blob: 3d6a5a43587ff2df14576ce452f9a43ca86f3d45 [file] [log] [blame]
A simple x86 firmware that can boot Linux.
Most of QEMU's 500-700 ms 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-uuid --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.
* in fw_cfg. This is fixed by putting kernel and initrd in a CoreBoot cbfs
image, and doing a memory copy from NVDIMM or flash instead of using fw_cfg.
Right now only flash is supported. 350 ms are saved, bringing the startup
time down to 60 ms.
Usage
=====
fw_cfg based example:
$ qemu-kvm -bios bios.bin \
-kernel /boot/vmlinuz-4.0.3-300.fc22.x86_64 \
-serial mon:stdio -append 'console=ttyS0,115200,8n1'
cbfs-based example (pflash isn't the definitive interface though):
$ dd if=/dev/zero of=boot.bin bs=4096 count=1
$ cbfstool cbfs.rom create -s 8m -B boot.bin -m x86 -o 0x1000
$ cbfstool cbfs.rom add -f /boot/vmlinuz-4.0.3-300.fc22.x86_64 -n vmlinuz -t raw
$ echo 'console=ttyS0,115200,8n1' > cmdline
$ cbfstool cbfs.rom add -f cmdline -n cmdline -t raw
$ qemu-kvm -drive if=pflash,file=bios.bin,readonly=on \
-drive if=pflash,file=cbfs.rom,readonly=on \
-serial mon:stdio
TODO
====
* ACPI tables
* SMBIOS tables
* Multiboot loading