Re: [PATCH 4/4] spapr: Improve spapr_reallocate_hpt() error reporting

[David Gibson]

On Mon, Oct 26, 2020 at 01:40:54PM +0100, Greg Kurz wrote:
> spapr_reallocate_hpt() has three users, two of which pass &error_fatal
> and the third one, htab_load(), passes &local_err, uses it to detect
> failures and simply propagates -EINVAL up to vmstate_load(), which will
> cause QEMU to exit. It is thus confusing that spapr_reallocate_hpt()
> doesn't return right away when an error is detected in some cases. Also,
> the comment suggesting that the caller is welcome to try to carry on
> seems like a remnant in this respect.
> 
> This can be improved:
> - change spapr_reallocate_hpt() to always report a negative errno on
>   failure, either as reported by KVM or -ENOSPC if the HPT is smaller
>   than what was asked,
> - use that to detect failures in htab_load() which is preferred over
>   checking &local_err,
> - propagate this negative errno to vmstate_load() because it is more
>   accurate than propagating -EINVAL for all possible errors.
> 
> Signed-off-by: Greg Kurz <groug@kaod.org>

Applied to ppc-for-5.2, thanks.

> ---
>  hw/ppc/spapr.c         |   18 ++++++++++--------
>  include/hw/ppc/spapr.h |    3 +--
>  2 files changed, 11 insertions(+), 10 deletions(-)
> 
> diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> index ff7de7da2875..12a012d9dd09 100644
> --- a/hw/ppc/spapr.c
> +++ b/hw/ppc/spapr.c
> @@ -1483,8 +1483,7 @@ void spapr_free_hpt(SpaprMachineState *spapr)
>      close_htab_fd(spapr);
>  }
>  
> -void spapr_reallocate_hpt(SpaprMachineState *spapr, int shift,
> -                          Error **errp)
> +int spapr_reallocate_hpt(SpaprMachineState *spapr, int shift, Error **errp)
>  {
>      ERRP_GUARD();
>      long rc;
> @@ -1496,7 +1495,7 @@ void spapr_reallocate_hpt(SpaprMachineState *spapr, int 
> shift,
>  
>      if (rc == -EOPNOTSUPP) {
>          error_setg(errp, "HPT not supported in nested guests");
> -        return;
> +        return -EOPNOTSUPP;
>      }
>  
>      if (rc < 0) {
> @@ -1504,8 +1503,7 @@ void spapr_reallocate_hpt(SpaprMachineState *spapr, int 
> shift,
>          error_setg_errno(errp, errno, "Failed to allocate KVM HPT of order 
> %d",
>                           shift);
>          error_append_hint(errp, "Try smaller maxmem?\n");
> -        /* This is almost certainly fatal, but if the caller really
> -         * wants to carry on with shift == 0, it's welcome to try */
> +        return -errno;
>      } else if (rc > 0) {
>          /* kernel-side HPT allocated */
>          if (rc != shift) {
> @@ -1513,6 +1511,7 @@ void spapr_reallocate_hpt(SpaprMachineState *spapr, int 
> shift,
>                         "Requested order %d HPT, but kernel allocated order 
> %ld",
>                         shift, rc);
>              error_append_hint(errp, "Try smaller maxmem?\n");
> +            return -ENOSPC;
>          }
>  
>          spapr->htab_shift = shift;
> @@ -1533,6 +1532,7 @@ void spapr_reallocate_hpt(SpaprMachineState *spapr, int 
> shift,
>      /* We're setting up a hash table, so that means we're not radix */
>      spapr->patb_entry = 0;
>      spapr_set_all_lpcrs(0, LPCR_HR | LPCR_UPRT);
> +    return 0;
>  }
>  
>  void spapr_setup_hpt(SpaprMachineState *spapr)
> @@ -2286,11 +2286,13 @@ static int htab_load(QEMUFile *f, void *opaque, int 
> version_id)
>      }
>  
>      if (section_hdr) {
> +        int ret;
> +
>          /* First section gives the htab size */
> -        spapr_reallocate_hpt(spapr, section_hdr, &local_err);
> -        if (local_err) {
> +        ret = spapr_reallocate_hpt(spapr, section_hdr, &local_err);
> +        if (ret < 0) {
>              error_report_err(local_err);
> -            return -EINVAL;
> +            return ret;
>          }
>          return 0;
>      }
> diff --git a/include/hw/ppc/spapr.h b/include/hw/ppc/spapr.h
> index bb47896f173b..2e89e36cfbdc 100644
> --- a/include/hw/ppc/spapr.h
> +++ b/include/hw/ppc/spapr.h
> @@ -846,8 +846,7 @@ void spapr_hotplug_req_add_by_count_indexed(SpaprDrcType 
> drc_type,
>  void spapr_hotplug_req_remove_by_count_indexed(SpaprDrcType drc_type,
>                                                 uint32_t count, uint32_t 
> index);
>  int spapr_hpt_shift_for_ramsize(uint64_t ramsize);
> -void spapr_reallocate_hpt(SpaprMachineState *spapr, int shift,
> -                          Error **errp);
> +int spapr_reallocate_hpt(SpaprMachineState *spapr, int shift, Error **errp);
>  void spapr_clear_pending_events(SpaprMachineState *spapr);
>  void spapr_clear_pending_hotplug_events(SpaprMachineState *spapr);
>  int spapr_max_server_number(SpaprMachineState *spapr);
> 
> 

-- 
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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