Re: [PATCH v3 05/21] x86/fpu/xstate: Add a new variable to indicate dynamic user states

[Borislav Petkov]

On Tue, Jan 19, 2021 at 06:57:26PM +0000, Bae, Chang Seok wrote:
> This series attempts to save the AMX state in the context switch buffer only

What is the context switch buffer?

I think you mean simply the xstate per-task buffer which is switched on
context switches...

> when needed -- so it is called out ‘dynamic’ user states.
> 
> The LBR state is saved in the perf buffer [1], and this state is named
> 'dynamic' supervisor states [2]. But some naming in the change has ‘dynamic’
> state only.
> 
> So, these two kinds of dynamic states are different and need to be named
> clearly.

Oh well, this is going to be a mess, there's also CET coming but at
least stuff is properly documented with comments - I guess thanks
dhansen :) - so we can fix it up later if something's still amiss.

> How about the changelog message like this:
> 
> "
> The context switch buffer is in preparation to be dynamic for user states.
> Introduce a new mask variable to indicate the 'dynamic' user states. The value
> is determined at boot time.
> 
> The perf subsystem has a separate buffer to save some states only when needed,
> not in every context switch. The states are named as 'dynamic' supervisor
> states. Some define and helper are not named with dynamic supervisor states,
> so rename them.
> 
> No functional change.
> “

Yah, better.

Thx.

-- 
Regards/Gruss,
    Boris.

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