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

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Message-ID: <CABe79T5w4hb572KHUhyrwAN7+Xxnz2jF9OGLpfTmAdHuLuO2Fw@mail.gmail.com>
Date:   Wed, 1 May 2019 20:52:58 +0530
From:   Srinath Mannam <srinath.mannam@...adcom.com>
To:     Bjorn Helgaas <helgaas@...nel.org>
Cc:     Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Joerg Roedel <joro@...tes.org>,
        Robin Murphy <robin.murphy@....com>, poza@...eaurora.org,
        Ray Jui <rjui@...adcom.com>,
        BCM Kernel Feedback <bcm-kernel-feedback-list@...adcom.com>,
        linux-pci@...r.kernel.org, iommu@...ts.linux-foundation.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4 0/3] PCIe Host request to reserve IOVA

Hi Bjorn,

Thank you. Please find my reply below.

On Wed, May 1, 2019 at 6:25 PM Bjorn Helgaas <helgaas@...nel.org> wrote:
>
> 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
I will send new patch with change in commit message as per your comment.
"s/bridge This list/bridge, this list/"

>
> 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).
>
I will send patch, for "DMA_BIT_MASK(sizeof(dma_addr_t) *
BITS_PER_BYTE)" change to "~(dma_addr_t)0".
> Eric reviewed the third (and pointed out a typo).
I will send a new patch to address this 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.
I am sorry to miss to respond..
In NO-IOMMU case, All inbound addresses allocated from dma APIs are
physical addresses of DDR.
All DDR physical addresses are fall inside given dma-ranges. so that,
without IOMMU_SUPPORT, will not
be any issue.

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