On 5/9/24 11:41, Chang S. Bae wrote: > On 5/9/2024 10:36 AM, Dave Hansen wrote: >> >> I'd probably just do this: >> >> + kernel_fpu_begin(); >> + // AMX *MUST* be in the init state for the wrmsr() to work. >> + // But, the more in the init state, the less state the test >> + // has to save and restore. Just zap everything. >> + restore_fpregs_from_fpstate(&init_fpstate, >> + fpu_user_cfg.max_features); >> + > > I assume that this snippet goes to the IFS driver side. Then, we need > to introduce and export a new wrapper for this. > restore_fpregs_from_fpstate() and its arguments are not accessible as > of now. Yes, a new wrapper to initialize all the user FPU state is fine. > Also, I think we should encapsulate them. If we follow this style, we > could have invoked tilerelease() directly from the idle driver, right? You could have... But I think the point there truly was to do a minimal amount of work because you're going idle and need to race to get there. The path to idle is super hot and you don't want to do _any_ additional work. It's worth writing highly AMX-specific code because generic code would be slow there. The IFS path is a super duper slow one. It takes *FOREVER*. I like the idea of being simple, dumb and slow.
