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Subject: Re: [PATCH v3 3/3] x86/acpi, x86/boot: Add multiprocessor wake-up
 support
To:     "Rafael J. Wysocki" <rafael@kernel.org>,
        Andi Kleen <ak@linux.intel.com>
Cc:     Rafael J Wysocki <rjw@rjwysocki.net>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>,
        "H . Peter Anvin" <hpa@zytor.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Len Brown <lenb@kernel.org>,
        Robert Moore <robert.moore@intel.com>,
        Erik Kaneda <erik.kaneda@intel.com>,
        ACPI Devel Maling List <linux-acpi@vger.kernel.org>,
        "open list:ACPI COMPONENT ARCHITECTURE (ACPICA)" <devel@acpica.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        the arch/x86 maintainers <x86@kernel.org>,
        Sean Christopherson <sean.j.christopherson@intel.com>
References: <20210426023941.729334-1-sathyanarayanan.kuppuswamy@linux.intel.com>
 <20210426023941.729334-4-sathyanarayanan.kuppuswamy@linux.intel.com>
 <97e14cdc-ea98-18b8-0c89-db52440a7716@linux.intel.com>
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 <4fa40e7a-bcb2-db0f-8dc5-28728b14377d@linux.intel.com>
 <20210510172237.GU4032392@tassilo.jf.intel.com>
 <CAJZ5v0iFsBWwXhqtLbTMicBSFme0HCvg+2xgtMgpkFMupk_Rkw@mail.gmail.com>
From:   "Kuppuswamy, Sathyanarayanan" 
        <sathyanarayanan.kuppuswamy@linux.intel.com>
Message-ID: <bc14b461-6431-c5ce-7117-854af8454900@linux.intel.com>
Date:   Mon, 10 May 2021 14:15:29 -0700
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On 5/10/21 10:24 AM, Rafael J. Wysocki wrote:
> The wakeup function can return an error when it is called for the
> second time on the same CPU.

To do this, we can only maintain the wakeup status of the CPUs. Can
you check whether following physid_mask based status maintenance is
acceptable?

--- a/arch/x86/kernel/acpi/boot.c
+++ b/arch/x86/kernel/acpi/boot.c
@@ -67,6 +67,7 @@ static u64 acpi_lapic_addr __initdata = APIC_DEFAULT_PHYS_BASE;

  static struct acpi_madt_multiproc_wakeup_mailbox *acpi_mp_wake_mailbox;
  static u64 acpi_mp_wake_mailbox_paddr;
+static physid_mask_t apic_id_wakemap = PHYSID_MASK_NONE;

  #ifdef CONFIG_X86_IO_APIC
  /*
@@ -347,6 +348,13 @@ static int acpi_wakeup_cpu(int apicid, unsigned long start_ip)

         acpi_mp_wake_mailbox_init();

+       /* Check if the given CPU (apicid) is already awake */
+       if (physid_isset(apicid, apic_id_wakemap)) {
+               pr_err("APIC ID %x is already awake, so failed to wakeup\n",
+                               apicid);
+               return -EINVAL;
+       }
+
         if (!acpi_mp_wake_mailbox)
                 return -EINVAL;

@@ -374,8 +382,18 @@ static int acpi_wakeup_cpu(int apicid, unsigned long start_ip)
         while (READ_ONCE(acpi_mp_wake_mailbox->command) && timeout--)
                 cpu_relax();

-       /* If timedout, return error */
-       return timeout ? 0 : -EIO;
+       if (timeout) {
+               /*
+                * If the CPU wakeup process is successful, store the
+                * status in apic_id_wakemap to prevent re-wakeup
+                * requests.
+                */
+               physid_set(apicid, apic_id_wakemap);
+               return 0;
+       }
+
+       /* If timed out (timeout == 0), return error */
+       return -EIO;
  }


-- 
Sathyanarayanan Kuppuswamy
Linux Kernel Developer