On Wed, Sep 16, 2020 at 16:58:03 +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@outlook.com>
> ---
>  src/cpu/cpu_arm.c | 43 +++++++++++++++++++++++++++++++++++++++----
>  1 file changed, 39 insertions(+), 4 deletions(-)
>
> diff --git a/src/cpu/cpu_arm.c b/src/cpu/cpu_arm.c
> index 939a3b8390..b420b14e86 100644
> --- a/src/cpu/cpu_arm.c
> +++ b/src/cpu/cpu_arm.c
> @@ -463,11 +463,46 @@ 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;
> +    virCPUCompareResult ret = VIR_CPU_COMPARE_IDENTICAL;

This looks a bit too complicated as there's no common code to be
executed for several ret values. Just drop this variable and return
directly wherever you set it.

> +
> +    /* 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)) {

Use STRNEQ_NULLABLE instead.

> +        VIR_DEBUG("Host CPU model does not match required CPU model %s",
> +                  cpu->model);

NULLSTR(cpu->model)

and I would also add NULLSTR(cpu->vendor) in the message just in case
the CPUs differ only in vendor.

> +
> +        if (failIncompatible) {
> +            ret = VIR_CPU_COMPARE_ERROR;
> +            virReportError(VIR_ERR_CPU_INCOMPATIBLE,
> +                           _("Host CPU model does not match required CPU model %s"),
> +                           cpu->model);
> +        } else {
> +            ret = VIR_CPU_COMPARE_INCOMPATIBLE;
> +        }
> +    }
> +
> +    return ret;
>  }
> 
>  static int

Jirka