Note: this version will likely trivially conflict with some cleanup patches I sent to Bjorn. So this is meant for review purposes only. If there are no objections, I'd like to look at getting it merged in the next cycle through the NTB tree.
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Changes in v2:
* Cleaned up the changes in intel_irq_remapping.c to make them less confusing and add a comment. (Per discussion with Jacob and Joerg)
* Fixed a nit from Bjorn and collected his Ack
* Added a Kconfig dependancy on CONFIG_PCI_MSI for CONFIG_NTB_MSI as the Kbuild robot hit a random config that didn't build without it.
* Worked in a callback for when the MSI descriptor changes so that the clients can resend the new address and data values to the peer. On my test system this was never necessary, but there may be other platforms where this can occur. I tested this by hacking in a path to rewrite the MSI descriptor when I change the cpu affinity of an IRQ. There's a bit of uncertainty over the latency of the change, but without hardware this can acctually occur on we can't test this. This was the result of a discussion with Dave.
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This patch series adds optional support for using MSI interrupts instead of NTB doorbells in ntb_transport. This is desirable seeing doorbells on current hardware are quite slow and therefore switching to MSI interrupts provides a significant performance gain. On switchtec hardware, a simple apples-to-apples comparison shows ntb_netdev/iperf numbers going from 3.88Gb/s to 14.1Gb/s when switching to MSI interrupts.
To do this, a couple changes are required outside of the NTB tree:
1) The IOMMU must know to accept MSI requests from aliased bused numbers seeing NTB hardware typically sends proxied request IDs through additional requester IDs. The first patch in this series adds support for the Intel IOMMU. A quirk to add these aliases for switchtec hardware was already accepted. See commit ad281ecf1c7d ("PCI: Add DMA alias quirk for Microsemi Switchtec NTB") for a description of NTB proxy IDs and why this is necessary.
2) NTB transport (and other clients) may often need more MSI interrupts than the NTB hardware actually advertises support for. However, seeing these interrupts will not be triggered by the hardware but through an NTB memory window, the hardware does not actually need support or need to know about them. Therefore we add the concept of Virtual MSI interrupts which are allocated just like any other MSI interrupt but are not programmed into the hardware's MSI table. This is done in Patch 2 and then made use of in Patch 3.
The remaining patches in this series add a library for dealing with MSI interrupts, a test client and finally support in ntb_transport.
The series is based off of v5.0-rc4 and I've tested it on top of a of the patches I've already sent to the NTB tree (though they are independent changes). A git repo is available here:
https://github.com/sbates130272/linux-p2pmem/ ntb_transport_msi_v2
Thanks,
Logan
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Logan Gunthorpe (12): iommu/vt-d: Implement dma_[un]map_resource() NTB: ntb_transport: Ensure the destination buffer is mapped for TX DMA iommu/vt-d: Add helper to set an IRTE to verify only the bus number iommu/vt-d: Allow interrupts from the entire bus for aliased devices PCI/MSI: Support allocating virtual MSI interrupts PCI/switchtec: Add module parameter to request more interrupts NTB: Introduce functions to calculate multi-port resource index NTB: Rename ntb.c to support multiple source files in the module NTB: Introduce MSI library NTB: Introduce NTB MSI Test Client NTB: Add ntb_msi_test support to ntb_test NTB: Add MSI interrupt support to ntb_transport
drivers/iommu/intel-iommu.c | 23 +- drivers/iommu/intel_irq_remapping.c | 32 +- drivers/ntb/Kconfig | 11 + drivers/ntb/Makefile | 3 + drivers/ntb/{ntb.c => core.c} | 0 drivers/ntb/msi.c | 415 +++++++++++++++++++++++ drivers/ntb/ntb_transport.c | 197 ++++++++++- drivers/ntb/test/Kconfig | 9 + drivers/ntb/test/Makefile | 1 + drivers/ntb/test/ntb_msi_test.c | 433 ++++++++++++++++++++++++ drivers/pci/msi.c | 55 ++- drivers/pci/switch/switchtec.c | 12 +- include/linux/msi.h | 8 + include/linux/ntb.h | 143 ++++++++ include/linux/pci.h | 9 + tools/testing/selftests/ntb/ntb_test.sh | 54 ++- 16 files changed, 1379 insertions(+), 26 deletions(-) rename drivers/ntb/{ntb.c => core.c} (100%) create mode 100644 drivers/ntb/msi.c create mode 100644 drivers/ntb/test/ntb_msi_test.c
-- 2.19.0