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Re: [Xen-devel] [PATCH V5 10/10] xen/arm64: increase MAX_VIRT_CPUS to 128 on arm64

Hi Chen,

On 31/05/2015 16:37, Chen Baozi wrote:

On May 31, 2015, at 21:40, Julien Grall <julien.grall@xxxxxxxxxx> wrote:

Hi Chen,

On 30/05/2015 12:07, Chen Baozi wrote:
From: Chen Baozi <baozich@xxxxxxxxx>

GIC-500 supports up to 128 cores in a single SoC. Increase MAX_VIRT_CPUS
to 128 on arm64.

Where did you find this restriction? AFAICT the changes you made in the vGICv3 
driver allow us to use up to 4096 CPUs.

In ARM DDI0516B (ARM CoreLinkTM GIC-500 Generic Interrupt Controller
Technical Reference Manual):

1.1 About the GIC-500

The GIC-500 is a build-time configurable interrupt controller that supports up 
to 128 cores.

And GIC-500 is the only GICv3 implementation as far as I know.

The only implementation hardware ;). The vGICv3 in both KVM and Xen are 2 other implementations but software.

For instance, with your series a cluster can use up to 16 cores but the GIC-500 is only supporting up to 8 cores...


Julien Grall

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