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Date: Mon, 19 Aug 2013 13:33:01 +0200
From: Laszlo Ersek <lersek@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH v3 1/2] memory: export migration page size
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To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Peter Maydell <peter.maydell@linaro.org>, Paolo Bonzini <pbonzini@redhat.com>, QEMU Developers <qemu-devel@nongnu.org>, Gerd Hoffmann <kraxel@redhat.com>

On 08/19/13 13:18, Michael S. Tsirkin wrote:
> On Mon, Aug 19, 2013 at 01:09:36PM +0200, Laszlo Ersek wrote:
>> On 08/19/13 12:21, Peter Maydell wrote:
>>> On 19 August 2013 10:59, Laszlo Ersek <lersek@redhat.com> wrote:
>>>> On 08/13/13 00:43, Michael S. Tsirkin wrote:
>>>>> Migration code assumes that each RAM block is a multiple of target page
>>>>> size.
>>>>
>>>> Isn't that a valid assumption, considering the TARGET_PAGE_ALIGN() macro
>>>> call in qemu_ram_alloc_from_ptr() [exec.c]?
>>>
>>> That macro only makes the size we store in the ramblock data
>>> structure be a multiple of the page size -- it does nothing to ensure
>>> that the actual memory that was passed in by the caller is the
>>> right size. (It will have the right effect where qemu_ram_alloc_from_ptr
>>> is allocating the memory itself, obviously.)
>>
>> Which is the case for 2/2, see my comments there:
>>
>> memory_region_init_ram()
>>   qemu_ram_alloc()
>>     qemu_ram_alloc_from_ptr()  <---- host==NULL
>>       TARGET_PAGE_ALIGN()
>>
>> Laszlo
> 
> The issue this addresses is not the size of RAM allocated.
> The issue is the size of the MR.
> Migration code assumes the size of the MR
> is a multiple of TARGET_PAGE_SIZE.

You're right. Thanks.
Laszlo