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Linux 5.1 Getting A Minor Spectre V2 Retpolines Optimization For Select Instances

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  • Linux 5.1 Getting A Minor Spectre V2 Retpolines Optimization For Select Instances

    Phoronix: Linux 5.1 Getting A Minor Spectre V2 Retpolines Optimization For Select Instances

    As the latest on the Spectre/Meltdown front for the Linux kernel, the in-development Linux 5.1 kernel is bringing an optimization for Retpolines "return trampolines" so GCC will generate more efficient code on x86/x86_64 in its mitigations against Spectre Variant Two...

    http://www.phoronix.com/scan.php?pag...poline-GCC-Opt

  • #2
    For non debug and non retpoline kernels those idiots can not flag the stupid error message out.
    https://git.kernel.org/pub/scm/linux.../bugs.c?h=v5.0


    Code:
    #ifdef CONFIG_DEBUG_KERNEL
    pr_err("Spectre mitigation: kernel not compiled with retpoline; no mitigation available!");
    #endif

    Comment


    • #3
      Originally posted by debianxfce View Post
      For non debug and non retpoline kernels those idiots can not flag the stupid error message out.
      https://git.kernel.org/pub/scm/linux.../bugs.c?h=v5.0


      Code:
      #ifdef CONFIG_DEBUG_KERNEL
      pr_err("Spectre mitigation: kernel not compiled with retpoline; no mitigation available!");
      #endif
      But you can though, so who cares?

      Comment


      • #4
        Originally posted by FireBurn View Post

        But you can though, so who cares?
        There are millions of home and embedded device users that do nothing with retpoline kernels. As you might see, using retpoline slows your system.

        Comment


        • #5
          Stupid question (but I'm sure I'll get a kind response lol) but is there any benefit to compiling the kernel without mitigations rather than switching the mitigations off at boot time with the kernel options?

          Comment


          • #6
            Originally posted by Murple View Post
            Stupid question (but I'm sure I'll get a kind response lol) but is there any benefit to compiling the kernel without mitigations rather than switching the mitigations off at boot time with the kernel options?
            Many users have tons of kernel command line parameters already. Remove code that you do need from the kernel, it works faster and is more stable. KISS.

            Comment


            • #7
              Originally posted by Murple View Post
              Stupid question (but I'm sure I'll get a kind response lol) but is there any benefit to compiling the kernel without mitigations rather than switching the mitigations off at boot time with the kernel options?
              No.

              But if you need to compile your own kernel already for other reasons (which isn't as hard as it may seem), then you might as well set the additional things on compile time.

              Comment


              • #8
                Originally posted by starshipeleven View Post
                No.

                But if you need to compile your own kernel already for other reasons (which isn't as hard as it may seem), then you might as well set the additional things on compile time.
                Yeah, this. Not much dependency hell.

                Comment


                • #9
                  Originally posted by Weasel View Post
                  Yeah, this. Not much dependency hell.
                  Why the fuck are you always dropping completely unrelated buzzwords lately?

                  How in the name of Jeezus are you relating the current situation, which is just choosing compile-time options of Linux kernel, to dependency hell.

                  Do you even know what is a Linux kernel, or what is dependency hell?

                  Comment


                  • #10
                    Originally posted by starshipeleven View Post
                    No.

                    But if you need to compile your own kernel already for other reasons (which isn't as hard as it may seem), then you might as well set the additional things on compile time.
                    Thanks. I don't mind compiling kernels but I wouldn't want to do it unnecessarily. I don't mind on a device where the kernel isn't updated often, but I try to run mainline as much as possible so it would be quite time consuming to maintain.

                    Comment

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