Subject: Re: kvm PCI assignment & VFIO ramblings

From: aafabbri <[email-masked]>
Date: Tue, 23 Aug 2011 09:54:27 -0700

On 8/23/11 4:04 AM, "Joerg Roedel" <[email-masked]> wrote:

> On Mon, Aug 22, 2011 at 08:52:18PM -0400, aafabbri wrote:
>> You have to enforce group/iommu domain assignment whether you have the
>> existing uiommu API, or if you change it to your proposed
>> ioctl(inherit_iommu) API.
>> 
>> The only change needed to VFIO here should be to make uiommu fd assignment
>> happen on the groups instead of on device fds.  That operation fails or
>> succeeds according to the group semantics (all-or-none assignment/same
>> uiommu).
> 
> That is makes uiommu basically the same as the meta-groups, right?

Yes, functionality seems the same, thus my suggestion to keep uiommu
explicit.  Is there some need for group-groups besides defining sets of
groups which share IOMMU resources?

I do all this stuff (bringing up sets of devices which may share IOMMU
domain) dynamically from C applications.  I don't really want some static
(boot-time or sysfs fiddling) supergroup config unless there is a good
reason KVM/power needs it.

As you say in your next email, doing it all from ioctls is very easy,
programmatically.

-Aaron Fabbri