linux-kernel - Re: [PATCH 3/5] irqchip/gic-v2: Parse and export virtual GIC information

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Message-ID: <56BB46DC.7080202@arm.com>
Date:	Wed, 10 Feb 2016 14:19:08 +0000
From:	Julien Grall <julien.grall@....com>
To:	Christoffer Dall <christoffer.dall@...aro.org>
Cc:	kvmarm@...ts.cs.columbia.edu, marc.zyngier@....com,
	fu.wei@...aro.org, kvm@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	wei@...hat.com, al.stone@...aro.org,
	Thomas Gleixner <tglx@...utronix.de>,
	Jason Cooper <jason@...edaemon.net>
Subject: Re: [PATCH 3/5] irqchip/gic-v2: Parse and export virtual GIC
 information

Hi Christoffer,

On 09/02/16 20:49, Christoffer Dall wrote:
>> +static void __init gic_acpi_setup_kvm_info(void)
>> +{
>> +	gic_v2_kvm_info.type = GIC_V2;
>> +
>> +	gic_v2_kvm_info.maint_irq = acpi_register_gsi(NULL,
>> +						      acpi_data.maint_irq,
>> +						      acpi_data.maint_irq_mode,
>> +						      ACPI_ACTIVE_HIGH);
>> +	gic_v2_kvm_info.vctrl_base = acpi_data.vctrl_base;
>> +	if (gic_v2_kvm_info.vctrl_base)
>> +		gic_v2_kvm_info.vctrl_size = SZ_8K;
>> +
>> +	gic_v2_kvm_info.vcpu_base = acpi_data.vcpu_base;
>> +	if (gic_v2_kvm_info.vcpu_base)
>> +		gic_v2_kvm_info.vcpu_size = SZ_8K;
>
> why are the sizes hard-coded to 8K in this case?

The MADT only provides the base addresses and not the size. The default 
value has been chosen based on the GICv2 spec (ARM IHI 0048B.b)
	* GICV: See 5.5
	* GICH: I can't find again the section about it. But the example 
bindings in 
Documents/devicetree/bindings/interrupt-controller/arm,gic.txt uses 8K.

I will add a comment in the code explaining where the 8K come from.

Cheers,

-- 
Julien Grall