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diff --git a/docs/qemu.md b/docs/qemu.md new file mode 100644 index 0000000..e17e33a --- /dev/null +++ b/docs/qemu.md @@ -0,0 +1,112 @@ +qemu usage walkthrough +====================== + +In this walk-through, we'll use an Ubuntu cloudimg along with the +[gpio sample server](../samples/gpio-pci-idio-16.c) to emulate a very simple GPIO +device. + +Building qemu +------------- + +`vfio-user` client support is not yet merged into `qemu`. Instead, download and +build [jlevon's master.vfio-user branch of +qemu](https://github.com/jlevon/qemu/tree/master.vfio-user); for example: + +``` +git clone -b master.vfio-user git@github.com:jlevon/qemu.git +cd qemu + +./configure --prefix=/usr --enable-kvm --enable-vnc --target-list=x86_64-softmmu --enable-debug --enable-vfio-user-client +make -j +``` + +Configuring the cloudimg +------------------------ + +Set up the necessary metadata files: + +``` +sudo apt install cloud-image-utils + +$ cat metadata.yaml +instance-id: iid-local01 +local-hostname: cloudimg + +$ cat user-data.yaml +#cloud-config +ssh_import_id: + - gh:jlevon + +cloud-localds seed.img user-data.yaml metadata.yaml +``` + +don't forget to replace `jlevon` with *your* github user name. + +Starting the server +------------------- + +Start the `gpio` server process: + +``` +rm -f /tmp/vfio-user.sock +./build/samples/gpio-pci-idio-16 -v /tmp/vfio-user.sock & +``` + +Booting the guest OS +-------------------- + +Make sure your system has hugepages available: + +``` +$ cat /proc/sys/vm/nr_hugepages +1024 +``` + +Now you should be able to start qemu: + +``` +$ imgpath=/path/to/bionic-server-cloudimg-amd64.img +$ sudo ~/src/build/qemu-system-x86_64 \ + -machine accel=kvm,type=q35 -cpu host -m 2G \ + -mem-prealloc -object memory-backend-file,id=ram-node0,prealloc=yes,mem-path=/dev/hugepages/gpio,share=yes,size=2G \ + -nographic \ + -device virtio-net-pci,netdev=net0 \ + -netdev user,id=net0,hostfwd=tcp::2222-:22 \ + -drive if=virtio,format=qcow2,file=$imgpath \ + -drive if=virtio,format=raw,file=seed.img \ + -device vfio-user-pci,socket=/tmp/vfio-user.sock +``` + +Log in to your VM and load the kernel driver: + +``` +$ ssh -p 2222 ubuntu@localhost +... +$ sudo apt install linux-modules-extra-$(uname -r) +$ sudo modprobe gpio-pci-idio-16 +``` + +Now we should be able to observe the emulated GPIO device's pins: + +``` +$ sudo su - +# cat /sys/class/gpio/gpiochip480/base > /sys/class/gpio/export +# for ((i=0;i<12;i++)); do cat /sys/class/gpio/OUT0/value; done +``` + +and the server should output something like: + +``` +gpio: region2: read 0 from (0:1) +gpio: region2: read 0 from (0:1) +gpio: region2: read 0 from (0:1) +gpio: region2: read 0x1 from (0:1) +gpio: region2: read 0x1 from (0:1) +gpio: region2: read 0x1 from (0:1) +gpio: region2: read 0x2 from (0:1) +gpio: region2: read 0x2 from (0:1) +gpio: region2: read 0x2 from (0:1) +gpio: region2: read 0x3 from (0:1) +gpio: region2: read 0x3 from (0:1) +gpio: region2: read 0x3 from (0:1) +``` |