From patchwork Thu Jan 19 17:05:02 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: =?utf-8?q?Alex_Benn=C3=A9e?= X-Patchwork-Id: 717267 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Received: from lists.gnu.org (lists.gnu.org [IPv6:2001:4830:134:3::11]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (No client certificate requested) by ozlabs.org (Postfix) with ESMTPS id 3v49fw28lVz9sxN for ; Fri, 20 Jan 2017 04:23:52 +1100 (AEDT) Authentication-Results: ozlabs.org; dkim=fail reason="signature verification failed" (1024-bit key; unprotected) header.d=linaro.org header.i=@linaro.org header.b="BLQz2ius"; dkim-atps=neutral Received: from localhost ([::1]:49897 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1cUGRB-0007MR-Pe for incoming@patchwork.ozlabs.org; Thu, 19 Jan 2017 12:23:49 -0500 Received: from eggs.gnu.org ([2001:4830:134:3::10]:40589) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1cUGGU-0005Ty-Qe for qemu-devel@nongnu.org; Thu, 19 Jan 2017 12:12:50 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1cUGGR-0001ev-Fa for qemu-devel@nongnu.org; Thu, 19 Jan 2017 12:12:46 -0500 Received: from mail-wm0-x231.google.com ([2a00:1450:400c:c09::231]:37050) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_128_CBC_SHA1:16) (Exim 4.71) (envelope-from ) id 1cUGGR-0001eV-9E for qemu-devel@nongnu.org; Thu, 19 Jan 2017 12:12:43 -0500 Received: by mail-wm0-x231.google.com with SMTP id c206so3172893wme.0 for ; Thu, 19 Jan 2017 09:12:43 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=Lt+rl+GLF1Sf8uLdRAdU34EpWGXby58jRfs08IrcAbE=; b=BLQz2iusjFQAcvGGXMOcxKl6FXmAM8SCLEbElktGl36z7J6+Jn3Tz6HBf9WRCyKmVR jLk1qdZHn0OSMbXbLd607ngsxWdd3eJvIJWTTuD9qKXmW7EKi5UDTYC3LJXd1g0K9ztT U0fy5MXx/sFdtU6x2z4Xhxo71+JKOB+778iOk= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=Lt+rl+GLF1Sf8uLdRAdU34EpWGXby58jRfs08IrcAbE=; b=lpvdwFyxd13p8HlwrPiuOhfCv3B1SXlm8ODesMzqn10g/1vp4rfbNlMIw/opZbJEtA CgqAtBj3jIPJR4tIaWlnTRRU2BZInNRB9eTBkO669W7wjXT2T2P9m/9SEEQaL1RSOriu E8g4yzqHDf4ia6WIjs6MUgBDr6hrGlG9Twa/jKYVWUEaz0GxMhxe6vK7sOqpn/y/32kP EmhuN6VttpTMbOrDB/7hvQANYZeo7mH/KT3gA+ahdBBVSKdLi2ZdccXkr3TaKt1Y6HFo s9muU1aMajYNjeUvf260+ttebGNXrgHwaDH9B15xSXXHY7rJHkV/pCcC0EO98pXxe+Y5 RN6w== X-Gm-Message-State: AIkVDXKhZV+pyUzGozFXixdYX7GzrvdzPDyQKaywIsaL4CwPCcZ5gIOM74Fd9uwk5sRm2Wf6 X-Received: by 10.28.178.142 with SMTP id b136mr8370771wmf.69.1484845962230; Thu, 19 Jan 2017 09:12:42 -0800 (PST) Received: from zen.linaro.local ([81.128.185.34]) by smtp.gmail.com with ESMTPSA id 191sm14086425wmo.21.2017.01.19.09.12.40 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 19 Jan 2017 09:12:40 -0800 (PST) Received: from zen.linaroharston (localhost [127.0.0.1]) by zen.linaro.local (Postfix) with ESMTP id 5EDA43E2A40; Thu, 19 Jan 2017 17:05:09 +0000 (GMT) From: =?UTF-8?q?Alex=20Benn=C3=A9e?= To: mttcg@listserver.greensocs.com, qemu-devel@nongnu.org, fred.konrad@greensocs.com, a.rigo@virtualopensystems.com, cota@braap.org, bobby.prani@gmail.com, nikunj@linux.vnet.ibm.com Date: Thu, 19 Jan 2017 17:05:02 +0000 Message-Id: <20170119170507.16185-23-alex.bennee@linaro.org> X-Mailer: git-send-email 2.11.0 In-Reply-To: <20170119170507.16185-1-alex.bennee@linaro.org> References: <20170119170507.16185-1-alex.bennee@linaro.org> MIME-Version: 1.0 X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 2a00:1450:400c:c09::231 Subject: [Qemu-devel] [PATCH v7 22/27] target-arm: don't generate WFE/YIELD calls for MTTCG X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: peter.maydell@linaro.org, claudio.fontana@huawei.com, jan.kiszka@siemens.com, mark.burton@greensocs.com, "open list:ARM" , serge.fdrv@gmail.com, pbonzini@redhat.com, =?UTF-8?q?Alex=20Benn=C3=A9e?= , bamvor.zhangjian@linaro.org, rth@twiddle.net Errors-To: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Sender: "Qemu-devel" The WFE and YIELD instructions are really only hints and in TCG's case they were useful to move the scheduling on from one vCPU to the next. In the parallel context (MTTCG) this just causes an unnecessary cpu_exit and contention of the BQL. Signed-off-by: Alex Bennée Reviewed-by: Richard Henderson --- target/arm/op_helper.c | 7 +++++++ target/arm/translate-a64.c | 8 ++++++-- target/arm/translate.c | 20 ++++++++++++++++---- 3 files changed, 29 insertions(+), 6 deletions(-) diff --git a/target/arm/op_helper.c b/target/arm/op_helper.c index e1a883c595..abfa7cdd39 100644 --- a/target/arm/op_helper.c +++ b/target/arm/op_helper.c @@ -436,6 +436,13 @@ void HELPER(yield)(CPUARMState *env) ARMCPU *cpu = arm_env_get_cpu(env); CPUState *cs = CPU(cpu); + /* When running in MTTCG we don't generate jumps to the yield and + * WFE helpers as it won't affect the scheduling of other vCPUs. + * If we wanted to more completely model WFE/SEV so we don't busy + * spin unnecessarily we would need to do something more involved. + */ + g_assert(!parallel_cpus); + /* This is a non-trappable hint instruction that generally indicates * that the guest is currently busy-looping. Yield control back to the * top level loop so that a more deserving VCPU has a chance to run. diff --git a/target/arm/translate-a64.c b/target/arm/translate-a64.c index d0352e2045..7e7131fe2f 100644 --- a/target/arm/translate-a64.c +++ b/target/arm/translate-a64.c @@ -1342,10 +1342,14 @@ static void handle_hint(DisasContext *s, uint32_t insn, s->is_jmp = DISAS_WFI; return; case 1: /* YIELD */ - s->is_jmp = DISAS_YIELD; + if (!parallel_cpus) { + s->is_jmp = DISAS_YIELD; + } return; case 2: /* WFE */ - s->is_jmp = DISAS_WFE; + if (!parallel_cpus) { + s->is_jmp = DISAS_WFE; + } return; case 4: /* SEV */ case 5: /* SEVL */ diff --git a/target/arm/translate.c b/target/arm/translate.c index c9186b6195..4301562527 100644 --- a/target/arm/translate.c +++ b/target/arm/translate.c @@ -4345,20 +4345,32 @@ static void gen_exception_return(DisasContext *s, TCGv_i32 pc) gen_rfe(s, pc, load_cpu_field(spsr)); } +/* + * For WFI we will halt the vCPU until an IRQ. For WFE and YIELD we + * only call the helper when running single threaded TCG code to ensure + * the next round-robin scheduled vCPU gets a crack. In MTTCG mode we + * just skip this instruction. Currently the SEV/SEVL instructions + * which are *one* of many ways to wake the CPU from WFE are not + * implemented so we can't sleep like WFI does. + */ static void gen_nop_hint(DisasContext *s, int val) { switch (val) { case 1: /* yield */ - gen_set_pc_im(s, s->pc); - s->is_jmp = DISAS_YIELD; + if (!parallel_cpus) { + gen_set_pc_im(s, s->pc); + s->is_jmp = DISAS_YIELD; + } break; case 3: /* wfi */ gen_set_pc_im(s, s->pc); s->is_jmp = DISAS_WFI; break; case 2: /* wfe */ - gen_set_pc_im(s, s->pc); - s->is_jmp = DISAS_WFE; + if (!parallel_cpus) { + gen_set_pc_im(s, s->pc); + s->is_jmp = DISAS_WFE; + } break; case 4: /* sev */ case 5: /* sevl */