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Comment by microtonal | Hacker News Reader

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The kernel patches are for Meltdown (aka Variant 3).

There are also Spectre fixes landing in kernels. E.g. Linux 4.14.14 added initial retpoline support:

https://lwn.net/Articles/744621/

The current LWN has very good coverage on the latest work on Spectre/Meltdown mitigation in the kernel:

https://lwn.net/SubscriberLink/744287/d868ef1ac3f68d70/

(Posting a subscriber link in good faith. If you like such content, please subscribe to LWN.net, they are excellent!)

> There are also Spectre fixes landing in kernels. E.g. Linux 4.14.14 added initial retpoline support:

Which has its own performance drawbacks, but the microcode update itself has even more. And you need the microcode update for Broadwell and newer for retpolines to work.

I thought the retpoline basically defeated speculation for certain longjmp/function calls. Why do you need a firmware update for that to work?

That subscriber link above explains why, but in the whitepaper I read, it said Broadwell, not only Skylake.

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