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

On 10/02/16 14:19, Julien Grall wrote:

Hi Christoffer,

On 09/02/16 20:49, Christoffer Dall wrote:

quoted

quoted

+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.

The GICH size can be found in the GIC400 TRM:

http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.ddi0471b/CHDBJDCB.html

The first 4kB are banked per CPU, while the next 4kB are exposing all
CPUs, each in a 512 bytes window. We don't give a damn about the second
page, but hey, it is there...

Of course, this is GIC400, not the architecture spec. So maybe
considering a 4kB size would be better, just in case someone is
braindead enough to produce another GICv2 implementation without the
aliases...

	M.
-- 
Jazz is not dead. It just smells funny...