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Comment by riledhel | Hacker News Reader

Does Windows have a patch for this too? Or just disabling HT is the safest option?

Windows does have a microcode update driver, as you would expect, so it can fix this.

However, looking at the microcode update driver on an updated Windows 10 as of right now, I don't see a recent enough microcode version to fix it. The latest updates appear to be from 2015.

That's pretty cool, I didn't know of this functionality. Is there a good resource on how to look it up?

I haven't seen a description of it anywhere that I can think of. The driver lives in C:\Windows\system32\mcupdate_{genuineintel,authenticamd}.dll. All it does is detect which CPU it's running on, and load the appropriate microcode.

Loading the microcode is straightforward---all you need to do is put a few values in the appropriate MSRs. This is described in the Intel manuals, Volume 3. The microcode itself is embedded in the above DLLs, as a big binary table. The latest entry I see is 20150812 for the Intel 0x40651, aka Haswell.

It's safe to assume that Windows distributes the microcode fixes as well.

For some reason, Debian says you need bios updates for certain machines, and Debian packaged microcode for others. I wouldn't be surprised if it is the same for Windows.

If they don't fix for Windows then they are killing 90% of their customers which they won't. So if it's not already out it will be soon. It is Linux which gets fixes late most of the time.

By my reading, it's fixed in Micro-code, so if you Windows Update, you already have it fixed.

I wonder if one could update the microcode using a ring 0 virtualization platform and Windows as a guest.

Nope, can only be done in the host and not VMs for security reasons.

..and microcode updates aren't persistent, they have to be applied every boot anyway.

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