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Date: Tue, 27 Apr 2010 08:28:15 -0600
Message-ID: <z2o8286e4ee1004270728z93d41deag9909be653873faa9@mail.gmail.com>
From: Cam Macdonell <cam@cs.ualberta.ca>
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Subject: [Qemu-devel] Re: [PATCH 10/10] introduce qemu_ram_map
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To: Anthony Liguori <anthony@codemonkey.ws>
Cc: Anthony Liguori <aliguori@us.ibm.com>, Marcelo Tosatti <mtosatti@redhat.com>, qemu-devel@nongnu.org, kvm@vger.kernel.org

On Mon, Apr 26, 2010 at 12:54 PM, Anthony Liguori <anthony@codemonkey.ws> w=
rote:
> On 04/26/2010 01:49 PM, Marcelo Tosatti wrote:
>>
>> On Mon, Apr 26, 2010 at 01:27:30PM -0500, Anthony Liguori wrote:
>>
>>>
>>> On 04/26/2010 12:59 PM, Marcelo Tosatti wrote:
>>>
>>>>
>>>> Which allows drivers to register an mmaped region into ram block
>>>> mappings.
>>>> To be used by device assignment driver.
>>>>
>>>
>>> This doesn't make much sense to me.
>>>
>>> Do you use this like:
>>>
>>> qemu_ram_map(64k, ptr);
>>> assert(qemu_ram_alloc(64k) =3D=3D ptr);
>>>
>>
>> No. hw/device-assignment.c in qemu-kvm mmaps
>> /sys/bus/pci/devices/x:y:z/resourcen (the PCI devices memory regions) to
>> the guest.
>>
>
> I understand, but how do you use qemu_ram_map() to actually map that memo=
ry
> to a given PCI device resource? =A0I assume you rely on it getting put on=
 the
> front of the list so that the next qemu_ram_alloc() will be at that
> location.

In my shared memory patch, I passed the offset returned from
qemu_ram_mmap to cpu_register_physical_memory from within the map
function passed to pci_register_bar.  Could the same not be done?  Is
there something incorrect with this approach?

>
> Regards,
>
> Anthony Liguori
>
>>> If so, I think this is not the best API. =A0I'd rather see
>>> qemu_ram_map() register a symbolic name for the region and for there
>>> to be a qemu_ram_alloc() variant that allocated by name.
>>>
>>> Regards,
>>>
>>> Anthony Liguori
>>>
>>>
>
>