Re: [PATCH v2 17/33] xive: Improve irq claim/free path

[Greg Kurz <groug@kaod.org>]

On Fri, 27 Sep 2019 15:50:12 +1000
David Gibson <david@gibson.dropbear.id.au> wrote:

> spapr_xive_irq_claim() returns a bool to indicate if it succeeded.
> But most of the callers and one callee use int return values and/or an
> Error * with more information instead.  In any case, ints are a more
> common idiom for success/failure states than bools (one never knows
> what sense they'll be in).
> 
> So instead change to an int return value to indicate presence of error
> + an Error * to describe the details through that call chain.
> 
> It also didn't actually check if the irq was already claimed, which is
> one of the primary purposes of the claim path, so do that.
> 
> spapr_xive_irq_free() also returned a bool... which no callers checked
> and was always true, so just drop it.
> 
> Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
> Reviewed-by: Cédric Le Goater <clg@kaod.org>
> ---
>  hw/intc/spapr_xive.c        | 20 +++++++++-----------
>  hw/intc/spapr_xive_kvm.c    |  8 ++++----
>  hw/ppc/spapr_irq.c          | 14 ++++++++------
>  include/hw/ppc/spapr_xive.h |  4 ++--
>  include/hw/ppc/xive.h       |  2 +-
>  5 files changed, 24 insertions(+), 24 deletions(-)
> 
> diff --git a/hw/intc/spapr_xive.c b/hw/intc/spapr_xive.c
> index 47b5ec0b56..04879abf2e 100644
> --- a/hw/intc/spapr_xive.c
> +++ b/hw/intc/spapr_xive.c
> @@ -528,12 +528,17 @@ static void spapr_xive_register_types(void)
>  
>  type_init(spapr_xive_register_types)
>  
> -bool spapr_xive_irq_claim(SpaprXive *xive, uint32_t lisn, bool lsi)
> +int spapr_xive_irq_claim(SpaprXive *xive, int lisn, bool lsi, Error **errp)
>  {
>      XiveSource *xsrc = &xive->source;
>  
>      assert(lisn < xive->nr_irqs);
>  
> +    if (xive_eas_is_valid(&xive->eat[lisn])) {
> +        error_setg(errp, "IRQ %d is not free", lisn);
> +        return -EBUSY;
> +    }
> +
>      /*
>       * Set default values when allocating an IRQ number
>       */
> @@ -543,24 +548,17 @@ bool spapr_xive_irq_claim(SpaprXive *xive, uint32_t lisn, bool lsi)
>      }
>  
>      if (kvm_irqchip_in_kernel()) {
> -        Error *local_err = NULL;
> -
> -        kvmppc_xive_source_reset_one(xsrc, lisn, &local_err);
> -        if (local_err) {
> -            error_report_err(local_err);
> -            return false;
> -        }
> +        return kvmppc_xive_source_reset_one(xsrc, lisn, errp);
>      }
>  
> -    return true;
> +    return 0;
>  }
>  
> -bool spapr_xive_irq_free(SpaprXive *xive, uint32_t lisn)
> +void spapr_xive_irq_free(SpaprXive *xive, int lisn)
>  {
>      assert(lisn < xive->nr_irqs);
>  
>      xive->eat[lisn].w &= cpu_to_be64(~EAS_VALID);
> -    return true;
>  }
>  
>  /*
> diff --git a/hw/intc/spapr_xive_kvm.c b/hw/intc/spapr_xive_kvm.c
> index 2006f96aec..51b334b676 100644
> --- a/hw/intc/spapr_xive_kvm.c
> +++ b/hw/intc/spapr_xive_kvm.c
> @@ -232,14 +232,14 @@ void kvmppc_xive_sync_source(SpaprXive *xive, uint32_t lisn, Error **errp)
>   * only need to inform the KVM XIVE device about their type: LSI or
>   * MSI.
>   */
> -void kvmppc_xive_source_reset_one(XiveSource *xsrc, int srcno, Error **errp)
> +int kvmppc_xive_source_reset_one(XiveSource *xsrc, int srcno, Error **errp)
>  {
>      SpaprXive *xive = SPAPR_XIVE(xsrc->xive);
>      uint64_t state = 0;
>  
>      /* The KVM XIVE device is not in use */
>      if (xive->fd == -1) {
> -        return;
> +        return -ENODEV;
>      }
>  
>      if (xive_source_irq_is_lsi(xsrc, srcno)) {
> @@ -249,8 +249,8 @@ void kvmppc_xive_source_reset_one(XiveSource *xsrc, int srcno, Error **errp)
>          }
>      }
>  
> -    kvm_device_access(xive->fd, KVM_DEV_XIVE_GRP_SOURCE, srcno, &state,
> -                      true, errp);
> +    return kvm_device_access(xive->fd, KVM_DEV_XIVE_GRP_SOURCE, srcno, &state,
> +                             true, errp);
>  }
>  
>  static void kvmppc_xive_source_reset(XiveSource *xsrc, Error **errp)
> diff --git a/hw/ppc/spapr_irq.c b/hw/ppc/spapr_irq.c
> index da9e80b24e..4951329959 100644
> --- a/hw/ppc/spapr_irq.c
> +++ b/hw/ppc/spapr_irq.c
> @@ -246,7 +246,13 @@ static void spapr_irq_init_xive(SpaprMachineState *spapr, Error **errp)
>  
>      /* Enable the CPU IPIs */
>      for (i = 0; i < nr_servers; ++i) {
> -        spapr_xive_irq_claim(spapr->xive, SPAPR_IRQ_IPI + i, false);
> +        Error *local_err = NULL;
> +
> +        spapr_xive_irq_claim(spapr->xive, SPAPR_IRQ_IPI + i, false, &local_err);
> +        if (local_err) {
> +            error_propagate(errp, local_err);
> +            return;
> +        }

Quoting the changelog

> So instead change to an int return value to indicate presence of error
> + an Error * to describe the details through that call chain.

Shouldn't this rather be:

        if (spapr_xive_irq_claim(spapr->xive, SPAPR_IRQ_IPI + i, false, errp)) {
            return;
        }

?

With or without that fixed,

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

>      }
>  
>      spapr_xive_hcall_init(spapr);
> @@ -255,11 +261,7 @@ static void spapr_irq_init_xive(SpaprMachineState *spapr, Error **errp)
>  static int spapr_irq_claim_xive(SpaprMachineState *spapr, int irq, bool lsi,
>                                  Error **errp)
>  {
> -    if (!spapr_xive_irq_claim(spapr->xive, irq, lsi)) {
> -        error_setg(errp, "IRQ %d is invalid", irq);
> -        return -1;
> -    }
> -    return 0;
> +    return spapr_xive_irq_claim(spapr->xive, irq, lsi, errp);
>  }
>  
>  static void spapr_irq_free_xive(SpaprMachineState *spapr, int irq)
> diff --git a/include/hw/ppc/spapr_xive.h b/include/hw/ppc/spapr_xive.h
> index bfd40f01d8..0df20a6590 100644
> --- a/include/hw/ppc/spapr_xive.h
> +++ b/include/hw/ppc/spapr_xive.h
> @@ -54,8 +54,8 @@ typedef struct SpaprXive {
>   */
>  #define SPAPR_XIVE_BLOCK_ID 0x0
>  
> -bool spapr_xive_irq_claim(SpaprXive *xive, uint32_t lisn, bool lsi);
> -bool spapr_xive_irq_free(SpaprXive *xive, uint32_t lisn);
> +int spapr_xive_irq_claim(SpaprXive *xive, int lisn, bool lsi, Error **errp);
> +void spapr_xive_irq_free(SpaprXive *xive, int lisn);
>  void spapr_xive_pic_print_info(SpaprXive *xive, Monitor *mon);
>  int spapr_xive_post_load(SpaprXive *xive, int version_id);
>  
> diff --git a/include/hw/ppc/xive.h b/include/hw/ppc/xive.h
> index 6d38755f84..fd3319bd32 100644
> --- a/include/hw/ppc/xive.h
> +++ b/include/hw/ppc/xive.h
> @@ -425,7 +425,7 @@ static inline uint32_t xive_nvt_cam_line(uint8_t nvt_blk, uint32_t nvt_idx)
>   * KVM XIVE device helpers
>   */
>  
> -void kvmppc_xive_source_reset_one(XiveSource *xsrc, int srcno, Error **errp);
> +int kvmppc_xive_source_reset_one(XiveSource *xsrc, int srcno, Error **errp);
>  void kvmppc_xive_source_set_irq(void *opaque, int srcno, int val);
>  void kvmppc_xive_cpu_connect(XiveTCTX *tctx, Error **errp);
>  void kvmppc_xive_cpu_synchronize_state(XiveTCTX *tctx, Error **errp);