From 8fca4b8b94319e663f0d71d199bfe7bfd0fab596 Mon Sep 17 00:00:00 2001
From: Helmut Grohne <helmut@subdivi.de>
Date: Tue, 5 Mar 2024 20:03:25 +0100
Subject: debvm-run: refactor bus management

Depending on the machine type, devices reside on different buses. For
most vms, we use the pci bus, but m68k uses the virtio ("device") bus.
Also if we were to use an x86 microvm, we'd also use virtio. This is
common to all devices and we can abstract it into a $BUS.
---
 bin/debvm-run | 42 ++++++++++++++++++++++--------------------
 1 file changed, 22 insertions(+), 20 deletions(-)

diff --git a/bin/debvm-run b/bin/debvm-run
index 3371b79..4dc35d3 100755
--- a/bin/debvm-run
+++ b/bin/debvm-run
@@ -354,17 +354,6 @@ set -- \
 	-initrd "/proc/self/fd/$INITRDFD" \
 	"$@"
 
-# If the image filename contains a comma, then that comma must be escaped by
-# prefixing it with another comma or otherwise output filenames are able to
-# inject drive options to qemu (and load the wrong file).
-IMAGE_ESCAPED="$(printf "%s" "$IMAGE" | sed 's/,/,,/g')"
-
-if ! check_skip root/dev; then
-	set -- \
-		-drive "media=disk,format=raw,discard=unmap,file=$IMAGE_ESCAPED,if=virtio,cache=unsafe" \
-		"$@"
-fi
-
 # Translate KERNELARCH (a Debian architecture) to a Debian CPU name.
 # This utilizes the QEMU Debian package symlink mapping that ensures that
 # calling qemu-system-${DEB_HOST_ARCH_CPU} will run the QEMU binary providing
@@ -373,9 +362,8 @@ KERNELARCHCPU="$(dpkg-architecture --force --host-arch "$KERNELARCH" --query DEB
 QEMU="qemu-system-$KERNELARCHCPU"
 CPU=
 MACHINE=
+BUS=pci
 MAX_SMP=
-NIC_DEV=virtio-net-pci,netdev=net0
-RNG_DEV=virtio-rng-pci,rng=rng0
 
 case "$KERNELARCHCPU" in
 	amd64)
@@ -393,8 +381,7 @@ case "$KERNELARCHCPU" in
 	m68k)
 		MACHINE="type=virt"
 		MAX_SMP=1
-		NIC_DEV=virtio-net-device,netdev=net0
-		RNG_DEV=virtio-rng-device,rng=rng0
+		BUS=device
 	;;
 	mips64el)
 		CPU=5KEc
@@ -415,6 +402,18 @@ case "$KERNELARCHCPU" in
 	;;
 esac
 
+# If the image filename contains a comma, then that comma must be escaped by
+# prefixing it with another comma or otherwise output filenames are able to
+# inject drive options to qemu (and load the wrong file).
+IMAGE_ESCAPED="$(printf "%s" "$IMAGE" | sed 's/,/,,/g')"
+
+if ! check_skip root/dev; then
+	set -- \
+		-drive "id=root,media=disk,format=raw,discard=unmap,file=$IMAGE_ESCAPED,if=none,cache=unsafe" \
+		-device "virtio-blk-$BUS,drive=root,serial=root" \
+		"$@"
+fi
+
 ENABLE_KVM=no
 if test "$ARCHITECTURE" = "$KERNELARCH"; then
 	ENABLE_KVM=yes
@@ -457,7 +456,7 @@ if test -z "$MAX_SMP" || test "$MAX_SMP" -gt 1; then
 fi
 if ! check_skip rngdev; then
 	set -- \
-		-device "$RNG_DEV" \
+		-device "virtio-rng-$BUS,rng=rng0" \
 		-object rng-random,filename=/dev/urandom,id=rng0 \
 		"$@"
 fi
@@ -479,14 +478,14 @@ else
 		;;
 		*)
 			set -- \
-				-device virtio-gpu-gl-pci \
+				-device "virtio-gpu-gl-$BUS" \
 				-display gtk,gl=on \
 				"$@"
 		;;
 	esac
 	set -- \
-		-device virtio-keyboard-pci \
-		-device virtio-tablet-pci \
+		-device "virtio-keyboard-$BUS" \
+		-device "virtio-tablet-$BUS" \
 		"$@"
 fi
 
@@ -503,7 +502,10 @@ if test -n "$KERNEL_CMDLINE"; then
 fi
 
 if ! check_skip network; then
-	set -- -netdev "user,id=net0$NETOPTS" -device "$NIC_DEV" "$@"
+	set -- \
+		-netdev "user,id=net0$NETOPTS" \
+		-device "virtio-net-$BUS,netdev=net0" \
+		"$@"
 fi
 
 echo "+ $QEMU $*" 1>&2
-- 
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