From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:60136) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1cCrjq-0008IC-By for qemu-devel@nongnu.org; Fri, 02 Dec 2016 12:35:11 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1cCrjn-0001bz-52 for qemu-devel@nongnu.org; Fri, 02 Dec 2016 12:35:10 -0500 Received: from mail-wm0-x235.google.com ([2a00:1450:400c:c09::235]:35642) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_128_CBC_SHA1:16) (Exim 4.71) (envelope-from ) id 1cCrjm-0001ao-Ix for qemu-devel@nongnu.org; Fri, 02 Dec 2016 12:35:07 -0500 Received: by mail-wm0-x235.google.com with SMTP id a197so23656093wmd.0 for ; Fri, 02 Dec 2016 09:35:05 -0800 (PST) From: =?UTF-8?q?Alex=20Benn=C3=A9e?= Date: Fri, 2 Dec 2016 17:34:54 +0000 Message-Id: <20161202173454.19179-1-alex.bennee@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Subject: [Qemu-devel] [PATCH for-2.8] target-arm/translate-a64: fix gen_load_exclusive List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: stefanha@redhat.com, peter.maydell@linaro.org Cc: qemu-devel@nongnu.org, cota@braap.org, =?UTF-8?q?Alex=20Benn=C3=A9e?= , "open list:ARM" While testing rth's latest TCG patches with risu I found ldaxp was broken. Investigating further I found it was broken by 1dd089d0 when the cmpxchg atomic work was merged. As part of that change the code attempted to be clever by doing a single 64 bit load and then shuffle the data around to set the two 32 bit registers. As I couldn't quite follow the endian magic I've simply partially reverted the change to the original code gen_load_exclusive code. This doesn't affect the cmpxchg functionality as that is all done on in gen_store_exclusive part which is untouched. I've also restored the comment that was removed (with a slight tweak to mention cmpxchg). Signed-off-by: Alex Bennée --- target-arm/translate-a64.c | 42 +++++++++++++++++++----------------------- 1 file changed, 19 insertions(+), 23 deletions(-) diff --git a/target-arm/translate-a64.c b/target-arm/translate-a64.c index de48747..6dc27a6 100644 --- a/target-arm/translate-a64.c +++ b/target-arm/translate-a64.c @@ -1839,41 +1839,37 @@ static void disas_b_exc_sys(DisasContext *s, uint32_t insn) } } +/* + * Load/Store exclusive instructions are implemented by remembering + * the value/address loaded, and seeing if these are the same + * when the store is performed. This is not actually the architecturally + * mandated semantics, but it works for typical guest code sequences + * and avoids having to monitor regular stores. + * + * The store exclusive uses the atomic cmpxchg primitives to avoid + * races in multi-threaded linux-user and when MTTCG softmmu is + * enabled. + */ static void gen_load_exclusive(DisasContext *s, int rt, int rt2, TCGv_i64 addr, int size, bool is_pair) { TCGv_i64 tmp = tcg_temp_new_i64(); - TCGMemOp be = s->be_data; + TCGMemOp memop = s->be_data + size; g_assert(size <= 3); + tcg_gen_qemu_ld_i64(tmp, addr, get_mem_index(s), memop); + if (is_pair) { + TCGv_i64 addr2 = tcg_temp_new_i64(); TCGv_i64 hitmp = tcg_temp_new_i64(); - if (size == 3) { - TCGv_i64 addr2 = tcg_temp_new_i64(); - - tcg_gen_qemu_ld_i64(tmp, addr, get_mem_index(s), - MO_64 | MO_ALIGN_16 | be); - tcg_gen_addi_i64(addr2, addr, 8); - tcg_gen_qemu_ld_i64(hitmp, addr2, get_mem_index(s), - MO_64 | MO_ALIGN | be); - tcg_temp_free_i64(addr2); - } else { - g_assert(size == 2); - tcg_gen_qemu_ld_i64(tmp, addr, get_mem_index(s), - MO_64 | MO_ALIGN | be); - if (be == MO_LE) { - tcg_gen_extr32_i64(tmp, hitmp, tmp); - } else { - tcg_gen_extr32_i64(hitmp, tmp, tmp); - } - } - + g_assert(size >= 2); + tcg_gen_addi_i64(addr2, addr, 1 << size); + tcg_gen_qemu_ld_i64(hitmp, addr2, get_mem_index(s), memop); + tcg_temp_free_i64(addr2); tcg_gen_mov_i64(cpu_exclusive_high, hitmp); tcg_gen_mov_i64(cpu_reg(s, rt2), hitmp); tcg_temp_free_i64(hitmp); - } else { - tcg_gen_qemu_ld_i64(tmp, addr, get_mem_index(s), size | MO_ALIGN | be); } tcg_gen_mov_i64(cpu_exclusive_val, tmp); -- 2.10.2