I guess that's true, I forgot about Apple making Rosetta 2 installable in Linux VMs.

Also though, since Rosetta 2 was released, it's had an incredibly slow implementation of x87 FPU operations, and anything that relies on x87 floating point math (including lots of games) is currently running about 100x slower than it ought to. Apple is aware of it but it's still not fixed in Ventura.

I hadn't heard of FEX before, looks interesting.

Huh, I thought everyone used SSE floats these days. I suppose there may be old games compiled with x87 floats, but I'd expect those to be made for CPUs so old that even slow x87 emulation wouldn't be a big issue.

What software do people have x87-related issues with?

The software I personally have the most issues with is Star Wars Episode 1: Racer, a 3d title from 1999 that from what I understand uses x87 math extensively. In Parallels (i.e. no Rosetta) it runs at 120fps easily, while in CrossOver the frame rate barely ekes above 20. Old titles like Half-Life, all other Source games, Fallout 3, SWTOR etc. all run vastly worse than they should, and many cannot run at playable framerates through Rosetta. Honestly, the problem most likely extends to more of Rosetta's floating point math than just x87.

The author of REAPER has also written about it some: https://user.cockos.com/~deadbeef/index.php?article=842

There's been lots of discussion about the issue in the Codeweavers forums, and Codeweavers points the blame squarely at Apple, who have been, predictably, very quiet about it.

FEX decided to not support page sizes >4k, which is fair (it's a lot of work), but it means that it won't be usable on Apple silicon, so that's not an option.

Afaik you can run kernels with 4k pagesize on apple Mx platform. It's just not optimal.

Does it? Or does Rosetta 2 run on Mac OS with a Linux shim to ask the host to kindly Rosetta-ify a given binary?

Pretty much immediately after the first developer beta providing Rosetta for Linux shipped, people tried to get it to work on non-Apple hardware, and succeeded: https://news.ycombinator.com/item?id=31662978

There's no macOS host to interact with on AWS Graviton3 instances.

Huh, I misunderstood the virtiofs mechanism.

Does Rosetta on Linux support 32 bit code? I believe FEX does.

Rosetta supports emulating 32-bit code.

On Linux? I know it has been confirmed on macOS. I haven’t heard anyone say they ran 32 bit code on Linux.

I should double-check but I seem to recall the functionality being present, although of course nobody uses it