QEMU Emulation for X86

Overview

The X86 QEMU board configuration is used to emulate the X86 architecture.

This board configuration provides support for a 32-bit Atom-class x86 CPU and the following devices:

HPET
Advanced Programmable Interrupt Controller (APIC)
NS16550 UART
E1000 Ethernet, CAN and VirtIO input devices on an emulated PCI bus
Simulated flash and EEPROM
QEMU ramfb display

The qemu_x86/atom/* variants exercise the same machine with a particular memory-management configuration (no MMU, 32-bit page tables, KPTI disabled, execute-in-place, or a relocated virtual address space); qemu_x86_tiny uses the same devicetree with only 384 KiB of RAM to test demand paging.

Hardware

Supported Features

The qemu_x86 board supports the hardware features listed below.

on-chip / on-board: Feature integrated in the SoC / present on the board.
2 / 2: Number of instances that are enabled / disabled.
Click on the label to see the first instance of this feature in the board/SoC DTS files.
vnd,foo: Compatible string for the Devicetree binding matching the feature.
Click on the link to view the binding documentation.

`qemu_x86/atom` target

On-target memory for this board target: 32 MiB of RAM, 4 MiB of Flash.

Type	Location	Description	Compatible
CPU	on-chip	Generic x86 qemu CPU1	`intel,x86`
CAN	on-board	Kvaser PCIcan1	`kvaser,pcican`
Display	on-board	QEMU RAM framebuffer display device1	`qemu,ramfb`
Ethernet	on-board	Intel E1000 Ethernet controller1	`intel,e1000`
Firmware	on-board	QEMU fw_cfg (I/O port transport)1	`qemu,fw-cfg-ioport`
Input	on-board	VIRTIO Input device1	`virtio,input`
Interrupt controller	on-chip	Intel I/O Advanced Programmable Interrupt Controller (APIC)1	`intel,ioapic`
Interrupt controller	on-chip	Local Advanced Programmable Interrupt Controller (APIC)1	`intel,loapic`
Multi-Function Device	on-chip	Motorola MC146818 MFD1	`motorola,mc146818-mfd`
MTD	on-board	Flash node2	`soc-nv-flash`
PCIe	on-board	Generic PCIe host controller1	`pcie-controller`
RTC	on-chip	Motorola MC146818 compatible Real Timer Clock1	`motorola,mc146818`
Serial controller	on-chip	ns16550 UART2	`ns16550`
Timer	on-chip	HPET (High-Precision Event Timer)1	`intel,hpet`
Virtio	on-board	VIRTIO over PCI1	`virtio,pci`

Devices

HPET System Clock Support

The configuration uses an HPET clock frequency of 25 MHz.

Serial Port

The board configuration uses a single serial communication channel that uses the NS16550 serial driver operating in polling mode. To override, enable the UART_INTERRUPT_DRIVEN Kconfig option, which allows the system to be interrupt-driven.

If SLIP networking is enabled (see below), an additional serial port will be used for it.

Known Problems or Limitations

The following platform features are unsupported:

Isolated Memory Regions
Serial port in Direct Memory Access (DMA) mode
Serial Peripheral Interface (SPI) flash
General-Purpose Input/Output (GPIO)
Inter-Integrated Circuit (I2C)
Ethernet
Supervisor Mode Execution Protection (SMEP)

Programming and Debugging

The qemu_x86 board supports the runners and associated west commands listed below.

	flash	debug	debugserver
qemu	✅ (default)	✅ (default)	✅

Applications for the qemu_x86 board configuration can be built and run in the usual way for emulated boards (see Building an Application and Run an Application for more details).

Flashing

While this board is emulated and you can’t “flash” it, you can use this configuration to run basic Zephyr applications and kernel tests in the QEMU emulated environment. For example, with the Basic Synchronization sample:

# From the root of the zephyr repository
west build -b qemu_x86 samples/synchronization
west build -t run

This will build an image with the synchronization sample app, boot it using QEMU, and display the following console output:

***** BOOTING ZEPHYR OS v1.8.99 - BUILD: Jun 27 2017 13:09:26 *****
threadA: Hello World from x86!
threadB: Hello World from x86!
threadA: Hello World from x86!
threadB: Hello World from x86!
threadA: Hello World from x86!
threadB: Hello World from x86!
threadA: Hello World from x86!
threadB: Hello World from x86!
threadA: Hello World from x86!
threadB: Hello World from x86!

Exit QEMU by pressing CTRL+A x.

Debugging

Refer to the detailed overview about Application Debugging.

Networking

The board supports SLIP networking over an emulated serial port (CONFIG_NET_SLIP_TAP=y). The detailed setup is described in Networking with QEMU.

It is also possible to use the QEMU built-in Ethernet adapter to connect to the host system. This is faster than using SLIP and is also the preferred way. See Networking with QEMU Ethernet for details.