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    • 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