Re: [Qemu-ppc] [PATCH 0/2] spapr/irq: remove the XICS offset adjustment for the dual machine

[Cédric Le Goater]

On 2/14/19 1:49 AM, David Gibson wrote:
> 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

s/IRQ number space/source numbers/

There is still some confusion in the way I use the terms "IRQ number" 
and "source number". These are two different number spaces. I should
pay more attention.

>> 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.

I will just drop patch "spapr/xics: ignore the lower 4K in the IRQ 
number space"

Thanks,

C.