elf: Fix tst-cpu-features-cpuinfo on some AMD systems (BZ #28090)

The SSBD feature is implemented in 2 different ways on AMD processors:
newer systems (Zen3) provides AMD_SSBD (function 8000_0008, EBX[24]),
while older system provides AMD_VIRT_SSBD (function 8000_0008, EBX[25]).
However for AMD_VIRT_SSBD, kernel shows both 'ssdb' and 'virt_ssdb' on
/proc/cpuinfo; while for AMD_SSBD only 'ssdb' is provided.

This now check is AMD_SSBD is set to check for 'ssbd', otherwise check
if AMD_VIRT_SSDB is set to check for 'virt_ssbd'.

Checked on x86_64-linux-gnu on a Ryzen 9 5900x.

Reviewed-by: H.J. Lu <hjl.tools@gmail.com>

diff --git a/manual/platform.texi b/manual/platform.texi
index 037dfc4..c56ba7d 100644 (file)
--- a/manual/platform.texi
+++ b/manual/platform.texi
@@ -190,6 +190,9 @@ The supported processor features are:
 @code{AMD_STIBP} -- Single thread indirect branch predictors (STIBP) for AMD cpus.
 
 @item
+@code{AMD_VIRT_SSBD} -- Speculative Store Bypass Disable (SSBD) for AMD cpus (older systems).
+
+@item
 @code{AMX_BF16} -- Tile computational operations on bfloat16 numbers.
 
 @item

diff --git a/sysdeps/x86/bits/platform/x86.h b/sysdeps/x86/bits/platform/x86.h
index 5509b1a..2b25760 100644 (file)
--- a/sysdeps/x86/bits/platform/x86.h
+++ b/sysdeps/x86/bits/platform/x86.h
@@ -282,6 +282,7 @@ enum
   x86_cpu_AMD_IBRS             = x86_cpu_index_80000008_ebx + 14,
   x86_cpu_AMD_STIBP            = x86_cpu_index_80000008_ebx + 15,
   x86_cpu_AMD_SSBD             = x86_cpu_index_80000008_ebx + 24,
+  x86_cpu_AMD_VIRT_SSBD                = x86_cpu_index_80000008_ebx + 25,
 
   x86_cpu_index_7_ecx_1_eax
     = (CPUID_INDEX_7_ECX_1 * 8 * 4 * sizeof (unsigned int)

diff --git a/sysdeps/x86/include/cpu-features.h b/sysdeps/x86/include/cpu-features.h
index 59e01df..a3f11ba 100644 (file)
--- a/sysdeps/x86/include/cpu-features.h
+++ b/sysdeps/x86/include/cpu-features.h
@@ -293,6 +293,7 @@ enum
 #define bit_cpu_AMD_IBRS       (1u << 14)
 #define bit_cpu_AMD_STIBP      (1u << 15)
 #define bit_cpu_AMD_SSBD       (1u << 24)
+#define bit_cpu_AMD_VIRT_SSBD  (1u << 25)
 
 /* CPUID_INDEX_7_ECX_1.  */
 
@@ -527,6 +528,7 @@ enum
 #define index_cpu_AMD_IBRS     CPUID_INDEX_80000008
 #define index_cpu_AMD_STIBP    CPUID_INDEX_80000008
 #define index_cpu_AMD_SSBD     CPUID_INDEX_80000008
+#define index_cpu_AMD_VIRT_SSBD        CPUID_INDEX_80000008
 
 /* CPUID_INDEX_7_ECX_1.  */
 
@@ -761,6 +763,7 @@ enum
 #define reg_AMD_IBRS           ebx
 #define reg_AMD_STIBP          ebx
 #define reg_AMD_SSBD           ebx
+#define reg_AMD_VIRT_SSBD      ebx
 
 /* CPUID_INDEX_7_ECX_1.  */
 

diff --git a/sysdeps/x86/tst-cpu-features-cpuinfo.c b/sysdeps/x86/tst-cpu-features-cpuinfo.c
index f457e86..76bf5b2 100644 (file)
--- a/sysdeps/x86/tst-cpu-features-cpuinfo.c
+++ b/sysdeps/x86/tst-cpu-features-cpuinfo.c
@@ -236,7 +236,18 @@ do_test (int argc, char **argv)
   if (cpu_features->basic.kind == arch_kind_intel)
     fails += CHECK_PROC (ssbd, SSBD);
   else if (cpu_features->basic.kind == arch_kind_amd)
-    fails += CHECK_PROC (ssbd, AMD_SSBD);
+    {
+      /* This feature is implemented in 2 different ways on AMD processors:
+        newer systems provides AMD_SSBD (function 8000_0008, EBX[24]),
+        while older system proviseds AMD_VIRT_SSBD (function 8000_008,
+        EBX[25]).  However for AMD_VIRT_SSBD, kernel shows both 'ssbd'
+        and 'virt_ssbd' on /proc/cpuinfo; while for AMD_SSBD only 'ssbd'
+        is provided.  */
+      if (HAS_CPU_FEATURE (AMD_SSBD))
+       fails += CHECK_PROC (ssbd, AMD_SSBD);
+      else if (HAS_CPU_FEATURE (AMD_VIRT_SSBD))
+       fails += CHECK_PROC (virt_ssbd, AMD_VIRT_SSBD);
+    }
   fails += CHECK_PROC (sse, SSE);
   fails += CHECK_PROC (sse2, SSE2);
   fails += CHECK_PROC (pni, SSE3);