Re: [PATCH v3 3/3] x86/acpi, x86/boot: Add multiprocessor wake-up support

[Kuppuswamy, Sathyanarayanan]

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