Re: [PATCH] KVM: Add wrapper script around QEMU to test kernels

[Jan Kiszka]

On 2011-08-24 23:38, Alexander Graf wrote:
> On LinuxCon I had a nice chat with Linus on what he thinks kvm-tool
> would be doing and what he expects from it. Basically he wants a
> small and simple tool he and other developers can run to try out and
> see if the kernel they just built actually works.
> 
> Fortunately, QEMU can do that today already! The only piece that was
> missing was the "simple" piece of the equation, so here is a script
> that wraps around QEMU and executes a kernel you just built.
> 
> If you do have KVM around and are not cross-compiling, it will use
> KVM. But if you don't, you can still fall back to emulation mode and
> at least check if your kernel still does what you expect. I only
> implemented support for s390x and ppc there, but it's easily extensible
> to more platforms, as QEMU can emulate (and virtualize) pretty much
> any platform out there.
> 
> If you don't have qemu installed, please do so before using this script. Your
> distro should provide a package for it (might even call it "kvm"). If not,
> just compile it from source - it's not hard!
> 
> To quickly get going, just execute the following as user:
> 
>     $ ./Documentation/run-qemu.sh -r / -a init=/bin/bash
> 
> This will drop you into a shell on your rootfs.
> 
> Happy hacking!
> 
> Signed-off-by: Alexander Graf <agraf@xxxxxxx>
> 
> ---
> 
> v1 -> v2:
> 
>   - fix naming of QEMU
>   - use grep -q for has_config
>   - support multiple -a args
>   - spawn gdb on execution
>   - pass through qemu options
>   - dont use qemu-system-x86_64 on i386
>   - add funny sentence to startup text
>   - more helpful error messages
> ---
>  scripts/run-qemu.sh |  334 +++++++++++++++++++++++++++++++++++++++++++++++++++
>  1 files changed, 334 insertions(+), 0 deletions(-)
>  create mode 100755 scripts/run-qemu.sh
> 
> diff --git a/scripts/run-qemu.sh b/scripts/run-qemu.sh
> new file mode 100755
> index 0000000..5d4e185
> --- /dev/null
> +++ b/scripts/run-qemu.sh
> @@ -0,0 +1,334 @@
> +#!/bin/bash
> +#
> +# QEMU Launcher
> +#
> +# This script enables simple use of the KVM and QEMU tool stack for
> +# easy kernel testing. It allows to pass either a host directory to
> +# the guest or a disk image. Example usage:
> +#
> +# Run the host root fs inside a VM:
> +#
> +# $ ./scripts/run-qemu.sh -r /
> +#
> +# Run the same with SDL:
> +#
> +# $ ./scripts/run-qemu.sh -r / --sdl
> +# 
> +# Or with a PPC build:
> +#
> +# $ ARCH=ppc ./scripts/run-qemu.sh -r /
> +# 
> +# PPC with a mac99 model by passing options to QEMU:
> +#
> +# $ ARCH=ppc ./scripts/run-qemu.sh -r / -- -M mac99
> +#
> +
> +USE_SDL=
> +USE_VNC=
> +USE_GDB=1
> +KERNEL_BIN=arch/x86/boot/bzImage
> +MON_STDIO=
> +KERNEL_APPEND2=
> +SERIAL=ttyS0
> +SERIAL_KCONFIG=SERIAL_8250
> +BASENAME=$(basename "$0")
> +
> +function usage() {
> +	echo "
> +$BASENAME allows you to execute a virtual machine with the Linux kernel
> +that you just built. To only execute a simple VM, you can just run it
> +on your root fs with \"-r / -a init=/bin/bash\"
> +
> +	-a, --append parameters
> +		Append the given parameters to the kernel command line.
> +
> +	-d, --disk image
> +		Add the image file as disk into the VM.
> +
> +	-D, --no-gdb
> +		Don't run an xterm with gdb attached to the guest.
> +
> +	-r, --root directory
> +		Use the specified directory as root directory inside the guest.
> +
> +	-s, --sdl
> +		Enable SDL graphical output.
> +
> +	-S, --smp cpus
> +		Set number of virtual CPUs.
> +
> +	-v, --vnc
> +		Enable VNC graphical output.
> +
> +Examples:
> +
> +	Run the host root fs inside a VM:
> +	$ ./scripts/run-qemu.sh -r /
> +
> +	Run the same with SDL:
> +	$ ./scripts/run-qemu.sh -r / --sdl
> +	
> +	Or with a PPC build:
> +	$ ARCH=ppc ./scripts/run-qemu.sh -r /
> +	
> +	PPC with a mac99 model by passing options to QEMU:
> +	$ ARCH=ppc ./scripts/run-qemu.sh -r / -- -M mac99
> +"
> +}
> +
> +function require_config() {
> +	if [ "$(grep CONFIG_$1=y .config)" ]; then
> +		return
> +	fi
> +
> +	echo "You need to enable CONFIG_$1 for run-qemu to work properly"
> +	exit 1
> +}
> +
> +function has_config() {
> +	grep -q "CONFIG_$1=y" .config
> +}
> +
> +function drive_if() {
> +	if has_config VIRTIO_BLK; then
> +		echo virtio
> +	elif has_config ATA_PIIX; then
> +		echo ide

+ require_config "BLK_DEV_SD"

Maybe there should also be a warning if no standard FS (ext[34], btrfs,
xfs etc.) is build into the kernel.

Another thing, but that's just a recommendation for initrd-free mode:
DEVTMPFS_MOUNT

> +	else
> +		echo "\
> +Your kernel must have either VIRTIO_BLK or ATA_PIIX
> +enabled for block device assignment" >&2
> +		exit 1
> +	fi
> +}
> +
> +GETOPT=`getopt -o a:d:Dhr:sS:v --long append,disk:,no-gdb,help,root:,sdl,smp:,vnc \
> +	-n "$(basename \"$0\")" -- "$@"`
> +
> +if [ $? != 0 ]; then
> +	echo "Terminating..." >&2
> +	exit 1
> +fi
> +
> +eval set -- "$GETOPT"
> +
> +while true; do
> +	case "$1" in
> +	-a|--append)
> +		KERNEL_APPEND2="$KERNEL_APPEND2 $KERNEL_APPEND2"

That should be

KERNEL_APPEND2="$KERNEL_APPEND2 $2"

> +		shift
> +		;;
> +	-d|--disk)
> +		QEMU_OPTIONS="$QEMU_OPTIONS -drive \
> +			file=$2,if=$(drive_if),cache=unsafe"

		if [ $? != 0 ]; then
			exit $?
		fi

> +		USE_DISK=1
> +		shift
> +		;;
> +	-D|--no-gdb)
> +		USE_GDB=
> +		;;
> +	-h|--help)
> +		usage
> +		exit 0
> +		;;
> +	-r|--root)
> +		ROOTFS="$2"
> +		shift
> +		;;
> +	-s|--sdl)
> +		USE_SDL=1
> +		;;
> +	-S|--smp)
> +		SMP="$2"
> +		shift
> +		;;
> +	-v|--vnc)
> +		USE_VNC=1
> +		;;
> +	--)
> +		shift
> +		break
> +		;;
> +	*)
> +		echo "Could not parse option: $1" >&2
> +		exit 1
> +		;;
> +	esac
> +	shift
> +done
> +
> +if [ ! "$ROOTFS" -a ! "$USE_DISK" ]; then
> +	echo "\
> +Error: Please specify at least -r or -d with a target \
> +FS to run off of" >&2
> +	exit 1
> +fi
> +
> +# Try to find the KVM accelerated QEMU binary
> +
> +[ "$ARCH" ] || ARCH=$(uname -m)
> +case $ARCH in
> +x86_64)
> +	KERNEL_BIN=arch/x86/boot/bzImage
> +	# SUSE and Red Hat call the binary qemu-kvm
> +	[ "$QEMU_BIN" ] || QEMU_BIN=$(which qemu-kvm 2>/dev/null)
> +
> +	# Debian and Gentoo call it kvm
> +	[ "$QEMU_BIN" ] || QEMU_BIN=$(which kvm 2>/dev/null)
> +
> +	# QEMU's own build system calls it qemu-system-x86_64
> +	[ "$QEMU_BIN" ] || QEMU_BIN=$(which qemu-system-x86_64 2>/dev/null)
> +	;;
> +i*86)
> +	KERNEL_BIN=arch/x86/boot/bzImage
> +	# SUSE and Red Hat call the binary qemu-kvm
> +	[ "$QEMU_BIN" ] || QEMU_BIN=$(which qemu-kvm 2>/dev/null)
> +
> +	# Debian and Gentoo call it kvm
> +	[ "$QEMU_BIN" ] || QEMU_BIN=$(which kvm 2>/dev/null)
> +
> +	KERNEL_BIN=arch/x86/boot/bzImage
> +	# i386 version of QEMU
> +	[ "$QEMU_BIN" ] || QEMU_BIN=$(which qemu 2>/dev/null)
> +	;;
> +s390*)
> +	KERNEL_BIN=arch/s390/boot/image
> +	[ "$QEMU_BIN" ] || QEMU_BIN=$(which qemu-system-s390x 2>/dev/null)
> +	;;
> +ppc*)
> +	KERNEL_BIN=vmlinux
> +
> +	IS_64BIT=
> +	has_config PPC64 && IS_64BIT=64
> +	if has_config PPC_85xx; then
> +		QEMU_OPTIONS="$QEMU_OPTIONS -M mpc8544ds"
> +	elif has_config PPC_PSERIES; then
> +		QEMU_OPTIONS="$QEMU_OPTIONS -M pseries"
> +		SERIAL=hvc0
> +		SERIAL_KCONFIG=HVC_CONSOLE
> +	elif has_config PPC_PMAC; then
> +		has_config SERIAL_PMACZILOG_TTYS || SERIAL=ttyPZ0
> +		SERIAL_KCONFIG=SERIAL_PMACZILOG
> +	else
> +		echo "Unknown PPC board" >&2
> +		exit 1
> +	fi
> +
> +	[ "$QEMU_BIN" ] || QEMU_BIN=$(which qemu-system-ppc${IS_64BIT} 2>/dev/null)
> +	;;
> +esac
> +
> +if [ ! -e "$QEMU_BIN" ]; then
> +	echo "\
> +Could not find a usable QEMU binary. Please install one from \
> +your distro or from source code using:
> +
> +  $ git clone git://git.qemu.org/qemu.git
> +  $ cd qemu
> +  $ ./configure
> +  $ make -j
> +  $ sudo make install
> +" >&2
> +	exit 1
> +fi
> +
> +# The binaries without kvm in their name can be too old to support KVM, so
> +# check for that before the user gets confused
> +if [ ! "$(echo $QEMU_BIN | grep kvm)" -a \
> +     ! "$($QEMU_BIN --help | egrep '^-machine')" ]; then
> +	echo "Your QEMU binary is too old, please update to at least 0.15." >&2
> +	exit 1
> +fi
> +QEMU_OPTIONS="$QEMU_OPTIONS -machine accel=kvm:tcg"
> +
> +# We need to check some .config variables to make sure we actually work
> +# on the respective kernel.
> +if [ ! -e .config ]; then
> +	echo "\
> +Please run this script on a fully compiled and configured
> +Linux kernel build directory" >&2
> +	exit 1
> +fi
> +
> +if [ ! -e "$KERNEL_BIN" ]; then
> +	echo "Could not find kernel binary: $KERNEL_BIN" >&2
> +	exit 1
> +fi
> +
> +QEMU_OPTIONS="$QEMU_OPTIONS -kernel $KERNEL_BIN"
> +
> +if [ "$USE_SDL" ]; then
> +	# SDL is the default, so nothing to do
> +	:
> +elif [ "$USE_VNC" ]; then
> +	QEMU_OPTIONS="$QEMU_OPTIONS -vnc :5"
> +else
> +	# When emulating a serial console, tell the kernel to use it as well
> +	QEMU_OPTIONS="$QEMU_OPTIONS -nographic"
> +	KERNEL_APPEND="$KERNEL_APPEND console=$SERIAL earlyprintk=serial"
> +	MON_STDIO=1
> +	require_config "$SERIAL_KCONFIG"
> +fi
> +
> +if [ "$ROOTFS" ]; then
> +	# Using rootfs with 9p
> +	require_config "NET_9P_VIRTIO"

+ require_config "9P_FS"

> +	KERNEL_APPEND="$KERNEL_APPEND \
> +root=/dev/root rootflags=rw,trans=virtio,version=9p2000.L rootfstype=9p"
> +
> +#Usage: -virtfs fstype,path=/share_path/,security_model=[mapped|passthrough|none],mount_tag=tag.
> +
> +
> +	QEMU_OPTIONS="$QEMU_OPTIONS \
> +-virtfs local,id=root,path=$ROOTFS,mount_tag=root,security_model=passthrough \
> +-device virtio-9p-pci,fsdev=root,mount_tag=/dev/root"
> +fi
> +
> +[ "$SMP" ] || SMP=1
> +
> +# User append args come last
> +KERNEL_APPEND="$KERNEL_APPEND $KERNEL_APPEND2"
> +
> +############### Execution #################
> +
> +QEMU_OPTIONS="$QEMU_OPTIONS -smp $SMP"
> +
> +echo "
> +	################# Linux QEMU launcher #################
> +
> +This script executes your currently built Linux kernel using QEMU. If KVM is
> +available, it will also use KVM for fast virtualization of your guest.
> +
> +The intent is to make it very easy to run your kernel. If you need to do more
> +advanced things, such as passing through real devices, please use QEMU command
> +line options and add them to the $BASENAME command line using --.
> +
> +This tool is for simplicity, not world dominating functionality coverage.
> +(just a hobby, won't be big and professional like libvirt)
> +
> +"
> +
> +if [ "$MON_STDIO" ]; then
> +	echo "\
> +### Your guest is bound to the current foreground shell. To quit the guest, ###
> +### please use Ctrl-A x                                                     ###
> +"
> +fi
> +
> +echo "  Executing: $QEMU_BIN $QEMU_OPTIONS -append \"$KERNEL_APPEND\""
> +echo
> +
> +GDB_PID=
> +if [ "$USE_GDB" -a "$DISPLAY" -a -x "$(which xterm)" -a -e "$(which gdb)" ]; then
> +	# Run a gdb console in parallel to the kernel
> +
> +	# XXX find out if port is in use
> +	PORT=$$
> +	xterm -T "$BASENAME" -e "sleep 2; gdb vmlinux -ex 'target remote localhost:$PORT' -ex c" &
> +	GDB_PID=$!
> +	QEMU_OPTIONS="$QEMU_OPTIONS -gdb tcp::$PORT"
> +fi
> +
> +$QEMU_BIN $QEMU_OPTIONS -append "$KERNEL_APPEND" "$@"
> +wait $GDB_PID &>/dev/null
> +

Nice that it forks off a gdb session. I will contribute my gdb helper
script soon (module symbol loading, dmesg, per-cpu variable lookup etc.)
so that it can be loaded automatically.

Jan

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