linux-kernel - Re: [PATCH] iommu/vt-d: Fix modify

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Date:   Mon, 22 Aug 2016 14:38:35 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Wanpeng Li <kernellwp@...il.com>
cc:     linux-kernel@...r.kernel.org, iommu@...ts.linux-foundation.org,
        Wanpeng Li <wanpeng.li@...mail.com>,
        Joerg Roedel <joro@...tes.org>, Ingo Molnar <mingo@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH] iommu/vt-d: Fix modify_irte NULL pointer

On Mon, 22 Aug 2016, Wanpeng Li wrote:

> From: Wanpeng Li <wanpeng.li@...mail.com>
> 
> native_smp_prepare_cpus
>   -> default_setup_apic_routing
>     -> enable_IR_x2apic
>       -> irq_remapping_prepare
>         -> intel_prepare_irq_remapping
>           -> parse_ioapics_under_ir   => return 0
> 		    -> ir_parse_ioapic_hpet_scope
> 		      -> ir_parse_one_ioapic_scope 	
>           -> intel_setup_irq_remapping		  
 
> IR table is setup even if noapic boot parameter is added.
> index ac59692..f1cb7c6 100644
> --- a/drivers/iommu/intel_irq_remapping.c
> +++ b/drivers/iommu/intel_irq_remapping.c
> @@ -854,6 +854,9 @@ static int ir_parse_one_ioapic_scope(struct acpi_dmar_device_scope *scope,
>  	count = (scope->length - sizeof(struct acpi_dmar_device_scope))
>  		/ sizeof(struct acpi_dmar_pci_path);
>  
> +	if (skip_ioapic_setup)
> +		return -ENODEV;

Why are you adding this in the iommu code? We should not call any of the apic
functions when apic is disabled.

Thanks,

	tglx