tools/cpuid: Plumb nested_virt down into xc_cpuid_apply_policy()

Nested Virt is the final special case in legacy CPUID handling.  Pass the
(poorly named) nested_hvm setting down into xc_cpuid_apply_policy() to break
the semantic dependency on HVM_PARAM_NESTEDHVM.

No functional change.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Acked-by: Wei Liu <wl@xen.org>

tools/libs/ctrl/include/xenctrl.h

@@ -1826,7 +1826,7 @@ struct xc_xend_cpuid {
  * cases, and the generated policy must be compatible with a 4.13.
  *
  * Either pass a full new @featureset (and @nr_features), or adjust individual
- * features (@pae, @itsc).
+ * features (@pae, @itsc, @nested_virt).
  *
  * Then (optionally) apply legacy XEND overrides (@xend) to the result.
  */
@@ -1834,7 +1834,7 @@ int xc_cpuid_apply_policy(xc_interface *xch,
                           uint32_t domid, bool restore,
                           const uint32_t *featureset,
                           unsigned int nr_features, bool pae, bool itsc,
-                          const struct xc_xend_cpuid *xend);
+                          bool nested_virt, const struct xc_xend_cpuid *xend);
 int xc_mca_op(xc_interface *xch, struct xen_mc *mc);
 int xc_mca_op_inject_v2(xc_interface *xch, unsigned int flags,
                         xc_cpumap_t cpumap, unsigned int nr_cpus);

tools/libs/guest/xg_cpuid_x86.c

@@ -427,7 +427,7 @@ static int xc_cpuid_xend_policy(
 
 int xc_cpuid_apply_policy(xc_interface *xch, uint32_t domid, bool restore,
                           const uint32_t *featureset, unsigned int nr_features,
-                          bool pae, bool itsc,
+                          bool pae, bool itsc, bool nested_virt,
                           const struct xc_xend_cpuid *xend)
 {
     int rc;
@@ -559,7 +559,11 @@ int xc_cpuid_apply_policy(xc_interface *xch, uint32_t domid, bool restore,
         p->extd.itsc = itsc;
 
         if ( di.hvm )
+        {
             p->basic.pae = pae;
+            p->basic.vmx = nested_virt;
+            p->extd.svm = nested_virt;
+        }
     }
 
     if ( !di.hvm )
@@ -625,14 +629,6 @@ int xc_cpuid_apply_policy(xc_interface *xch, uint32_t domid, bool restore,
             }
             break;
         }
-
-        /*
-         * These settings are necessary to cause earlier HVM_PARAM_NESTEDHVM
-         * to be reflected correctly in CPUID.  Xen will discard these bits if
-         * configuration hasn't been set for the domain.
-         */
-        p->basic.vmx = true;
-        p->extd.svm = true;
     }
 
     rc = x86_cpuid_copy_to_buffer(p, leaves, &nr_leaves);

tools/libxl/libxl_cpuid.c

@@ -422,6 +422,7 @@ void libxl__cpuid_legacy(libxl_ctx *ctx, uint32_t domid, bool restore,
 {
     bool pae = true;
     bool itsc;
+    bool nested_virt = libxl_defbool_val(info->nested_hvm);
 
     /*
      * For PV guests, PAE is Xen-controlled (it is the 'p' that differentiates
@@ -452,7 +453,7 @@ void libxl__cpuid_legacy(libxl_ctx *ctx, uint32_t domid, bool restore,
             info->tsc_mode == LIBXL_TSC_MODE_ALWAYS_EMULATE);
 
     xc_cpuid_apply_policy(ctx->xch, domid, restore, NULL, 0,
-                          pae, itsc, info->cpuid);
+                          pae, itsc, nested_virt, info->cpuid);
 }
 
 static const char *input_names[2] = { "leaf", "subleaf" };