• Linus Torvalds's avatar
    Merge tag 'cxl-for-6.3' of git://git.kernel.org/pub/scm/linux/kernel/git/cxl/cxl · 7c3dc440
    Linus Torvalds authored
    Pull Compute Express Link (CXL) updates from Dan Williams:
     "To date Linux has been dependent on platform-firmware to map CXL RAM
      regions and handle events / errors from devices. With this update we
      can now parse / update the CXL memory layout, and report events /
      errors from devices. This is a precursor for the CXL subsystem to
      handle the end-to-end "RAS" flow for CXL memory. i.e. the flow that
      for DDR-attached-DRAM is handled by the EDAC driver where it maps
      system physical address events to a field-replaceable-unit (FRU /
      endpoint device). In general, CXL has the potential to standardize
      what has historically been a pile of memory-controller-specific error
      handling logic.
    
      Another change of note is the default policy for handling RAM-backed
      device-dax instances. Previously the default access mode was "device",
      mmap(2) a device special file to access memory. The new default is
      "kmem" where the address range is assigned to the core-mm via
      add_memory_driver_managed(). This saves typical users from wondering
      why their platform memory is not visible via free(1) and stuck behind
      a device-file. At the same time it allows expert users to deploy
      policy to, for example, get dedicated access to high performance
      memory, or hide low performance memory from general purpose kernel
      allocations. This affects not only CXL, but also systems with
      high-bandwidth-memory that platform-firmware tags with the
      EFI_MEMORY_SP (special purpose) designation.
    
      Summary:
    
       - CXL RAM region enumeration: instantiate 'struct cxl_region' objects
         for platform firmware created memory regions
    
       - CXL RAM region provisioning: complement the existing PMEM region
         creation support with RAM region support
    
       - "Soft Reservation" policy change: Online (memory hot-add)
         soft-reserved memory (EFI_MEMORY_SP) by default, but still allow
         for setting aside such memory for dedicated access via device-dax.
    
       - CXL Events and Interrupts: Takeover CXL event handling from
         platform-firmware (ACPI calls this CXL Memory Error Reporting) and
         export CXL Events via Linux Trace Events.
    
       - Convey CXL _OSC results to drivers: Similar to PCI, let the CXL
         subsystem interrogate the result of CXL _OSC negotiation.
    
       - Emulate CXL DVSEC Range Registers as "decoders": Allow for
         first-generation devices that pre-date the definition of the CXL
         HDM Decoder Capability to translate the CXL DVSEC Range Registers
         into 'struct cxl_decoder' objects.
    
       - Set timestamp: Per spec, set the device timestamp in case of
         hotplug, or if platform-firwmare failed to set it.
    
       - General fixups: linux-next build issues, non-urgent fixes for
         pre-production hardware, unit test fixes, spelling and debug
         message improvements"
    
    * tag 'cxl-for-6.3' of git://git.kernel.org/pub/scm/linux/kernel/git/cxl/cxl: (66 commits)
      dax/kmem: Fix leak of memory-hotplug resources
      cxl/mem: Add kdoc param for event log driver state
      cxl/trace: Add serial number to trace points
      cxl/trace: Add host output to trace points
      cxl/trace: Standardize device information output
      cxl/pci: Remove locked check for dvsec_range_allowed()
      cxl/hdm: Add emulation when HDM decoders are not committed
      cxl/hdm: Create emulated cxl_hdm for devices that do not have HDM decoders
      cxl/hdm: Emulate HDM decoder from DVSEC range registers
      cxl/pci: Refactor cxl_hdm_decode_init()
      cxl/port: Export cxl_dvsec_rr_decode() to cxl_port
      cxl/pci: Break out range register decoding from cxl_hdm_decode_init()
      cxl: add RAS status unmasking for CXL
      cxl: remove unnecessary calling of pci_enable_pcie_error_reporting()
      dax/hmem: build hmem device support as module if possible
      dax: cxl: add CXL_REGION dependency
      cxl: avoid returning uninitialized error code
      cxl/pmem: Fix nvdimm registration races
      cxl/mem: Fix UAPI command comment
      cxl/uapi: Tag commands from cxl_query_cmd()
      ...
    7c3dc440
probe.c 86.1 KB