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SubjectRe: [PATCH v8 01/13] x86/apic: Construct a selector for the interrupt delivery mode
Hi Dou,

On 08/28/17 at 11:20am, Dou Liyang wrote:
> +static int __init apic_intr_mode_select(void)
> +{
> + /* Check kernel option */
> + if (disable_apic) {
> + pr_info("APIC disabled via kernel command line\n");
> + return APIC_PIC;
> + }
> +

I am not very familiar with cpu registers, not sure if we can adjust
below code flow as:

/* If APIC is integrated, check local APIC only */
if (lapic_is_integrated() && !boot_cpu_has(X86_FEATURE_APIC)) {
disable_apic = 1;
pr_info("APIC disabled by BIOS\n");
return APIC_PIC;
}

/* If APIC is on a separate chip, check if smp_found_config is found*/
if (!lapic_is_integrated() && !smp_found_config) {
disable_apic = 1;
return APIC_PIC;
}
~~~~ Now, I haven't think of why smp_found_config has to be
checked here.

In this way, we don't need the CONFIG_X86_64 checking since it's
contained in lapic_is_integrated() already. And the checking is obvious
for understanding. Just not very sure if the checking is adequate.

Just my personal opinion.

> + /* Check BIOS */
> +#ifdef CONFIG_X86_64
> + /* On 64-bit, the APIC must be integrated, Check local APIC only */
> + if (!boot_cpu_has(X86_FEATURE_APIC)) {
> + disable_apic = 1;
> + pr_info("APIC disabled by BIOS\n");
> + return APIC_PIC;
> + }
> +#else
> + /*
> + * On 32-bit, check whether there is a separate chip or integrated
> + * APIC
> + */
> +
> + /* Has a separate chip ? */
> + if (!boot_cpu_has(X86_FEATURE_APIC) && !smp_found_config) {
> + disable_apic = 1;
> +
> + return APIC_PIC;
> + }
> +
> + /* Has a local APIC ? */
> + if (!boot_cpu_has(X86_FEATURE_APIC) &&
> + APIC_INTEGRATED(boot_cpu_apic_version)) {
> + disable_apic = 1;
> + pr_err(FW_BUG "Local APIC %d not detected, force emulation\n",
> + boot_cpu_physical_apicid);
> +
> + return APIC_PIC;
> + }
> +#endif
> +
> + /* Check MP table or ACPI MADT configuration */
> + if (!smp_found_config) {
> + disable_ioapic_support();
> +
> + if (!acpi_lapic)
> + pr_info("APIC: ACPI MADT or MP tables are not detected\n");
> +
> + return APIC_VIRTUAL_WIRE;
> + }
> +
> + return APIC_SYMMETRIC_IO;
> +}
> +
> /*
> * An initial setup of the virtual wire mode.
> */
> --
> 2.5.5
>
>
>

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