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Date: Fri, 24 Oct 2008 13:37:14 -0200
From: Glauber Costa <glommer@redhat.com>
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Subject: [Qemu-devel] Re: [PATCH 01/32] use anonymous memory for kqemu.
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To: Anthony Liguori <aliguori@us.ibm.com>
Cc: Jan Kiszka <jan.kiszka@siemens.com>, jes@sgi.com, qemu-devel@nongnu.org, avi@qumranet.com, dmitry.baryshkov@siemens.com

On Thu, Oct 23, 2008 at 09:25:12AM -0500, Anthony Liguori wrote:
> Jan Kiszka wrote:
>> Anthony Liguori wrote:
>>   
>>> The idea behind this patch is that currently kqemu uses /dev/shm for
>>> memory allocations instead of anonymous memory (like the rest of 
>>> QEMU). Instead of introducing YA hook, we can just switch kqemu to 
>>> use
>>> anonymous memory and eliminate the special case.
>>>
>>> If I recall correctly, the reason for using /dev/shm was concern that
>>> get_user_pages() didn't do the right thing for anonymous memory and the
>>> use of /dev/shm was a hack around that.  However, I'm not sure that was
>>> ever the case.  Certainly, with any sufficiently modern kernel
>>> get_user_pages() does what one would expect.  KVM uses get_user_pages()
>>> on anonymous memory in roughly the same way kqemu uses it now.
>>>
>>> So I think it's safe to make the switch.  Fabrice, what do you think?
>>>     
>>
>> This hack-around, was it purely Linux-motivated? Or did/do other OSes
>> have similar issues?
>>   
>
> /dev/shm doesn't exist on anything but Linux.
>
> Regards,
I'm dropping this from the accel series until we reach a conclusion.
This is not exactly needed for the health of the series, just for kqemu
decoupling. This can proceed in parallel.

>
> Anthony Liguori
>
>> Jan
>>
>>   
>