[RFC v6 00/10] vfio-pci: Allow to mmap sub-page MMIO BARs and MSI-X table
From: Yongji Xie
Date: Mon Apr 18 2016 - 06:55:20 EST
Current vfio-pci implementation disallows to mmap
sub-page(size < PAGE_SIZE) MMIO BARs and MSI-X table. This is because
sub-page BARs' mmio page may be shared with other BARs and MSI-X table
should not be accessed directly from the guest for security reasons.
But it will easily cause some performance issues for mmio accesses
in guest when vfio passthrough sub-page BARs or BARs containing MSI-X
table on PPC64 platform. This is because PAGE_SIZE is 64KB by default
on PPC64 platform and the big page may easily hit the sub-page MMIO
BARs' unmmapping and cause the unmmaping of the mmio page which
MSI-X table locate in, which lead to mmio emulation in host.
For sub-page MMIO BARs' unmmapping, this patchset modifies
resource_alignment kernel parameter to enforce the alignment of all
MMIO BARs to be at least PAGE_SZIE so that sub-page BAR's mmio page
will not be shared with other BARs. And we also add shadow resources
to the vfio device and put them into the holes of mmio pages in case
that hot-add device's BARs are assigned into the holes. Then we can
mmap sub-page MMIO BARs safely.
For MSI-X table's unmmapping, we think MSI-X table is safe to access
directly from userspace if hardware supports the capability of
interrupt remapping which can ensure that a given pci device can
only shoot the MSIs assigned for it. But the implenmentation of
this capability is arch-independent. To have a universal way
to test this capability on PCI side for different archs, we introduce
a new bus_flags PCI_BUS_FLAGS_MSI_REMAP.
With this patchset applied, we can get almost 100% improvement on
performance for small block 4k random read when we passthrough a FC
HBA containing sub-page BARs and MSI-X BARs to guest on PPC64 in
The patch 8 are based on the proposed patchset.
- Rebase on vfio/next with patchset applied
- Fix some bugs of v5
- Add three patches to make PCI_BUS_FLAGS_MSI_REMAP as
a universal flag to test IRQ remapping
- Rebase on vfio/next
- Change the order of patch 1,2,3
- Move the warning "resource_alignment will not work with
PCI_PROBE_ONLY set" from documentation to kernel log
- Remove IORESOURCE_WINDOW
- Add description for parameter "resize"
- Add PCIBIOS_MIN_ALIGNMENT to force all MMIO BARs to
get minimum alignment
- Add shadow resources to make sure sub-page BAR's mmio
page will not be shared with hot-add BARs.
- Add a new bit to pci_bus_flags to indicate the capbility
of interrupt remapping on PPC64
- Remove IOMMU_CAP_INTR_REMAP on PPC64
- Add a property msi_remap to vfio_pci_device to cache the
capbility of interrupt remapping
- Rebase on v4.5-rc6 with patchset applied.
- Remove resource_page_aligned kernel parameter
- Fix some problems with resource_alignment kernel parameter
- Modify resource_alignment kernel parameter to support multiple
- Remove host bridge attribute: msi_filtered
- Use IOMMU_CAP_INTR_REMAP to check if MSI-X table can be mmapped
- Add IOMMU_CAP_INTR_REMAP for IODA host bridge on PPC64 platform
- Rebase on new linux kernel mainline with the patchset applied.
- Add a function to check whether PCI BARs'mmio page is shared with
- Add a host bridge attribute to indicate PCI host bridge support
filtering of MSIs.
- Use the new host bridge attribute to check if MSI-X table can
be mmapped instead of CONFIG_EEH.
- Remove Kconfig option VFIO_PCI_MMAP_MSIX
- Rebase on v4.4-rc6 with the patchset applied.
- Use kernel parameter to enforce all MMIO BARs to be page aligned
on PCI core code instead of doing it on PPC64 arch code.
- Remove flags: VFIO_DEVICE_FLAGS_PCI_PAGE_ALIGNED
Yongji Xie (10):
PCI: Ignore resource_alignment if PCI_PROBE_ONLY was set
PCI: Do not Use IORESOURCE_STARTALIGN to identify bridge resources
PCI: Add a new option for resource_alignment to reassign alignment
PCI: Add support for enforcing all MMIO BARs to be page aligned
vfio-pci: Allow to mmap sub-page MMIO BARs if the mmio page is exclusive
PCI: Add a new PCI_BUS_FLAGS_MSI_REMAP flag
iommu: Set PCI_BUS_FLAGS_MSI_REMAP if IOMMU have capability of IRQ remapping
PCI: Set PCI_BUS_FLAGS_MSI_REMAP if MSI controller supports IRQ remapping
pci-ioda: Set PCI_BUS_FLAGS_MSI_REMAP for IODA host bridge
vfio-pci: Allow to mmap MSI-X table if interrupt remapping is supported
Documentation/kernel-parameters.txt | 7 +-
arch/powerpc/include/asm/pci.h | 2 +
arch/powerpc/platforms/powernv/pci-ioda.c | 8 +++
drivers/iommu/iommu.c | 15 +++++
drivers/pci/msi.c | 12 ++++
drivers/pci/pci.c | 105 +++++++++++++++++++++++------
drivers/pci/probe.c | 3 +
drivers/pci/setup-bus.c | 9 ++-
drivers/vfio/pci/vfio_pci.c | 65 +++++++++++++++---
drivers/vfio/pci/vfio_pci_private.h | 8 +++
drivers/vfio/pci/vfio_pci_rdwr.c | 3 +-
include/linux/msi.h | 6 +-
include/linux/pci.h | 1 +
13 files changed, 208 insertions(+), 36 deletions(-)