[PATCH] acpi memory hotplug, add parameter to disable memory hotplug for kexec

[Prarit Bhargava <prarit@redhat.com>]

When booting a kexec/kdump kernel on a system that has specific memory hotplug
regions the boot will fail with warnings like:

[    2.939467] swapper/0: page allocation failure: order:9, mode:0x84d0
[    2.946564] CPU: 0 PID: 1 Comm: swapper/0 Not tainted
3.10.0-65.el7.x86_64 #1
[    2.954532] Hardware name: QCI QSSC-S4R/QSSC-S4R, BIOS
QSSC-S4R.QCI.01.00.S013.032920111005 03/29/2011
[    2.964926]  0000000000000000 ffff8800341bd8c8 ffffffff815bcc67
ffff8800341bd950
[    2.973224]  ffffffff8113b1a0 ffff880036339b00 0000000000000009
00000000000084d0
[    2.981523]  ffff8800341bd950 ffffffff815b87ee 0000000000000000
0000000000000200
[    2.989821] Call Trace:
[    2.992560]  [<ffffffff815bcc67>] dump_stack+0x19/0x1b
[    2.998300]  [<ffffffff8113b1a0>] warn_alloc_failed+0xf0/0x160
[    3.004817]  [<ffffffff815b87ee>] ?
__alloc_pages_direct_compact+0xac/0x196
[    3.012594]  [<ffffffff8113f14f>] __alloc_pages_nodemask+0x7ff/0xa00
[    3.019692]  [<ffffffff815b417c>] vmemmap_alloc_block+0x62/0xba
[    3.026303]  [<ffffffff815b41e9>] vmemmap_alloc_block_buf+0x15/0x3b
[    3.033302]  [<ffffffff815b1ff6>] vmemmap_populate+0xb4/0x21b
[    3.039718]  [<ffffffff815b461d>] sparse_mem_map_populate+0x27/0x35
[    3.046717]  [<ffffffff815b400f>] sparse_add_one_section+0x7a/0x185
[    3.053720]  [<ffffffff815a1e9f>] __add_pages+0xaf/0x240
[    3.059656]  [<ffffffff81047359>] arch_add_memory+0x59/0xd0
[    3.065877]  [<ffffffff815a21d9>] add_memory+0xb9/0x1b0
[    3.071713]  [<ffffffff81333b9c>] acpi_memory_device_add+0x18d/0x26d
[    3.078813]  [<ffffffff81309a01>] acpi_bus_device_attach+0x7d/0xcd
[    3.085719]  [<ffffffff8132379d>] acpi_ns_walk_namespace+0xc8/0x17f
[    3.092716]  [<ffffffff81309984>] ? acpi_bus_type_and_status+0x90/0x90
[    3.100004]  [<ffffffff81309984>] ? acpi_bus_type_and_status+0x90/0x90
[    3.107293]  [<ffffffff81323c8c>] acpi_walk_namespace+0x95/0xc5
[    3.113904]  [<ffffffff8130a6d6>] acpi_bus_scan+0x8b/0x9d
[    3.119933]  [<ffffffff81a2019a>] acpi_scan_init+0x63/0x160
[    3.126153]  [<ffffffff81a1ffb5>] acpi_init+0x25d/0x2a6
[    3.131987]  [<ffffffff81a1fd58>] ? acpi_sleep_proc_init+0x2a/0x2a
[    3.138889]  [<ffffffff810020e2>] do_one_initcall+0xe2/0x190
[    3.145210]  [<ffffffff819e20c4>] kernel_init_freeable+0x17c/0x207
[    3.152111]  [<ffffffff819e18d0>] ? do_early_param+0x88/0x88
[    3.158430]  [<ffffffff8159fea0>] ? rest_init+0x80/0x80
[    3.164264]  [<ffffffff8159feae>] kernel_init+0xe/0x180
[    3.170097]  [<ffffffff815cca2c>] ret_from_fork+0x7c/0xb0
[    3.176123]  [<ffffffff8159fea0>] ? rest_init+0x80/0x80
[    3.181956] Mem-Info:
[    3.184490] Node 0 DMA per-cpu:
[    3.188007] CPU    0: hi:    0, btch:   1 usd:   0
[    3.193353] Node 0 DMA32 per-cpu:
[    3.197060] CPU    0: hi:   42, btch:   7 usd:   0
[    3.202410] active_anon:0 inactive_anon:0 isolated_anon:0
[    3.202410]  active_file:0 inactive_file:0 isolated_file:0
[    3.202410]  unevictable:0 dirty:0 writeback:0 unstable:0
[    3.202410]  free:872 slab_reclaimable:13 slab_unreclaimable:1880
[    3.202410]  mapped:0 shmem:0 pagetables:0 bounce:0
[    3.202410]  free_cma:0

because the system has run out of memory at boot time.  This occurs
because of the following sequence in the boot:

Main kernel boots and sets E820 map.  The second kernel is booted with a
map generated by the kdump service using memmap= and memmap=exactmap.
These parameters are added to the kernel parameters of the kexec/kdump
kernel.   The kexec/kdump kernel has limited memory resources so as not
to severely impact the main kernel.

The system then panics and the kdump/kexec kernel boots.  During this boot
ACPi is initialized and the kernel (as can be seen above) traverses the
ACPI namespace and finds an entry for a memory device to be hotadded.

ie)

[    3.053720]  [<ffffffff815a1e9f>] __add_pages+0xaf/0x240
[    3.059656]  [<ffffffff81047359>] arch_add_memory+0x59/0xd0
[    3.065877]  [<ffffffff815a21d9>] add_memory+0xb9/0x1b0
[    3.071713]  [<ffffffff81333b9c>] acpi_memory_device_add+0x18d/0x26d
[    3.078813]  [<ffffffff81309a01>] acpi_bus_device_attach+0x7d/0xcd
[    3.085719]  [<ffffffff8132379d>] acpi_ns_walk_namespace+0xc8/0x17f
[    3.092716]  [<ffffffff81309984>] ? acpi_bus_type_and_status+0x90/0x90
[    3.100004]  [<ffffffff81309984>] ? acpi_bus_type_and_status+0x90/0x90
[    3.107293]  [<ffffffff81323c8c>] acpi_walk_namespace+0x95/0xc5
[    3.113904]  [<ffffffff8130a6d6>] acpi_bus_scan+0x8b/0x9d
[    3.119933]  [<ffffffff81a2019a>] acpi_scan_init+0x63/0x160
[    3.126153]  [<ffffffff81a1ffb5>] acpi_init+0x25d/0x2a6

At this point the kernel adds page table information and the the kexec/kdump
kernel runs out of memory.

This patchset resolves the problem by adding a kernel parameter,
no_memory_hotplug, to disable ACPI memory hotplug.  It can be added by default
as a parameter to the kexec/kdump kernel so the kernel boots correctly.

Signed-off-by: Prarit Bhargava <prarit@redhat.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: Len Brown <lenb@kernel.org>
Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
---
 Documentation/kernel-parameters.txt |    3 +++
 drivers/acpi/acpi_memhotplug.c      |   12 ++++++++++++
 2 files changed, 15 insertions(+)

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index b9e9bd8..df256cc 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -2117,6 +2117,9 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
 
 	nomce		[X86-32] Machine Check Exception
 
+	no_memory_hotplug [ACPI] Disable memory hotplug.  Useful for kexec
+			  and kdump kernels.
+
 	nomfgpt		[X86-32] Disable Multi-Function General Purpose
 			Timer usage (for AMD Geode machines).
 
diff --git a/drivers/acpi/acpi_memhotplug.c b/drivers/acpi/acpi_memhotplug.c
index 551dad7..cbd328f 100644
--- a/drivers/acpi/acpi_memhotplug.c
+++ b/drivers/acpi/acpi_memhotplug.c
@@ -361,7 +361,19 @@ static void acpi_memory_device_remove(struct acpi_device *device)
 	acpi_memory_device_free(mem_device);
 }
 
+static int no_memory_hotplug;
+
 void __init acpi_memory_hotplug_init(void)
 {
+	if (no_memory_hotplug)
+		return;
+
 	acpi_scan_add_handler_with_hotplug(&memory_device_handler, "memory");
 }
+
+static int __init disable_memory_hotplug(char *str)
+{
+	no_memory_hotplug = 1;
+	return 1;
+}
+__setup("no_memory_hotplug", disable_memory_hotplug);
-- 
1.7.9.3