qboot

A simple x86 firmware that can boot Linux.

Most of QEMU's startup time is spent:

• in the dynamic linker. This can be reduced by 150 ms simply by compiling a stripped down QEMU:

  ./configure --disable-libssh2 --disable-tcmalloc --disable-glusterfs
  --disable-seccomp --disable-{bzip2,snappy,lzo} --disable-usb-redir
  --disable-libusb --disable-smartcard-nss --disable-libnfs
  --disable-libiscsi --disable-rbd --disable-spice --disable-attr
  --disable-cap-ng --disable-linux-aio --disable-brlapi
  --disable-vnc-{jpeg,tls,sasl,png,ws} --disable-rdma --disable-bluez
  --disable-fdt --disable-curl --disable-curses --disable-sdl
  --disable-gtk --disable-tpm --disable-vte --disable-vnc
  --disable-xen --disable-opengl --target-list=x86_64-softmmu

• in the BIOS. qboot saves another 150 ms.

• until QEMU 2.7+, in fw_cfg. qboot uses the DMA interface which is pretty much instantaneous.

Compile qboot

Clone the source:

$ git clone https://github.com/bonzini/qboot.git

Compile the qboot firmware (you may need to install the relevant build time dependancies):

$ meson build && ninja -C build

The result will be a 64K file named bios.bin under the build/ directory.

Usage

$ qemu-kvm -bios bios.bin \
  -kernel /boot/vmlinuz-4.0.3-300.fc22.x86_64 \
  -serial mon:stdio -append 'console=ttyS0,115200,8n1'

TODO

• Add the possibility to configure out PIC and PCI bridge initialization