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Date: Thu, 15 Jul 2010 07:45:06 -0500
From: Anthony Liguori <anthony@codemonkey.ws>
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Subject: Re: [Qemu-devel] Re: [RFC PATCH 4/7] ide: IOMMU support
References: <1279086307-9596-1-git-send-email-eduard.munteanu@linux360.ro>
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To: Joerg Roedel <joro@8bytes.org>
Cc: avi@redhat.com, Eduard - Gabriel Munteanu <eduard.munteanu@linux360.ro>, Paul Brook <paul@codesourcery.com>, kvm@vger.kernel.org, qemu-devel@nongnu.org

On 07/15/2010 04:10 AM, Joerg Roedel wrote:
> On Wed, Jul 14, 2010 at 04:29:18PM -0500, Anthony Liguori wrote:
>    
>> On 07/14/2010 03:13 PM, Paul Brook wrote:
>>      
>>> Well, ok, the function name needs fixing too.  However I think the only thing
>>> missing from the current API is that it does not provide a way to determine
>>> which device is performing the access.
>>>        
>> I agree with Paul.
>>
>> The right approach IMHO is to convert devices to use bus-specific
>> functions to access memory.  The bus specific functions should have a
>> device argument as the first parameter.
>>      
> If this means a seperate interface for device dma accesses and not fold
> that functionality into the cpu_physical_memory* interface I agree too :-)
>    

No.  PCI devices should never call cpu_physical_memory*.

PCI devices should call pci_memory*.

ISA devices should call isa_memory*.

All device memory accesses should go through their respective buses.  
There can be multiple IOMMUs at different levels of the device 
hierarchy.  If you don't provide bus-level memory access functions that 
chain through the hierarchy, it's extremely difficult to implement all 
the necessary hooks to perform the translations at different places.

Regards,

Anthony Liguori

> 		Joerg
>
>