linux-kernel - Re: [PATCH v3 2/3] x86/fpu: Add a helper to prepare AMX state for low-power CPU idle

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Message-ID: <8735ium8bv.ffs@tglx>
Date:   Sun, 03 Apr 2022 18:37:40 +0200
From:   Thomas Gleixner <tglx@...utronix.de>
To:     "Chang S. Bae" <chang.seok.bae@...el.com>,
        linux-kernel@...r.kernel.org, x86@...nel.org,
        linux-pm@...r.kernel.org
Cc:     dave.hansen@...ux.intel.com, peterz@...radead.org, bp@...en8.de,
        rafael@...nel.org, ravi.v.shankar@...el.com,
        chang.seok.bae@...el.com
Subject: Re: [PATCH v3 2/3] x86/fpu: Add a helper to prepare AMX state for
 low-power CPU idle

On Thu, Mar 24 2022 at 19:22, Chang S. Bae wrote:
> When a CPU enters an idle state, non-initialized states left in large
> registers may be the cause of preventing deeper low-power states.
>
> The new helper ensures the AMX state is initialized to make the CPU
> ready for low-power states. It will be used by the intel idle driver.

What about AVX...AVX512? Are they harmless in that regard?

If so, then the first sentence above is confusing and should clearly
spell out that it's AMX which causes that problem.

In not, then why are we not putting them into init too?

Thanks,

        tglx