Re: Candidate Linux ABI for Intel AMX and hypothetical new related features

[Florian Weimer]

* Len Brown:

> 5. If the feature is enabled in XCR0, the user happily uses it.
>
>     For AMX, Linux implements "transparent first use"
>     so that it doesn't have to allocate 8KB context switch
>     buffers for tasks that don't actually use AMX.
>     It does this by arming XFD for all tasks, and taking a #NM
>     to allocate a context switch buffer only for those tasks
>     that actually execute AMX instructions.

What happens if the kernel cannot allocate that additional context
switch buffer?

Thanks,
Florian