From patchwork Wed Feb 1 15:05:49 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: 722576 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 3vD6NV6M9Qz9sxS for ; Thu, 2 Feb 2017 02:23:54 +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="k1aH+u+2"; dkim-atps=neutral Received: from localhost ([::1]:51535 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1cYwlE-0007k6-67 for incoming@patchwork.ozlabs.org; Wed, 01 Feb 2017 10:23:52 -0500 Received: from eggs.gnu.org ([2001:4830:134:3::10]:39267) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1cYwde-0000D7-FW for qemu-devel@nongnu.org; Wed, 01 Feb 2017 10:16:08 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1cYwda-00020s-Bc for qemu-devel@nongnu.org; Wed, 01 Feb 2017 10:16:02 -0500 Received: from mail-wm0-x235.google.com ([2a00:1450:400c:c09::235]:35420) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_128_CBC_SHA1:16) (Exim 4.71) (envelope-from ) id 1cYwda-00020U-5b for qemu-devel@nongnu.org; Wed, 01 Feb 2017 10:15:58 -0500 Received: by mail-wm0-x235.google.com with SMTP id b65so43711565wmf.0 for ; Wed, 01 Feb 2017 07:15:58 -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=4PUkoa7bFUKSHUw/G0Y7vj5HjOKRMyccT0nstjdRiFM=; b=k1aH+u+2uQ1AWvdQEADXq5jsHrnFgxo7YobK/nr3Bt0QfoVxhnZoi/VST+Ewh0o+Cp JKDxK7yXK2a7epLLHUwVMaz+V2NnhKp3P0DHn5zM29Aa5/R1DxPxh5XnDSbGhYh3+rHv /Xsr8zBYQFfdAE4DrPCrj5NH4omUvr/3ObKyY= 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=4PUkoa7bFUKSHUw/G0Y7vj5HjOKRMyccT0nstjdRiFM=; b=hfkbf/BcUoV+A5tASPMnxs4Q+pOl3wGxG5NlS+vzVfl3rEYib7rlaYj5DtA50z5qRZ erWRG+8lfjNeemAc1O4XR+k3JaoH30xaSrwlQ7zfqbDfd0R0DWLya5DKCF3+MrAjQ7DD 8B9kahICPe/C3G0Xq8xQN5x/HRQcaebEm5bbIguQu6WlMKm14ulaQafBZdTeFdF3xX8G oYZ++JxRk4PsCh+M8D136xWUQosWC0kCTfLL+Fg/pbGTRMBoLOpaqJHE1/Y8rfMqWAE+ TTM7AVMTI2tpVwtB4vtkfYYAY0KQGVGcaKrK5jlaqNyGzJGs9RsTKEcR9Lr0Q0wf8XLx nuLQ== X-Gm-Message-State: AIkVDXL0vJzfoNDodre/pIfwa4iWn/D8nmuxRiUG7DNV8S0OoyGdB9NIEZ/r4nxuiamQgFBM X-Received: by 10.28.158.74 with SMTP id h71mr3648725wme.59.1485962157112; Wed, 01 Feb 2017 07:15:57 -0800 (PST) Received: from zen.linaro.local ([81.128.185.34]) by smtp.gmail.com with ESMTPSA id 10sm22152979wmi.23.2017.02.01.07.15.53 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 01 Feb 2017 07:15:53 -0800 (PST) Received: from zen.linaroharston (localhost [127.0.0.1]) by zen.linaro.local (Postfix) with ESMTP id 060B73E0F68; Wed, 1 Feb 2017 15:05:55 +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: Wed, 1 Feb 2017 15:05:49 +0000 Message-Id: <20170201150553.9381-22-alex.bennee@linaro.org> X-Mailer: git-send-email 2.11.0 In-Reply-To: <20170201150553.9381-1-alex.bennee@linaro.org> References: <20170201150553.9381-1-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::235 Subject: [Qemu-devel] [PATCH v9 21/25] 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, 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 Reviewed-by: Peter Maydell --- 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 493c627bcf..24faa7c60c 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 */