Re: [Qemu-devel] [PATCH 2/4] sparp_pci: simplify how the PCI LSIs are allocated

[Greg Kurz <groug@kaod.org>]

On Fri, 18 May 2018 18:44:03 +0200
Cédric Le Goater <clg@kaod.org> wrote:

> PCI LSIs are today allocated one by one using the IRQ alloc_block
> routine. Change the code sequence to first allocate a PCI_NUM_PINS
> block. It will help us providing a generic IRQ framework to the
> machine.
> 
> Signed-off-by: Cédric Le Goater <clg@kaod.org>
> ---
>  hw/ppc/spapr_pci.c | 21 ++++++++++-----------
>  1 file changed, 10 insertions(+), 11 deletions(-)
> 
> diff --git a/hw/ppc/spapr_pci.c b/hw/ppc/spapr_pci.c
> index 39a14980d397..4fd97ffe4c6e 100644
> --- a/hw/ppc/spapr_pci.c
> +++ b/hw/ppc/spapr_pci.c
> @@ -1546,6 +1546,8 @@ static void spapr_phb_realize(DeviceState *dev, Error **errp)
>      sPAPRTCETable *tcet;
>      const unsigned windows_supported =
>          sphb->ddw_enabled ? SPAPR_PCI_DMA_MAX_WINDOWS : 1;
> +    uint32_t irq;
> +    Error *local_err = NULL;
>  
>      if (!spapr) {
>          error_setg(errp, TYPE_SPAPR_PCI_HOST_BRIDGE " needs a pseries machine");
> @@ -1694,18 +1696,15 @@ static void spapr_phb_realize(DeviceState *dev, Error **errp)
>      QLIST_INSERT_HEAD(&spapr->phbs, sphb, list);
>  
>      /* Initialize the LSI table */
> -    for (i = 0; i < PCI_NUM_PINS; i++) {
> -        uint32_t irq;
> -        Error *local_err = NULL;
> -
> -        irq = spapr_irq_alloc_block(spapr, 1, true, false, &local_err);
> -        if (local_err) {
> -            error_propagate(errp, local_err);
> -            error_prepend(errp, "can't allocate LSIs: ");
> -            return;
> -        }
> +    irq = spapr_irq_alloc_block(spapr, PCI_NUM_PINS, true, false, &local_err);
> +    if (local_err) {
> +        error_propagate(errp, local_err);
> +        error_prepend(errp, "can't allocate LSIs: ");
> +        return;
> +    }
>  

It isn't strictly equivalent. The current code would be happy with
sparse IRQ numbers, while the proposed one wouldn't... Anyway, this
cannot happen since we don't have PHB hotplug.

Reviewed-by: Greg Kurz <groug@kaod.org>

> -        sphb->lsi_table[i].irq = irq;
> +    for (i = 0; i < PCI_NUM_PINS; i++) {
> +        sphb->lsi_table[i].irq = irq + i;
>      }
>  
>      /* allocate connectors for child PCI devices */