Hacker Read

gaia · 2017-05-03 08:52:27+00:00

ACUConfig is the Intel recommended way, per the mitigation guide (at least for now, until a patch is released).

nsuser3 | karma 100 | avg karma 2.44 · | 2019-10-13 09:30:26+00:00

Some mitigations also apply to AMD CPUs.

rurban | karma 5612 | avg karma 0.84 · | 2019-11-06 10:40:31+00:00

He is aware, but sidestepped these issues. so this code is only recommended on the newest Cannon Lake processors, but we really want to know for which CPU which method is best. What about AMD Rome e.g.?

Vecr | karma 1224 | avg karma 0.89 · | 2023-10-14 20:28:02

Depends on what CPU you are running, on Zen 4 it's not supported to disable the mitigations and caused bugs/crashes. I think they did fix that exact crash but I'd still not recommend it. New CPUs from both AMD and Intel are designed to be run with at least the default mitigations on.

igammarays | karma 3397 | avg karma 4.23 · | 2022-01-07 06:42:23

Between shenanigans like this and Spectre/Meltdown mitigations giving me a ~20% performance hit [1], I avoid Intel like the plague if I have the choice.

[1] https://arxiv.org/pdf/1807.08703.pdf

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GameOfTrolls | karma 2 | avg karma 0.02 · | 2018-01-03 23:54:31+00:00

Intel FUD. AMD is not affected.

sebazzz | karma 3584 | avg karma 2.19 · | 2019-11-25 15:26:20+00:00

This almost calls from a microcode patch or kernel driver from AMD to mitigate this, if at all possible.

michaelmrose | karma 10452 | avg karma 1.57 · | 2021-06-19 21:45:21

Is this equally true for AMD CPUs? Does the kernel offer different mitigations per CPU or one unified set of strategies?

arthur2e5 | karma 1100 | avg karma 3.33 · | 2020-09-01 07:08:20+00:00

The new mkl_serv_intel_cpu_true() function seems to have been known since Agner Fog's 2019 update. I am quite surprised that no changes to the feature indicator was needed though.

If you are publishing an application, I still recommend using the intel_dispatch_patch.zip.

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dralley | karma 13928 | avg karma 4.7 · | 2018-01-02 23:59:13+00:00

No, other way around. The patch which decreases Intel performance has already occurred. This patch AMD saying "we don't need this, so we're disabling it for AMD CPUs."

b1gtuna | karma 202 | avg karma 2.06 · | 2018-01-02 18:07:50+00:00

I thought it was clear that this patch only applies to AMD. However, reading the comments here confuses me. How's does the performance on Intel drops with this?

shaklee3 | karma 2976 | avg karma 1.62 · | 2020-03-07 16:12:10

I believe AMD has been contributing upstream to intel-cmt-cat, and Intel has accepted those patches.

mcbits | karma 2217 | avg karma 2.51 · | 2019-09-08 14:14:52

Since AMD has equally no obligation to Intel users, they can submit a patch that replaces Intel's

    if (intel)
        fast();
    else
        slow();

with

    if (amd)
        fast();
    else
        slow();

Or maybe there's a better way.

sznio | karma 403 | avg karma 3.8 · | 2023-08-07 11:20:56

I disabled these mitigations on my i5-2500k a year ago and it felt like buying a new CPU. Sandy Bridge was hit hard.

c2h5oh | karma 1424 | avg karma 5.09 · | 2018-08-14 18:45:19+00:00

Or just keep using AMD CPUs, because yet again they are unaffected https://www.amd.com/en/corporate/security-updates

throwaway7767 | karma 2104 | avg karma 3.22 · | 2015-12-10 05:31:15

Interesting. I guess they must have finally stopped intentionally crippling ICC for non-intel processors[0].

[0] http://www.agner.org/optimize/blog/read.php?i=49#49

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onli | karma 8293 | avg karma 3.7 · | 2018-04-19 14:09:22+00:00

Here are two benchmarks supporting this: https://www.eurogamer.net/articles/digitalfoundry-2018-does-..., https://www.tomshardware.com/reviews/gaming-performance-melt.... I remember it like that as well.

anthk | karma 3504 | avg karma 0.6 · | 2021-03-15 09:57:40+00:00

>Tuned.

Intel on HPCs.

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fuckstick | karma 425 | avg karma 3.32 · | 2022-11-04 19:28:24

A bunch of people keep saying this with no substantiation - the best we saw was a link to the latest Intel optimization manual that quite specifically refutes this claim. I even quoted it upthread.

Do you have anything substantial to add to that?

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rdtsc | karma 41164 | avg karma 4.52 · | 2018-11-18 14:01:48+00:00

This is how it should be. And this is going to net positive thing for AMD.

If performance takes a hit by about 20% it is going to be noticeable. Next up I think people will start looking to upgrade to a faster CPU just to get back to last week's performance metrics. They might now consider AMD.

If AMD finds this affects them less they should sponsor security researchers writing proof of concept exploits to convince people that that turning off the mitigation is an absolute no-no, so it will for force people to take a performance hit and go shopping for CPUs.

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