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  1. #46
    Join Date
    Mar 2006
    Posts
    691

    Re: Meltdown and Spectre

    And this is what you'll see
    $ grep . /sys/devices/system/cpu/vulnerabilities/*
    /sys/devices/system/cpu/vulnerabilities/meltdown:Mitigation: PTI
    /sys/devices/system/cpu/vulnerabilities/spectre_v1:Mitigation: __user pointer sanitization
    /sys/devices/system/cpu/vulnerabilities/spectre_v2:Mitigation: Full generic retpoline
    jbkt23
    Thinkpad x200 Intel P8600, x40
    Acer AMD A10-7800 R7

  2. #47
    Join Date
    Jan 2014
    Location
    London
    Posts
    17

    Re: Meltdown and Spectre

    So there's a central world-readable point to get information about all hardware vulnerabilities a machine has? Did anyone think this through?

    $ ls -lhdZ /sys/devices/system/cpu/vulnerabilities/
    drwxr-xr-x. 2 root root system_u:object_r:sysfs_t:s0 0 Mar 11 17:47 /sys/devices/system/cpu/vulnerabilities/

    $  tail /sys/devices/system/cpu/vulnerabilities/*
    ==> /sys/devices/system/cpu/vulnerabilities/meltdown <==
    Mitigation: PTI

    ==> /sys/devices/system/cpu/vulnerabilities/spectre_v1 <==
    Mitigation: __user pointer sanitization

    ==> /sys/devices/system/cpu/vulnerabilities/spectre_v2 <==
    Mitigation: Full generic retpoline

    Last edited by JohnnyB; 11th March 2018 at 07:05 PM. Reason: Added example

  3. #48
    Join Date
    Jan 2014
    Location
    London
    Posts
    17

    Re: Meltdown and Spectre

    I just put together a benchmark comparison with Phoronix on OpenBenchmarking.org. Same exact machine (bare metal HP Z600) both 4.13 and 4.15 kernels tested. The differences are much more miniscule - like I would expect. Real world performance feels worse.

    HP Z600 Xeon Westmere, Kernel 4.13 vs Kernel 4.15:
    https://openbenchmarking.org/result/...TY-Z600XEONW98

  4. #49
    Join Date
    Jan 2014
    Location
    London
    Posts
    17

    Re: Meltdown and Spectre

    Note I can confirm that disabling Page Table Isolation on kernel cmd definitely restores previous performance within 4.15+ kernels. Definitely not recommended as it's not secure, but PTI on Westmere makes Fedora 27 darn near useless as a workstation. Clicks and keystrokes often suffer from 1-3 second lag. Very unfortunate.

    Code:
    pti=off

  5. #50
    Join Date
    Jan 2014
    Location
    London
    Posts
    17

    Re: Meltdown and Spectre

    Update - I've found this is only related to Xorg and Compiz and have filed a bug: https://bugs.launchpad.net/compiz/+bug/1759793

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