[PATCH] x86, acpi memory hotplug, add parameter to disable memory hotplug

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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 (which is a
completely new kernel boot).  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 can also be reproduced with a "regular" kernel by using the
memmap=exactmap and mem=X parameters on the main kernel and booting.

This patchset resolves the problem by adding a kernel parameter,
acpi_no_memhotplug, to disable ACPI memory hotplug.  ACPI memory hotplug
should also be disabled by default when a user specified a memory mapping with
"memmap=exactmap" or "mem=X".

Signed-off-by: Prarit Bhargava <prarit@xxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: "H. Peter Anvin" <hpa@xxxxxxxxx>
Cc: x86@xxxxxxxxxx
Cc: Len Brown <lenb@xxxxxxxxxx>
Cc: "Rafael J. Wysocki" <rjw@xxxxxxxxxxxxx>
Cc: Linn Crosetto <linn@xxxxxx>
Cc: Pekka Enberg <penberg@xxxxxxxxxx>
Cc: Yinghai Lu <yinghai@xxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Toshi Kani <toshi.kani@xxxxxx>
Cc: Tang Chen <tangchen@xxxxxxxxxxxxxx>
Cc: Wen Congyang <wency@xxxxxxxxxxxxxx>
Cc: Vivek Goyal <vgoyal@xxxxxxxxxx>
Cc: kosaki.motohiro@xxxxxxxxx
Cc: dyoung@xxxxxxxxxx
Cc: Toshi Kani <toshi.kani@xxxxxx>
Cc: linux-acpi@xxxxxxxxxxxxxxx
Cc: linux-mm@xxxxxxxxx
---
 Documentation/kernel-parameters.txt |    3 +++
 arch/x86/kernel/e820.c              |    4 ++++
 drivers/acpi/acpi_memhotplug.c      |   18 ++++++++++++++++++
 include/linux/memory_hotplug.h      |    9 +++++++++
 4 files changed, 34 insertions(+)

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index b9e9bd8..ea93f75 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -343,6 +343,9 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
 			no: ACPI OperationRegions are not marked as reserved,
 			no further checks are performed.
 
+	acpi_no_memhotplug [ACPI] Disable memory hotplug.  Useful for kexec
+			   and kdump kernels.
+
 	add_efi_memmap	[EFI; X86] Include EFI memory map in
 			kernel's map of available physical RAM.
 
diff --git a/arch/x86/kernel/e820.c b/arch/x86/kernel/e820.c
index 174da5f..3c431fe 100644
--- a/arch/x86/kernel/e820.c
+++ b/arch/x86/kernel/e820.c
@@ -20,6 +20,7 @@
 #include <linux/firmware-map.h>
 #include <linux/memblock.h>
 #include <linux/sort.h>
+#include <linux/memory_hotplug.h>
 
 #include <asm/e820.h>
 #include <asm/proto.h>
@@ -834,6 +835,8 @@ static int __init parse_memopt(char *p)
 		return -EINVAL;
 	e820_remove_range(mem_size, ULLONG_MAX - mem_size, E820_RAM, 1);
 
+	set_acpi_no_memhotplug();
+
 	return 0;
 }
 early_param("mem", parse_memopt);
@@ -857,6 +860,7 @@ static int __init parse_memmap_one(char *p)
 #endif
 		e820.nr_map = 0;
 		userdef = 1;
+		set_acpi_no_memhotplug();
 		return 0;
 	}
 
diff --git a/drivers/acpi/acpi_memhotplug.c b/drivers/acpi/acpi_memhotplug.c
index 551dad7..d104a7d 100644
--- a/drivers/acpi/acpi_memhotplug.c
+++ b/drivers/acpi/acpi_memhotplug.c
@@ -361,7 +361,25 @@ static void acpi_memory_device_remove(struct acpi_device *device)
 	acpi_memory_device_free(mem_device);
 }
 
+static bool acpi_no_memhotplug;
+
+void set_acpi_no_memhotplug(void)
+{
+	acpi_no_memhotplug = true;
+	pr_info_once("ACPI: Memory Hotplug Disabled\n");
+}
+
 void __init acpi_memory_hotplug_init(void)
 {
+	if (acpi_no_memhotplug)
+		return;
+
 	acpi_scan_add_handler_with_hotplug(&memory_device_handler, "memory");
 }
+
+static int __init disable_acpi_memory_hotplug(char *str)
+{
+	set_acpi_no_memhotplug();
+	return 1;
+}
+__setup("acpi_no_memhotplug", disable_acpi_memory_hotplug);
diff --git a/include/linux/memory_hotplug.h b/include/linux/memory_hotplug.h
index 4ca3d95..3cdb6e0 100644
--- a/include/linux/memory_hotplug.h
+++ b/include/linux/memory_hotplug.h
@@ -12,6 +12,15 @@ struct pglist_data;
 struct mem_section;
 struct memory_block;
 
+#ifdef CONFIG_ACPI_HOTPLUG_MEMORY
+/* set flag to disable ACPI memory hotplug */
+extern void set_acpi_no_memhotplug(void);
+#else
+static inline void set_acpi_no_memhotplug(void)
+{
+}
+#endif
+
 #ifdef CONFIG_MEMORY_HOTPLUG
 
 /*
-- 
1.7.9.3

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