn't create more subchannels than there
+	 * are VCPUs on the node but it is possible when not all present VCPUs
+	 * on the node are initialized by guest. Clear the alloced_cpus_in_node
+	 * to start over.
+	 */
+	if (cpumask_equal(&primary->alloced_cpus_in_node,
+			  cpumask_of_node(primary->numa_node)))
+		cpumask_clear(&primary->alloced_cpus_in_node);
+
 	while (true) {
 		cur_cpu = cpumask_next(cur_cpu, &available_mask);
 		if (cur_cpu >= nr_cpu_ids) {


Patches currently in stable-queue which might be from vkuznets@redhat.com are

queue-4.4/0038-drivers-hv-cleanup-synic-msrs-if-vmbus-connect-faile.patch
queue-4.4/0097-Drivers-hv-vmbus-avoid-infinite-loop-in-init_vp_inde.patch
queue-4.4/0118-clocksource-Allow-unregistering-the-watchdog.patch
queue-4.4/0099-Drivers-hv-vmbus-don-t-manipulate-with-clocksources-.patch
queue-4.4/0127-x86-hyperv-Avoid-reporting-bogus-NMI-status-for-Gen2.patch
queue-4.4/0098-Drivers-hv-vmbus-avoid-scheduling-in-interrupt-conte.patch