• Linus Torvalds's avatar
    Merge branch 'x86-pti-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip · 4b783176
    Linus Torvalds authored
    Pull STIBP fallout fixes from Thomas Gleixner:
     "The performance destruction department finally got it's act together
      and came up with a cure for the STIPB regression:
    
       - Provide a command line option to control the spectre v2 user space
         mitigations. Default is either seccomp or prctl (if seccomp is
         disabled in Kconfig). prctl allows mitigation opt-in, seccomp
         enables the migitation for sandboxed processes.
    
       - Rework the code to handle the conditional STIBP/IBPB control and
         remove the now unused ptrace_may_access_sched() optimization
         attempt
    
       - Disable STIBP automatically when SMT is disabled
    
       - Optimize the switch_to() logic to avoid MSR writes and invocations
         of __switch_to_xtra().
    
       - Make the asynchronous speculation TIF updates synchronous to
         prevent stale mitigation state.
    
      As a general cleanup this also makes retpoline directly depend on
      compiler support and removes the 'minimal retpoline' option which just
      pretended to provide some form of security while providing none"
    
    * 'x86-pti-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (31 commits)
      x86/speculation: Provide IBPB always command line options
      x86/speculation: Add seccomp Spectre v2 user space protection mode
      x86/speculation: Enable prctl mode for spectre_v2_user
      x86/speculation: Add prctl() control for indirect branch speculation
      x86/speculation: Prepare arch_smt_update() for PRCTL mode
      x86/speculation: Prevent stale SPEC_CTRL msr content
      x86/speculation: Split out TIF update
      ptrace: Remove unused ptrace_may_access_sched() and MODE_IBRS
      x86/speculation: Prepare for conditional IBPB in switch_mm()
      x86/speculation: Avoid __switch_to_xtra() calls
      x86/process: Consolidate and simplify switch_to_xtra() code
      x86/speculation: Prepare for per task indirect branch speculation control
      x86/speculation: Add command line control for indirect branch speculation
      x86/speculation: Unify conditional spectre v2 print functions
      x86/speculataion: Mark command line parser data __initdata
      x86/speculation: Mark string arrays const correctly
      x86/speculation: Reorder the spec_v2 code
      x86/l1tf: Show actual SMT state
      x86/speculation: Rework SMT state change
      sched/smt: Expose sched_smt_present static key
      ...
    4b783176
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