[PATCH V2] Modify virCPUarmCompare to perform compare actions

[Peter Krempa]

On Wed, Sep 16, 2020 at 11:04:58 +0800, Zhenyu Zheng wrote:
> Modify virCPUarmCompare in cpu_arm.c to perform compare action.
> This patch only adds host to host CPU compare, the rest cases
> remains the same. This is useful for source and destination host
> compare during migrations to avoid migration between different
> CPU models that have different CPU freatures.
> 
> Signed-off-by: Zhenyu Zheng <zheng.zhenyu at outlook.com>
> ---
>  src/cpu/cpu_arm.c | 51 +++++++++++++++++++++++++++++++++++++++++++----
>  1 file changed, 47 insertions(+), 4 deletions(-)
> 
> diff --git a/src/cpu/cpu_arm.c b/src/cpu/cpu_arm.c
> index 939a3b8390..e8581ec31f 100644
> --- a/src/cpu/cpu_arm.c
> +++ b/src/cpu/cpu_arm.c
> @@ -463,11 +463,54 @@ virCPUarmBaseline(virCPUDefPtr *cpus,
>  }
>  
>  static virCPUCompareResult
> -virCPUarmCompare(virCPUDefPtr host G_GNUC_UNUSED,
> -                 virCPUDefPtr cpu G_GNUC_UNUSED,
> -                 bool failMessages G_GNUC_UNUSED)
> +virCPUarmCompare(virCPUDefPtr host,
> +                 virCPUDefPtr cpu,
> +                 bool failIncompatible
> +)
>  {
> -    return VIR_CPU_COMPARE_IDENTICAL;
> +    g_autofree char *message = NULL;
> +    virCPUCompareResult ret = VIR_CPU_COMPARE_IDENTICAL;
> +
> +    /* Only support host to host CPU compare for ARM*/
> +    if (cpu->type != VIR_CPU_TYPE_HOST)
> +        return ret;
> +
> +    if (!host || !host->model) {
> +        if (failIncompatible) {
> +            virReportError(VIR_ERR_CPU_INCOMPATIBLE, "%s",
> +                           _("unknown host CPU"));
> +            ret = VIR_CPU_COMPARE_ERROR;
> +        } else {
> +            VIR_WARN("unknown host CPU");
> +            ret = VIR_CPU_COMPARE_INCOMPATIBLE;
> +        }
> +        return ret;
> +    }
> +
> +    /* Compare vendor and model to check if CPUs are identical */
> +    if (STRNEQ(host->vendor, cpu->vendor) ||
> +        STRNEQ(host->model, cpu->model)) {
> +        VIR_DEBUG("host CPU model does not match required CPU model %s",
> +                  cpu->model);
> +        if (message) {

'message' was initialized to NULL here so this code won't ever be
executed.

> +            message = g_strdup_printf(_("host CPU model does not match required "
> +                                        "CPU model %s"),
> +                                      cpu->model);
> +        }
> +
> +        ret = VIR_CPU_COMPARE_INCOMPATIBLE;
> +    }
> +
> +    if (failIncompatible && ret == VIR_CPU_COMPARE_INCOMPATIBLE) {
> +        ret = VIR_CPU_COMPARE_ERROR;
> +        if (message) {
> +            virReportError(VIR_ERR_CPU_INCOMPATIBLE, "%s", message);

Neither this code since it will still be NULL.

Also please don't store the error message in a random variable, but
rather use a specific virReportError call. If you want to omit it in
certain cases, just skip the whole virReportError call.

> +        } else {
> +            virReportError(VIR_ERR_CPU_INCOMPATIBLE, NULL);
> +        }
> +    }
> +
> +    return ret;
>  }
>  
>  static int
> -- 
> 2.20.1
> 
>