Subject: Re: kvm PCI assignment & VFIO ramblings

From: Joerg Roedel <[email-masked]>
Date: Tue, 23 Aug 2011 13:09:42 +0200

On Tue, Aug 23, 2011 at 02:54:43AM -0400, Benjamin Herrenschmidt wrote:
> Possibly, the question that interest me the most is what interface will
> KVM end up using. I'm also not terribly fan with the (perceived)
> discrepancy between using uiommu to create groups but using the group fd
> to actually do the mappings, at least if that is still the plan.
> 
> If the separate uiommu interface is kept, then anything that wants to be
> able to benefit from the ability to put multiple devices (or existing
> groups) into such a "meta group" would need to be explicitly modified to
> deal with the uiommu APIs.
> 
> I tend to prefer such "meta groups" as being something you create
> statically using a configuration interface, either via sysfs, netlink or
> ioctl's to a "control" vfio device driven by a simple command line tool
> (which can have the configuration stored in /etc and re-apply it at
> boot).

Hmm, I don't think that these groups are static for the systems
run-time. They only exist for the lifetime of a guest per default, at
least on x86. Thats why I prefer to do this grouping using VFIO and not
some sysfs interface (which would be the third interface beside the
ioctls and netlink a VFIO user needs to be aware of). Doing this in the
ioctl interface just makes things easier.

	Joerg

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