On Thu, Dec 20, 2018 at 05:59:46PM +0000, Jean-Philippe Brucker wrote: > On 19/12/2018 23:09, Michael S. Tsirkin wrote: > > On Thu, Dec 13, 2018 at 12:50:29PM +0000, Jean-Philippe Brucker wrote: > >>>> [3] git://linux-arm.org/linux-jpb.git virtio-iommu/v0.9.1 > >>>> git://linux-arm.org/kvmtool-jpb.git virtio-iommu/v0.9 > >>> > >>> Unfortunatly gitweb seems to be broken on linux-arm.org. What is missing > >>> in this patch-set to make this work on x86? > >> > >> You should be able to access it here: > >> http://www.linux-arm.org/git?p=linux-jpb.git;a=shortlog;h=refs/heads/virtio-iommu/devel > >> > >> That branch contains missing bits for x86 support: > >> > >> * ACPI support. We have the code but it's waiting for an IORT spec > >> update, to reserve the IORT node ID. I expect it to take a while, given > >> that I'm alone requesting a change for something that's not upstream or > >> in hardware. > > > > Frankly I think you should take a hard look at just getting the data > > needed from the PCI device itself. You don't need to depend on virtio, > > it can be a small driver that gets you that data from the device config > > space and then just goes away. > > > > If you want help with writing such a small driver let me know. > > > > If there's an advantage to virtio-iommu then that would be its > > portability, and it all goes out of the window because > > of dependencies on ACPI and DT and OF and the rest of the zoo. > > But the portable solutions are ACPI and DT. > > Describing the DMA dependency through a device would require the guest > to probe the device before all others. How do we communicate this? > * pass a kernel parameter saying something like "probe_first=00:01.0" > * make sure that the PCI root complex is probed before any other > platform device (since the IOMMU can manage DMA of platform devices). My idea was to just find and probe the specific device. > * change DT, ACPI and PCI core code to handle this probe_first kernel > parameter. > > Better go with something standard, that any OS and hypervisor knows how > to use, and that other IOMMU devices already use. > > >> * DMA ops for x86 (see "HACK" commit). I'd like to use dma-iommu but I'm > >> not sure how to implement the glue that sets dma_ops properly. > >> > >> Thanks, > >> Jean > > > > OK so IIUC you are looking into Christoph's suggestions to fix that up? > > Eventually yes. I'll give it a try next year, once the dma-iommu changes > are on the list. It's not a priority for me, given that x86 already has > a pvIOMMU with VT-d, and that Arm still needs one. Well that's a kind of a weak usecase, isn't it? Can we just build VTD on ARM? diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig index d9a25715650e..009fa98e9363 100644 --- a/drivers/iommu/Kconfig +++ b/drivers/iommu/Kconfig @@ -174,7 +174,7 @@ config DMAR_TABLE config INTEL_IOMMU bool "Support for Intel IOMMU using DMA Remapping Devices" - depends on PCI_MSI && ACPI && (X86 || IA64_GENERIC) + depends on PCI_MSI && ACPI && (X86 || IA64_GENERIC || ARM) select IOMMU_API select IOMMU_IOVA select NEED_DMA_MAP_STATE didn't try this one ... > It shouldn't block > this series. > > > There's still a bit of time left before the merge window, > > maybe you can make above changes. > > I'll wait to see if Joerg has other concerns about the design or the > code, and resend in January. I think that IOMMU driver changes should go > through his tree. > > Thanks, > Jean Sorry which changes do you mean? -- MST
