Re: [Qemu-devel] [Qemu-ppc] [PATCH for-2.12 v2 00/12] spapr: introduce an IRQ allocator at the machine level

[Cédric Le Goater]

David,

On 11/09/2017 10:14 AM, Cédric Le Goater wrote:
> Hello,
> 
> Currently, the ICSState 'ics' object of the sPAPR machine acts as the
> global interrupt source handler and also as the IRQ number allocator
> for the machine. Some IRQ numbers are allocated very early in the
> machine initialization sequence to populate the device tree, and this
> is a problem to introduce the new POWER XIVE interrupt model, as it
> needs to share the IRQ numbers with the older model.
> 
> To prepare ground for XIVE, here is a proposal adding a set of new
> XICSFabric operations to let the machine handle directly the IRQ
> number allocation and to decorrelate the allocation from the interrupt
> source object :
> 
>     bool (*irq_test)(XICSFabric *xi, int irq);
>     int (*irq_alloc_block)(XICSFabric *xi, int count, int align);
>     void (*irq_free_block)(XICSFabric *xi, int irq, int num);
>     bool (*irq_is_lsi)(XICSFabric *xi, int irq);
> 
> In these prototypes, the 'irq' parameter refers to a number in the
> global IRQ number space.
> 
> On the sPAPR platform, these operations are simply backed by a bitmap
> and to handle migration compatibility, we introduce a machine class
> flag 'has_irq_bitmap', which is set to false for older machines.

Talking with Greg, I have found a better solution to handle migration 
compatibility which is to do like the phb_placement. That is to use 
two sets of XICS IRQ operations : one for the latest pseries machine 
using the bitmap and another one for the older pseries machine using 
the ICSIRQState. It impacts mostly patch 5.

This solution is cleaner and I will send a v3 in my morning unless
you start reviewing and have some obvious comments in the v2 series.


Thanks,

C. 


> To completely remove the use of the ICSState object (required to
> introduce XIVE), we also need to change how the nature of an
> interrupt, MSI or LSI, is stored. Today, this is done using the flag
> attribute of the ICSIRQState array. We change that by splitting the
> IRQ number space of the machine in two: first the LSIs and then the
> MSIs. This has the benefit to keep the LSI IRQ numbers in a well known
> range which is useful for PHB hotplug.
> 
> The git repo for this pachset can be found here along with the latest
> XIVE model:
> 
>     https://github.com/legoater/qemu/commits/xive
> 
> Thanks,
> 
> C.
> 
> Tests :
> 
>  - make check on each patch
>  - migration :
>      qemu-2.12 (pseries-2.12) <->  qemu-2.12 (pseries-2.12)
>      qemu-2.12 (pseries-2.10) <->  qemu-2.12 (pseries-2.10)
>      qemu-2.10 (pseries-2.10) <->  qemu-2.12 (pseries-2.10)
> 
> Changes since v1 :
> 
>  - reorganised patchset to introduce the XICSFabric operations before
>    the major changes: bitmap and IRQ number space split   
>  - introduced a reference bitmap to save some state in migration
> 
> Cédric Le Goater (12):
>   spapr: add pseries 2.12 machine type
>   ppc/xics: remove useless if condition
>   spapr: introduce new XICSFabric operations for an IRQ allocator
>   spapr: move current IRQ allocation under the machine
>   spapr: introduce an IRQ allocator using a bitmap
>   spapr: store a reference IRQ bitmap
>   spapr: introduce an 'irq_base' number
>   spapr: remove the use of ics_valid_irq()
>   spapr: introduce a XICSFabric is_lsi() operation
>   spapr: split the IRQ number space for LSI interrupts
>   sparp: merge ics_set_irq_type() in irq_alloc_block() operation
>   spapr: use sPAPRMachineState in spapr_ics_ prototypes
> 
>  hw/intc/trace-events   |   2 -
>  hw/intc/xics.c         |  37 ++++++-----
>  hw/intc/xics_kvm.c     |   4 +-
>  hw/intc/xics_spapr.c   |  76 ++++-----------------
>  hw/ppc/pnv.c           |  34 ++++++++++
>  hw/ppc/pnv_psi.c       |   4 --
>  hw/ppc/spapr.c         | 174 
> ++++++++++++++++++++++++++++++++++++++++++++++++-
>  hw/ppc/spapr_events.c  |   4 +-
>  hw/ppc/spapr_pci.c     |   8 +--
>  hw/ppc/spapr_vio.c     |   2 +-
>  hw/ppc/trace-events    |   2 +
>  include/hw/ppc/spapr.h |   6 ++
>  include/hw/ppc/xics.h  |  20 ++++--
>  13 files changed, 267 insertions(+), 106 deletions(-)
>