bug 1795857<\/a> from October 2018 asking for it. But such sidelines problem doesn’t get much attention, so it’s not included as of January 2019.<\/p>\n\n\n\nGo to the source<\/h3>\n\n\n
Then I thought that it’s only a module, and I could build it myself from the sources of the kernel. I didn’t know if it was easy under Ubuntu, but I already build kernels on Gentoo for 15 years, so I wanted to give it a try.<\/p>\n\n\n
First I installed the kernel sources package:<\/p>\n\n\n\n
apt-get install linux-source-4.18.0<\/pre>\n\n\n\nWhen I looked at its content I was disappointed, because it’s only a tarball, but it’s easy enough to decompress:<\/p>\n\n\n\n
cd \/usr\/src\/linux-source-4.18.0\/
tar xjf linux-source-4.18.0.tar.bz2
cd linux-source-4.18.0\/ <\/pre>\n\n\n\nI tried the usual make oldconfig<\/code> but some packages are necessary to make it work:<\/p>\n\n\n\napt-get install bison
apt-get install flex
apt-get install libelf-dev<\/pre>\n\n\n\nFrom this point, I could go forward with my idea:<\/p>\n\n\n\n
make oldconfig
make menuconfig<\/pre>\n\n\n\nIn the menus I searched and enabled the module CONFIG_DRM_BOCHS=m<\/code>
Then I launched the compilation:<\/p>\n\n\n\nmake modules<\/pre>\n\n\n\nNow you have time to take a break and get coffee, because Ubuntu enables many modules that are compiled by this command. It also takes space: the whole kernel tree with all compilation results and intermediate files amounts to 15 Gb !<\/p>\n\n\n\n
At the end of this compilation, I installed manually the only module I’m interested in, because I don’t want to cripple the modules installed from standard packages:<\/p>\n\n\n\n
mkdir \/lib\/modules\/4.18.0-12-generic\/kernel\/drivers\/gpu\/drm\/bochs
cp drivers\/gpu\/drm\/bochs\/*.ko \/lib\/modules\/4.18.0-12-generic\/kernel\/drivers\/gpu\/drm\/bochs
depmod -a<\/pre>\n\n\n\nNow is the moment of truth, I try to load this module in the running kernel:<\/p>\n\n\n\n
modprobe bochs-drm<\/pre>\n\n\n\nIt didn’t work, but it was not obvious because modprobe<\/code> didn’t show any message, so I searched elsewhere and found something in dmesg<\/code> output:<\/p>\n\n\n\nbochs_drm: version magic '4.18.17 SMP mod_unload ' should be '4.18.0-12-generic SMP mod_unload ' <\/pre>\n\n\n\nI didn’t know where this was defined nor if I could do something about it. If it’s not the same version, maybe I’ve the wrong kernel sources !<\/p>\n\n\n\n
However I found it in the main Makefile<\/code> of the kernel so I decided to make a further attempt by changing the values in that file, even though I’ve no idea of the potential consequences… So I changed the values:<\/p>\n\n\n\nSUBLEVEL = 17
EXTRAVERSION =<\/pre>\n\n\n\nTo the values expected by the running kernel:<\/p>\n\n\n\n
SUBLEVEL = 0
EXTRAVERSION = -12-generic<\/pre>\n\n\n\nThen I restarted a clean compilation:<\/p>\n\n\n\n
make clean
make modules
# Get more coffee
cp drivers\/gpu\/drm\/bochs\/*.ko \/lib\/modules\/4.18.0-12-generic\/kernel\/drivers\/gpu\/drm\/bochs
depmod -a
modprobe bochs-drm
systemctl start sddm<\/pre>\n\n\n\nAnd then I got SDDM back on screen !<\/p>\n\n\n\n
I hope bochs-drm<\/code> will be included in future standard kernels, as asked for in bug 1795857<\/a>, because until it is included, these steps will be necessary after each update of the standard kernel.<\/p>\n\n\n\nConclusion<\/h2>\n\n\n\n
That was not a simple solution to my problem. Did it work ? Yes ! Do I recommend it to anyone ? No, this method is too brittle and takes too much time.<\/p>\n\n\n\n
But it shows how Open Source makes it possible to solve your problems without the help of the author or packager of the software you want to use, and even do things that where not anticipated by them.<\/p>\n","protected":false},"excerpt":{"rendered":"
Upgrade, then reboot… After the upgrade from 18.04 to 18.10, SDDM failed to start. This happened with kernel 4.18.0-10 and 4.15.0-36 (it was the chance to discover grub-reboot). The machine is a virtual machine, and PCI devices are using virtio-pci driver for example. I looked into \/var\/log\/Xorg.0.log and found many error messages, the first one…<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[8],"tags":[],"class_list":["post-83","post","type-post","status-publish","format-standard","hentry","category-linux"],"_links":{"self":[{"href":"https:\/\/mickael.bucas.name\/blog\/wp-json\/wp\/v2\/posts\/83","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/mickael.bucas.name\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/mickael.bucas.name\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/mickael.bucas.name\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/mickael.bucas.name\/blog\/wp-json\/wp\/v2\/comments?post=83"}],"version-history":[{"count":5,"href":"https:\/\/mickael.bucas.name\/blog\/wp-json\/wp\/v2\/posts\/83\/revisions"}],"predecessor-version":[{"id":91,"href":"https:\/\/mickael.bucas.name\/blog\/wp-json\/wp\/v2\/posts\/83\/revisions\/91"}],"wp:attachment":[{"href":"https:\/\/mickael.bucas.name\/blog\/wp-json\/wp\/v2\/media?parent=83"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/mickael.bucas.name\/blog\/wp-json\/wp\/v2\/categories?post=83"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/mickael.bucas.name\/blog\/wp-json\/wp\/v2\/tags?post=83"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}