linux-kernel - Re: Cannot hot remove a memory device

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Date:	Fri, 09 Aug 2013 00:12:22 +0200
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Toshi Kani <toshi.kani@...com>
Cc:	Yasuaki Ishimatsu <isimatu.yasuaki@...fujitsu.com>,
	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

On Thursday, August 08, 2013 11:15:20 AM Toshi Kani wrote:
> On Fri, 2013-08-02 at 18:04 -0600, 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:
>  :
> > > > 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.
> 
> FYI: I have submitted the patch blow to close this part of the issue...
> 
> https://lkml.org/lkml/2013/8/8/396

That looks good to me, but we'd still need to make it possible to have
memory blocks smaller than 128 MB ...

Rafael

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