linux-kernel - RE: [PATCH 5/5 v11] iommu/fsl: Freescale PAMU driver and iommu implementation.

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Message-ID: <C5ECD7A89D1DC44195F34B25E172658D45883B@039-SN2MPN1-013.039d.mgd.msft.net>
Date:	Thu, 4 Apr 2013 13:00:23 +0000
From:	Sethi Varun-B16395 <B16395@...escale.com>
To:	Alex Williamson <alex.williamson@...hat.com>,
	Joerg Roedel <joro@...tes.org>
CC:	Yoder Stuart-B08248 <B08248@...escale.com>,
	Wood Scott-B07421 <B07421@...escale.com>,
	"iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>,
	"linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"galak@...nel.crashing.org" <galak@...nel.crashing.org>,
	"benh@...nel.crashing.org" <benh@...nel.crashing.org>
Subject: RE: [PATCH 5/5 v11] iommu/fsl: Freescale PAMU driver and iommu
 implementation.



> -----Original Message-----
> From: Alex Williamson [mailto:alex.williamson@...hat.com]
> Sent: Wednesday, April 03, 2013 11:32 PM
> To: Joerg Roedel
> Cc: Sethi Varun-B16395; Yoder Stuart-B08248; Wood Scott-B07421;
> iommu@...ts.linux-foundation.org; linuxppc-dev@...ts.ozlabs.org; linux-
> kernel@...r.kernel.org; galak@...nel.crashing.org;
> benh@...nel.crashing.org
> Subject: Re: [PATCH 5/5 v11] iommu/fsl: Freescale PAMU driver and iommu
> implementation.
> 
> On Tue, 2013-04-02 at 18:18 +0200, Joerg Roedel wrote:
> > Cc'ing Alex Williamson
> >
> > Alex, can you please review the iommu-group part of this patch?
> 
> Sure, it looks pretty reasonable.  AIUI, all PCI devices are below some
> kind of host bridge that is either new and supports partitioning or old
> and doesn't.  I don't know if that's a visibility or isolation
> requirement, perhaps PCI ACS-ish.  In the new host bridge case, each
> device gets a group.  This seems not to have any quirks for multifunction
> devices though.  On AMD and Intel IOMMUs we test multifunction device ACS
> support to determine whether all the functions should be in the same
> group.  Is there any reason to trust multifunction devices on PAMU?
> 
[Sethi Varun-B16395] In the case where we can partition endpoints we can distinguish transactions based on the bus,device,function number combination. This support is available in the PCIe controller (host bridge).

> I also find it curious what happens to the iommu group of the host
> bridge.  In the partitionable case the host bridge group is removed, in
> the non-partitionable case the host bridge group becomes the group for
> the children, removing the host bridge.  It's unique to PAMU so far that
> these host bridges are even in an iommu group (x86 only adds pci
> devices), but I don't see it as necessarily wrong leaving it in either
> scenario.  Does it solve some problem to remove them from the groups?
> Thanks,
[Sethi Varun-B16395] The PCIe controller isn't a partitionable entity, it would always be owned by the host.

-Varun