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

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Date:   Fri, 19 Jan 2018 14:42:17 +0800
From:   Dou Liyang <douly.fnst@...fujitsu.com>
To:     Baoquan He <bhe@...hat.com>, <linux-kernel@...r.kernel.org>
CC:     <mingo@...hat.com>, <tglx@...utronix.de>, <hpa@...or.com>,
        <x86@...nel.org>, <rostedt@...dmis.org>, <jgross@...e.com>,
        <peterz@...radead.org>, <uobergfe@...hat.com>, <joro@...tes.org>
Subject: Re: [RESEND PATCH 3/3] x86/apic: Clean up the names of legacy irq
 mode setting related functions

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)
>