Re: [PATCH v2] Intel IOMMU patch to reprocess RMRR info

[Joerg Roedel <joro-zLv9SwRftAIdnm+yROfE0A@public.gmane.org>]

On Fri, Sep 28, 2012 at 12:36:05PM -0400, Linda Knippers wrote:
> I can only speak to the HP servers.  We have been shipping devices
> 'for a while' that provide sensor-type data to the platform.  The
> device does DMA writes to a range of memory (the RMRR) and
> iLO does DMA reads of that data.

And what PCI request-ids are used for these DMA transfers? Are this
request-ids which belong to devices Linux handles on its own?

> If we address Alex's comments and we make a change to disallow the
> devices (non-USB devices?) with RMRRs from being assigned to
> a guest, will those changes be considered?

This is overkill in my eyes. It means that *any* device which has an
RMRR defined, whether it is on your platform or not, can not be assigned
to a guest.

I think it is better to have the RMRR regions mapped in the domains used
for DMA-API mappings and disallow to assign these devices to guests. For
devices where this breaks we can implement some quirk-solution and
disallow guest assignment. But disallowing assignment of devices with
RMRR defined in general is pure overkill.


	Joerg