This convers the existing README.virtio to reST, and puts it under the develop/driver-model/ directory.
Signed-off-by: Bin Meng bmeng.cn@gmail.com ---
doc/develop/driver-model/index.rst | 1 + .../driver-model/virtio.rst} | 90 +++++++++++++------ 2 files changed, 63 insertions(+), 28 deletions(-) rename doc/{README.virtio => develop/driver-model/virtio.rst} (86%)
diff --git a/doc/develop/driver-model/index.rst b/doc/develop/driver-model/index.rst index fd4575db9b..10a76256b0 100644 --- a/doc/develop/driver-model/index.rst +++ b/doc/develop/driver-model/index.rst @@ -27,3 +27,4 @@ subsystems soc-framework spi-howto usb-info + virtio diff --git a/doc/README.virtio b/doc/develop/driver-model/virtio.rst similarity index 86% rename from doc/README.virtio rename to doc/develop/driver-model/virtio.rst index d3652f2e2f..8ac9c94caf 100644 --- a/doc/README.virtio +++ b/doc/develop/driver-model/virtio.rst @@ -1,11 +1,10 @@ -# SPDX-License-Identifier: GPL-2.0+ -# -# Copyright (C) 2018, Bin Meng bmeng.cn@gmail.com +.. SPDX-License-Identifier: GPL-2.0+ +.. sectionauthor:: Bin Meng bmeng.cn@gmail.com
VirtIO Support ==============
-This document describes the information about U-Boot support for VirtIO [1] +This document describes the information about U-Boot support for VirtIO_ devices, including supported boards, build instructions, driver details etc.
What's VirtIO? @@ -15,7 +14,7 @@ just the guest's device driver "knows" it is running in a virtual environment, and cooperates with the hypervisor. This enables guests to get high performance network and disk operations, and gives most of the performance benefits of paravirtualization. In the U-Boot case, the guest is U-Boot itself, while the -virtual environment are normally QEMU [2] targets like ARM, RISC-V and x86. +virtual environment are normally QEMU_ targets like ARM, RISC-V and x86.
Status ------ @@ -49,6 +48,8 @@ Building U-Boot for pre-configured QEMU targets is no different from others. For example, we can do the following with the CROSS_COMPILE environment variable being properly set to a working toolchain for ARM:
+.. code-block:: bash + $ make qemu_arm_defconfig $ make
@@ -56,11 +57,13 @@ You can even create a QEMU ARM target with VirtIO devices showing up on both MMIO and PCI buses. In this case, you can enable the PCI transport driver from 'make menuconfig':
-Device Drivers ---> - ... - VirtIO Drivers ---> - ... - [*] PCI driver for virtio devices +.. code-block:: none + + Device Drivers ---> + ... + VirtIO Drivers ---> + ... + [*] PCI driver for virtio devices
Other drivers are at the same location and can be tuned to suit the needs.
@@ -74,6 +77,8 @@ Testing The following QEMU command line is used to get U-Boot up and running with VirtIO net and block devices on ARM.
+.. code-block:: bash + $ qemu-system-arm -nographic -machine virt -bios u-boot.bin \ -netdev tap,ifname=tap0,id=net0 \ -device virtio-net-device,netdev=net0 \ @@ -82,6 +87,8 @@ VirtIO net and block devices on ARM.
On x86, command is slightly different to create PCI VirtIO devices.
+.. code-block:: bash + $ qemu-system-i386 -nographic -bios u-boot.rom \ -netdev tap,ifname=tap0,id=net0 \ -device virtio-net-pci,netdev=net0 \ @@ -93,6 +100,8 @@ parameters. It is also possible to specify both MMIO and PCI VirtIO devices. For example, the following commnad creates 3 VirtIO devices, with 1 on MMIO and 2 on PCI bus.
+.. code-block:: bash + $ qemu-system-arm -nographic -machine virt -bios u-boot.bin \ -netdev tap,ifname=tap0,id=net0 \ -device virtio-net-pci,netdev=net0 \ @@ -104,6 +113,8 @@ and 2 on PCI bus. By default QEMU creates VirtIO legacy devices by default. To create non-legacy (aka modern) devices, pass additional device property/value pairs like below:
+.. code-block:: bash + $ qemu-system-i386 -nographic -bios u-boot.rom \ -netdev tap,ifname=tap0,id=net0 \ -device virtio-net-pci,netdev=net0,disable-legacy=true,disable-modern=false \ @@ -112,6 +123,8 @@ By default QEMU creates VirtIO legacy devices by default. To create non-legacy
A 'virtio' command is provided in U-Boot shell.
+.. code-block:: none + => virtio virtio - virtio block devices sub-system
@@ -127,10 +140,14 @@ A 'virtio' command is provided in U-Boot shell.
To probe all the VirtIO devices, type:
+.. code-block:: none + => virtio scan
Then we can show the connected block device details by:
+.. code-block:: none + => virtio info Device 0: QEMU VirtIO Block Device Type: Hard Disk @@ -138,6 +155,8 @@ Then we can show the connected block device details by:
And list the directories and files on the disk by:
+.. code-block:: none + => ls virtio 0 / <DIR> 4096 . <DIR> 4096 .. @@ -167,6 +186,8 @@ Driver Internals ---------------- There are 3 level of drivers in the VirtIO driver family.
+.. code-block:: none + +---------------------------------------+ | virtio device drivers | | +-------------+ +------------+ | @@ -199,20 +220,26 @@ The transport drivers provide a set of ops (struct dm_virtio_ops) for the real virtio device driver to call. These ops APIs's parameter is designed to remind the caller to pass the correct 'struct udevice' id of the virtio device, eg:
-int virtio_get_status(struct udevice *vdev, u8 *status) +.. code-block:: C + + int virtio_get_status(struct udevice *vdev, u8 *status)
So the parameter 'vdev' indicates the device should be the real virtio device. But we also have an API like:
-struct virtqueue *vring_create_virtqueue(unsigned int index, unsigned int num, - unsigned int vring_align, - struct udevice *udev) +.. code-block:: C + + struct virtqueue *vring_create_virtqueue(unsigned int index, unsigned int num, + unsigned int vring_align, + struct udevice *udev)
Here the parameter 'udev' indicates the device should be the transport device. Similar naming is applied in other functions that are even not APIs, eg:
-static int virtio_uclass_post_probe(struct udevice *udev) -static int virtio_uclass_child_pre_probe(struct udevice *vdev) +.. code-block:: C + + static int virtio_uclass_post_probe(struct udevice *udev) + static int virtio_uclass_child_pre_probe(struct udevice *vdev)
So it's easy to tell which device these functions are operating on.
@@ -223,20 +250,29 @@ ID 2) are supported. If you want to develop new driver for new devices, please follow the guideline below.
1. add new device ID in virtio.h -#define VIRTIO_ID_XXX X + +.. code-block:: C + + #define VIRTIO_ID_XXX X
2. update VIRTIO_ID_MAX_NUM to be the largest device ID plus 1
3. add new driver name string in virtio.h -#define VIRTIO_XXX_DRV_NAME "virtio-xxx" + +.. code-block:: C + + #define VIRTIO_XXX_DRV_NAME "virtio-xxx"
4. create a new driver with name set to the name string above -U_BOOT_DRIVER(virtio_xxx) = { - .name = VIRTIO_XXX_DRV_NAME, - ... - .remove = virtio_reset, - .flags = DM_FLAG_ACTIVE_DMA, -} + +.. code-block:: C + + U_BOOT_DRIVER(virtio_xxx) = { + .name = VIRTIO_XXX_DRV_NAME, + ... + .remove = virtio_reset, + .flags = DM_FLAG_ACTIVE_DMA, + }
Note the driver needs to provide the remove method and normally this can be hooked to virtio_reset(). The driver flags should contain DM_FLAG_ACTIVE_DMA @@ -247,7 +283,5 @@ for the remove method to be called before jumping to OS.
6. do funny stuff with the driver
-References ----------- -[1] http://docs.oasis-open.org/virtio/virtio/v1.0/virtio-v1.0.pdf -[2] https://www.qemu.org +.. _VirtIO: http://docs.oasis-open.org/virtio/virtio/v1.0/virtio-v1.0.pdf +.. _QEMU: https://www.qemu.org