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SubjectRe: [PATCH v4 0/3] PCIe Host request to reserve IOVA
Hi Bjorn,

Thanks for review. Please find my reply below.

On Sat, Apr 13, 2019 at 4:04 AM Bjorn Helgaas <helgaas@kernel.org> 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.
>
> If I understand correctly, devices below these PCIe host bridges can
> DMA only to the listed address ranges, and you prevent devices from
> doing DMA to the holes between the listed ranges by reserving the
> holes in dma-iommu.
Yes, devices below these PCIe host bridges can DMA only to the listed
address ranges,
and this patch prevents to allocate DMA(IOVA) addresses in the holes
of listed ranges.
>
> Apparently there's something that makes sure driver dma_map_*() always
> goes through dma-iommu? I traced as far as seeing that dma-iommu
> depends on CONFIG_IOMMU_DMA, and that arm64 selects CONFIG_IOMMU_DMA
> if CONFIG_IOMMU_SUPPORT, but then the trail got cold. I didn't see
> what selects CONFIG_IOMMU_SUPPORT.
IOMMU_SUPPORT depends on MMU.
>
> This does look like what Robin suggested, as far as I can tell.
> Hopefully he'll take a look and give his reviewed-by. Thanks for
> persevering!
Thank you.

Regards,
Srinath.
>
> > 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(-)
> >
> > --
> > 2.7.4
> >

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