Re: [PATCH 16/20] spapr, xics, xive: Better use of assert()s on irq claim/free paths

["Cédric Le Goater" <clg@kaod.org>]

On 25/09/2019 08:45, David Gibson wrote:
> The irq claim and free paths for both XICS and XIVE check for some
> validity conditions.  Some of these represent genuine runtime failures,
> however others - particularly checking that the basic irq number is in a
> sane range - could only fail in the case of bugs in the callin code.
> Therefore use assert()s instead of runtime failures for those.
> 
> In addition the non backend-specific part of the claim/free paths should
> only be used for PAPR external irqs, that is in the range SPAPR_XIRQ_BASE
> to the maximum irq number.  Put assert()s for that into the top level
> dispatchers as well.
> 
> Signed-off-by: David Gibson <david@gibson.dropbear.id.au>

Reviewed-by: Cédric Le Goater <clg@kaod.org>

> ---
>  hw/intc/spapr_xive.c |  8 ++------
>  hw/ppc/spapr_irq.c   | 18 ++++++++++--------
>  2 files changed, 12 insertions(+), 14 deletions(-)
> 
> diff --git a/hw/intc/spapr_xive.c b/hw/intc/spapr_xive.c
> index c1c97192a7..47b5ec0b56 100644
> --- a/hw/intc/spapr_xive.c
> +++ b/hw/intc/spapr_xive.c
> @@ -532,9 +532,7 @@ bool spapr_xive_irq_claim(SpaprXive *xive, uint32_t lisn, bool lsi)
>  {
>      XiveSource *xsrc = &xive->source;
>  
> -    if (lisn >= xive->nr_irqs) {
> -        return false;
> -    }
> +    assert(lisn < xive->nr_irqs);
>  
>      /*
>       * Set default values when allocating an IRQ number
> @@ -559,9 +557,7 @@ bool spapr_xive_irq_claim(SpaprXive *xive, uint32_t lisn, bool lsi)
>  
>  bool spapr_xive_irq_free(SpaprXive *xive, uint32_t lisn)
>  {
> -    if (lisn >= xive->nr_irqs) {
> -        return false;
> -    }
> +    assert(lisn < xive->nr_irqs);
>  
>      xive->eat[lisn].w &= cpu_to_be64(~EAS_VALID);
>      return true;
> diff --git a/hw/ppc/spapr_irq.c b/hw/ppc/spapr_irq.c
> index c40357a985..261d66ba17 100644
> --- a/hw/ppc/spapr_irq.c
> +++ b/hw/ppc/spapr_irq.c
> @@ -118,11 +118,7 @@ static int spapr_irq_claim_xics(SpaprMachineState *spapr, int irq, bool lsi,
>      ICSState *ics = spapr->ics;
>  
>      assert(ics);
> -
> -    if (!ics_valid_irq(ics, irq)) {
> -        error_setg(errp, "IRQ %d is invalid", irq);
> -        return -1;
> -    }
> +    assert(ics_valid_irq(ics, irq));
>  
>      if (!ics_irq_free(ics, irq - ics->offset)) {
>          error_setg(errp, "IRQ %d is not free", irq);
> @@ -138,9 +134,9 @@ static void spapr_irq_free_xics(SpaprMachineState *spapr, int irq)
>      ICSState *ics = spapr->ics;
>      uint32_t srcno = irq - ics->offset;
>  
> -    if (ics_valid_irq(ics, irq)) {
> -        memset(&ics->irqs[srcno], 0, sizeof(ICSIRQState));
> -    }
> +    assert(ics_valid_irq(ics, irq));
> +
> +    memset(&ics->irqs[srcno], 0, sizeof(ICSIRQState));
>  }
>  
>  static void spapr_irq_print_info_xics(SpaprMachineState *spapr, Monitor *mon)
> @@ -628,6 +624,9 @@ void spapr_irq_init(SpaprMachineState *spapr, Error **errp)
>  
>  int spapr_irq_claim(SpaprMachineState *spapr, int irq, bool lsi, Error **errp)
>  {
> +    assert(irq >= SPAPR_XIRQ_BASE);
> +    assert(irq < (spapr->irq->nr_xirqs + SPAPR_XIRQ_BASE));
> +
>      return spapr->irq->claim(spapr, irq, lsi, errp);
>  }
>  
> @@ -635,6 +634,9 @@ void spapr_irq_free(SpaprMachineState *spapr, int irq, int num)
>  {
>      int i;
>  
> +    assert(irq >= SPAPR_XIRQ_BASE);
> +    assert((irq+num) <= (spapr->irq->nr_xirqs + SPAPR_XIRQ_BASE));
> +
>      for (i = irq; i < (irq + num); i++) {
>          spapr->irq->free(spapr, irq);
>      }
>