Re: [PATCH v2 1/2] x86/fpu: Extend kernel_fpu_begin_mask() to initialize AMX state

[Chang S. Bae]

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.

Also, I think we should encapsulate them. If we follow this style, we 
could have invoked tilerelease() directly from the idle driver, right?

>          wrmsrl(MSR_ACTIVATE_SCAN, params->activate->data);
>          rdmsrl(MSR_SCAN_STATUS, status.data);
>
> +	kernel_fpu_end();