linux-kernel - Re: kdump failed because of hotplug memory adding in kdump kernel

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Date:	Thu, 9 Jan 2014 11:22:02 +0800
From:	Baoquan <bhe@...hat.com>
To:	"Rafael J. Wysocki" <rjw@...ysocki.net>
Cc:	Vivek Goyal <vgoyal@...hat.com>, linux-acpi@...r.kernel.org,
	zhangyanfei@...fujitsu.com, tangchen@...fujitsu.com,
	kexec@...ts.infradead.org, linux-kernel@...r.kernel.org,
	dyoung@...hat.com
Subject: Re: kdump failed because of hotplug memory adding in kdump kernel

On 01/09/14 at 12:07am, Rafael J. Wysocki wrote:
> On Wednesday, January 08, 2014 10:58:29 AM Vivek Goyal wrote:
> > On Wed, Jan 08, 2014 at 11:26:43PM +0800, Baoquan wrote:
> > 
> > [..]
> > > [    1.592222] acpi PNP0A03:03: fail to add MMCONFIG information, can't access extended PCI configuration space under this bridge.
> > > [    1.605045] PCI host bridge to bus 0000:ff
> > > [    1.609615] pci_bus 0000:ff: root bus resource [bus ff]
> > > [    1.632117] System RAM resource [mem 0x01000000-0x7bffffff] cannot be added
> > > [    1.639892] init_memory_mapping: [mem 0x100000000-0x87fffffff]
> > > [    1.717793] swapper/0: page allocation failure: order:9, mode:0x84d0
> > > [    1.724884] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 3.10.0-59.el7.x86_64 #1
> > > [    1.732842] Hardware name: QCI QSSC-S4R/QSSC-S4R, BIOS QSSC-S4R.QCI.01.00.S001.032520101647 03/25/2010
> > > [    1.743224]  0000000000000000 ffff8800339878c8 ffffffff815b64ad ffff880033987950
> > > [    1.751513]  ffffffff8113a980 ffff88003673ab28 00000000000001fe 0000000000000001
> > > [    1.759804]  ffff880000000040 ffffffff810bc28a 0000000000000000 0000000000000200
> > > [    1.768096] Call Trace:                                                                                                                                            [348/1928]
> > > [    1.770834]  [<ffffffff815b64ad>] dump_stack+0x19/0x1b
> > > [    1.776561]  [<ffffffff8113a980>] warn_alloc_failed+0xf0/0x160
> > > [    1.783076]  [<ffffffff810bc28a>] ? on_each_cpu_mask+0x2a/0x60
> > > [    1.789581]  [<ffffffff8113e92f>] __alloc_pages_nodemask+0x7ff/0xa00
> > > [    1.796672]  [<ffffffff815ada2c>] vmemmap_alloc_block+0x62/0xba
> > > [    1.803274]  [<ffffffff815ada99>] vmemmap_alloc_block_buf+0x15/0x3b
> > > [    1.810263]  [<ffffffff815ab8a6>] vmemmap_populate+0xb4/0x21b
> > > [    1.816673]  [<ffffffff815adecd>] sparse_mem_map_populate+0x27/0x35
> > > [    1.823665]  [<ffffffff815ad8bf>] sparse_add_one_section+0x7a/0x185
> > > [    1.830659]  [<ffffffff8159b74f>] __add_pages+0xaf/0x240
> > > [    1.836588]  [<ffffffff81047359>] arch_add_memory+0x59/0xd0
> > > [    1.842804]  [<ffffffff8159ba89>] add_memory+0xb9/0x1b0
> > > [    1.848638]  [<ffffffff8132dd2c>] acpi_memory_device_add+0x18d/0x26d
> > > [    1.855728]  [<ffffffff81303b91>] acpi_bus_device_attach+0x7d/0xcd
> > > [    1.862625]  [<ffffffff8131d92d>] acpi_ns_walk_namespace+0xc8/0x17f
> > > [    1.869616]  [<ffffffff81303b14>] ? acpi_bus_type_and_status+0x90/0x90
> > > [    1.876896]  [<ffffffff81303b14>] ? acpi_bus_type_and_status+0x90/0x90
> > > [    1.884177]  [<ffffffff8131de1c>] acpi_walk_namespace+0x95/0xc5
> > > [    1.890780]  [<ffffffff81304866>] acpi_bus_scan+0x8b/0x9d
> > > [    1.896805]  [<ffffffff81a14a15>] acpi_scan_init+0x63/0x160
> > > [    1.903021]  [<ffffffff81a14830>] acpi_init+0x25d/0x2a6
> > 
> > So basically acpi thinks that some memory block is a hot plug memory
> > and tries to add it. And that consumes lots of memory and we don't have
> > that memory in second kernel.
> 
> That's not exactly the case.  What seems to happen is that there is an ACPI
> memory object in the ACPI namespace and the ACPI memory hotplug driver
> attempts to bind to it.  That driver attempts to find removable memory blocks
> associated with that object and to add them to the memory map.

Yeah, since kdump kernel will detect rsdp for legacy machine in the
first 1K of the EBDA or between E0000 and FFFFF. 

> 
> Why don't you simply append acpi=off to the kexec command line?  That should
> make the problem go away.

acpi=off doesn't work, kdump kernel hang immediately after crash is
triggered. Because acpi information is needed by kdump kernel, we can't
disable it.

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