Re: [Qemu-devel] [Qemu-ppc] [PATCH v2] spapr: quantify error messages regarding capability settings

[Greg Kurz <groug@kaod.org>]

On Thu,  1 Aug 2019 13:38:19 +1000
Daniel Black <daniel@linux.ibm.com> wrote:

> Its not immediately obvious how cap-X=Y setting need to be applied
> to the command line so, for spapr capability error messages, this
> has been clarified to:
> 
>   ..[try] appending -machine cap-X=Y
> 
> The wrong value messages have been left as is, as the user has found
> the right location.
> 
> Signed-off-by: Daniel Black <daniel@linux.ibm.com>
> ---
> v2 Improved error message thanks David Gibson
> 
> Left the "appending" as its not obvious more that one -machine
> arguement is allowed.
> ---
>  hw/ppc/spapr_caps.c | 47 ++++++++++++++++++++++++++++++---------------
>  1 file changed, 32 insertions(+), 15 deletions(-)
> 
> diff --git a/hw/ppc/spapr_caps.c b/hw/ppc/spapr_caps.c
> index bbb001f84a..1c0222a081 100644
> --- a/hw/ppc/spapr_caps.c
> +++ b/hw/ppc/spapr_caps.c
> @@ -37,6 +37,8 @@
>  
>  #include "hw/ppc/spapr.h"
>  
> +#define CAPABILITY_ERROR(X) "appending -machine " X

I would make that:

#define CAPABILITY_HINT() "try appending -machine " X

because it is really an hint for the user, not an
error, and all original strings have "try", except...

> +
>  typedef struct SpaprCapPossible {
>      int num;            /* size of vals array below */
>      const char *help;   /* help text for vals */
> @@ -194,10 +196,12 @@ static void cap_htm_apply(SpaprMachineState *spapr, uint8_t val, Error **errp)
>      }
>      if (tcg_enabled()) {
>          error_setg(errp,
> -                   "No Transactional Memory support in TCG, try cap-htm=off");
> +                   "No Transactional Memory support in TCG, try "
> +                   CAPABILITY_ERROR("cap-htm=off"));
>      } else if (kvm_enabled() && !kvmppc_has_cap_htm()) {
>          error_setg(errp,
> -"KVM implementation does not support Transactional Memory, try cap-htm=off"
> +"KVM implementation does not support Transactional Memory, try "
> +                   CAPABILITY_ERROR("cap-htm=off")
>              );
>      }
>  }
> @@ -215,7 +219,8 @@ static void cap_vsx_apply(SpaprMachineState *spapr, uint8_t val, Error **errp)
>       * rid of anything that doesn't do VMX */
>      g_assert(env->insns_flags & PPC_ALTIVEC);
>      if (!(env->insns_flags2 & PPC2_VSX)) {
> -        error_setg(errp, "VSX support not available, try cap-vsx=off");
> +        error_setg(errp, "VSX support not available, try "
> +                   CAPABILITY_ERROR("cap-vsx=off"));
>      }
>  }
>  
> @@ -229,7 +234,8 @@ static void cap_dfp_apply(SpaprMachineState *spapr, uint8_t val, Error **errp)
>          return;
>      }
>      if (!(env->insns_flags2 & PPC2_DFP)) {
> -        error_setg(errp, "DFP support not available, try cap-dfp=off");
> +        error_setg(errp, "DFP support not available, try "
> +                   CAPABILITY_ERROR("cap-dfp=off"));
>      }
>  }
>  
> @@ -249,11 +255,13 @@ static void cap_safe_cache_apply(SpaprMachineState *spapr, uint8_t val,
>      if (tcg_enabled() && val) {
>          /* TCG only supports broken, allow other values and print a warning */
>          error_setg(&local_err,
> -                   "TCG doesn't support requested feature, cap-cfpc=%s",
> +                   "TCG doesn't support requested feature, "
> +                   CAPABILITY_ERROR("cap-cfpc=%s"),

... this one, but it doesn't look like a hint to me. It just tells which
is the unsupported cap.

>                     cap_cfpc_possible.vals[val]);
>      } else if (kvm_enabled() && (val > kvm_val)) {
>          error_setg(errp,
> -"Requested safe cache capability level not supported by kvm, try cap-cfpc=%s",
> +"Requested safe cache capability level not supported by kvm, try "
> +                   CAPABILITY_ERROR("cap-cfpc=%s"),
>                     cap_cfpc_possible.vals[kvm_val]);

Also, we have a dedicated API for hints, which are only printed under
the monitor but ignored under QMP.

Not sure why it isn't used here but it should be something like:

        error_setg(errp, 
                   "Requested safe cache capability level not supported by kvm");
        error_append_hint(errp, CAPABILITY_HINT("cap-cfpc=%s") "\n",
                          cap_cfpc_possible.vals[kvm_val]);

>      }
>  
> @@ -281,7 +289,8 @@ static void cap_safe_bounds_check_apply(SpaprMachineState *spapr, uint8_t val,
>                     cap_sbbc_possible.vals[val]);
>      } else if (kvm_enabled() && (val > kvm_val)) {
>          error_setg(errp,
> -"Requested safe bounds check capability level not supported by kvm, try cap-sbbc=%s",
> +"Requested safe bounds check capability level not supported by kvm, try "
> +                   CAPABILITY_ERROR("cap-sbbc=%s"),
>                     cap_sbbc_possible.vals[kvm_val]);
>      }
>  
> @@ -312,7 +321,8 @@ static void cap_safe_indirect_branch_apply(SpaprMachineState *spapr,
>                     cap_ibs_possible.vals[val]);
>      } else if (kvm_enabled() && (val > kvm_val)) {
>          error_setg(errp,
> -"Requested safe indirect branch capability level not supported by kvm, try cap-ibs=%s",
> +"Requested safe indirect branch capability level not supported by kvm, try "
> +                   CAPABILITY_ERROR("cap-ibs=%s"),
>                     cap_ibs_possible.vals[kvm_val]);
>      }
>  
> @@ -401,11 +411,13 @@ static void cap_nested_kvm_hv_apply(SpaprMachineState *spapr,
>  
>      if (tcg_enabled()) {
>          error_setg(errp,
> -                   "No Nested KVM-HV support in tcg, try cap-nested-hv=off");
> +                   "No Nested KVM-HV support in tcg, try "
> +                   CAPABILITY_ERROR("cap-nested-hv=off"));
>      } else if (kvm_enabled()) {
>          if (!kvmppc_has_cap_nested_kvm_hv()) {
>              error_setg(errp,
> -"KVM implementation does not support Nested KVM-HV, try cap-nested-hv=off");
> +"KVM implementation does not support Nested KVM-HV, try "
> +                       CAPABILITY_ERROR("cap-nested-hv=off"));
>          } else if (kvmppc_set_cap_nested_kvm_hv(val) < 0) {
>                  error_setg(errp,
>  "Error enabling cap-nested-hv with KVM, try cap-nested-hv=off");
> @@ -435,10 +447,12 @@ static void cap_large_decr_apply(SpaprMachineState *spapr,
>  
>          if (!kvm_nr_bits) {
>              error_setg(errp,
> -                       "No large decrementer support, try cap-large-decr=off");
> +                       "No large decrementer support, try "
> +                        CAPABILITY_ERROR("cap-large-decr=off"));
>          } else if (pcc->lrg_decr_bits != kvm_nr_bits) {
>              error_setg(errp,
> -"KVM large decrementer size (%d) differs to model (%d), try -cap-large-decr=off",
> +"KVM large decrementer size (%d) differs to model (%d), try "
> +                CAPABILITY_ERROR("cap-large-decr=off"),
>                  kvm_nr_bits, pcc->lrg_decr_bits);
>          }
>      }
> @@ -454,7 +468,8 @@ static void cap_large_decr_cpu_apply(SpaprMachineState *spapr,
>      if (kvm_enabled()) {
>          if (kvmppc_enable_cap_large_decr(cpu, val)) {
>              error_setg(errp,
> -                       "No large decrementer support, try cap-large-decr=off");
> +                       "No large decrementer support, try "
> +                       CAPABILITY_ERROR("cap-large-decr=off"));
>          }
>      }
>  
> @@ -474,10 +489,12 @@ static void cap_ccf_assist_apply(SpaprMachineState *spapr, uint8_t val,
>      if (tcg_enabled() && val) {
>          /* TODO - for now only allow broken for TCG */
>          error_setg(errp,
> -"Requested count cache flush assist capability level not supported by tcg, try cap-ccf-assist=off");
> +"Requested count cache flush assist capability level not supported by tcg, try "
> +                   CAPABILITY_ERROR("cap-ccf-assist=off"));
>      } else if (kvm_enabled() && (val > kvm_val)) {
>          error_setg(errp,
> -"Requested count cache flush assist capability level not supported by kvm, try cap-ccf-assist=off");
> +"Requested count cache flush assist capability level not supported by kvm, try "
> +                   CAPABILITY_ERROR("cap-ccf-assist=off"));
>      }
>  }
>