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    Merge branch 'x86-cache-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip · eb254f32
    Linus Torvalds authored
    Pull x86 cache allocation interface from Thomas Gleixner:
     "This provides support for Intel's Cache Allocation Technology, a cache
      partitioning mechanism.
    
      The interface is odd, but the hardware interface of that CAT stuff is
      odd as well.
    
      We tried hard to come up with an abstraction, but that only allows
      rather simple partitioning, but no way of sharing and dealing with the
      per package nature of this mechanism.
    
      In the end we decided to expose the allocation bitmaps directly so all
      combinations of the hardware can be utilized.
    
      There are two ways of associating a cache partition:
    
       - Task
    
         A task can be added to a resource group. It uses the cache
         partition associated to the group.
    
       - CPU
    
         All tasks which are not member of a resource group use the group to
         which the CPU they are running on is associated with.
    
         That allows for simple CPU based partitioning schemes.
    
      The main expected user sare:
    
       - Virtualization so a VM can only trash only the associated part of
         the cash w/o disturbing others
    
       - Real-Time systems to seperate RT and general workloads.
    
       - Latency sensitive enterprise workloads
    
       - In theory this also can be used to protect against cache side
         channel attacks"
    
    [ Intel RDT is "Resource Director Technology". The interface really is
      rather odd and very specific, which delayed this pull request while I
      was thinking about it. The pull request itself came in early during
      the merge window, I just delayed it until things had calmed down and I
      had more time.
    
      But people tell me they'll use this, and the good news is that it is
      _so_ specific that it's rather independent of anything else, and no
      user is going to depend on the interface since it's pretty rare. So if
      push comes to shove, we can just remove the interface and nothing will
      break ]
    
    * 'x86-cache-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (31 commits)
      x86/intel_rdt: Implement show_options() for resctrlfs
      x86/intel_rdt: Call intel_rdt_sched_in() with preemption disabled
      x86/intel_rdt: Update task closid immediately on CPU in rmdir and unmount
      x86/intel_rdt: Fix setting of closid when adding CPUs to a group
      x86/intel_rdt: Update percpu closid immeditately on CPUs affected by changee
      x86/intel_rdt: Reset per cpu closids on unmount
      x86/intel_rdt: Select KERNFS when enabling INTEL_RDT_A
      x86/intel_rdt: Prevent deadlock against hotplug lock
      x86/intel_rdt: Protect info directory from removal
      x86/intel_rdt: Add info files to Documentation
      x86/intel_rdt: Export the minimum number of set mask bits in sysfs
      x86/intel_rdt: Propagate error in rdt_mount() properly
      x86/intel_rdt: Add a missing #include
      MAINTAINERS: Add maintainer for Intel RDT resource allocation
      x86/intel_rdt: Add scheduler hook
      x86/intel_rdt: Add schemata file
      x86/intel_rdt: Add tasks files
      x86/intel_rdt: Add cpus file
      x86/intel_rdt: Add mkdir to resctrl file system
      x86/intel_rdt: Add "info" files to resctrl file system
      ...
    eb254f32