V3: - Rebased against latest dmaengine/next tree. - Updated API doc with new kernel version and dates. - Changed to allow driver to load without ENQCMD support. - Break out some patches that can be sent ahead of this series for inclusion. v2: - Dropped device feature enabling (GregKH) - Dropped PCI device feature enabling (Bjorn) - https://members.pcisig.com/wg/PCI-SIG/document/14237 - After some internal discussion, we have decided to hold off on the enabling of DMWR due to the following reasons. 1. Most first gen hw will not have the feature bits. 2. First gen hw that support the feature are all Root Complex integrated endpoints. 3. PCI devices that are not RCiEP’s with this capability won’t surface for a few years so we can wait until we can test the full code. - Dropped special ioremap (hch) - Added proper support for WQ flush (tony, dan) - Changed descriptor submission to use sbitmap_queue for blocking. (dan) Driver stage 1 postings for context: [1] The patch series has compilation and functional dependency on Fenghua's "Tag application address space for devices" patch series for the ENQCMD CPU command enumeration and the PASID MSR support. [2] First patch in the series is only there to assist with compilation. Can be dropped once Fenghua’s series is accepted by the x86 maintainers. == Background == A typical DMA device requires the driver to translate application buffers to hardware addresses, and a kernel-user transition to notify the hardware of new work. Shared Virtual Addressing (SVA) allows the processor and device to use the same virtual addresses without requiring software to translate between the address spaces. ENQCMD is a new instruction on Intel Platforms that allows user applications to directly notify hardware of new work, much like how doorbells are used in some hardware, but it carries a payload along with it. ENQCMDS is the supervisor version (ring0) of ENQCMD. == ENQCMDS == Introduce enqcmds(), a helper funciton that copies an input payload to a 64B aligned destination and confirms whether the payload was accepted by the device or not. enqcmds() wraps the new ENQCMDS CPU instruction. The ENQCMDS is a ring 0 CPU instruction that performs similar to the ENQCMD instruction. Descriptor submission must use ENQCMD(S) for shared workqueues (swq) on an Intel DSA device. == Shared WQ support == Introduce shared workqueue (swq) support for the idxd driver. The current idxd driver contains dedicated workqueue (dwq) support only. A dwq accepts descriptors from a MOVDIR64B instruction. MOVDIR64B is a posted instruction on the PCIe bus, it does not wait for any response from the device. If the wq is full, submitted descriptors are dropped. A swq utilizes the ENQCMDS in ring 0, which is a non-posted instruction. The zero flag would be set to 1 if the device rejects the descriptor or if the wq is full. A swq can be shared between multiple users (kernel or userspace) due to not having to keep track of the wq full condition for submission. A swq requires PASID and can only run with SVA support. == IDXD SVA support == Add utilization of PASID to support Shared Virtual Addressing (SVA). With PASID support, the descriptors can be programmed with host virtual address (HVA) rather than IOVA. The hardware will work with the IOMMU in fulfilling page requests. With SVA support, a user app using the char device interface can now submit descriptors without having to pin the virtual memory range it wants to DMA in its own address space. The series does not add SVA support for the dmaengine subsystem. That support is coming at a later time. [1]: https://lore.kernel.org/lkml/157965011794.73301.15960052071729101309.stgit@xxxxxxxxxxxxxxxxxxxxxxxxxx/ [2]: https://lkml.org/lkml/2020/6/30/1266 [3]: https://software.intel.com/en-us/articles/intel-sdm [4]: https://software.intel.com/en-us/download/intel-scalable-io-virtualization-technical-specification [5]: https://software.intel.com/en-us/download/intel-data-streaming-accelerator-preliminary-architecture-specification [6]: https://01.org/blogs/2019/introducing-intel-data-streaming-accelerator [7]: https://intel.github.io/idxd/ [8]: https://github.com/intel/idxd-driver idxd-stage2 --- Dave Jiang (5): x86/asm: move the raw asm in iosubmit_cmds512() to special_insns.h x86/asm: add enqcmds() to support ENQCMDS instruction dmaengine: idxd: add shared workqueue support dmaengine: idxd: clean up descriptors with fault error dmaengine: idxd: add ABI documentation for shared wq Fenghua Yu (1): x86/cpufeatures: Enumerate ENQCMD and ENQCMDS instructions Documentation/ABI/stable/sysfs-driver-dma-idxd | 14 ++ arch/x86/include/asm/cpufeatures.h | 1 arch/x86/include/asm/io.h | 45 +++++--- arch/x86/include/asm/special_insns.h | 17 +++ arch/x86/kernel/cpu/cpuid-deps.c | 1 drivers/dma/Kconfig | 13 ++ drivers/dma/idxd/cdev.c | 47 ++++++++ drivers/dma/idxd/device.c | 91 ++++++++++++++- drivers/dma/idxd/dma.c | 9 -- drivers/dma/idxd/idxd.h | 26 ++++ drivers/dma/idxd/init.c | 91 ++++++++++++--- drivers/dma/idxd/irq.c | 143 ++++++++++++++++++++++-- drivers/dma/idxd/registers.h | 14 ++ drivers/dma/idxd/submit.c | 33 +++++- drivers/dma/idxd/sysfs.c | 127 +++++++++++++++++++++ 15 files changed, 602 insertions(+), 70 deletions(-) --
