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[2001:4830:134:3::11]) by mx.google.com with ESMTPS id 125si3329321qkk.68.2017.01.27.03.28.20 for (version=TLS1 cipher=AES128-SHA bits=128/128); Fri, 27 Jan 2017 03:28:21 -0800 (PST) Received-SPF: pass (google.com: domain of qemu-devel-bounces+patch=linaro.org@nongnu.org designates 2001:4830:134:3::11 as permitted sender) client-ip=2001:4830:134:3::11; Authentication-Results: mx.google.com; dkim=fail header.i=@linaro.org; spf=pass (google.com: domain of qemu-devel-bounces+patch=linaro.org@nongnu.org designates 2001:4830:134:3::11 as permitted sender) smtp.mailfrom=qemu-devel-bounces+patch=linaro.org@nongnu.org; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=linaro.org Received: from localhost ([::1]:44521 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1cX4hW-0007cl-Hk for patch@linaro.org; Fri, 27 Jan 2017 06:28:18 -0500 Received: from eggs.gnu.org ([2001:4830:134:3::10]:49524) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1cX40J-0007bK-0T for qemu-devel@nongnu.org; Fri, 27 Jan 2017 05:43:40 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1cX40I-0004eN-0S for qemu-devel@nongnu.org; Fri, 27 Jan 2017 05:43:39 -0500 Received: from mail-wm0-x22b.google.com ([2a00:1450:400c:c09::22b]:35981) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_128_CBC_SHA1:16) (Exim 4.71) (envelope-from ) id 1cX40H-0004db-QU for qemu-devel@nongnu.org; Fri, 27 Jan 2017 05:43:37 -0500 Received: by mail-wm0-x22b.google.com with SMTP id c85so110758373wmi.1 for ; Fri, 27 Jan 2017 02:43:37 -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=/0U3sUBP4xqPfuNeLa547JecXLGhyPmtSpeOtWjU9bA=; b=N5cGg8WLze8OIomn8N8OS3cDJK77CoFc7ufgY90abA9uztToGukkZZXTW+reZAcd3u HWN3qOZwn1iHErbq01XdtHbVklyP0n08stkJ0i3sssVDnZ6ijD9i1go8axMsUYp90Lu3 /We02zRk5Wtb0jZ5VxUx8QKsmKs2WTLA/aGh0= 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=/0U3sUBP4xqPfuNeLa547JecXLGhyPmtSpeOtWjU9bA=; b=WXL7uKAeaLsSXQFWeUgFuD7ztb4TKa+RSKAPiPnRwEcxZs1Eo3Gpz2S8aw0+uKvFvR nYA1jS+uxi5BtXaCxfeXndbrAxUY76/BYAA8OPNls6Vh8khCrZ3pqlbV6AOtAvRP8g0I b3LfpD3PdMjZzSdPRN9lZnf8O7FT6at87gtf5oh9huMHpsQBRa4Ei/X9YK0Q9/0epsVx LwP6uvHAJc2ITTPakHppPoBs7Tq49qhd4esdTqd+sCNz4mYcGKjbKcHhSk0ZEs6XI69n g80BGZvdqzxmmbUlum2FI9xJolJNhmMfM6rTUJd4Uz1mrZfo3mm/nZzQy7AmDf6NRuD2 A8pQ== X-Gm-Message-State: AIkVDXKWzT1v96f8+tmqBT91r6WxRSqjJRvyZtAf9fQOgHdCI+BfQdJCk8xhUqigsDXeMGgp X-Received: by 10.223.150.183 with SMTP id u52mr6681583wrb.180.1485513816682; Fri, 27 Jan 2017 02:43:36 -0800 (PST) Received: from zen.linaro.local ([81.128.185.34]) by smtp.gmail.com with ESMTPSA id p49sm7164475wrb.10.2017.01.27.02.43.33 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 27 Jan 2017 02:43:33 -0800 (PST) Received: from zen.linaroharston (localhost [127.0.0.1]) by zen.linaro.local (Postfix) with ESMTP id 27FCF3E376D; Fri, 27 Jan 2017 10:35:07 +0000 (GMT) From: =?utf-8?q?Alex_Benn=C3=A9e?= To: Date: Fri, 27 Jan 2017 10:35:01 +0000 Message-Id: <20170127103505.18606-22-alex.bennee@linaro.org> X-Mailer: git-send-email 2.11.0 In-Reply-To: <20170127103505.18606-1-alex.bennee@linaro.org> References: <20170127103505.18606-1-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::22b Subject: [Qemu-devel] [PATCH v8 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 , "open list:ARM" , =?utf-8?q?Alex_Benn=C3=A9e?= , "open list:All patches CC here" Errors-To: qemu-devel-bounces+patch=linaro.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(-) -- 2.11.0 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 88a4df6959..05162f335e 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 dc67887918..444a24c2b6 100644 --- a/target/arm/translate.c +++ b/target/arm/translate.c @@ -4343,20 +4343,32 @@ 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 */