From c3a589fd9fcbf295a7402a4b188dc9277d505f4f Mon Sep 17 00:00:00 2001 From: Heiko Carstens Date: Tue, 18 Feb 2025 12:11:34 +0100 Subject: [PATCH] s390/boot: Fix ESSA detection The cmma_test_essa() inline assembly uses tmp as input and output, however tmp is specified as output only, which allows the compiler to optimize the initialization of tmp away. Therefore the ESSA detection may or may not work depending on previous contents of the register that the compiler selected for tmp. Fix this by using the correct constraint modifier. Fixes: 468a3bc2b7b9 ("s390/cmma: move parsing of cmma kernel parameter to early boot code") Cc: stable@vger.kernel.org Signed-off-by: Heiko Carstens Reviewed-by: Vasily Gorbik Signed-off-by: Vasily Gorbik --- arch/s390/boot/startup.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/s390/boot/startup.c b/arch/s390/boot/startup.c index 885bd1dd2c82..9276e0576d0a 100644 --- a/arch/s390/boot/startup.c +++ b/arch/s390/boot/startup.c @@ -86,7 +86,7 @@ static int cmma_test_essa(void) : [reg1] "=&d" (reg1), [reg2] "=&a" (reg2), [rc] "+&d" (rc), - [tmp] "=&d" (tmp), + [tmp] "+&d" (tmp), "+Q" (get_lowcore()->program_new_psw), "=Q" (old) : [psw_old] "a" (&old),