The patch below does not apply to the 4.9-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 8604895a34d92f5e186ceb931b0d1b384030ea3d Mon Sep 17 00:00:00 2001

From: Michael Bringmann mwb@linux.vnet.ibm.com Date: Thu, 20 Sep 2018 11:45:13 -0500 Subject: [PATCH] powerpc/pseries: Fix unitialized timer reset on migration

After migration of a powerpc LPAR, the kernel executes code to update the system state to reflect new platform characteristics.

Such changes include modifications to device tree properties provided to the system by PHYP. Property notifications received by the post_mobility_fixup() code are passed along to the kernel in general through a call to of_update_property() which in turn passes such events back to all modules through entries like the '.notifier_call' function within the NUMA module.

When the NUMA module updates its state, it resets its event timer. If this occurs after a previous call to stop_topology_update() or on a system without VPHN enabled, the code runs into an unitialized timer structure and crashes. This patch adds a safety check along this path toward the problem code.

An example crash log is as follows.

ibmvscsi 30000081: Re-enabling adapter! ------------[ cut here ]------------ kernel BUG at kernel/time/timer.c:958! Oops: Exception in kernel mode, sig: 5 [#1] LE SMP NR_CPUS=2048 NUMA pSeries Modules linked in: nfsv3 nfs_acl nfs tcp_diag udp_diag inet_diag lockd unix_diag af_packet_diag netlink_diag grace fscache sunrpc xts vmx_crypto pseries_rng sg binfmt_misc ip_tables xfs libcrc32c sd_mod ibmvscsi ibmveth scsi_transport_srp dm_mirror dm_region_hash dm_log dm_mod CPU: 11 PID: 3067 Comm: drmgr Not tainted 4.17.0+ #179 ... NIP mod_timer+0x4c/0x400 LR reset_topology_timer+0x40/0x60 Call Trace: 0xc0000003f9407830 (unreliable) reset_topology_timer+0x40/0x60 dt_update_callback+0x100/0x120 notifier_call_chain+0x90/0x100 __blocking_notifier_call_chain+0x60/0x90 of_property_notify+0x90/0xd0 of_update_property+0x104/0x150 update_dt_property+0xdc/0x1f0 pseries_devicetree_update+0x2d0/0x510 post_mobility_fixup+0x7c/0xf0 migration_store+0xa4/0xc0 kobj_attr_store+0x30/0x60 sysfs_kf_write+0x64/0xa0 kernfs_fop_write+0x16c/0x240 __vfs_write+0x40/0x200 vfs_write+0xc8/0x240 ksys_write+0x5c/0x100 system_call+0x58/0x6c

Fixes: 5d88aa85c00b ("powerpc/pseries: Update CPU maps when device tree is updated") Cc: stable@vger.kernel.org # v3.10+ Signed-off-by: Michael Bringmann mwb@linux.vnet.ibm.com Signed-off-by: Michael Ellerman mpe@ellerman.id.au

diff --git a/arch/powerpc/mm/numa.c b/arch/powerpc/mm/numa.c index 35ac5422903a..b5a71baedbc2 100644 --- a/arch/powerpc/mm/numa.c +++ b/arch/powerpc/mm/numa.c @@ -1452,7 +1452,8 @@ static struct timer_list topology_timer;

static void reset_topology_timer(void) { - mod_timer(&topology_timer, jiffies + topology_timer_secs * HZ); + if (vphn_enabled) + mod_timer(&topology_timer, jiffies + topology_timer_secs * HZ); }

#ifdef CONFIG_SMP