Re: [PATCH 2/7] spapr, xive: Turn "nr-ends" property into "nr-servers" property

[David Gibson <david@gibson.dropbear.id.au>]

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On Thu, Oct 03, 2019 at 02:01:13PM +0200, Greg Kurz wrote:
> The sPAPR XIVE object has an nr_ends field which happens to be a
> multiple of spapr_max_server_number(). It is currently set with
> the help of "nr-ends" property. This is a bit unfortunate since
> it exposes to the sPAPR irq frontend what should remain an
> implemantation detail within the XIVE backend.
> 
> It will be possible soon to inform the XIVE KVM device about the
> range of VCPU ids that may be used in the VM, as returned by the
> spapr_max_server_number() function. This will allow the device
> to substantially reduce the consumption of scarce resources
> in the XIVE HW.
> 
> For both reasons, replace the "nr-ends" property with an "nr-servers"
> one. The existing nr_ends field must be kept though since it tells how
> many ENDs are migrated, it is derived from "nr-servers" at realize time
> for simplicity. Convert spapr_dt_xive() to use it as well.
> 
> Signed-off-by: Greg Kurz <groug@kaod.org>
> ---
>  hw/intc/spapr_xive.c        |   21 ++++++++++++++++-----
>  hw/ppc/spapr_irq.c          |    2 +-
>  include/hw/ppc/spapr_xive.h |    1 +
>  3 files changed, 18 insertions(+), 6 deletions(-)
> 
> diff --git a/hw/intc/spapr_xive.c b/hw/intc/spapr_xive.c
> index 04879abf2e7a..62888ddc68db 100644
> --- a/hw/intc/spapr_xive.c
> +++ b/hw/intc/spapr_xive.c
> @@ -99,6 +99,15 @@ int spapr_xive_end_to_target(uint8_t end_blk, uint32_t end_idx,
>      return 0;
>  }
>  
> +static uint32_t spapr_xive_vcpu_id_to_end_idx(uint32_t vcpu_id)
> +{
> +    /*
> +     * 8 XIVE END structures per CPU. One for each available
> +     * priority
> +     */
> +    return vcpu_id << 3;
> +}
> +
>  static void spapr_xive_cpu_to_end(PowerPCCPU *cpu, uint8_t prio,
>                                    uint8_t *out_end_blk, uint32_t *out_end_idx)
>  {
> @@ -109,7 +118,7 @@ static void spapr_xive_cpu_to_end(PowerPCCPU *cpu, uint8_t prio,
>      }
>  
>      if (out_end_idx) {
> -        *out_end_idx = (cpu->vcpu_id << 3) + prio;
> +        *out_end_idx = spapr_xive_vcpu_id_to_end_idx(cpu->vcpu_id) + prio;
>      }
>  }
>  
> @@ -283,11 +292,13 @@ static void spapr_xive_realize(DeviceState *dev, Error **errp)
>          return;
>      }
>  
> -    if (!xive->nr_ends) {
> -        error_setg(errp, "Number of interrupt needs to be greater 0");
> +    if (!xive->nr_servers) {
> +        error_setg(errp, "Number of interrupt servers must be greater than 0");
>          return;
>      }
>  
> +    xive->nr_ends = spapr_xive_vcpu_id_to_end_idx(xive->nr_servers);

I'd prefer not to store both nr_servers and nr_servers * 8 in the
structure.  I think you just want xive->nr_servers, then derive it any
any places that current look at xive->nr_ends.

>      /*
>       * Initialize the internal sources, for IPIs and virtual devices.
>       */
> @@ -489,7 +500,7 @@ static const VMStateDescription vmstate_spapr_xive = {
>  
>  static Property spapr_xive_properties[] = {
>      DEFINE_PROP_UINT32("nr-irqs", SpaprXive, nr_irqs, 0),
> -    DEFINE_PROP_UINT32("nr-ends", SpaprXive, nr_ends, 0),
> +    DEFINE_PROP_UINT32("nr-servers", SpaprXive, nr_servers, 0),

Technically speaking the user can reach in using -global and modify
QOM properties like this, so this is arguably an interface breakage.
That said, I've always thought it was kind of a problem that the way
QOM is used internally thereby exposes as interface a bunch of things
that are really intended to be internal.

So... I'm inclined to go ahead with this anyway.  I won't tell if you
don't.

>      DEFINE_PROP_UINT64("vc-base", SpaprXive, vc_base, SPAPR_XIVE_VC_BASE),
>      DEFINE_PROP_UINT64("tm-base", SpaprXive, tm_base, SPAPR_XIVE_TM_BASE),
>      DEFINE_PROP_END_OF_LIST(),
> @@ -1550,7 +1561,7 @@ void spapr_dt_xive(SpaprMachineState *spapr, uint32_t nr_servers, void *fdt,
>      /* Interrupt number ranges for the IPIs */
>      uint32_t lisn_ranges[] = {
>          cpu_to_be32(0),
> -        cpu_to_be32(nr_servers),
> +        cpu_to_be32(xive->nr_servers),
>      };
>      /*
>       * EQ size - the sizes of pages supported by the system 4K, 64K,
> diff --git a/hw/ppc/spapr_irq.c b/hw/ppc/spapr_irq.c
> index 457eabe24cda..025fd00143a2 100644
> --- a/hw/ppc/spapr_irq.c
> +++ b/hw/ppc/spapr_irq.c
> @@ -591,7 +591,7 @@ void spapr_irq_init(SpaprMachineState *spapr, Error **errp)
>           * 8 XIVE END structures per CPU. One for each available
>           * priority
>           */
> -        qdev_prop_set_uint32(dev, "nr-ends", nr_servers << 3);
> +        qdev_prop_set_uint32(dev, "nr-servers", nr_servers);
>          qdev_init_nofail(dev);
>  
>          spapr->xive = SPAPR_XIVE(dev);
> diff --git a/include/hw/ppc/spapr_xive.h b/include/hw/ppc/spapr_xive.h
> index 0df20a6590a5..4a4a6fc6be7f 100644
> --- a/include/hw/ppc/spapr_xive.h
> +++ b/include/hw/ppc/spapr_xive.h
> @@ -22,6 +22,7 @@ typedef struct SpaprXive {
>      /* Internal interrupt source for IPIs and virtual devices */
>      XiveSource    source;
>      hwaddr        vc_base;
> +    uint32_t      nr_servers;

This is a basic paraneter, not really related to the internal source
structure, so I'd move it up above that comment there.

>  
>      /* END ESB MMIOs */
>      XiveENDSource end_source;
> 

-- 
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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