The novx parameter disables the vector facility but the HWCAP_S390_VXRS bit in the ELf hardware capabilies is always set if the machine has the vector facility. If the user space program uses the "vx" string in the features field of /proc/cpuinfo to utilize vector instruction it will crash if the novx kernel paramter is set.

Convert setup_hwcaps to an arch_initcall and use MACHINE_HAS_VX to decide if the HWCAPS_S390_VXRS bit needs to be set.

Reported-by Ulrich Weigand <[email protected]>

Reviewed-by Heiko Carstens <[email protected]>

Signed-off-by Martin Schwidefsky <[email protected]>

Signed-off-by Greg Kroah-Hartman <[email protected]>

---
 arch/s390/kernel/setup.c |   15 +++++++--------
 1 file changed, 7 insertions(+), 8 deletions(-)

arch/s390/kernel/setup.c +7 -8

@@ -688,7 +688,7 @@ static void __init setup_memory(void)
 /*
  * Setup hardware capabilities.
  */
-static void __init setup_hwcaps(void)
+static int __init setup_hwcaps(void)
 {
 	static const int stfl_bits[6] = { 0, 2, 7, 17, 19, 21 };
 	struct cpuid cpu_id;

@@ -754,9 +754,11 @@ static void __init setup_hwcaps(void)
 		elf_hwcap |= HWCAP_S390_TE;
 
 	/*
-	 * Vector extension HWCAP_S390_VXRS is bit 11.
+	 * Vector extension HWCAP_S390_VXRS is bit 11. The Vector extension
+	 * can be disabled with the "novx" parameter. Use MACHINE_HAS_VX
+	 * instead of facility bit 129.
 	 */
-	if (test_facility(129))
+	if (MACHINE_HAS_VX)
 		elf_hwcap |= HWCAP_S390_VXRS;
 	get_cpu_id(&cpu_id);
 	add_device_randomness(&cpu_id, sizeof(cpu_id));

@@ -793,7 +795,9 @@ static void __init setup_hwcaps(void)
 		strcpy(elf_platform, "z13");
 		break;
 	}
+	return 0;
 }
+arch_initcall(setup_hwcaps);
 
 /*
  * Add system information as device randomness

@@ -881,11 +885,6 @@ void __init setup_arch(char **cmdline_p)
         cpu_init();
 
 	/*
-	 * Setup capabilities (ELF_HWCAP & ELF_PLATFORM).
-	 */
-	setup_hwcaps();
-
-	/*
 	 * Create kernel page tables and switch to virtual addressing.
 	 */
         paging_init();

Patches currently in stable-queue which might be from [email protected] are

queue-4.2/s390-setup-fix-novx-parameter.patch