Re: [Qemu-devel] [RFC PATCH] spapr/irq: force XICS interrupt mode on non P9 machines

[David Gibson]

On Sun, Mar 17, 2019 at 09:33:42PM +0100, Cédric Le Goater wrote:
> There is no need to propose the 'dual' interrupt mode interrupt device
> on POWER7/8 machines and the XIVE mode will not operate. Simply force
> XICS in this case.
> 
> This makes the check in spapr_machine_init() redundant on XIVE-only
> machines.
> 
> Signed-off-by: Cédric Le Goater <address@hidden>

This is not my preferred approach.  If the user explicitly selects
xive or dual mode with a POWER8 cpu, we should hard error, rather than
forcing a different mode from the one requested.

We do need to make sure we default to xics mode with POWER8, even on
new machine types.

> ---
>  hw/ppc/spapr_irq.c | 10 ++++++++++
>  1 file changed, 10 insertions(+)
> 
> diff --git a/hw/ppc/spapr_irq.c b/hw/ppc/spapr_irq.c
> index f2ca1bb66c9d..d27ae68915a1 100644
> --- a/hw/ppc/spapr_irq.c
> +++ b/hw/ppc/spapr_irq.c
> @@ -16,6 +16,7 @@
>  #include "hw/ppc/spapr_xive.h"
>  #include "hw/ppc/xics.h"
>  #include "hw/ppc/xics_spapr.h"
> +#include "cpu-models.h"
>  #include "sysemu/kvm.h"
>  
>  #include "trace.h"
> @@ -655,6 +656,7 @@ SpaprIrq spapr_irq_dual = {
>  void spapr_irq_init(SpaprMachineState *spapr, Error **errp)
>  {
>      MachineState *machine = MACHINE(spapr);
> +    Error *local_err = NULL;
>  
>      if (machine_kernel_irqchip_split(machine)) {
>          error_setg(errp, "kernel_irqchip split mode not supported on 
> pseries");
> @@ -667,6 +669,14 @@ void spapr_irq_init(SpaprMachineState *spapr, Error 
> **errp)
>          return;
>      }
>  
> +    /* Force XICS on non P9 machines */
> +    if (!ppc_type_check_compat(machine->cpu_type, CPU_POWERPC_LOGICAL_3_00,
> +                              0, spapr->max_compat_pvr)) {
> +        error_setg(&local_err, "forcing XICS interrupt controller");
> +        warn_report_err(local_err);
> +        spapr->irq = &spapr_irq_xics;
> +    }
> +
>      /* Initialize the MSI IRQ allocator. */
>      if (!SPAPR_MACHINE_GET_CLASS(spapr)->legacy_irq_allocation) {
>          spapr_irq_msi_init(spapr, spapr->irq->nr_msis);

-- 
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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