Re: [PATCH] VFIO driver: Non-privileged user level PCI drivers

[Joerg Roedel]

On Tue, Jun 01, 2010 at 03:41:55PM +0300, Avi Kivity wrote:
> On 06/01/2010 01:46 PM, Michael S. Tsirkin wrote:

>> Main difference is that vhost works fine with unlocked
>> memory, paging it in on demand. iommu needs to unmap
>> memory when it is swapped out or relocated.
>>
> So you'd just take the memory map and not pin anything.  This way you  
> can reuse the memory map.
>
> But no, it doesn't handle the dirty bitmap, so no go.

IOMMU mapped memory can not be swapped out because we can't do demand
paging on io-page-faults with current devices. We have to pin _all_
userspace memory that is mapped into an IOMMU domain.

	Joerg

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