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Re: [Qemu-devel] [PATCH 0/2] spapr/irq: remove the XICS offset adjustmen

From: David Gibson
Subject: Re: [Qemu-devel] [PATCH 0/2] spapr/irq: remove the XICS offset adjustment for the dual machine
Date: Thu, 14 Feb 2019 11:49:03 +1100
User-agent: Mutt/1.10.1 (2018-07-13)

On Wed, Feb 13, 2019 at 10:07:54PM +0100, Cédric Le Goater wrote:
> Hello,
> When using the 'dual' interrupt mode, the source numbers of both sPAPR
> IRQ backends are aligned to share a common IRQ number space and to use
> a similar mapping of the machine qemu_irq array which is indexed by
> the source number.
> The XICS IRQ number range initially being [ 0x1000 - 0x2000 ], this
> requires to change the XICS ICSState offset to 0 and to provision for
> an extra 4K of source numbers and qemu_irqs which will never be used
> by the machine when running under the XICS interrupt mode. This is not
> an optimal solution.
> Moreover, the KVM support for the 'dual' interrupt mode will require
> some adjustments. The XICS KVM device considers that the IRQ numbers
> start at XICS_IRQ_BASE (0x1000) and we have no way to inform KVM of
> the offset change. We will need to ignore the lower 4K numbers when
> capturing or restoring the source states from the XICS KVM device.
> The first patch allocates an IRQ number space of the expected size for
> the XICS sPAPR IRQ backend. The overall IRQ number space size and the
> qemu_irq array size is still the one required by the 'dual' sPAPR IRQ
> backend, that is, in sync with XIVE. The second patch removes the
> ICSState offset adjustment. This last change adds some benefits as it
> simplifies greatly the qirq() method of the 'dual' sPAPR IRQ
> backend.

Ah, much nicer.  Applied to ppc-for-4.0, thanks.

> C.
> Cédric Le Goater (2):
>   spapr/irq: add an 'nr_irq' parameter to initialize the backend.
>   spapr/irq: remove the XICS offset adjustment
>  include/hw/ppc/spapr_irq.h |  2 +-
>  hw/ppc/spapr_irq.c         | 45 ++++++++++----------------------------
>  2 files changed, 12 insertions(+), 35 deletions(-)

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_!

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