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Comment by sp332 | Hacker News Reader

https://mobile.twitter.com/taviso/status/1630695259935219713

Apparently some Ryzen models have no fixed microcode available. You can boot with clearcpuid=xsaves as a workaround, probably at some performance cost.

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As I understood the email thread, they do have microcode updates but they weren't actually released anywhere but in some crusty vendors BIOS update, so you can only get them if someone fished them out of there.

i.e. thats what this repo seems to be: https://github.com/platomav/CPUMicrocodes

The person who reported the bug in their family 0x17 model 0x60 Renoir SoC said it wasn't fixed even by the latest BIOS-supplied microcode available.

The reality is most consumer motherboards rarely post updates especially after the first year or so. You'll tend to get updates to fix CPU compatability for newer CPUs if the motherboard is still on sale, but otherwise most long term BIOS updates seem largely to be from enterprise vendors (Dell, Lenovo, etc) and much less common on consumer or gaming type hardware.

I think most people rely on the operating system to (amazingly) hot patch it during boot. Intel and AMD both publish them and are integrated regularly into most distros (and the linux-firmware git tree). Surprising/weird that they haven't released the Renoir ones.

Also seems Tavis had a bug where Debian wasn't applying them on boot for one reason but didn't give details. Wonder what it was.

> The reality is most consumer motherboards rarely post updates especially after the first year or so

I can’t confirm that. My current board is the MSI X570-A PRO. First BIOS was 2019-06-20, the latest 2022-08-19. And that’s still updating versions and settings. After 3 years, and I’m expecting more. This has also been my experience with other boards. MB updates tend to last several years.

You have that like exactly backwards. You'll get a lot fewer bios updates from Dell or Lenovo than you will from MSI, Asus, Gigabyte, etc.. consumer / gaming motherboard lines. My 5 year old X370-F GAMING is still getting BIOS updates. Others, like MSI, practically forced AMD to continue issuing AGESA updates for X370 & X470 chipsets after AMD had announced official end of support - they got AMD to change course and add new CPU support to those old chipsets.

But otherwise all the major consumer / gaming motherboards pick up new AGESA updates quickly & consistently, even when they're EOL platforms.

I have a really old GA-Z87X-UD5H, it got NVME support five years after release. Probably by accident, but still.

Since this is about Linux, the microcodes it applies on boot can be found in the linux-firmware repository. For AMD microcode, in particular https://git.kernel.org/pub/scm/linux/kernel/git/firmware/lin...

However, for some unexplainable reason AMD doesn't tend to update the microcodes in that repo particularly often, leaving it up to BIOS vendors and users updating their BIOS.

No obvious reason for a performance cost. If XSAVEC is available, performance should be essentially identical to XSAVES.

I had to look up the difference between XSAVES and XSAVEC: "Execution of XSAVES is similar to that of XSAVEC. XSAVES differs from XSAVEC in that it can save state components corresponding to bits set in the IA32_XSS MSR and that it may use the modified optimization."

In this case it seems like the "modified optimization" is where the bug lies.

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