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Re: [Xen-devel] [PATCH v4 05/17] xen/arm: ITS: implement hw_irq_controller for LPIs

Hi Vijay,

On 11/07/2015 16:40, Vijay Kilari wrote:
diff --git a/xen/include/asm-arm/gic.h b/xen/include/asm-arm/gic.h
index e9d5f36..44c2317 100644
--- a/xen/include/asm-arm/gic.h
+++ b/xen/include/asm-arm/gic.h
@@ -20,6 +20,9 @@

  #define NR_GIC_SGI         16
+#define FIRST_GIC_LPI      8192
+#define NR_GIC_LPI         4096
+#define MAX_LPI            (FIRST_GIC_LPI + NR_GIC_LPI)

MAX_LPI and NR_GIC_LPI should be obtained from the hardware at init time
and put somewhere, like a global nr_lpis perhaps, to be used throughout.

  This MAX_LPI and NR_GIC_LPI is Xen limitation where in we
are allocating irq_descriptors statically upto NR_GIC_LPI.

Why? The design doc [1] suggested to allocate dynamically the irq_desc array for LPI at boot.

Using a static array will grow up the Xen binary by close to 4096 LPIs * 60 bytes (rough estimate) = 240 KB.

And this is for any AArch64 platform, no matter that ITS is in used or not.


[1] http://xenbits.xen.org/people/ianc/vits/draftG.html#irq-descriptors

Julien Grall

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