improve qemu tooling, and document it

scripts/connect-qemu.sh

@@ -0,0 +1,2 @@
+#!/usr/bin/env sh
+nix-shell -p socat --run "socat -,raw,echo=0,icanon=0,isig=0,icrnl=0,escape=0x0f    unix-connect:$1"

scripts/run-qemu.sh

@@ -0,0 +1,22 @@
+#!/usr/bin/env nix-shell
+#! nix-shell -i bash -p qemu
+
+if test "$1" = "--background" ; then
+    socket=$2
+    echo "running in background, socket is $socket"
+    flags="--daemonize -chardev socket,id=sock,path=$2,server=on,wait=off,mux=on -mon chardev=sock,mode=readline -serial chardev:sock  "
+    shift;shift
+else
+    flags="-serial mon:stdio"
+fi
+
+qemu-system-mips \
+    -M malta -m 256 \
+    -echr 16 \
+    -append "default console=ttyS0,38400n8 panic=10 oops=panic init=/bin/init  loglevel=8 root=/dev/vda" \
+    -drive file=$2,format=raw,readonly=on,if=virtio \
+    -netdev socket,id=access,mcast=230.0.0.1:1234 \
+    -device virtio-net-pci,disable-legacy=on,disable-modern=off,netdev=access,mac=ba:ad:1d:ea:21:02 \
+    -netdev socket,id=lan,mcast=230.0.0.1:1235 \
+    -device virtio-net-pci,disable-legacy=on,disable-modern=off,netdev=lan,mac=ba:ad:1d:ea:21:01 \
+    -kernel $1 -display none $flags