From patchwork Mon Jun 19 14:23:30 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Richard Henderson X-Patchwork-Id: 1796616 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@legolas.ozlabs.org Authentication-Results: legolas.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=nongnu.org (client-ip=209.51.188.17; helo=lists.gnu.org; envelope-from=qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org; receiver=) Authentication-Results: legolas.ozlabs.org; dkim=pass (2048-bit key; unprotected) header.d=linaro.org header.i=@linaro.org header.a=rsa-sha256 header.s=google header.b=iL7duy8M; dkim-atps=neutral Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-ECDSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by legolas.ozlabs.org (Postfix) with ESMTPS id 4QlBqJ4NQrz20XQ for ; Tue, 20 Jun 2023 00:24:44 +1000 (AEST) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1qBFnJ-0004FL-6z; Mon, 19 Jun 2023 10:23:49 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1qBFnD-0004Dt-NL for qemu-devel@nongnu.org; Mon, 19 Jun 2023 10:23:45 -0400 Received: from mail-wm1-x333.google.com ([2a00:1450:4864:20::333]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.90_1) (envelope-from ) id 1qBFnB-0000jd-3u for qemu-devel@nongnu.org; Mon, 19 Jun 2023 10:23:42 -0400 Received: by mail-wm1-x333.google.com with SMTP id 5b1f17b1804b1-3f906d8fca3so19903885e9.1 for ; Mon, 19 Jun 2023 07:23:40 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; t=1687184620; x=1689776620; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:to:from:from:to:cc:subject:date:message-id :reply-to; bh=qMEBKL6knLVKab7hTTzt13ET959rfX68OW/IE4hZmWo=; b=iL7duy8Mm1gdLHukDRVquaxKLu4bLM1ooJVce2XzoXPc1lcAdRCKzvsdCOstMpsjjd z9KCJITAoO3MuzADbmiijkOFrKhrMKdS8Dc9FkD1BocsAUGe3O7F4sD17ueABJg18YjT RjBngxskh9c5rSQAID3HhRkD8jLHw81BGDR8ouJNQ3rI29r8RHCkYotUibnkyCsQ+7ye fy2w5ANlpQme/dR359aQFnSjEqkxkbc51jDcdB3ZgW+2nv5jlw+khEdPrQ0aGyTjVXOa MaCJdIVbbM0lkWs0M2KN2YXQ1u44aii2JNWBNKO0rnY34itTGG1mWuu7Y296vUiH0UGt r+1g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1687184620; x=1689776620; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=qMEBKL6knLVKab7hTTzt13ET959rfX68OW/IE4hZmWo=; b=jKdXX6ej+pPX8JsR5Ti7lcPNcVRluCGIrQ3HPwd9I7BsFCBmio2WhdwAd9Bcot1bvZ 6wMbKbeHHYaqIBvjLl0Xm59XscYMqyHycthU4l9CaEdBJ32OYbB8rL5QCI0LmzD3SQfB bGYn0VTe9QS1RSQNJUTzof55kCBqdM+1lFS760SWTsNSDCSnHv6EpiEADjCyFn4FmAsr AY3aBhl+HZ8xbhZcVyG7UcNybY5z7YbPV6dH96FEnQ3sY1ug/KnJ/jHacDHFX6JODJqQ mTArssA60wWv/QZSrVNOM53oD64Y9ro/cs8P3Gm6SKDbFj+sFPa+xWxyVYLGg7L1Fz3J wodQ== X-Gm-Message-State: AC+VfDz6KhqTpvOeamlGu4S5omfidlKTtfZrakGwEbP4jU95L9sfp1zT ap9pe1D+T7ZcE/63F735PPb+HYFGVQgJjlE5J5izuyUf X-Google-Smtp-Source: ACHHUZ6+G9RkA5fnzXwxBI8r4R3g1AjKgwpGd07jKy5r39ZXDN5AvDPXOutte/na/Dr5ir5qLHWkAg== X-Received: by 2002:a7b:cb4e:0:b0:3f7:f884:7be3 with SMTP id v14-20020a7bcb4e000000b003f7f8847be3mr7275839wmj.4.1687184619815; Mon, 19 Jun 2023 07:23:39 -0700 (PDT) Received: from stoup.lan (sar95-h02-176-184-10-225.dsl.sta.abo.bbox.fr. [176.184.10.225]) by smtp.gmail.com with ESMTPSA id k25-20020a7bc419000000b003f96d10eafbsm4143467wmi.12.2023.06.19.07.23.38 for (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 19 Jun 2023 07:23:39 -0700 (PDT) From: Richard Henderson To: qemu-devel@nongnu.org Subject: [PATCH v3 2/5] tcg: Do not elide memory barriers for !CF_PARALLEL in system mode Date: Mon, 19 Jun 2023 16:23:30 +0200 Message-Id: <20230619142333.429028-3-richard.henderson@linaro.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20230619142333.429028-1-richard.henderson@linaro.org> References: <20230619142333.429028-1-richard.henderson@linaro.org> MIME-Version: 1.0 Received-SPF: pass client-ip=2a00:1450:4864:20::333; envelope-from=richard.henderson@linaro.org; helo=mail-wm1-x333.google.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Sender: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org The virtio devices require proper memory ordering between the vcpus and the iothreads. Signed-off-by: Richard Henderson --- tcg/tcg-op.c | 14 +++++++++++++- 1 file changed, 13 insertions(+), 1 deletion(-) diff --git a/tcg/tcg-op.c b/tcg/tcg-op.c index c07de5d9f8..7aadb37756 100644 --- a/tcg/tcg-op.c +++ b/tcg/tcg-op.c @@ -102,7 +102,19 @@ void tcg_gen_br(TCGLabel *l) void tcg_gen_mb(TCGBar mb_type) { - if (tcg_ctx->gen_tb->cflags & CF_PARALLEL) { +#ifdef CONFIG_USER_ONLY + bool parallel = tcg_ctx->gen_tb->cflags & CF_PARALLEL; +#else + /* + * It is tempting to elide the barrier in a uniprocessor context. + * However, even with a single cpu we have i/o threads running in + * parallel, and lack of memory order can result in e.g. virtio + * queue entries being read incorrectly. + */ + bool parallel = true; +#endif + + if (parallel) { tcg_gen_op1(INDEX_op_mb, mb_type); } }