Re: [PATCH 16/21] libs/guest: make a cpu policy compatible with older Xen versions

[Jan Beulich <jbeulich@xxxxxxxx>]

On 23.03.2021 10:58, Roger Pau Monne wrote:
> --- a/tools/libs/guest/xg_cpuid_x86.c
> +++ b/tools/libs/guest/xg_cpuid_x86.c
> @@ -436,6 +436,7 @@ int xc_cpuid_apply_policy(xc_interface *xch, uint32_t 
> domid, bool restore,
>      unsigned int i, nr_leaves, nr_msrs;
>      xen_cpuid_leaf_t *leaves = NULL;
>      struct cpuid_policy *p = NULL;
> +    struct cpu_policy policy = { };
>      uint32_t err_leaf = -1, err_subleaf = -1, err_msr = -1;
>      uint32_t host_featureset[FEATURESET_NR_ENTRIES] = {};
>      uint32_t len = ARRAY_SIZE(host_featureset);
> @@ -504,12 +505,8 @@ int xc_cpuid_apply_policy(xc_interface *xch, uint32_t 
> domid, bool restore,
>       */
>      if ( restore )
>      {
> -        p->basic.rdrand = test_bit(X86_FEATURE_RDRAND, host_featureset);
> -
> -        if ( di.hvm )
> -        {
> -            p->feat.mpx = test_bit(X86_FEATURE_MPX, host_featureset);
> -        }
> +        policy.cpuid = p;
> +        xc_cpu_policy_make_compatible(xch, &policy, di.hvm);
>      }

The comment ahead of this if() wants moving to ...

> @@ -1230,3 +1227,33 @@ int xc_cpu_policy_calc_compatible(xc_interface *xch,
>  
>      return rc;
>  }
> +
> +int xc_cpu_policy_make_compatible(xc_interface *xch, xc_cpu_policy_t policy,
> +                                  bool hvm)
> +{
> +    xc_cpu_policy_t host;
> +    int rc;
> +
> +    host = xc_cpu_policy_init();
> +    if ( !host )
> +    {
> +        errno = ENOMEM;
> +        return -1;
> +    }
> +
> +    rc = xc_cpu_policy_get_system(xch, XEN_SYSCTL_cpu_policy_host, host);
> +    if ( rc )
> +    {
> +        ERROR("Failed to get host policy");
> +        goto out;
> +    }
> +
> +    policy->cpuid->basic.rdrand = host->cpuid->basic.rdrand;
> +
> +    if ( hvm )
> +        policy->cpuid->feat.mpx = host->cpuid->feat.mpx;

... or cloning ahead of these two.

Jan