Re: [for-5.0 PATCH v2 0/4] spapr: Use less XIVE HW resources in KVM

[David Gibson]

On Tue, Nov 26, 2019 at 05:46:12PM +0100, Greg Kurz wrote:
> On POWER9 systems, the XICS-on-XIVE and XIVE KVM devices currently
> allocate a bunch of VPs in the XIVE HW to accomodate the highest
> VCPU id that may be possibly used in a VM. This limits the number
> of VMs that can run with an in-kernel interrupt controller to 63
> per POWER9 chip, irrespectively of its number of HW threads, eg.
> up to 96 on a POWER9 Nimbus socket. This is an unfortunate waste
> of scarce HW resources since a typical VM doesn't need that much
> VPs to run.
> 
> This series exploits new attributes of the XICS-on-XIVE and XIVE
> KVM devices that allow userspace to tune the numbers of VPs it
> really needs. Support for this attributes has just reached linux
> mainline.
> 
> In combination with recent commit 29cb4187497d "spapr: Set VSMT to
> smp_threads by default" which makes VCPU ids contiguous, it is
> possible to start more than 200 VMs instead of 127 on an AC922
> system (two sockets, 144 HW threads).
> 
> Changes in v2:
> - add an nr_servers argument to the activate() handler instead of
>   a QOM property for XIVE and a XICSFabric method for XICS-on-XIVE.
> - even if the last two patches haven't changed much, the code base
>   itself has, so I've deliberately dropped Cedric's R-b tags

Applied to ppc-for-5.0, thanks.

-- 
David Gibson                    | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au  | minimalist, thank you.  NOT _the_ _other_
                                | _way_ _around_!
http://www.ozlabs.org/~dgibson

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