New Spectre hole
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  1. #1
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    New Spectre hole

    Phoronix " The Spectre "SWAPGS" Mitigation Performance Impact " reports of a patch to Linux / Windows for a new attack vector and the consequences of adding this patch to Linux.

    Is it time that we get a separate kernel, one based on AMD which is not susceptible to Spectre attacks. Performance loss was shown to be significant for this last Kernel patch.

    Or can the modules for Intel and AMD be distributed with dracut and the intram construction selecting AMD's versions of modules, rather than Intels.

    With the sum of the spectre issues, the added patches contribute to a good 5 to 10 percent loss of cpu performance per cpu core.
    Last edited by lsatenstein; 8th August 2019 at 09:50 PM.
    Leslie in Montreal

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    Re: New Spectre hole

    Why?, you can enable or disable the mitigations in the general kernel. If you don't want them, turn them off using the interfaces in /sys/devices/system/cpu/vulnerabilities/ to see what's vulnerable and these to turn those off:

    echo 0 > /sys/kernel/debug/x86/pti_enabled
    echo 0 > /sys/kernel/debug/x86/retp_enabled
    echo 0 > /sys/kernel/debug/x86/ibrs_enabled

    https://access.redhat.com/articles/3311301

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    Re: New Spectre hole

    Quote Originally Posted by marko
    Why?, you can enable or disable the mitigations in the general kernel. If you don't want them, turn them off using the interfaces in /sys/devices/system/cpu/vulnerabilities/ to see what's vulnerable and these to turn those off:

    echo 0 > /sys/kernel/debug/x86/pti_enabled
    echo 0 > /sys/kernel/debug/x86/retp_enabled
    echo 0 > /sys/kernel/debug/x86/ibrs_enabled

    https://access.redhat.com/articles/3311301
    Thank you Marko for the above.
    I wonder if I would notice a difference, given my use is as a desktop system.
    By the way, it works with SUSE's Tumbleweed, but with Fedora,
    the path is write protected. Ergo even with cd /sys/kernel/debug/x86/ followed by echo 0 >pti_enabled
    results are blocked.
    Last edited by lsatenstein; 14th August 2019 at 03:37 PM.
    Leslie in Montreal

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    http://forums.fedoraforum.org/showth...40#post1697840

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