On Tue, Apr 16, 2019 at 05:28:36PM +0530, Srinath Mannam wrote: > On Sat, Apr 13, 2019 at 4:04 AM Bjorn Helgaas <helgaas@xxxxxxxxxx> 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. Yes, I see that IOMMU_SUPPORT depends on MMU (in drivers/iommu/Kconfig). But that doesn't *select* IOMMU_SUPPORT; it only means you *can't* select it unless MMU has already been selected. I think you only get dma-iommu if you choose to select IOMMU_SUPPORT via menuconfig or whatever, and the current config rules allow you to turn that off. Maybe that's OK, I dunno. If you do turn it off, I guess we'll ignore the holes in "dma-ranges" and devices will be able to DMA to the holes. > > 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 > > >
