On Fri, Oct 12, 2012 at 09:09:45AM -0700, Fenghua Yu wrote:
> From: Fenghua Yu <fenghua...@intel.com>
>
> Instead of waiting for STARTUP after INITs, BSP will execute the BIOS
> boot-strap
> code which is not a desired behavior for waking up BSP. To avoid the
> boot-strap
> code, wake up CPU0 by NMI instead.
>
> This works to wake up soft offlined CPU0 only. If CPU0 is hard offlined (i.e.
> physically hot removed and then hot added), NMI won't wake it up. We'll change
> this code in the future to wake up hard offlined CPU0 if real platform and
> request are available.
>
> AP is still waken up as before by INIT, SIPI, SIPI sequence.
>
> Signed-off-by: Fenghua Yu <fenghua...@intel.com>
> ---
> arch/x86/include/asm/cpu.h | 1 +
> arch/x86/kernel/smpboot.c | 112 +++++++++++++++++++++++++++++++++++++++++--
> 2 files changed, 107 insertions(+), 6 deletions(-)
[ … ]
> @@ -727,8 +745,47 @@ static int __cpuinit do_boot_cpu(int apicid, int cpu,
> struct task_struct *idle)
> */
> if (apic->wakeup_secondary_cpu)
> boot_error = apic->wakeup_secondary_cpu(apicid, start_ip);
> - else
> - boot_error = wakeup_secondary_cpu_via_init(apicid, start_ip);
> + else {
> + if (cpu)
> + /*
> + * Wake up AP by INIT, INIT, STARTUP sequence.
> + */
> + boot_error = wakeup_secondary_cpu_via_init(apicid,
> + start_ip);
> + else {
> + /*
> + * Instead of waiting for STARTUP after INITs, BSP will
> + * execute the BIOS boot-strap code which is not a
> + * desired behavior for waking up BSP. To avoid the
> + * boot-strap code, wake up CPU0 by NMI instead.
> + *
> + * This works to wake up soft offlined CPU0 only. If
> + * CPU0 is hard offlined (i.e. physically hot removed
> + * and then hot added), NMI won't wake it up. We'll
> + * change this code in the future to wake up hard
> + * offlined CPU0 if real platform and request are
> + * available.
> + */
> + int id;
> +
> + enable_start_cpu0 = 1;
> + /*
> + * Register a NMI handler to help wake up CPU0.
> + */
> + boot_error = register_nmi_handler(NMI_LOCAL,
> + wakeup_cpu0_nmi, 0, "wake_cpu0");
> +
> + if (!boot_error) {
> + cpu0_nmi_registered = 1;
> + if (apic->dest_logical == APIC_DEST_LOGICAL)
> + id = cpu0_logical_apicid;
> + else
> + id = apicid;
> + boot_error = wakeup_secondary_cpu_via_nmi(id,
> + start_ip);
> + }
This whole else-part for cpu 0 could be carved out into a separate
function so that you can save yourself the awkward code indentation and
make this a lot more readable.
Thanks.
--
Regards/Gruss,
Boris.
--
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