Re: [RFC PATCH v3 0/5] vfio-pci: Allow to mmap sub-page MMIO BARs and MSI-X table on PPC64 platform
Ping... Alex, any comment? Regards, Yongji Xie On 2016/1/15 15:06, Yongji Xie wrote: 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 these 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 adds a kernel parameter for PCI resource allocator to enforce the alignment of all MMIO BARs to be at least PAGE_SZIE and make it enabled by default on PPC64 platform so that sub-page BAR's mmio page will not be shared with other BARs. Then we can mmap sub-page MMIO BARs in vfio-pci driver with this parameter enabled. For MSI-X table's unmmapping, we think MSI-X table is safe to access directly from userspace if PCI host bridge support filtering of MSIs which can ensure that a given pci device can only shoot the MSIs assigned for it. So we add a pci_host_bridge attribute to indicate if this PCI host bridge supports filtering of MSIs. Then we can mmap MSI-X table with this attribute set. With this patchset applied, we can get almost 100% improvement on performance for mmio accesses when we passthrough sub-page BARs to guest in our test. The two vfio related patches(patch 2 and patch 5) are based on the proposed patchset[1]. Changelog v3: - Rebase on new linux kernel mainline with the patchset[1] applied. - Add a function to check whether PCI BARs'mmio page is shared with other BARs. - 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 Changelog v2: - Rebase on v4.4-rc6 with the patchset[1] 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 VFIO_DEVICE_FLAGS_PCI_MSIX_MMAP - Add a Kconfig option to support for mmapping MSI-X table. [1] https://lkml.org/lkml/2015/11/23/748 Yongji Xie (5): 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 host bridge attribute to indicate filtering of MSIs is supported powerpc/powernv/pci-ioda: Enable msi_filtered bit for any IODA host bridge vfio-pci: Allow to mmap MSI-X table if host bridge supports filtering of MSIs Documentation/kernel-parameters.txt |5 + arch/powerpc/include/asm/pci.h| 11 + arch/powerpc/platforms/powernv/pci-ioda.c |6 + drivers/pci/host-bridge.c |6 + drivers/pci/pci.c | 35 + drivers/pci/pci.h |8 ++- drivers/vfio/pci/vfio_pci.c | 13 --- include/linux/pci.h |7 ++ 8 files changed, 87 insertions(+), 4 deletions(-) ___ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
[RFC PATCH v3 0/5] vfio-pci: Allow to mmap sub-page MMIO BARs and MSI-X table on PPC64 platform
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 these 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 adds a kernel parameter for PCI resource allocator to enforce the alignment of all MMIO BARs to be at least PAGE_SZIE and make it enabled by default on PPC64 platform so that sub-page BAR's mmio page will not be shared with other BARs. Then we can mmap sub-page MMIO BARs in vfio-pci driver with this parameter enabled. For MSI-X table's unmmapping, we think MSI-X table is safe to access directly from userspace if PCI host bridge support filtering of MSIs which can ensure that a given pci device can only shoot the MSIs assigned for it. So we add a pci_host_bridge attribute to indicate if this PCI host bridge supports filtering of MSIs. Then we can mmap MSI-X table with this attribute set. With this patchset applied, we can get almost 100% improvement on performance for mmio accesses when we passthrough sub-page BARs to guest in our test. The two vfio related patches(patch 2 and patch 5) are based on the proposed patchset[1]. Changelog v3: - Rebase on new linux kernel mainline with the patchset[1] applied. - Add a function to check whether PCI BARs'mmio page is shared with other BARs. - 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 Changelog v2: - Rebase on v4.4-rc6 with the patchset[1] 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 VFIO_DEVICE_FLAGS_PCI_MSIX_MMAP - Add a Kconfig option to support for mmapping MSI-X table. [1] https://lkml.org/lkml/2015/11/23/748 Yongji Xie (5): 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 host bridge attribute to indicate filtering of MSIs is supported powerpc/powernv/pci-ioda: Enable msi_filtered bit for any IODA host bridge vfio-pci: Allow to mmap MSI-X table if host bridge supports filtering of MSIs Documentation/kernel-parameters.txt |5 + arch/powerpc/include/asm/pci.h| 11 + arch/powerpc/platforms/powernv/pci-ioda.c |6 + drivers/pci/host-bridge.c |6 + drivers/pci/pci.c | 35 + drivers/pci/pci.h |8 ++- drivers/vfio/pci/vfio_pci.c | 13 --- include/linux/pci.h |7 ++ 8 files changed, 87 insertions(+), 4 deletions(-) -- 1.7.9.5 ___ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
