Re: [RFC PATCH 2/6] x86/apic: Construct a framework for setuping APIC mode as soon as possible

[Dou Liyang]

Hi Thomas,

At 04/05/2017 07:46 PM, Thomas Gleixner wrote:
> On Wed, 29 Mar 2017, Dou Liyang wrote:
>
> > Now, there are two ways to setup local apic and io-apic in X86 arch:
> >   1. In an SMP-capable system, it will be done when preparing the
> > cpus in native_smp_prepare_boot_cpu().
> >   2. If UP_LATE_INIT is y, it will be done in smp_init()
> >
> > And, there are many switches in kernel which can determine the way of
> > APIC mode setup, as shown below:
> >
> >   1. kconfig :
> >      CONFIG_X86_64; CONFIG_X86_LOCAL_APIC; CONFIG_x86_IO_APIC
> >   2. kernel option: disable_apic; skip_ioapic_setup
> >   3. BIOS : boot_cpu_has(X86_FEATURE_APIC)
> >   4. MP table: smp_found_config
> >   5. ACPI: acpi_lapic; acpi_ioapic; nr_ioapic
> >
> > The setup is late which cause the dump-capture kernel hangs with 'notsc'
> > option in 1st kernel option. and the use of these switches is messily.
> >
> > Before make the APIC mode setup earlier, construct a framework first to
> > prepare for the work and make the logic clear.
>
> Calling that a framework is slightly exaggerated. It's a selector function
> for the interrupt delivery mode.

Yes, Selector is what I want.

To tell the truth, I've been looking for a word that can summarize this
patch for a long time. :)


> >  #ifdef CONFIG_X86_X2APIC
> > diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c
> > index f4fc949..bf4ccd0 100644
> > --- a/arch/x86/kernel/apic/apic.c
> > +++ b/arch/x86/kernel/apic/apic.c
> > @@ -1153,6 +1153,63 @@ void __init sync_Arb_IDs(void)
> >  			APIC_INT_LEVELTRIG | APIC_DM_INIT);
> >  }
> >
> > +enum apic_bsp_mode {
> > +	APIC_BSP_MODEL_PIC = 0,
> > +	APIC_BSP_MODEL_VIRTUAL_WIRE,
> > +	APIC_BSP_MODEL_SYMMETRIC_IO,
> > +	APIC_BSP_MODEL_COUNT
> > +};
> > +
> > +static int __init apic_bsp_mode_check(void)
> > +{
> > +
> > +	/* Check kernel option */
> > +	if (disable_apic) {
> > +		pr_info("APIC disabled by kernel option\n");
>
> kernel option is ambiguous. "APIC disabled via kernel command line" is telling
> clearly where this comes from.

Thanks, will modify in my next version.

> > +		return APIC_BSP_MODEL_PIC;
> > +	}
> > +	/* Check BOIS */
> > +#ifdef CONFIG_X86_64
> > +	/* On 64-bit, The APIC is integrated, So, must have APIC feature */
> > +	if (!boot_cpu_has(X86_FEATURE_APIC)) {
> > +		disable_apic = 1;
> > +		pr_info("Apic disabled by BIOS\n");
>
> Please use APIC consistently.

Oops, Yes.

> > +		return APIC_BSP_MODEL_PIC;
> > +	}
> > +#else
> > +	if (!boot_cpu_has(X86_FEATURE_APIC) &&
> > +		APIC_INTEGRATED(boot_cpu_apic_version)) {
> > +		pr_err("BIOS bug, local APIC #%d not detected!...\n",
> > +			boot_cpu_physical_apicid);
>
> Please make that
>
> 		pr_err(FW_BUG, "Local APIC %d not detected, force emulation",
> 		       boot_cpu_physical_apicid);
>
> and for consistency reasosns this should also set disable_apic to 1.
>
> > +		return APIC_BSP_MODEL_PIC;

Yes. I will.

> > +	}
> > +#endif
> > +	/*
> > +	 * Check MP table, if neither an integrated nor a separate chip
> > +	 * doesn't exist.
> > +	 */
> > +	if (!boot_cpu_has(X86_FEATURE_APIC) && !smp_found_config) {
> > +		pr_info("BOIS don't support APIC, and no SMP configuration.\n");
>
> s/BOIS/BIOS/
>
> and for consistency reasosns this should also set disable_apic to 1.

OK.

> > +		return APIC_BSP_MODEL_PIC;
> > +	}
> > +
> > +	/* Check MP table, ps: if the virtual wire has been setup */
> > +	if (!smp_found_config) {
> > +		disable_ioapic_support();
> > +
> > +		/* Check local APIC, if SMP_NO_CONFIG */
> > +		if (!acpi_lapic)
> > +			pr_info("SMP motherboard not detected\n");
> > +
> > +		return APIC_BSP_MODEL_VIRTUAL_WIRE;
> > +	}
> > +
> > +	/* Other checks of ACPI options will be done in each setup function */
> > +
> > +	return APIC_BSP_MODEL_SYMMETRIC_IO;
> > +}
> > +
> >  /*
> >   * Setup the through-local-APIC virtual wire mode.
> >   */
> > @@ -1202,6 +1259,22 @@ void apic_virture_wire_mode_setup(void)
> >  	apic_write(APIC_LVT1, value);
> >  }
> >
> > +/* init the interrupt routing model for the BSP */
> > +void __init init_bsp_APIC(void)
> > +{
> > +	switch (apic_bsp_mode_check()) {
> > +	case APIC_BSP_MODEL_PIC:
> > +		pr_info("Keep in PIC mode(8259)\n");
> > +		return;
> > +	case APIC_BSP_MODEL_VIRTUAL_WIRE:
> > +		pr_info("switch to virtual wire model.\n");
>
> Please consistently start sentences with upper case letters.

Yes, I will check all the sentences and comments again carefully.

Thanks,
	Liyang
> Thanks,
>
> 	tglx