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Wed, 14 Jul 2021 02:37:23 -0700 (PDT) Received: from zen.linaroharston ([51.148.130.216]) by smtp.gmail.com with ESMTPSA id d8sm1854280wrv.20.2021.07.14.02.37.20 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 14 Jul 2021 02:37:20 -0700 (PDT) Received: from zen.lan (localhost [127.0.0.1]) by zen.linaroharston (Postfix) with ESMTP id CCC1D1FF93; Wed, 14 Jul 2021 10:37:19 +0100 (BST) From: =?UTF-8?q?Alex=20Benn=C3=A9e?= To: qemu-devel@nongnu.org Subject: [PATCH v1 02/21] docs: collect the disparate device emulation docs into one section Date: Wed, 14 Jul 2021 10:37:00 +0100 Message-Id: <20210714093719.21429-3-alex.bennee@linaro.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20210714093719.21429-1-alex.bennee@linaro.org> References: <20210714093719.21429-1-alex.bennee@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=2a00:1450:4864:20::434; envelope-from=alex.bennee@linaro.org; helo=mail-wr1-x434.google.com X-Spam_score_int: -1 X-Spam_score: -0.2 X-Spam_bar: / X-Spam_report: (-0.2 / 5.0 requ) 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 autolearn=ham autolearn_force=no X-Spam_action: no action 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: , Cc: =?UTF-8?q?Alex=20Benn=C3=A9e?= Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" While we are at it add a brief preamble that explains some of the common concepts in QEMU's device emulation which will hopefully lead to less confusing about our dizzying command line options. Signed-off-by: Alex Bennée --- docs/system/device-emulation.rst | 78 +++++++++++++++++++++++ docs/system/{ => devices}/ivshmem.rst | 0 docs/system/{ => devices}/net.rst | 0 docs/system/{ => devices}/nvme.rst | 0 docs/system/{ => devices}/usb.rst | 0 docs/system/{ => devices}/virtio-pmem.rst | 0 docs/system/index.rst | 6 +- 7 files changed, 79 insertions(+), 5 deletions(-) create mode 100644 docs/system/device-emulation.rst rename docs/system/{ => devices}/ivshmem.rst (100%) rename docs/system/{ => devices}/net.rst (100%) rename docs/system/{ => devices}/nvme.rst (100%) rename docs/system/{ => devices}/usb.rst (100%) rename docs/system/{ => devices}/virtio-pmem.rst (100%) diff --git a/docs/system/device-emulation.rst b/docs/system/device-emulation.rst new file mode 100644 index 0000000000..a0f00bc340 --- /dev/null +++ b/docs/system/device-emulation.rst @@ -0,0 +1,78 @@ +.. _device-emulation: + +Device Emulation +---------------- + +QEMU supports the emulation of a large number of devices from +peripherals such network cards and USB devices to integrated systems +on a chip (SoCs). Configuration of these is often a source of +confusion so it helps to have an understanding of some of the terms +used to describes devices within QEMU. + +Common Terms +~~~~~~~~~~~~ + +Device Front End +================ + +A device front end is how a device is presented to the guest. The type +of device presented should match the hardware that the guest operating +system is expecting to see. All devices can be specified with the +``--device`` command line option. Running QEMU with the command line +options ``--device help`` will list all devices it is aware of. Using +the command line ``--device foo,help`` will list the additional +configuration options available for that device. + +A front end is often paired with a back end, which describes how the +host's resources are used in the emulation. + +Device Buses +============ + +All devices exist on a BUS. Depending on the machine model you choose +(``-M foo``) a number of buses will have been automatically created. +In most cases the BUS a device is attached to can be inferred, for +example PCI devices are generally automatically allocated to the next +free slot of the PCI bus. However in complicated configurations you +can explicitly specify what bus a device is attached to and its +address. Some devices, for example a PCI SCSI host controller, will +add an additional bus to the system that other devices can be attached +to. + +Device Back End +=============== + +The back end describes how the data from the emulated device will be +processed by QEMU. The configuration of the back end is usually +specific to the class of device being emulated. For example serial +devices will be backed by a ``--chardev`` which can redirect the data +to a file or socket or some other system. Storage devices are handled +by ``--blockdev`` which will specify how blocks are handled, for +example being stored in a qcow2 file or accessing a raw host disk +partition. Back ends can sometimes be stacked to implement features +like snapshots. + +While the choice of back end is generally transparent to the guest +there are cases where features will not be reported to the guest if +the back end is unable to support it. + +Device Pass Through +=================== + +Device pass through is where the device is actually given access to +the underlying hardware. This can be as simple as exposing a single +USB device on the host system to the guest or dedicating a video card +in a PCI slot to the exclusive use of the guest. + + +Emulated Devices +~~~~~~~~~~~~~~~~ + +.. toctree:: + :maxdepth: 1 + + devices/ivshmem.rst + devices/net.rst + devices/nvme.rst + devices/usb.rst + devices/virtio-pmem.rst diff --git a/docs/system/ivshmem.rst b/docs/system/devices/ivshmem.rst similarity index 100% rename from docs/system/ivshmem.rst rename to docs/system/devices/ivshmem.rst diff --git a/docs/system/net.rst b/docs/system/devices/net.rst similarity index 100% rename from docs/system/net.rst rename to docs/system/devices/net.rst diff --git a/docs/system/nvme.rst b/docs/system/devices/nvme.rst similarity index 100% rename from docs/system/nvme.rst rename to docs/system/devices/nvme.rst diff --git a/docs/system/usb.rst b/docs/system/devices/usb.rst similarity index 100% rename from docs/system/usb.rst rename to docs/system/devices/usb.rst diff --git a/docs/system/virtio-pmem.rst b/docs/system/devices/virtio-pmem.rst similarity index 100% rename from docs/system/virtio-pmem.rst rename to docs/system/devices/virtio-pmem.rst diff --git a/docs/system/index.rst b/docs/system/index.rst index 6092eb2d91..641d243ba4 100644 --- a/docs/system/index.rst +++ b/docs/system/index.rst @@ -16,15 +16,12 @@ Contents: quickstart invocation + device-emulation keys mux-chardev monitor images - net virtio-net-failover - usb - nvme - ivshmem linuxboot generic-loader guest-loader @@ -35,7 +32,6 @@ Contents: gdb managed-startup cpu-hotplug - virtio-pmem pr-manager targets security -- 2.20.1