crypto: xor - Check for osxsave as well as avx in crypto/xor

commit edb6f294 upstream.

This affects xen pv guests with sufficiently old versions of xen and
sufficiently new hardware.  On such a system, a guest with a btrfs
root won't even boot.
Signed-off-by: John Haxby <john.haxby@oracle.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Reported-by: Michael Marineau <michael.marineau@coreos.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

arch/x86/include/asm/xor_avx.h

@@ -167,12 +167,12 @@ static struct xor_block_template xor_block_avx = {
 
 #define AVX_XOR_SPEED \
 do { \
-	if (cpu_has_avx) \
+	if (cpu_has_avx && cpu_has_osxsave) \
 		xor_speed(&xor_block_avx); \
 } while (0)
 
 #define AVX_SELECT(FASTEST) \
-	(cpu_has_avx ? &xor_block_avx : FASTEST)
+	(cpu_has_avx && cpu_has_osxsave ? &xor_block_avx : FASTEST)
 
 #else