Re: [PATCH v3 15/16] iommu: introduce page response function

[Jean-Philippe Brucker]

On 07/12/17 21:56, Alex Williamson wrote:
[...]
>> Seems like VFIO should enforce this quota, since the IOMMU layer doesn't
>> know which device is assigned to which VM. If it's the IOMMU that enforces
>> quotas per device and a VM has 15 devices assigned, then the guest can
>> still DoS the IOMMU.
> 
> VFIO also doesn't know about VMs.  We know that devices attached to the
> same container are probably used by the same user, but once we add
> viommu, each device(group) uses its own container and we have no idea
> they're associated.  So, no to VM based accounting, and it seems like
> an IOMMU problem, X number of outstanding requests per device.  Thanks,

Ok. It's not clear anyway how the architecture and implementations expect
us to virtualize stall, I'll try to clarify it.

Thanks,
Jean