elf: Fix tst-cpu-features-cpuinfo for KVM guests on some AMD systems [BZ #28704]

On KVM guests running on some AMD systems, the IBRS feature is reported
as a synthetic feature using the Intel feature, while the cpuinfo entry
keeps the same. Handle that by first checking the presence of the Intel
feature on AMD systems.

Fixes bug 28704.

diff --git a/sysdeps/x86/tst-cpu-features-cpuinfo.c b/sysdeps/x86/tst-cpu-features-cpuinfo.c
index 2d4927f5e52dc260d18efe3988d4ef6a70db21cf..830aaca2ecae971b0e480022f650b531625415f0 100644 (file)
--- a/sysdeps/x86/tst-cpu-features-cpuinfo.c
+++ b/sysdeps/x86/tst-cpu-features-cpuinfo.c
@@ -169,7 +169,14 @@ do_test (int argc, char **argv)
   else if (cpu_features->basic.kind == arch_kind_amd)
     {
       fails += CHECK_PROC (ibpb, AMD_IBPB);
-      fails += CHECK_PROC (ibrs, AMD_IBRS);
+
+      /* The IBRS feature on AMD processors is reported using the Intel feature
+       * on KVM guests (synthetic bit).  In both cases the cpuinfo entry is the
+       * same.  */
+      if (HAS_CPU_FEATURE (IBRS_IBPB))
+        fails += CHECK_PROC (ibrs, IBRS_IBPB);
+      else
+        fails += CHECK_PROC (ibrs, AMD_IBRS);
       fails += CHECK_PROC (stibp, AMD_STIBP);
     }
   fails += CHECK_PROC (ibt, IBT);