linux-kernel - Re: [PATCH v5 1/1] x86/acpi, x86/boot: Add multiprocessor wake-up support

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Date:   Mon, 24 May 2021 06:42:53 -0700
From:   "Kuppuswamy, Sathyanarayanan" 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>
To:     Mika Penttilä <mika.penttila@...tfour.com>,
        Rafael J Wysocki <rjw@...ysocki.net>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H . Peter Anvin" <hpa@...or.com>,
        Peter Zijlstra <peterz@...radead.org>
Cc:     Len Brown <lenb@...nel.org>,
        Kuppuswamy Sathyanarayanan <knsathya@...nel.org>,
        Sean Christopherson <seanjc@...gle.com>,
        Andi Kleen <ak@...ux.intel.com>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 1/1] x86/acpi, x86/boot: Add multiprocessor wake-up
 support



On 5/23/21 11:40 PM, Mika Penttilä wrote:
> 
> So this isn't supporting suspend/resume if AP cannot started again?

Yes. You are correct. It can be used only once per AP. Please find the
spec reference below.

/*
  * According to the ACPI specification r6.4, sec 5.2.12.19, the
  * mailbox-based wakeup mechanism cannot be used more than once
  * for the same CPU, so skip sending wake commands to already
  * awake CPU.
  */

-- 
Sathyanarayanan Kuppuswamy
Linux Kernel Developer