Re: [Xen-devel] Xen virtual IOMMU high level design doc V2

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 18.10.16 at 16:14, <tianyu.lan@xxxxxxxxx> wrote:
> 1.1 Enable more than 255 vcpu support
> HPC cloud service requires VM provides high performance parallel
> computing and we hope to create a huge VM with >255 vcpu on one machine
> to meet such requirement.Ping each vcpus on separated pcpus. More than
> 255 vcpus support requires X2APIC and Linux disables X2APIC mode if
> there is no interrupt remapping function which is present by vIOMMU.
> Interrupt remapping function helps to deliver interrupt to #vcpu >255.
> So we need to add vIOMMU before enabling >255 vcpus.

I continue to dislike this completely neglecting that we can't even
have >128 vCPU-s at present. Once again - there's other work to
be done prior to lack of vIOMMU becoming the limiting factor.

Jan

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