Date:	Mon, 5 Aug 2013 16:59:20 +0900
From:	Yasuaki Ishimatsu <isimatu.yasuaki@...fujitsu.com>
To:	Toshi Kani <toshi.kani@...com>, "Rafael J. Wysocki" <rjw@...k.pl>
CC:	<rafael.j.wysocki@...el.com>,
	<vasilis.liaskovitis@...fitbricks.com>,
	<linux-kernel@...r.kernel.org>, <linux-acpi@...r.kernel.org>,
	<tangchen@...fujitsu.com>, <wency@...fujitsu.com>
Subject: Re: Cannot hot remove a memory device

(2013/08/05 13:00), Yasuaki Ishimatsu wrote:
> (2013/08/04 9:37), Toshi Kani wrote:
>> On Sat, 2013-08-03 at 03:01 +0200, Rafael J. Wysocki wrote:
>>> On Friday, August 02, 2013 06:04:40 PM Toshi Kani wrote:
>>>> On Sat, 2013-08-03 at 01:43 +0200, Rafael J. Wysocki wrote:
>>>>> On Friday, August 02, 2013 03:46:15 PM Toshi Kani wrote:
>>>>>> On Thu, 2013-08-01 at 23:43 +0200, Rafael J. Wysocki wrote:
>>>>>>> Hi,
>>>>>>>
>>>>>>> Thanks for your report.
>>>>>>>
>>>>>>> On Thursday, August 01, 2013 05:37:21 PM Yasuaki Ishimatsu wrote:
>>>>>>>> By following commit, I cannot hot remove a memory device.
>>>>>>>>
>>>>>>>> ACPI / memhotplug: Bind removable memory blocks to ACPI device nodes
>>>>>>>> commit e2ff39400d81233374e780b133496a2296643d7d
>>>>>>>>
>>>>>>>> Details are follows:
>>>>>>>> When I add a memory device, acpi_memory_enable_device() always fails
>>>>>>>> as follows:
>>>>>>>>
>>>>>>>> ...
>>>>>>>> [ 1271.114116]  [ffffea121c400000-ffffea121c7fffff] PMD -> [ffff880813c00000-ffff880813ffffff] on node 3
>>>>>>>> [ 1271.128682]  [ffffea121c800000-ffffea121cbfffff] PMD -> [ffff880813800000-ffff880813bfffff] on node 3
>>>>>>>> [ 1271.143298]  [ffffea121cc00000-ffffea121cffffff] PMD -> [ffff880813000000-ffff8808133fffff] on node 3
>>>>>>>> [ 1271.157799]  [ffffea121d000000-ffffea121d3fffff] PMD -> [ffff880812c00000-ffff880812ffffff] on node 3
>>>>>>>> [ 1271.172341]  [ffffea121d400000-ffffea121d7fffff] PMD -> [ffff880812800000-ffff880812bfffff] on node 3
>>>>>>>> [ 1271.186872]  [ffffea121d800000-ffffea121dbfffff] PMD -> [ffff880812400000-ffff8808127fffff] on node 3
>>>>>>>> [ 1271.201481]  [ffffea121dc00000-ffffea121dffffff] PMD -> [ffff880812000000-ffff8808123fffff] on node 3
>>>>>>>> [ 1271.216041]  [ffffea121e000000-ffffea121e3fffff] PMD -> [ffff880811c00000-ffff880811ffffff] on node 3
>>>>>>>> [ 1271.230623]  [ffffea121e400000-ffffea121e7fffff] PMD -> [ffff880811800000-ffff880811bfffff] on node 3
>>>>>>>> [ 1271.245148]  [ffffea121e800000-ffffea121ebfffff] PMD -> [ffff880811400000-ffff8808117fffff] on node 3
>>>>>>>> [ 1271.259683]  [ffffea121ec00000-ffffea121effffff] PMD -> [ffff880811000000-ffff8808113fffff] on node 3
>>>>>>>> [ 1271.274194]  [ffffea121f000000-ffffea121f3fffff] PMD -> [ffff880810c00000-ffff880810ffffff] on node 3
>>>>>>>> [ 1271.288764]  [ffffea121f400000-ffffea121f7fffff] PMD -> [ffff880810800000-ffff880810bfffff] on node 3
>>>>>>
>>>>>> It appears that each memory object only has 64MB of memory.  This is
>>>>>> less than the memory block size, which is 128MB.  This means that a
>>>>>> single memory block associates with two ACPI memory device objects.
>>>>>
>>>>> That'd be bad.
>>>>>
>>>>> How did that work before if that indeed is the case?
>>>>
>>>> Well, it looks to me that it has never worked before...
>>>>
>>>>>>>> ...
>>>>>>>> [ 1271.325841] acpi PNP0C80:03: acpi_memory_enable_device() error
>>>>>>>
>>>>>>> Well, the only new way acpi_memory_enable_device() can fail after that commit
>>>>>>> is a failure in acpi_bind_memory_blocks().
>>>>>>
>>>>>> Agreed.
>>>>>>
>>>>>>> This means that either handle is NULL, which I think we can exclude, because
>>>>>>> acpi_memory_enable_device() wouldn't be called at all if that were the case, or
>>>>>>> there's a more subtle error in acpi_bind_one().
>>>>>>>
>>>>>>> One that comes to mind is that we may be calling acpi_bind_one() twice for the
>>>>>>> same memory region, in which it will trigger -EINVAL from the sanity check in
>>>>>>> there.
>>>>>>
>>>>>> I think it fails with -EINVAL at the place with dev_warn(dev, "ACPI
>>>>>> handle is already set\n").  When two ACPI memory objects associate with
>>>>>> a same memory block, the bind procedure of the 2nd ACPI memory object
>>>>>> sees that ACPI_HANDLE(dev) is already set to the 1st ACPI memory object.
>>>>>
>>>>> That sound's plausible, but I wonder how we can fix that?
>>>>>
>>>>> There's no way for a single physical device to have two different ACPI
>>>>> "companions".  It looks like the memory blocks should be 64 M each in that
>>>>> case.  Or we need to create two child devices for each memory block and
>>>>> associate each of them with an ACPI object.  That would lead to complications
>>>>> in the user space interface, though.
>>>>
>>>> Right.  Even bigger issue is that I do not think __add_pages() and
>>>> __remove_pages() can add / delete a memory chunk that is less than
>>>> 128MB.  128MB is the granularity of them.  So, we may just have to fail
>>>> this case gracefully.
>>>
>>> Sigh.
>>>
>>> BTW, why do you think they are 64 M each (it's late and I'm obviously tired)?
>>
>> Oops!  Sorry, I had confused the above messages with the one in
>> init_memory_mapping(), which shows a memory range being added, i.e. the
>> size of an ACPI memory device object.  But the above messages actually
>> came from vmemmap_populate_hugepages(), which was called during boot-up.
>> So, these messages have nothing to do with ACPI memory device objects.
>> And even worse, I do not seem to be able to count a number of zeros...
>> In the above messages, each memory range is 4MB (0x400000), not 64MB
>> (0x4000000)...  My bad. :-(
>>
>> So, while we may still need to do something for the less-than-128MB
>> issue, Yasuaki may be hitting a different one.  Let's wait for Yasuaki
>> to give us more info.
>
> acpi_bind_memory_blocks() failed with -ENOSPC.
>
> int acpi_bind_one(struct device *dev, acpi_handle handle)
> {
> ...
>      /* allocate physical node id according to physical_node_id_bitmap */
>      physical_node->node_id =
>          find_first_zero_bit(acpi_dev->physical_node_id_bitmap,
>          ACPI_MAX_PHYSICAL_NODE);
>      if (physical_node->node_id >= ACPI_MAX_PHYSICAL_NODE) {
>          retval = -ENOSPC; => here
>          goto err_free;
>      }
>
> When adding memory device, acpi_bind_memroy_blocks() calls acpi_bind_one()
> "memory device size / 128MiB" times. So ACPI_MAX_PHYSICAL_NODE need to
> be set "memory device size / 128MiB" or more. But ACPI_MAX_PHYSICAL_NODE is 32.
> So acpi_bind_memory_blocks() always failed with -ENOSPC.
>

> I'll test again after increasing ACPI_MAX_PHYSICAL_NODE to enough size.

Additional info:
When I increased ACPI_MAX_PHYSICAL_NODE to 1024 and change size of
acpi_device_physical_node->node_it into u32, I could hot remove memory
device. But even if ACPI_MAX_PHYSICAL_NODE is set to 1024, same problem
will occurs since it just supports 124GiB memory. So we need a way to change
ACPI_MAX_PHYSICAL_NODE dynamically.

Thanks,
Yasuaki Ishimatsu

>
> Thanks,
> Yasuaki Ishimatsu
>
>>
>> Thanks,
>> -Toshi
>>
>>
>>
>>
>>
>>
>>
>>
>>
>


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