On Fri, 23 Jun 2017 15:06:37 +1000 Alexey Kardashevskiy <aik@xxxxxxxxx> wrote: > 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 ? I don't have a strong opinion either way, so long as it's fully described what the flag indicates. > 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? Interrupt remapping being enabled is implicit in IOMMU_CAP_INTR_REMAP, neither intel or amd iommu export the capability unless enabled. Nobody cares if it's supported but not enabled. Thanks, 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(-) > >> > > > >
