Yaya48
cf256aa081
Upstream: https://gitlab.com/qemu-project/qemu.git Upstream-Commit: d2e570cc0f97b936902a5b1b86b73c0f5998b475
91 lines
2.1 KiB
ReStructuredText
91 lines
2.1 KiB
ReStructuredText
.. SPDX-License-Identifier: GPL-2.0-or-later
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===================================
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Testing VFIO display with mdev mdpy
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===================================
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.. contents:: Table of Contents
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The kernel provides a sample mediated device driver, ``mdpy``
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(``samples/vfio-mdev/mdpy.c``), that exposes a fake framebuffer through the VFIO
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display region interface. It can be used to test VFIO display support, including
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hotplug, without any real GPU hardware.
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The kernel modules
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==================
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The ``mdpy`` driver depends on the ``mdev`` subsystem. Enable, build and load
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the modules.
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The minimal set is::
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CONFIG_SAMPLE_VFIO_MDEV_MDPY=m
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CONFIG_SAMPLE_VFIO_MDEV_MDPY_FB=m # guest framebuffer driver
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CONFIG_VFIO_MDEV is selected automatically.
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Verify that the driver registered successfully:
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.. code-block:: bash
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ls /sys/devices/virtual/mdpy/mdpy/mdev_supported_types/
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Creating an mdev instance
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=========================
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Available types correspond to different resolutions (e.g. ``mdpy-vga``
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for 640x480, ``mdpy-xga`` for 1024x768, ``mdpy-hd`` for 1920x1080).
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Each mdev instance is identified by a UUID:
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.. code-block:: bash
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uuid=$(uuidgen)
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echo "$uuid" > /sys/devices/virtual/mdpy/mdpy/mdev_supported_types/mdpy-xga/create
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To remove the instance later:
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.. code-block:: bash
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echo 1 > /sys/bus/mdev/devices/$uuid/remove
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Make sure your user has the necessary permissions to access the vfio group.
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(ex: chmod 666 /dev/vfio/16)
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Starting QEMU
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=============
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Boot-time attachment
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--------------------
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.. code-block:: bash
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qemu-system-x86_64 -machine q35 -m 1G \
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-device vfio-pci,sysfsdev=/sys/bus/mdev/devices/$uuid,display=on \
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-display gtk,gl=on
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Hotplug via HMP
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---------------
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Start QEMU with a PCIe root port (required for PCIe hotplug) and a
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monitor:
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.. code-block:: bash
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qemu-system-x86_64 -machine q35 -m 1G \
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-device pcie-root-port,id=rp0,slot=1 \
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-display gtk,gl=on \
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-monitor stdio
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Then at the ``(qemu)`` prompt:
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.. code-block:: none
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device_add vfio-pci,sysfsdev=/sys/bus/mdev/devices/<uuid>,display=on,bus=rp0,id=mdpy0
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To hot-unplug:
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.. code-block:: none
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device_del mdpy0
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