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[81.2.115.148]) by smtp.gmail.com with ESMTPSA id p16sm2688564wmg.22.2020.03.12.04.44.20 for (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 12 Mar 2020 04:44:20 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; h=from:to:subject:date:message-id:in-reply-to:references:mime-version :content-transfer-encoding; bh=eBeviPrcWH2dai694kmgJG+Ywc1WYHHnCivC/RAq/0g=; b=xvH3pfMrGHi1BcGKbUq1vR52SrR8gcFFdtwAx9gSd+caqvZG0yByMlDcgS9/oRt8Fe AsPQbfIjpSnglGMupWoLe3AW207cn5hKpjIlaumkfyOMfZU9+lJpZ4s5iQ5rRR6Cjjqf TDcw4U9SXYXwkQzgyEZrJHVDUd2jb2eRMVIyElzfWLD5iwuYocqJeG7pBqEyvzDTKRqE hlQQKPTHAZnJApGHACivVmEJG+J/805Rpy/36aIQqzlaxgd9dXFjNSPn22u9DZBNV+1d kQ+g4k09FUOxsOWmHdbgDxIkdxpzcroi8bFtluMtKXfZygvxpTHXs31/OroQr0D9YN2d vgXQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=eBeviPrcWH2dai694kmgJG+Ywc1WYHHnCivC/RAq/0g=; b=IkwJzXAzUbWkS5VOBEPTCqxUo+LsEntQu3BVz55IroLVFUUJyY0xGkYAvFkge0UYGN TPn9feepiQgeR73MreO32+gtUVDhpNlZJyemsS/gieFal9xzf5izqd9VxZ2qEDz2bxIv 5EMlmzKRjQ871xlmFFbSMGhxWO/Eq2+ZzIkBUtT/7o0SYXqxVwgQDelsWQoGxu8WtUKn i4FhL0IfA61/n4fLxeIT0RvIegfUqfp5KIVhgRFSp3JRdmYslmX3BCgO/7aqqsCyuiRq Wv1qbvmE4g3jLqNapCPtmCz08SKDjbu877HrBx60rPDpEQc4e7gAJllq4T0Q+c2F1mDg WoUA== X-Gm-Message-State: ANhLgQ2nFA4dxgPldf2nGobQMBgBiungKsdMyb4K4EiGsYR3EVnzJRqg n/3XsAJPW+oofqAZyKP44+e3RQVKpEtwmg== X-Google-Smtp-Source: ADFU+vvhspBUKYHgtA7IEj/VLpATN4ocKPDs216Xmvm0pe5I2tMjyyqI3nftazUGfuAM3IkzSKfjaA== X-Received: by 2002:a7b:c454:: with SMTP id l20mr4699475wmi.189.1584013461450; Thu, 12 Mar 2020 04:44:21 -0700 (PDT) From: Peter Maydell To: qemu-devel@nongnu.org Subject: [PULL 10/12] docs/system/target-arm.rst: Add some introductory text Date: Thu, 12 Mar 2020 11:44:06 +0000 Message-Id: <20200312114408.16891-11-peter.maydell@linaro.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20200312114408.16891-1-peter.maydell@linaro.org> References: <20200312114408.16891-1-peter.maydell@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable X-detected-operating-system: by eggs.gnu.org: Genre and OS details not recognized. X-Received-From: 2a00:1450:4864:20::344 X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: "Qemu-devel" X-ZohoMail-DKIM: pass (identity @linaro.org) Now we've moved the various bits of per-board documentation into their own files, the top level document is a little bare. Add some introductory information, including a note that many of the board models we support are currently undocumented. (Most sections of this new text were originally written by me for the wiki page https://wiki.qemu.org/Documentation/Platforms/ARM) Signed-off-by: Peter Maydell Reviewed-by: Alex Benn=C3=A9e Reviewed-by: Niek Linnenbank Message-id: 20200309215818.2021-4-peter.maydell@linaro.org --- docs/system/target-arm.rst | 66 ++++++++++++++++++++++++++++++++++++-- 1 file changed, 64 insertions(+), 2 deletions(-) diff --git a/docs/system/target-arm.rst b/docs/system/target-arm.rst index c7df6fc1f97..86ea6f2f568 100644 --- a/docs/system/target-arm.rst +++ b/docs/system/target-arm.rst @@ -1,9 +1,71 @@ .. _ARM-System-emulator: =20 -ARM System emulator +Arm System emulator ------------------- =20 -Use the executable ``qemu-system-arm`` to simulate a ARM machine. +QEMU can emulate both 32-bit and 64-bit Arm CPUs. Use the +``qemu-system-aarch64`` executable to simulate a 64-bit Arm machine. +You can use either ``qemu-system-arm`` or ``qemu-system-aarch64`` +to simulate a 32-bit Arm machine: in general, command lines that +work for ``qemu-system-arm`` will behave the same when used with +``qemu-system-aarch64``. + +QEMU has generally good support for Arm guests. It has support for +nearly fifty different machines. The reason we support so many is that +Arm hardware is much more widely varying than x86 hardware. Arm CPUs +are generally built into "system-on-chip" (SoC) designs created by +many different companies with different devices, and these SoCs are +then built into machines which can vary still further even if they use +the same SoC. Even with fifty boards QEMU does not cover more than a +small fraction of the Arm hardware ecosystem. + +The situation for 64-bit Arm is fairly similar, except that we don't +implement so many different machines. + +As well as the more common "A-profile" CPUs (which have MMUs and will +run Linux) QEMU also supports "M-profile" CPUs such as the Cortex-M0, +Cortex-M4 and Cortex-M33 (which are microcontrollers used in very +embedded boards). For most boards the CPU type is fixed (matching what +the hardware has), so typically you don't need to specify the CPU type +by hand, except for special cases like the ``virt`` board. + +Choosing a board model +=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D + +For QEMU's Arm system emulation, you must specify which board +model you want to use with the ``-M`` or ``--machine`` option; +there is no default. + +Because Arm systems differ so much and in fundamental ways, typically +operating system or firmware images intended to run on one machine +will not run at all on any other. This is often surprising for new +users who are used to the x86 world where every system looks like a +standard PC. (Once the kernel has booted, most userspace software +cares much less about the detail of the hardware.) + +If you already have a system image or a kernel that works on hardware +and you want to boot with QEMU, check whether QEMU lists that machine +in its ``-machine help`` output. If it is listed, then you can probably +use that board model. If it is not listed, then unfortunately your image +will almost certainly not boot on QEMU. (You might be able to +extract the filesystem and use that with a different kernel which +boots on a system that QEMU does emulate.) + +If you don't care about reproducing the idiosyncrasies of a particular +bit of hardware, such as small amount of RAM, no PCI or other hard +disk, etc., and just want to run Linux, the best option is to use the +``virt`` board. This is a platform which doesn't correspond to any +real hardware and is designed for use in virtual machines. You'll +need to compile Linux with a suitable configuration for running on +the ``virt`` board. ``virt`` supports PCI, virtio, recent CPUs and +large amounts of RAM. It also supports 64-bit CPUs. + +Board-specific documentation +=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D + +Unfortunately many of the Arm boards QEMU supports are currently +undocumented; you can get a complete list by running +``qemu-system-aarch64 --machine help``. =20 .. toctree:: =20 --=20 2.20.1