On 23/06/17 07:11, Alex Williamson wrote: > On Thu, 15 Jun 2017 15:48:42 +1000 > Alexey Kardashevskiy <aik@xxxxxxxxx> wrote: > >> Here is a patchset which Yongji was working on before >> leaving IBM LTC. Since we still want to have this functionality >> in the kernel (DPDK is the first user), here is a rebase >> on the current upstream. >> >> >> Current vfio-pci implementation disallows to mmap the page >> containing MSI-X table in case that users can write directly >> to MSI-X table and generate an incorrect MSIs. >> >> However, this will cause some performance issue when there >> are some critical device registers in the same page as the >> MSI-X table. We have to handle the mmio access to these >> registers in QEMU emulation rather than in guest. >> >> To solve this issue, this series allows to expose MSI-X table >> to userspace when hardware enables the capability of interrupt >> remapping which can ensure that a given PCI device can only >> shoot the MSIs assigned for it. And we introduce a new bus_flags >> PCI_BUS_FLAGS_MSI_REMAP to test this capability on PCI side >> for different archs. >> >> The patch 3 are based on the proposed patchset[1]. >> >> Changelog >> v3: >> - rebased on the current upstream > > There's something not forthcoming here, the last version I see from > Yongji is this one: > > https://lists.linuxfoundation.org/pipermail/iommu/2016-June/017245.html > > Which was a 6-patch series where patches 2-4 tried to apply > PCI_BUS_FLAGS_MSI_REMAP for cases that supported other platforms. That > doesn't exist here, so it's not simply a rebase. Patch 1/ seems to > equate this new flag to the IOMMU capability IOMMU_CAP_INTR_REMAP, but > nothing is done here to match them together. That patch also mentions > the work Eric has done for similar features on ARM, but again those > patches are dropped. It seems like an incomplete feature now. Thanks, Thanks! I suspected this is not the latest but could not find anything better than we use internally for tests, and I could not reach Yongji for comments whether this was the latest update. As I am reading the patches, I notice that the "msi remap" term is used all over the place. While this remapping capability may be the case for x86/arm (and therefore the IOMMU_CAP_INTR_REMAP flag makes sense), powernv does not do remapping but provides hardware isolation. When we are allowing MSIX BAR mapping to the userspace - the isolation is what we really care about. Will it make sense to rename PCI_BUS_FLAGS_MSI_REMAP to PCI_BUS_FLAGS_MSI_ISOLATED ? Another thing - the patchset enables PCI_BUS_FLAGS_MSI_REMAP when IOMMU just advertises IOMMU_CAP_INTR_REMAP, not necessarily uses it, should the patchset actually look at something like irq_remapping_enabled in drivers/iommu/amd_iommu.c instead? > > Alex > >> v2: >> - Make the commit log more clear >> - Replace pci_bus_check_msi_remapping() with pci_bus_msi_isolated() >> so that we could clearly know what the function does >> - Set PCI_BUS_FLAGS_MSI_REMAP in pci_create_root_bus() instead >> of iommu_bus_notifier() >> - Reserve VFIO_REGION_INFO_FLAG_CAPS when we allow to mmap MSI-X >> table so that we can know whether we allow to mmap MSI-X table >> in QEMU >> >> [1] https://www.mail-archive.com/linux-kernel%40vger.kernel.org/msg1138820.html >> >> >> This is based on sha1 >> 63f700aab4c1 Linus Torvalds "Merge tag 'xtensa-20170612' of git://github.com/jcmvbkbc/linux-xtensa". >> >> Please comment. Thanks. >> >> >> >> Yongji Xie (3): >> PCI: Add a new PCI_BUS_FLAGS_MSI_REMAP flag >> pci-ioda: Set PCI_BUS_FLAGS_MSI_REMAP for IODA host bridge >> vfio-pci: Allow to expose MSI-X table to userspace if interrupt >> remapping is enabled >> >> include/linux/pci.h | 1 + >> arch/powerpc/platforms/powernv/pci-ioda.c | 8 ++++++++ >> drivers/vfio/pci/vfio_pci.c | 18 +++++++++++++++--- >> drivers/vfio/pci/vfio_pci_rdwr.c | 3 ++- >> 4 files changed, 26 insertions(+), 4 deletions(-) >> > -- Alexey
