linux-kernel - [PATCH 4.1 017/102] s390/setup: fix novx parameter

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Date:	Sat, 19 Sep 2015 10:27:29 -0700
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org, Ulrich Weigand <uweigand@...ibm.com>,
	Heiko Carstens <heiko.carstens@...ibm.com>,
	Martin Schwidefsky <schwidefsky@...ibm.com>
Subject: [PATCH 4.1 017/102] s390/setup: fix novx parameter

4.1-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Martin Schwidefsky <schwidefsky@...ibm.com>

commit 89b1145e93771d727645c96e323539c029b63f1c upstream.

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 <uweigand@...ibm.com>
Reviewed-by: Heiko Carstens <heiko.carstens@...ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@...ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

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

--- a/arch/s390/kernel/setup.c
+++ b/arch/s390/kernel/setup.c
@@ -683,7 +683,7 @@ 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;
@@ -749,9 +749,11 @@ 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));
@@ -788,7 +790,9 @@ static void __init setup_hwcaps(void)
 		strcpy(elf_platform, "z13");
 		break;
 	}
+	return 0;
 }
+arch_initcall(setup_hwcaps);
 
 /*
  * Add system information as device randomness
@@ -871,11 +875,6 @@ 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();


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