From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id ACE3AC77B7A for ; Thu, 18 May 2023 11:12:21 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1pzbXp-0004ub-C5; Thu, 18 May 2023 07:11:41 -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 1pzbXl-0004uD-FI for qemu-devel@nongnu.org; Thu, 18 May 2023 07:11:37 -0400 Received: from mail-wm1-x32a.google.com ([2a00:1450:4864:20::32a]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.90_1) (envelope-from ) id 1pzbXj-0006U8-VB for qemu-devel@nongnu.org; Thu, 18 May 2023 07:11:37 -0400 Received: by mail-wm1-x32a.google.com with SMTP id 5b1f17b1804b1-3f4271185daso18353725e9.2 for ; Thu, 18 May 2023 04:11:35 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; t=1684408294; x=1687000294; h=content-transfer-encoding:mime-version:message-id:in-reply-to:date :subject:cc:to:from:user-agent:references:from:to:cc:subject:date :message-id:reply-to; bh=NZ3nQMGOxUQHSwfAZvqeRwdh0cwuqvViTTcbn2Dkiq4=; b=BrIafM9tzS5YqB3/yLQD/gcWXGhlzDL4BHRK6yjKsJpI4N9p1bA5dOCBzAqa65Wznv Mw7koBNq9QiOVK/OWpQf0DEl+qn2L4BjUJbHuQnjBn9Jicbsxzc+Dutg0l31xEPWTxUD XWpjEZKBKvnORvbYxUrg9PAKC0fHEyzufLifK9Rce179QtHBhL+k2Oj/Wdgm30/3Pjqk lwnSDwb3D9y0UX/dKJfvfJTR1iFK2nv1WbiMN1bmrLqtKNw2P4UCDOSzb6+d8AUIZWE1 qMfK0v9dnmcFD9guZ8eYVick7GfYY1MMBNLy4el9wOWE7kA7fW9871ODrlJg1Vmk/dE2 X3pg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1684408294; x=1687000294; h=content-transfer-encoding:mime-version:message-id:in-reply-to:date :subject:cc:to:from:user-agent:references:x-gm-message-state:from:to :cc:subject:date:message-id:reply-to; bh=NZ3nQMGOxUQHSwfAZvqeRwdh0cwuqvViTTcbn2Dkiq4=; b=LmwifbBabI3kM2zS+veoG5WG3bDxUmsq3QieM3EedpKANwXHwxqlTEnwXPEwhvkAP7 IjJC8+2dm5OKyqM8epFOUjPSo/dmeVVKB4wgIDAf3DQ7BxZadoE33effZMg0e6sAbKYd rSLs5Myq2kRGTowokZhAYyD+msDwRBwjz/oxMprKcH3gGOc6ejCpzRksszKp1JrR6gyb c8/oDQ4m4jaeJL+SVnnc0WHapfa0P0dcuX53GmhsNsf/tjiPo/jhNmCT5TuZefm8Cr8g wLXUQn2itCbaPY2GIryk9Gj5hj3qNucM64J+laC9OXLGhkuj/uORSyqAd8drn2Nu6u1w MCpQ== X-Gm-Message-State: AC+VfDy5Ija73Z/1TrWJQk5HsxsKQFzIpQqOKc2EleEfH0JKQZC5tleW SYNkm59xMIkNsTunwjSFtPrszA== X-Google-Smtp-Source: ACHHUZ7/Hlb3L5dUKkxNeNY7ToH8X0V+XXJth9gS7JYdkMgDZ9WxlY3xrvPV572q82c3c7dvDdjAfA== X-Received: by 2002:a7b:ce09:0:b0:3f5:14ed:80bf with SMTP id m9-20020a7bce09000000b003f514ed80bfmr1248525wmc.30.1684408294068; Thu, 18 May 2023 04:11:34 -0700 (PDT) Received: from zen.linaroharston ([85.9.250.243]) by smtp.gmail.com with ESMTPSA id r11-20020adff70b000000b003021288a56dsm1783010wrp.115.2023.05.18.04.11.33 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 18 May 2023 04:11:33 -0700 (PDT) Received: from zen (localhost [127.0.0.1]) by zen.linaroharston (Postfix) with ESMTP id 0EEC81FFBB; Thu, 18 May 2023 12:11:33 +0100 (BST) References: <20230516104420.407912-1-alex.bennee@linaro.org> User-agent: mu4e 1.11.6; emacs 29.0.91 From: Alex =?utf-8?Q?Benn=C3=A9e?= To: Peter Maydell Cc: qemu-devel@nongnu.org, qemu-arm@nongnu.org, Anders Roxell , Evgeny Iakovlev Subject: Re: [RFC PATCH] target/arm: add RAZ/WI handling for DBGDTR[TX|RX] Date: Thu, 18 May 2023 12:09:47 +0100 In-reply-to: Message-ID: <87a5y1nbbv.fsf@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Received-SPF: pass client-ip=2a00:1450:4864:20::32a; envelope-from=alex.bennee@linaro.org; helo=mail-wm1-x32a.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=unavailable 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+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Peter Maydell writes: > On Tue, 16 May 2023 at 11:44, Alex Benn=C3=A9e w= rote: >> >> The commit b3aa2f2128 (target/arm: provide stubs for more external >> debug registers) was added to handle HyperV's unconditional usage of >> Debug Communications Channel. It turns out that Linux will similarly >> break if you enable CONFIG_HVC_DCC "ARM JTAG DCC console". >> >> Extend the registers we RAZ/WI set to avoid this. > > Applied to target-arm.next, thanks. > > (In theory we could implement the DCC and wire it up to a > chardev, which might be a cute way of getting early debug.) I wondered about that - does DCC give you anything that you can't get with semihosting (which I think also can support earlycon)? I found it a little unclear if this is an always available feature. Should you expect any modern Cortex/Arm chip to support DCC when attached to jtag? --=20 Alex Benn=C3=A9e Virtualisation Tech Lead @ Linaro