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  1. #1
    Join Date
    Jun 2008
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    Question Meltdown & Spectre fix turn off

    Hello,

    I have crazy request. How to turn off "fix" of meltdown & spectre?

    I have isolated pc from network and I don't want to have "slowdown" of kernel fixes. Can I avoid it?

    Regards

  2. #2
    Join Date
    Jan 2015
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    Al Ain, UAE
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    783

    Re: Meltdown & Spectre fix turn off

    Yes, you can turn it off with the 'nopti' boot option:

    https://fedoramagazine.org/kpti-new-...gate-meltdown/
    --
    Have fun!
    http://www.aeronetworks.ca

  3. #3
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    Jun 2008
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    Re: Meltdown & Spectre fix turn off

    Thank you! It really helped!

  4. #4
    Join Date
    Sep 2009
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    2,170

    Re: Meltdown & Spectre fix turn off

    Quote Originally Posted by flyingdutchman
    Yes, you can turn it off with the 'nopti' boot option:

    https://fedoramagazine.org/kpti-new-...gate-meltdown/
    According to the 10th post in the thread started in that article, AMD has stated that their processors are unaffected by Meltdown. So AMD users may as well disable the patch in general.

    dd_wizard

  5. #5
    Join Date
    Jul 2005
    Posts
    873

    Re: Meltdown & Spectre fix turn off

    Quote Originally Posted by flyingdutchman
    Yes, you can turn it off with the 'nopti' boot option:

    https://fedoramagazine.org/kpti-new-...gate-meltdown/
    Nice article. How can a reputable publication like fedoramagazine fail to show the date published for the article? What good is the article if you don't know when it was written?
    ======
    Doug G
    ======

  6. #6
    Join Date
    Dec 2013
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    Re: Meltdown & Spectre fix turn off

    Click image for larger version. 

Name:	Screenshot_20180107_114220.png 
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    the date is there

  7. #7
    Join Date
    Dec 2008
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    ex-EU
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    Re: Meltdown & Spectre fix turn off

    K, so after the proper panic all over the world, I just tried the fixed kernel CentOS provides.
    After boot, sure enough, I have the affected system and it applies fix.
    Code:
    # cat /sys/kernel/debug/x86/pti_enabled 
    1
    So I made quick bench in prime95 with both, older unpatched and the patched kernel. As expected from the info on the net, difference here is so negligible that there is no need to bother.
    Then I tried some games, including Tesla Effect in wine. Since I didn't notice anything at all just by playing it, no proper benchmarks are needed. So again, in this scenario, no problem.
    And so of course, common computer usage remains basically the same.

    I guess that it's mainly the cloud providers that will really be upset by this. Supercomputers are mostly isolated so are likely not panicking here either.
    Databases and heavy I/O is the biggest problem it seems, so as for disabling the fix, do you really need to?

  8. #8
    Join Date
    Dec 2013
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    United Kingdom
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    5,967

    Re: Meltdown & Spectre fix turn off

    So far I've not noticed any performance issues with my systems after applying fixes either. I'd recommend trying the updates first before disabling anything

  9. #9
    Join Date
    Jun 2005
    Location
    Montreal, Que, Canada
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    5,042

    Re: Meltdown & Spectre fix turn off

    I am a little lost. Can I add nopti to /etc/grub.d/99_nopti.sh where 99_nopti.sh is a script I would write to update every new grub.cfg?

    Does the nopti go on the following line from my grub.cfg?

    linux16 /vmlinuz-4.14.11-300.fc27.x86_64 root=UUID=4cc00e19-b4d0-4028-a636-1d4b7f329502 ro rhgb quiet LANG=en_CA.UTF-8 nopti
    Leslie in Montreal

    Interesting web sites list
    http://forums.fedoraforum.org/showth...40#post1697840

  10. #10
    Join Date
    Sep 2009
    Posts
    2,170

    Re: Meltdown & Spectre fix turn off

    You can add it to the GRUB_CMDLINE_LINUX= line in /etc/default/grub.

    dd_wizard

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