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== Comment: #0 - Daniel Henrique Barboza <danie...@br.ibm.com> - 2017-08-08
09:13:31 ==
- Host information: Ubuntu 16.10 running upstream QEMU
$ uname -a
Linux louis 4.10.0-20-generic #22-Ubuntu SMP Thu Apr 20 09:22:16 UTC 2017
ppc64le ppc64le ppc64le GNU/Linux
$ cat /proc/cpuinfo
processor : 0
cpu : POWER8E (raw), altivec supported
clock : 2061.000000MHz
revision : 2.1 (pvr 004b 0201)
(...)
timebase : 512000000
platform : PowerNV
model : 8247-42L
machine : PowerNV 8247-42L
firmware : OPAL
- qemu command line that launched the Ubuntu 17.10 ppc64el guest:
sudo ./qemu-system-ppc64 -name migrate_qemu -boot strict=on --enable-kvm
-device nec-usb-xhci,id=usb,bus=pci.0,addr=0xf -device spapr-
vscsi,id=scsi0,reg=0x2000 -smp 1,maxcpus=4,sockets=4,cores=1,threads=1
--machine pseries,accel=kvm,usb=off,dump-guest-core=off -m
4G,slots=32,maxmem=32G -drive
file=/home/danielhb/vm_imgs/ub1710.qcow2,format=qcow2,if=none,id=drive-
virtio-disk0,cache=none -device virtio-blk-
pci,scsi=off,bus=pci.0,addr=0x2,drive=drive-virtio-disk0,id=virtio-
disk0,bootindex=1 -nographic
- guest information: Ubuntu 17.10 ppc64el:
root@ubuntu1710:~# uname -a
Linux ubuntu1710 4.11.0-10-generic #15-Ubuntu SMP Thu Jun 29 15:02:54 UTC 2017
ppc64le ppc64le ppc64le GNU/Linux
root@ubuntu1710:~#
- Problem: hotplugging a LMB generates a guest kernel Oops:
root@ubuntu1710:~# QEMU 2.9.90 monitor - type 'help' for more information
(qemu)
(qemu) object_add memory-backend-ram,id=ram1,size=1G
(qemu) device_add pc-dimm,id=dimm1,memdev=ram1
(qemu) [ 126.850952] kernel BUG at
/build/linux-S1V_3d/linux-4.11.0/mm/memory_hotplug.c:2185!
[ 126.851285] Oops: Exception in kernel mode, sig: 5 [#1]
[ 126.851428] SMP NR_CPUS=2048
[ 126.851428] NUMA
[ 126.851546] pSeries
[ 126.851714] Modules linked in: vmx_crypto ib_iser rdma_cm iw_cm ib_cm
ib_core configfs iscsi_tcp libiscsi_tcp libiscsi scsi_transport_iscsi ip_tables
x_tables autofs4 btrfs raid10 raid456 async_raid6_recov async_memcpy async_pq
async_xor async_tx xor raid6_pq libcrc32c raid1 raid0 multipath linear ibmvscsi
crc32c_vpmsum virtio_blk
[ 126.852447] CPU: 0 PID: 5 Comm: kworker/u8:0 Not tainted 4.11.0-10-generic
#15-Ubuntu
[ 126.852656] Workqueue: pseries hotplug workque pseries_hp_work_fn
[ 126.852828] task: c0000000fea80000 task.stack: c0000000fe118000
[ 126.853000] NIP: c000000000350268 LR: c0000000003501e0 CTR: 0000000000000000
[ 126.853190] REGS: c0000000fe11b780 TRAP: 0700 Not tainted
(4.11.0-10-generic)
[ 126.853390] MSR: 800000000282b033 <SF,VEC,VSX,EE,FP,ME,IR,DR,RI,LE>
[ 126.853396] CR: 42002422 XER: 20000000
[ 126.853672] CFAR: c0000000003501e4 SOFTE: 1
[ 126.853672] GPR00: c0000000003501e0 c0000000fe11ba00 c00000000149eb00
0000000000000001
[ 126.853672] GPR04: c0000000f9901480 c0000000ffe21c00 000000000000003e
0000000000000003
[ 126.853672] GPR08: 0000000000000002 0000000000000003 0000000000000003
303078302d303030
[ 126.853672] GPR12: 0000000000002200 c00000000fb80000 c000000000110008
c0000000fe1810c0
[ 126.853672] GPR16: c0000000fe050ea8 0000000000000010 c0000000fffffc30
c0000000fffffea0
[ 126.853672] GPR20: c0000000f951a1a4 0000000000000004 0000000000000001
0000000000000010
[ 126.853672] GPR24: 0000000000000001 c0000000f951a1a0 0000000000000004
0000000000000000
[ 126.853672] GPR28: 0000000000000000 0000000000000001 0000000010000000
0000000140000000
[ 126.855221] NIP [c000000000350268] remove_memory+0xf8/0x100
[ 126.855338] LR [c0000000003501e0] remove_memory+0x70/0x100
[ 126.855453] Call Trace:
[ 126.855520] [c0000000fe11ba00] [c0000000003501e0] remove_memory+0x70/0x100
(unreliable)
[ 126.855684] [c0000000fe11ba40] [c0000000000b0880] dlpar_add_lmb+0x370/0x3f0
[ 126.855822] [c0000000fe11bb20] [c0000000000b174c] dlpar_memory+0x7cc/0xd20
[ 126.855959] [c0000000fe11bbf0] [c0000000000a9af8]
handle_dlpar_errorlog+0xa8/0x170
[ 126.856118] [c0000000fe11bc60] [c0000000000a9c54]
pseries_hp_work_fn+0x94/0xa0
[ 126.856275] [c0000000fe11bc90] [c0000000001071d0]
process_one_work+0x2b0/0x5a0
[ 126.856430] [c0000000fe11bd20] [c000000000107568] worker_thread+0xa8/0x670
[ 126.856563] [c0000000fe11bdc0] [c000000000110164] kthread+0x164/0x1b0
[ 126.856695] [c0000000fe11be30] [c00000000000b4e8]
ret_from_kernel_thread+0x5c/0x74
[ 126.856846] Instruction dump:
[ 126.856931] 60000000 387f0060 48824b19 60000000 38210040 e8010010 eb81ffe0
eba1ffe8
[ 126.857088] ebc1fff0 ebe1fff8 7c0803a6 4e800020 <0fe00000> 00000000 3c4c0115
3842e890
[ 126.857243] ---[ end trace 76fab848b8f01d0a ]---
[ 126.859577]
Investigating the cause I've found this kernel commit:
commit 943db62c316c578f8e2cc6fb81a5f641096b29bf
Author: Nathan Fontenot <nf...@linux.vnet.ibm.com>
Date: Wed Feb 15 13:45:30 2017 -0500
powerpc/pseries: Revert 'Auto-online hotplugged memory'
This reverts commit ec999072442a ("powerpc/pseries: Auto-online
hotplugged memory"), and 9dc512819e4b ("powerpc: Fix unused function
warning 'lmb_to_memblock'").
Using the auto-online acpability does online added memory but does not
update the associated device struct to indicate that the memory is
online. This causes the pseries memory DLPAR code to fail when trying to
remove a LMB that was previously removed and added back. This happens
when validating that the LMB is removable.
This patch reverts to the previous behavior of calling device_online()
to online the LMB when it is DLPAR added and moves the lmb_to_memblock()
routine out of CONFIG_MEMORY_HOTREMOVE now that we call it for add.
This commit removed a specific kernel configuration in the revert:
--- a/arch/powerpc/configs/pseries_defconfig
+++ b/arch/powerpc/configs/pseries_defconfig
@@ -58,7 +58,6 @@ CONFIG_KEXEC_FILE=y
CONFIG_IRQ_ALL_CPUS=y
CONFIG_MEMORY_HOTPLUG=y
CONFIG_MEMORY_HOTREMOVE=y
-CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE=y
CONFIG_KSM=y
CONFIG_TRANSPARENT_HUGEPAGE=y
Using the vanilla kernel from Linus I've got the following default config for
pseries:
[danielhb@arthas linux]$ ARCH=powerpc make pseries_defconfig
#
# configuration written to .config
#
[danielhb@arthas linux]$ grep -R 'HOTPLUG_DEFAULT' .
./mm/Kconfig:config MEMORY_HOTPLUG_DEFAULT_ONLINE
./mm/memory_hotplug.c:#ifndef CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE
./.config:# CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE is not set
./Documentation/admin-guide/kernel-parameters.txt:
CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE kernel config
./Documentation/memory-hotplug.txt:The default depends on the
CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE kernel config
[danielhb@arthas linux]$
As we can see from the grep result, the .config was generated without the
CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE option and there is no other place in the
code where it is set to Y.
In the mm/Kconfig we have:
(...)
config MEMORY_HOTPLUG_DEFAULT_ONLINE
bool "Online the newly added memory blocks by default"
default n
depends on MEMORY_HOTPLUG
help
(...)
This shows that the default value for this option is N, which makes
sense with the change made in the patch - the absence of the option in
.config disables the auto_online_blocks feature.
However, the guest Ubuntu 17.10 ppc64el kernel is setting this option
to Y:
root@ubuntu1710:~# cat /boot/config-4.11.0-10-generic | grep HOTPLUG_DEFAULT
CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE=y
root@ubuntu1710:~#
I am not sure if the intent was to enable just for x86 or all architectures
but, as is, this is breaking memory hotplug in pseries after the mentioned
kernel commit 943db62c316c578f8e2cc6fb81a5f641096b29bf. Given that the default
behavior when the option is not set is N, my suggestion is to change the
MEMORY_HOTPLUG_DEFAULT_ONLINE to 'not set' in any ppc64el config file in the
Ubuntu build, following the defconfig we have in the vanilla kernel.
- Workarounds:
The most obvious one: if I recompile the Ubuntu 17.10 kernel without
this option (or setting it to 'n'), LMB hotplug works.
Another possible workaround, further documented in the kernel commits
that introduced the CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE option, is to
manually set the auto_online blocks to 'offline'. Doing that prior to
the hotplug avoids the kernel Oops:
root@ubuntu1710:~# echo offline > /sys/devices/system/memory/auto_online_blocks
root@ubuntu1710:~#
root@ubuntu1710:~# grep Mem /proc/meminfo
MemTotal: 4169088 kB
MemFree: 3725632 kB
MemAvailable: 3917056 kB
root@ubuntu1710:~#
root@ubuntu1710:~# QEMU 2.9.90 monitor - type 'help' for more information
(qemu)
(qemu) object_add memory-backend-ram,id=ram0,size=1G
(qemu) device_add pc-dimm,id=dimm0,memdev=ram0
(qemu)
root@ubuntu1710:~#
root@ubuntu1710:~# grep Mem /proc/meminfo
MemTotal: 5217664 kB
MemFree: 4772864 kB
MemAvailable: 4956928 kB
root@ubuntu1710:~#
We can see, it is possible to normally hotplug memory if we manually
disable auto_online_blocks.
Additional notes:
- This same problem was also reported against Fedora 26 guests here:
https://bugzilla.redhat.com/show_bug.cgi?id=1476380.
- Ever since I've opened this Red Hat bug there were some developments in the
PPC kernel mailing list, but none that actually solves the problem seem here in
the upstream 4.13+ kernel. The safest course of action is disable this option
until things are sorted out upstrea.
Let me know if you need any extra information about the issue or the
tests.
Thanks,
Daniel
== Comment: #5 - Nathan D. Fontenot <nfont...@us.ibm.com> - 2017-08-15 11:23:54
==
This problem is resolved by a recent commit upstream (commit id 1a367063ca0c)
commit 1a367063ca0c1c6f6f54b5abd7b4836b0866a07b
Author: Nathan Fontenot <nf...@linux.vnet.ibm.com>
Date: Wed Aug 2 14:03:22 2017 -0400
powerpc/pseries: Check memory device state before onlining/offlining
When DLPAR adding or removing memory we need to check the device
offline status before trying to online/offline the memory. This is
needed because calls to device_online() and device_offline() will
return non-zero for memory that is already online and offline
respectively.
This update resolves two scenarios. First, for a kernel built with
auto-online memory enabled (CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE=y),
memory will be onlined as part of calls to add_memory(). After adding
the memory the pseries DLPAR code tries to online it and fails since
the memory is already online. The DLPAR code then tries to remove the
memory which produces the oops message below because the memory is not
offline.
The second scenario occurs when removing memory that is already
offline, i.e. marking memory offline (via sysfs) and then trying to
remove that memory. This doesn't work because offlining the already
offline memory does not succeed and the DLPAR code then fails the
DLPAR remove operation.
The fix for both scenarios is to check the device.offline status
before making the calls to device_online() or device_offline().
kernel BUG at mm/memory_hotplug.c:1936!
...
NIP [c0000000002ca428] .remove_memory+0xb8/0xc0
LR [c0000000002ca3cc] .remove_memory+0x5c/0xc0
Call Trace:
.remove_memory+0x5c/0xc0 (unreliable)
.dlpar_add_lmb+0x384/0x400
.dlpar_memory+0x5dc/0xca0
.handle_dlpar_errorlog+0x74/0xe0
.pseries_hp_work_fn+0x2c/0x90
.process_one_work+0x17c/0x460
.worker_thread+0x88/0x500
.kthread+0x15c/0x1a0
.ret_from_kernel_thread+0x58/0xc0
Fixes: 943db62c316c ("powerpc/pseries: Revert 'Auto-online hotplugged memo
Signed-off-by: Nathan Fontenot <nf...@linux.vnet.ibm.com>
[mpe: Use bool, add explicit rc=0 case, change log typos & formatting]
Signed-off-by: Michael Ellerman <m...@ellerman.id.au>
diff --git a/arch/powerpc/platforms/pseries/hotplug-memory.c b/arch/powerpc/pl
index ca9b2f4..9e3afd2 100644
--- a/arch/powerpc/platforms/pseries/hotplug-memory.c
+++ b/arch/powerpc/platforms/pseries/hotplug-memory.c
@@ -336,7 +336,38 @@ static struct memory_block *lmb_to_memblock(struct of_drc
return mem_block;
}
+static int dlpar_change_lmb_state(struct of_drconf_cell *lmb, bool online)
+{
+ struct memory_block *mem_block;
+ int rc;
+
+ mem_block = lmb_to_memblock(lmb);
+ if (!mem_block)
+ return -EINVAL;
+
+ if (online && mem_block->dev.offline)
+ rc = device_online(&mem_block->dev);
+ else if (!online && !mem_block->dev.offline)
+ rc = device_offline(&mem_block->dev);
+ else
+ rc = 0;
+
+ put_device(&mem_block->dev);
+
+ return rc;
+}
+
+static int dlpar_online_lmb(struct of_drconf_cell *lmb)
+{
+ return dlpar_change_lmb_state(lmb, true);
+}
+
#ifdef CONFIG_MEMORY_HOTREMOVE
+static int dlpar_offline_lmb(struct of_drconf_cell *lmb)
+{
+ return dlpar_change_lmb_state(lmb, false);
+}
+
static int pseries_remove_memblock(unsigned long base, unsigned int memblock_
{
unsigned long block_sz, start_pfn;
@@ -431,19 +462,13 @@ static int dlpar_add_lmb(struct of_drconf_cell *);
static int dlpar_remove_lmb(struct of_drconf_cell *lmb)
{
- struct memory_block *mem_block;
unsigned long block_sz;
int nid, rc;
if (!lmb_is_removable(lmb))
return -EINVAL;
- mem_block = lmb_to_memblock(lmb);
- if (!mem_block)
- return -EINVAL;
-
- rc = device_offline(&mem_block->dev);
- put_device(&mem_block->dev);
+ rc = dlpar_offline_lmb(lmb);
if (rc)
return rc;
@@ -737,20 +762,6 @@ static int dlpar_memory_remove_by_ic(u32 lmbs_to_remove,
}
#endif /* CONFIG_MEMORY_HOTREMOVE */
-static int dlpar_online_lmb(struct of_drconf_cell *lmb)
-{
- struct memory_block *mem_block;
- int rc;
-
- mem_block = lmb_to_memblock(lmb);
- if (!mem_block)
- return -EINVAL;
-
- rc = device_online(&mem_block->dev);
- put_device(&mem_block->dev);
- return rc;
-}
-
static int dlpar_add_lmb(struct of_drconf_cell *lmb)
{
unsigned long block_sz;
** Affects: linux (Ubuntu)
Importance: Undecided
Assignee: Ubuntu on IBM Power Systems Bug Triage (ubuntu-power-triage)
Status: New
** Tags: architecture-ppc64le bugnameltc-157382 severity-high
targetmilestone-inin1710
--
Ubuntu 17.10 ppc64el guest with MEMORY_HOTPLUG_DEFAULT_ONLINE=y gets a "kernel
BUG at mm/memory_hotplug.c:2185" when hotplugging LMBs with QEMU upstream
https://bugs.launchpad.net/bugs/1710922
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