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

[Julien Grall <julien.grall@xxxxxxxxxx>]

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...
Regards,

--
Julien Grall

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