Re: [PATCH v2 0/4] spapr/xive: Allocate vCPU IPIs from the vCPU contexts

[David Gibson]

On Thu, Aug 20, 2020 at 03:45:43PM +0200, Cédric Le Goater wrote:
> Hello,
> 
> 
> When QEMU switches to the XIVE interrupt mode, it creates all the
> guest interrupts at the level of the KVM device. These interrupts are
> backed by real HW interrupts from the IPI interrupt pool of the XIVE
> controller.
> 
> Currently, this is done from the QEMU main thread, which results in
> allocating all interrupts from the chip on which QEMU is running. IPIs
> are not distributed across the system and the load is not well
> balanced across the interrupt controllers.
> 
> Change the vCPU IPI allocation to run from the vCPU context. The
> associated XIVE IPI interrupt will be allocated on the chip on which
> the vCPU is running and improve distribution of the IPIs in the system.
> When the vCPUs are pinned, this will make the IPI local to the chip of
> the vCPU. It will reduce rerouting between interrupt controllers and
> gives better performance.
> 
> 
> I did some basic migration testing with the 'dual' and 'xive' modes,
> also tried CPU hoplug. I haven't tried migration with older pseries
> machine.

LGTM, applied to ppc-for-5.2.

-- 
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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