Re: [RESEND PATCH 3/3] x86/apic: Clean up the names of legacy irq mode setting related functions

From: Dou Liyang
Date: Fri Jan 19 2018 - 01:43:18 EST


Hi Baoquan,

At 01/05/2018 12:39 PM, Baoquan He wrote:
[...]
/*
- * Not an __init, needed by kexec/kdump code.
- * For safety IO-APIC and Local APIC need be cleared before this.
+ * In legacy irq mode, full DOS compatibility with the uniprocessor PC/AT is
+ * provided by using the APICs in conjunction with standard 8259A-equivalent
+ * programmable interrupt controllers (PICs). It's necessary to deliver legacy
+ * interrupts even when APIC mode is not enabled. This is required by kexec/
+ * kdump before enter into the 2nd kernel.
*/
void switch_to_legacy_irq_mode(void)
{
if (!nr_legacy_irqs())
return;
- x86_io_apic_ops.disable();
+ ioapic_set_virtual_wire_mode();
+
+ if (boot_cpu_has(X86_FEATURE_APIC) || apic_from_smp_config())
+ lapic_set_legacy_irq_mode(ioapic_i8259.pin != -1);

Seems these two function, ioapic/lapic_set_legacy_irq_mode should be
exclusive.

But We do that because both the through-lapic and through-ioapic virtual wire mode need setup the APIC_SPIV_APIC_ENABLED which is only located in
the lapic_set_legacy_irq_mode(). So we need call them both.

IMO, this cleanup may not make it clear. we can separate these two mode totally or just keep it like before.

Thanks,
dou.
}
#ifdef CONFIG_X86_32
diff --git a/arch/x86/kernel/x86_init.c b/arch/x86/kernel/x86_init.c
index 1151ccd72ce9..c30f0f273dbd 100644
--- a/arch/x86/kernel/x86_init.c
+++ b/arch/x86/kernel/x86_init.c
@@ -148,5 +148,5 @@ void arch_restore_msi_irqs(struct pci_dev *dev)
struct x86_io_apic_ops x86_io_apic_ops __ro_after_init = {
.read = native_io_apic_read,
- .disable = native_disable_io_apic,
+ .disable = switch_to_legacy_irq_mode,
};
diff --git a/drivers/iommu/irq_remapping.c b/drivers/iommu/irq_remapping.c
index 49721b4e1975..751472ddf536 100644
--- a/drivers/iommu/irq_remapping.c
+++ b/drivers/iommu/irq_remapping.c
@@ -37,7 +37,7 @@ static void irq_remapping_disable_io_apic(void)
* now.
*/
if (boot_cpu_has(X86_FEATURE_APIC) || apic_from_smp_config())
- disconnect_bsp_APIC(0);
+ lapic_set_legacy_irq_mode(0);
}
static void __init irq_remapping_modify_x86_ops(void)