Potential fix for pull request finding

Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>

Author: bernhardkaindl

tests/nested-svm-vmrun/main.c

@@ -95,15 +95,16 @@ static void build_l2_vmcb(void)
      * Flat 64-bit segments, mirroring how XTF sets up L1.
      * Encoded segment attributes (P|DPL|S|Type|...|G|D/B|L|AVL):
      *   CS: present, ring 0, code, exec/read,                  L=1 -> 0xa9b
-     *   DS/ES/SS/FS/GS: present, ring 3, data, read/write, G=1 -> 0xcf3 (DPL3)
+     *   DS/ES/FS/GS: present, ring 3, data, read/write, G=1 -> 0xcf3 (DPL3)
+     *   SS: NULL selector in hvm64, so mark it unusable/null.
      */
     l2_vmcb.cs.sel = __KERN_CS;
     l2_vmcb.cs.attr = 0xa9b;
     l2_vmcb.cs.limit = ~0u;
 
     l2_vmcb.ss.sel = __KERN_DS;
-    l2_vmcb.ss.attr = 0xcf3;
-    l2_vmcb.ss.limit = ~0u;
+    l2_vmcb.ss.attr = 0;
+    l2_vmcb.ss.limit = 0;
 
     l2_vmcb.ds.sel = __USER_DS;
     l2_vmcb.ds.attr = 0xcf3;