From 68aa851aa21741ab0a3c019b641d6ce72f68b3d5 Mon Sep 17 00:00:00 2001 From: Sven Schnelle Date: Tue, 29 Jan 2019 20:14:02 +0100 Subject: [PATCH] target/hppa: fix PSW Q bit behaviour to match hardware PA-RISC specification says: "Setting the PSW Q-bit, PSW{28}, to 1 with this instruction, if it was not already 1, is an undefined operation." However, at least HP-UX 10.20 sets the Q bit from 0 to 1 with the SSM instruction. Tested this both on HP9000/712 and HP9000/785/C3750, both machines set the Q bit from 0 to 1 without exception. This makes HP-UX 10.20 progress a little bit further. Signed-off-by: Sven Schnelle Message-Id: <20190129191402.29539-1-svens@stackframe.org> [rth: Add a comment to the code as well.] Signed-off-by: Richard Henderson --- target/hppa/op_helper.c | 14 +++++++++----- 1 file changed, 9 insertions(+), 5 deletions(-) diff --git a/target/hppa/op_helper.c b/target/hppa/op_helper.c index 912e8d5be4..6bf478e7b0 100644 --- a/target/hppa/op_helper.c +++ b/target/hppa/op_helper.c @@ -665,11 +665,15 @@ void HELPER(reset)(CPUHPPAState *env) target_ureg HELPER(swap_system_mask)(CPUHPPAState *env, target_ureg nsm) { target_ulong psw = env->psw; - /* ??? On second reading this condition simply seems - to be undefined rather than a diagnosed trap. */ - if (nsm & ~psw & PSW_Q) { - hppa_dynamic_excp(env, EXCP_ILL, GETPC()); - } + /* + * Setting the PSW Q bit to 1, if it was not already 1, is an + * undefined operation. + * + * However, HP-UX 10.20 does this with the SSM instruction. + * Tested this on HP9000/712 and HP9000/785/C3750 and both + * machines set the Q bit from 0 to 1 without an exception, + * so let this go without comment. + */ env->psw = (psw & ~PSW_SM) | (nsm & PSW_SM); return psw & PSW_SM; }