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Re: [Qemu-devel] Re: [RFC PATCH 4/7] ide: IOMMU support


From: Anthony Liguori
Subject: Re: [Qemu-devel] Re: [RFC PATCH 4/7] ide: IOMMU support
Date: Thu, 15 Jul 2010 07:45:06 -0500
User-agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1.10) Gecko/20100528 Lightning/1.0b1 Thunderbird/3.0.5

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





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