Re: [Xen-devel] [PATCH v6 12/12] docs: Describe PVHv2's VCPU hotplug procedure

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Tue, 3 Jan 2017, Boris Ostrovsky wrote:
> Signed-off-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
> Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
> ---
> CC: George Dunlap <George.Dunlap@xxxxxxxxxxxxx>
> CC: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
> CC: Stefano Stabellini <sstabellini@xxxxxxxxxx>
> CC: Tim Deegan <tim@xxxxxxx>
> ---
> Changes in v6:
> * No GPE0 update is needed anymore.
> 
>  docs/misc/hvmlite.markdown | 11 +++++++++++
>  1 file changed, 11 insertions(+)
> 
> diff --git a/docs/misc/hvmlite.markdown b/docs/misc/hvmlite.markdown
> index 898b8ee..472edee 100644
> --- a/docs/misc/hvmlite.markdown
> +++ b/docs/misc/hvmlite.markdown
> @@ -75,3 +75,14 @@ info structure that's passed at boot time (field 
> rsdp_paddr).
>  
>  Description of paravirtualized devices will come from XenStore, just as it's
>  done for HVM guests.
> +
> +## VCPU hotplug ##
> +
> +VCPU hotplug (e.g. 'xl vcpu-set <domain> <num_vcpus>') for PVHv2 guests
> +follows ACPI model where change in domain's number of VCPUS (stored in
> +domain.avail_vcpus) results in an SCI being sent to the guest. The guest
> +then executes DSDT's PRSC method, updating MADT enable status for the
> +affected VCPU.
> +
> +Updating VCPU number is achieved by having the toolstack issue a write to
> +ACPI's XEN_ACPI_CPU_MAP.

Looking at 1483452256-2879-10-git-send-email-boris.ostrovsky@xxxxxxxxxx,
this is done via domctl. I think it is worth documenting that.

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