linux-kernel - Re: [PATCH v4 0/3] PCIe Host request to reserve IOVA

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Message-ID: <20190501125530.GA15590@google.com>
Date:   Wed, 1 May 2019 07:55:31 -0500
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Lorenzo Pieralisi <lorenzo.pieralisi@....com>
Cc:     Srinath Mannam <srinath.mannam@...adcom.com>,
        Joerg Roedel <joro@...tes.org>,
        Robin Murphy <robin.murphy@....com>, poza@...eaurora.org,
        Ray Jui <rjui@...adcom.com>,
        bcm-kernel-feedback-list@...adcom.com, linux-pci@...r.kernel.org,
        iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 0/3] PCIe Host request to reserve IOVA

On Wed, May 01, 2019 at 12:30:38PM +0100, Lorenzo Pieralisi wrote:
> On Fri, Apr 12, 2019 at 08:43:32AM +0530, Srinath Mannam wrote:
> > Few SOCs have limitation that their PCIe host can't allow few inbound
> > address ranges. Allowed inbound address ranges are listed in dma-ranges
> > DT property and this address ranges are required to do IOVA mapping.
> > Remaining address ranges have to be reserved in IOVA mapping.
> > 
> > PCIe Host driver of those SOCs has to list resource entries of allowed
> > address ranges given in dma-ranges DT property in sorted order. This
> > sorted list of resources will be processed and reserve IOVA address for
> > inaccessible address holes while initializing IOMMU domain.
> > 
> > This patch set is based on Linux-5.0-rc2.
> > 
> > Changes from v3:
> >   - Addressed Robin Murphy review comments.
> >     - pcie-iproc: parse dma-ranges and make sorted resource list.
> >     - dma-iommu: process list and reserve gaps between entries
> > 
> > Changes from v2:
> >   - Patch set rebased to Linux-5.0-rc2
> > 
> > Changes from v1:
> >   - Addressed Oza review comments.
> > 
> > Srinath Mannam (3):
> >   PCI: Add dma_ranges window list
> >   iommu/dma: Reserve IOVA for PCIe inaccessible DMA address
> >   PCI: iproc: Add sorted dma ranges resource entries to host bridge
> > 
> >  drivers/iommu/dma-iommu.c           | 19 ++++++++++++++++
> >  drivers/pci/controller/pcie-iproc.c | 44 ++++++++++++++++++++++++++++++++++++-
> >  drivers/pci/probe.c                 |  3 +++
> >  include/linux/pci.h                 |  1 +
> >  4 files changed, 66 insertions(+), 1 deletion(-)
> 
> Bjorn, Joerg,
> 
> this series should not affect anything in the mainline other than its
> consumer (ie patch 3); if that's the case should we consider it for v5.2
> and if yes how are we going to merge it ?

I acked the first one

Robin reviewed the second
(https://lore.kernel.org/lkml/e6c812d6-0cad-4cfd-defd-d7ec427a6538@arm.com)
(though I do agree with his comment about DMA_BIT_MASK()), Joerg was OK
with it if Robin was
(https://lore.kernel.org/lkml/20190423145721.GH29810@8bytes.org).

Eric reviewed the third (and pointed out a typo).

My Kconfiggery never got fully answered -- it looks to me as though it's
possible to build pcie-iproc without the DMA hole support, and I thought
the whole point of this series was to deal with those holes
(https://lore.kernel.org/lkml/20190418234241.GF126710@google.com).  I would
have expected something like making pcie-iproc depend on IOMMU_SUPPORT.
But Srinath didn't respond to that, so maybe it's not an issue and it
should only affect pcie-iproc anyway.

So bottom line, I'm fine with merging it for v5.2.  Do you want to merge
it, Lorenzo, or ...?

Bjorn