[Xen-devel] Re: [PATCH] AMD IOMMU: Hanlde sibling device assignment correctly

[Keir Fraser <keir.fraser@xxxxxxxxxxxxx>]

On 7/5/08 11:17, "Wei Wang2" <wei.wang2@xxxxxxx> wrote:

>> This patch seems to do more than you suggest, for example adding an extra
>> iommu hook into setup.c for dom0.
> My idea is to let dom0 construct pci device list according to
> configuration of pciback.hide=(). If a device is not hidden from dom0,
> it might be in use by dom0, then it could be dangerous to assign any of
> its siblings to other passthru domain. It is not very clean to hook into
> setup.c but I failed to find any better way to this  :(

I might be confused about how this works. Are you saying that if a domU gets
a device passed-thru that is a sibling of a dom0-driven device, then dom0
will mistakenly have its device's DMAs remapped according to the domU
mappings that get set up?

Is it possible to do this more dynamically from the tools? I.e, working out
sibling groups at the time we build a pass-thru domain, and at that point
fail the pass-thru if dom0 or any other domU is driving any device in the
group? Seems a nicer level to do the checks and raise errors. You might want
to some conflict checking in Xen, of course, just to sanity-check that noone
tries to set up two different mappings on the same HT or PCIe identifier.

Basically I think this patch is ugly. :-)

 -- Keir



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