Now, there are many switches in kernel which are used to determine the final interrupt delivery mode, 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) CPU Capability: boot_cpu_has(X86_FEATURE_APIC) 4) MP table: smp_found_config 5) ACPI: acpi_lapic; acpi_ioapic; nr_ioapic These switches are disordered and scattered and there are also some dependencies between each other. These make the code difficult to maintain and read. Construct a selector to unify them into a single function, then, Use this selector to get an interrupt delivery mode directly. Signed-off-by: Dou Liyang <[email protected]> --- The selector logic: +------------+ |disable_apic+--------------------+ +------------+ true | |false | | | +------------v------------------+ | |!boot_cpu_has(X86_FEATURE_APIC)+-------+ +-------------------------------+ true | |false | | | +-------v---------+ v |!smp_found_config| PIC MODE +---------------+-+ |false |true | | v +---v---------+ SYMMETRIC IO MODE | !acpi_lapic | +------+------+ | v VIRTUAL WIRE MODE v2 --> v3: modify some comments. arch/x86/kernel/apic/apic.c | 61 +++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 61 insertions(+) diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c index 6bf7249..3342f144 100644 --- a/arch/x86/kernel/apic/apic.c +++ b/arch/x86/kernel/apic/apic.c @@ -1157,6 +1157,67 @@ void __init sync_Arb_IDs(void) APIC_INT_LEVELTRIG | APIC_DM_INIT); } +enum apic_interrupt_mode { + APIC_PIC = 0, + APIC_VIRTUAL_WIRE, + APIC_SYMMETRIC_IO, + APIC_MODE_COUNT +}; + +static int __init apic_interrupt_mode_select(void) +{ + /* Check kernel option */ + if (disable_apic) { + pr_info("APIC disabled via kernel command line\n"); + return APIC_PIC; + } + + /* Check BIOS */ +#ifdef CONFIG_X86_64 + /* On 64-bit, the APIC must be integrated */ + 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 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; + } + + /* Has a separate chip ? */ + if (!boot_cpu_has(X86_FEATURE_APIC) && !smp_found_config) { + disable_apic = 1; + + return APIC_PIC; + } +#endif + + /* Check MP table or ACPI MADT configuration */ + if (!smp_found_config) { + disable_ioapic_support(); + + if (!acpi_lapic) + pr_info("ACPI MADT or MP table not detected\n"); + + return APIC_VIRTUAL_WIRE; + } + + /* Other checks of APIC options will be done in each setup function */ + + return APIC_SYMMETRIC_IO; +} + /* * Setup the through-local-APIC virtual wire mode. */ -- 2.5.5
