Re: [PATCH v2 1/1] spapr_caps.c: check user input before warning about TCG only caps

[Greg Kurz]

On Wed, 20 Jan 2021 07:54:06 -0300
Daniel Henrique Barboza <danielhb413@gmail.com> wrote:

> Commit 006e9d361869 added warning messages for cap-cfpc, cap-ibs and
> cap-sbbc when enabled under TCG. Commit 8ff43ee404d3 did the same thing
> when introducing cap-ccf-assist.
> 
> These warning messages, although benign to the machine launch, can make
> users a bit confused. E.g:
> 
> $ sudo ./ppc64-softmmu/qemu-system-ppc64
> qemu-system-ppc64: warning: TCG doesn't support requested feature, 
> cap-cfpc=workaround
> qemu-system-ppc64: warning: TCG doesn't support requested feature, 
> cap-sbbc=workaround
> qemu-system-ppc64: warning: TCG doesn't support requested feature, 
> cap-ibs=workaround
> qemu-system-ppc64: warning: TCG doesn't support requested feature, 
> cap-ccf-assist=on
> 
> We're complaining about "TCG doesn't support requested feature" when the
> user didn't request any of those caps in the command line.
> 
> Check if these caps were set in the command line before sending an user
> warning.
> 
> Signed-off-by: Daniel Henrique Barboza <danielhb413@gmail.com>
> ---

Heh I've just posted a mail suggesting you to do something like that :)

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

>  hw/ppc/spapr_caps.c | 47 ++++++++++++++++++++++++++++++++++-----------
>  1 file changed, 36 insertions(+), 11 deletions(-)
> 
> diff --git a/hw/ppc/spapr_caps.c b/hw/ppc/spapr_caps.c
> index 9341e9782a..629c24a96d 100644
> --- a/hw/ppc/spapr_caps.c
> +++ b/hw/ppc/spapr_caps.c
> @@ -244,9 +244,15 @@ static void cap_safe_cache_apply(SpaprMachineState 
> *spapr, uint8_t val,
>      uint8_t kvm_val =  kvmppc_get_cap_safe_cache();
>  
>      if (tcg_enabled() && val) {
> -        /* TCG only supports broken, allow other values and print a warning 
> */
> -        warn_report("TCG doesn't support requested feature, cap-cfpc=%s",
> -                    cap_cfpc_possible.vals[val]);
> +        /*
> +         * TCG only supports broken, allow other values and print a warning
> +         * in case the user attempted to set a different value in the command
> +         * line.
> +         */
> +        if (spapr->cmd_line_caps[SPAPR_CAP_CFPC] != SPAPR_CAP_BROKEN) {
> +            warn_report("TCG doesn't support requested feature, cap-cfpc=%s",
> +                        cap_cfpc_possible.vals[val]);
> +        }
>      } else if (kvm_enabled() && (val > kvm_val)) {
>          error_setg(errp,
>                     "Requested safe cache capability level not supported by 
> KVM");
> @@ -269,9 +275,15 @@ static void 
> cap_safe_bounds_check_apply(SpaprMachineState *spapr, uint8_t val,
>      uint8_t kvm_val =  kvmppc_get_cap_safe_bounds_check();
>  
>      if (tcg_enabled() && val) {
> -        /* TCG only supports broken, allow other values and print a warning 
> */
> -        warn_report("TCG doesn't support requested feature, cap-sbbc=%s",
> -                    cap_sbbc_possible.vals[val]);
> +        /*
> +         * TCG only supports broken, allow other values and print a warning
> +         * in case the user attempted to set a different value in the command
> +         * line.
> +         */
> +        if (spapr->cmd_line_caps[SPAPR_CAP_SBBC] != SPAPR_CAP_BROKEN) {
> +            warn_report("TCG doesn't support requested feature, cap-sbbc=%s",
> +                        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");
> @@ -297,9 +309,15 @@ static void 
> cap_safe_indirect_branch_apply(SpaprMachineState *spapr,
>      uint8_t kvm_val = kvmppc_get_cap_safe_indirect_branch();
>  
>      if (tcg_enabled() && val) {
> -        /* TCG only supports broken, allow other values and print a warning 
> */
> -        warn_report("TCG doesn't support requested feature, cap-ibs=%s",
> -                    cap_ibs_possible.vals[val]);
> +        /*
> +         * TCG only supports broken, allow other values and print a warning
> +         * in case the user attempted to set a different value in the command
> +         * line.
> +         */
> +        if (spapr->cmd_line_caps[SPAPR_CAP_IBS] != SPAPR_CAP_BROKEN) {
> +            warn_report("TCG doesn't support requested feature, cap-ibs=%s",
> +                        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");
> @@ -483,8 +501,15 @@ static void cap_ccf_assist_apply(SpaprMachineState 
> *spapr, uint8_t val,
>      uint8_t kvm_val = kvmppc_get_cap_count_cache_flush_assist();
>  
>      if (tcg_enabled() && val) {
> -        /* TCG doesn't implement anything here, but allow with a warning */
> -        warn_report("TCG doesn't support requested feature, 
> cap-ccf-assist=on");
> +        /*
> +         * TCG doesn't implement anything here, but allow with a warning
> +         * in case the user attempted to set a different value in the command
> +         * line.
> +         */
> +        if (spapr->cmd_line_caps[SPAPR_CAP_CCF_ASSIST] != SPAPR_CAP_OFF) {
> +            warn_report("TCG doesn't support requested feature, "
> +                        "cap-ccf-assist=on");
> +        }
>      } else if (kvm_enabled() && (val > kvm_val)) {
>          uint8_t kvm_ibs = kvmppc_get_cap_safe_indirect_branch();
>