Re: [Qemu-devel] [PATCH v6 5/7] vfio: Introduce VFIO address spaces

[Alexey Kardashevskiy]

On 05/23/2014 09:28 PM, Alexander Graf wrote:
> 
> On 23.05.14 06:59, Alexey Kardashevskiy wrote:
>> From: David Gibson <address@hidden>
>>
>> The only model so far supported for VFIO passthrough devices is the model
>> usually used on x86, where all of the guest's RAM is mapped into the
>> (host) IOMMU and there is no IOMMU visible in the guest.
>>
>> This patch begins to relax this model, introducing the notion of a
>> VFIOAddressSpace.  This represents a logical DMA address space which will
>> be visible to one or more VFIO devices by appropriate mapping in the (host)
>> IOMMU.  Thus the currently global list of containers becomes local to
>> a VFIOAddressSpace, and we verify that we don't attempt to add a VFIO
>> group to multiple address spaces.
>>
>> For now, only one VFIOAddressSpace is created and used, corresponding to
>> main system memory, that will change in future patches.
>>
>> Signed-off-by: David Gibson <address@hidden>
>> Signed-off-by: Alexey Kardashevskiy <address@hidden>
> 
> Don't we already have a DMA address space in the PCI bus? We could just use
> that one instead, no?

I do not know about x86, but for spapr that VFIOAddressSpace is nothing but
wrapper around an AddressSpace from the SPAPR PHB.


-- 
Alexey