ACPI / memhotplug: add parameter to disable memory hotplug

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

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

  [<ffffffff815a1e9f>] __add_pages+0xaf/0x240
  [<ffffffff81047359>] arch_add_memory+0x59/0xd0
  [<ffffffff815a21d9>] add_memory+0xb9/0x1b0
  [<ffffffff81333b9c>] acpi_memory_device_add+0x18d/0x26d
  [<ffffffff81309a01>] acpi_bus_device_attach+0x7d/0xcd
  [<ffffffff8132379d>] acpi_ns_walk_namespace+0xc8/0x17f
  [<ffffffff81309984>] ? acpi_bus_type_and_status+0x90/0x90
  [<ffffffff81309984>] ? acpi_bus_type_and_status+0x90/0x90
  [<ffffffff81323c8c>] acpi_walk_namespace+0x95/0xc5
  [<ffffffff8130a6d6>] acpi_bus_scan+0x8b/0x9d
  [<ffffffff81a2019a>] acpi_scan_init+0x63/0x160
  [<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 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.
Signed-off-by: Prarit Bhargava <prarit@redhat.com>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Toshi Kani <toshi.kani@hp.com>
Acked-by: David Rientjes <rientjes@google.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

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 kdump
+			   kernels.
+
 	add_efi_memmap	[EFI; X86] Include EFI memory map in
 			kernel's map of available physical RAM.
 

drivers/acpi/acpi_memhotplug.c

@@ -360,7 +360,19 @@ static void acpi_memory_device_remove(struct acpi_device *device)
 	acpi_memory_device_free(mem_device);
 }
 
+static bool __initdata acpi_no_memhotplug;
+
 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)
+{
+	acpi_no_memhotplug = true;
+	return 1;
+}
+__setup("acpi_no_memhotplug", disable_acpi_memory_hotplug);