qemu-system-s390x emulator on Ubuntu how-to

qemu-s390x-debian-rules.patch

--- qemu-2.5+dfsg/debian/rules	2016-04-19 18:48:46.000000000 +0300
+++ qemu-2.5+dfsg.new/debian/rules	2017-07-25 23:38:18.882758751 +0300
@@ -132,9 +132,13 @@ ifeq ($(enable_linux_user),enable)
 	$(MAKE) -C user-static-build V=${V} $(foreach t,${user_targets},subdir-${t}-linux-user)
 endif
 
-ifneq ($(filter $(DEB_HOST_ARCH),s390 s390x),)
-	$(MAKE) -C qemu-build/pc-bios/s390-ccw V=${V}
-endif
+#ifneq ($(filter $(DEB_HOST_ARCH),s390 s390x),)
+	$(MAKE) -C qemu-build/pc-bios/s390-ccw V=${V}	\
+			CC=s390x-linux-gnu-gcc-5 	\
+			AS=s390x-linux-gnu-as 		\
+			CPP="s390x-linux-gnu-gcc-5 -E"	\
+			STRIP="s390x-linux-gnu-strip"
+#endif
 	touch $@
 
 clean:	debian/control
@@ -223,9 +227,9 @@ endif
 ifneq ($(filter $(DEB_HOST_ARCH),ppc64 ppc64el powerpc),)
 	install -D -m755 debian/kvm.powerpc debian/qemu-kvm/usr/bin/kvm
 endif
-ifneq ($(filter $(DEB_HOST_ARCH),s390 s390x),)
+#ifneq ($(filter $(DEB_HOST_ARCH),s390 s390x),)
 	install -D -m755 qemu-build/pc-bios/s390-ccw/s390-ccw.img debian/qemu-system-s390x/usr/share/qemu/s390-ccw.img
-endif
+#endif
 
 ifeq ($(VENDOR),UBUNTU)
 # apport hook is ubuntu-specific
@@ -296,7 +300,7 @@ endif
 	dh_installinit -pqemu-guest-agent
 endif
 	dh_link ${ai}
-	dh_strip ${ai}
+	#dh_strip ${ai}
 	dh_compress ${ai}
 	dh_fixperms ${ai}
 	dh_makeshlibs ${ai}
--- qemu-2.5+dfsg/pc-bios/s390-ccw/Makefile	2015-12-12 14:16:02.000000000 +0200
+++ qemu-2.5+dfsg.new/pc-bios/s390-ccw/Makefile	2017-07-25 23:36:24.634406520 +0300
@@ -20,7 +20,7 @@ s390-ccw.elf: $(OBJECTS)
 	$(call quiet-command,$(CC) $(LDFLAGS) -o $@ $(OBJECTS),"  Building $(TARGET_DIR)$@")
 
 s390-ccw.img: s390-ccw.elf
-	$(call quiet-command,strip --strip-unneeded $< -o $@,"  Stripping $(TARGET_DIR)$@")
+	$(call quiet-command,$(STRIP) --strip-unneeded $< -o $@,"  Stripping $(TARGET_DIR)$@")
 
 $(OBJECTS): Makefile
 

qemu-system-s390x-tcg.rst

How to build s390x emulator (tcg) on Ubuntu 16.04:

1. Download qemu's source code using apt:

$ apt source qemu

2. Install all build requirements according to [1]:

$ sudo mk-build-deps -i -r qemu

3. Install s390x cross compiler:

$ sudo apt install -y gcc-5-multilib-s390x-linux-gnu

4. Change debian/rules to always build s390x bootloader via cross-compiler, by applying the provided patch:

$ cd qemu-2.5+dfsg
$ patch -p1 < ~/qemu-s390x-debian-rules.patch

5. Build according to [1], this will take some time:

$ fakeroot debian/rules binary
...

6. Install resulting qemu-system-s390x package:

$ sudo apt install ../qemu-system-s390x_2.5+dfsg-5ubuntu10.14_amd64.deb

7. Use virt-manager[2] to setup the host, don't use CDROMs as they are not supported. Rather, download and use latest debian's installer kernel and initrd:

$ wget -c http://ftp.debian.org/debian/dists/stable/main/installer-s390x/current/images/generic/kernel.debian \
  http://ftp.debian.org/debian/dists/stable/main/installer-s390x/current/images/generic/initrd.debian

8. Use above as initrd and kernel on 'Boot Options' tab under 'Direct kernel boot'. Installation only possible via console.

[1] https://wiki.debian.org/BuildingAPackage

[2] https://virt-manager.org/