[SOLVED] Recompiled kernel, PC doesn't boot

Message

irets · Post by **irets** » Tue Feb 24, 2026 8:03 am

I disabled IOMMU support from my kernel, recompiled it and now it gets stuck during the boot phase.
Afterwards I copied .config.old over current .config so I should be back at the starting position, right? But no.
The framebuffer tuxes which indicate online CPUs disappear when the hang happens.
When it gets stuck the last thing I see is it detecting my devices. There are no errors on my screen.
It gets stuck so early in the boot process that /var/log/syslog doesn't get written into.

Here's the config: http://0x0.st/PQrf.txt

Code: Select all

# emerge --info
Portage 3.0.72 (python 3.13.11-final-0, default/linux/amd64/23.0/split-usr, gcc-15, glibc-2.41-r6, 6.12.41-wired-x86_64 x86_64)
=================================================================
System uname: Linux-6.12.41-wired-x86_64-x86_64-Intel-R-_Core-TM-_i7-4790K_CPU_@_4.00GHz-with-glibc2.41
KiB Mem:    16327908 total,  13183164 free
KiB Swap:   20954176 total,  20954176 free
Timestamp of repository gentoo: Sun, 25 Jan 2026 01:15:00 +0000
Head commit of repository gentoo: a80b96e6438a5c37448b6642d3ae17bd53e7c061
Timestamp of repository guru: Sat, 24 Jan 2026 13:46:53 +0000
Head commit of repository guru: 4e29a99feb81e8f6f6f1e8c90e32ae6b4d3cfd04

Head commit of repository steam-overlay: 76e0daaeafe4f2b28a1049074bc3ad16660fae5a

sh bash 5.3_p9
ld GNU ld (Gentoo 2.45.1 p1) 2.45.1
ccache version 4.12.1 [disabled]
app-misc/pax-utils:        1.3.8::gentoo
app-shells/bash:           5.3_p9::gentoo
dev-build/autoconf:        2.72-r6::gentoo
dev-build/automake:        1.18.1::gentoo
dev-build/cmake:           4.1.4::gentoo
dev-build/libtool:         2.5.4::gentoo
dev-build/make:            4.4.1-r102::gentoo
dev-build/meson:           1.9.1::gentoo
dev-java/java-config:      2.3.4::gentoo
dev-lang/perl:             5.42.0-r1::gentoo
dev-lang/python:           3.13.11::gentoo, 3.14.0_p1::gentoo
dev-lang/rust:             1.91.0::gentoo
dev-lang/rust-bin:         1.91.0::gentoo
dev-util/ccache:           4.12.1::gentoo
llvm-core/clang:           19.1.7-r1::gentoo, 21.1.8::gentoo
llvm-core/lld:             19.1.7::gentoo, 21.1.8::gentoo
llvm-core/llvm:            19.1.7::gentoo, 21.1.8::gentoo
sys-apps/baselayout:       2.18::gentoo
sys-apps/openrc:           0.62.10::gentoo
sys-apps/sandbox:          2.46::gentoo
sys-devel/binutils:        2.45.1::gentoo
sys-devel/binutils-config: 5.6::gentoo
sys-devel/gcc:             15.2.1_p20251122::gentoo
sys-devel/gcc-config:      2.12.2::gentoo
sys-kernel/linux-headers:  6.12::gentoo (virtual/os-headers)
sys-libs/glibc:            2.41-r6::gentoo
Repositories:

gentoo
    location: /var/db/repos/gentoo
    sync-type: rsync
    sync-uri: rsync://rsync.gentoo.org/gentoo-portage
    priority: -1000
    volatile: False
    sync-rsync-verify-metamanifest: yes
    sync-rsync-verify-jobs: 1
    sync-rsync-extra-opts: 
    sync-rsync-verify-max-age: 24

guru
    location: /var/db/repos/guru
    sync-type: git
    sync-uri: https://github.com/gentoo-mirror/guru.git
    masters: gentoo
    volatile: False

steam-overlay
    location: /usr/local/portage/steam-overlay
    sync-type: git
    sync-uri: https://github.com/anyc/steam-overlay.git
    masters: gentoo
    priority: 50
    volatile: True

localrepo
    location: /var/db/repos/localrepo
    masters: gentoo
    priority: 100
    volatile: False

ACCEPT_KEYWORDS="amd64"
ACCEPT_LICENSE="@FREE"
CBUILD="x86_64-pc-linux-gnu"
CFLAGS="-march=native -O2 -pipe"
CHOST="x86_64-pc-linux-gnu"
CONFIG_PROTECT="/etc /usr/lib64/libreoffice/program/sofficerc /usr/share/gnupg/qualified.txt /var/bind"
CONFIG_PROTECT_MASK="/etc/ca-certificates.conf /etc/dconf /etc/env.d /etc/fonts/fonts.conf /etc/gconf /etc/gentoo-release /etc/revdep-rebuild /etc/sandbox.d /etc/terminfo"
CXXFLAGS="-march=native -O2 -pipe"
DISTDIR="/var/cache/distfiles"
ENV_UNSET="CARGO_HOME DBUS_SESSION_BUS_ADDRESS DISPLAY GDK_PIXBUF_MODULE_FILE GOBIN GOPATH PERL5LIB PERL5OPT PERLPREFIX PERL_CORE PERL_MB_OPT PERL_MM_OPT XAUTHORITY XDG_CACHE_HOME XDG_CONFIG_HOME XDG_DATA_HOME XDG_RUNTIME_DIR XDG_STATE_HOME"
FCFLAGS="-march=native -O2 -pipe"
FEATURES="assume-digests binpkg-docompress binpkg-dostrip binpkg-logs buildpkg-live candy config-protect-if-modified distlocks ebuild-locks fixlafiles ipc-sandbox merge-sync merge-wait multilib-strict network-sandbox news parallel-fetch pid-sandbox pkgdir-index-trusted preserve-libs protect-owned qa-unresolved-soname-deps sandbox strict unknown-features-warn unmerge-logs unmerge-orphans userfetch userpriv usersandbox usersync xattr"
FFLAGS="-march=native -O2 -pipe"
GENTOO_MIRRORS="ftp://mirror.netcologne.de/gentoo/ https://mirror.netcologne.de/gentoo/ http://mirror.netcologne.de/gentoo/ rsync://mirror.netcologne.de/gentoo/"
INSTALL_MASK="/lib/systemd/*/*.service /usr/lib/systemd/*/*.service"
LANG="en_US.utf8"
LDFLAGS="-Wl,-O1 -Wl,--as-needed -Wl,-z,pack-relative-relocs"
LEX="flex"
MAKEOPTS="-j4"
PKGDIR="/var/cache/binpkgs"
PORTAGE_COMPRESS="bzip2"
PORTAGE_CONFIGROOT="/"
PORTAGE_RSYNC_OPTS="--recursive --links --safe-links --perms --times --omit-dir-times --compress --force --whole-file --delete --stats --human-readable --timeout=180 --exclude=/distfiles --exclude=/local --exclude=/packages --exclude=/.git"
PORTAGE_TMPDIR="/var/tmp"
SHELL="/bin/bash"
USE="X acl alsa amd64 bzip2 cet crypt elogind gdbm iconv ipv6 libtirpc multilib ncurses nls openmp pam pcre pulseaudio readline seccomp split-usr ssl test-rust udev unicode xattr xinerama zlib" ABI_X86="64" ADA_TARGET="gcc_15" APACHE2_MODULES="authn_core authz_core socache_shmcb unixd actions alias auth_basic authn_anon authn_dbm authn_file authz_dbm authz_groupfile authz_host authz_owner authz_user autoindex cache cgi cgid dav dav_fs dav_lock deflate dir env expires ext_filter file_cache filter headers include info log_config logio mime mime_magic negotiation rewrite setenvif speling status unique_id userdir usertrack vhost_alias" CALLIGRA_FEATURES="karbon sheets words" COLLECTD_PLUGINS="df interface irq load memory rrdtool swap syslog" CPU_FLAGS_X86="aes avx avx2 f16c fma3 mmx mmxext pclmul popcnt rdrand sse sse2 sse3 sse4_1 sse4_2 ssse3" ELIBC="glibc" GPSD_PROTOCOLS="ashtech aivdm earthmate evermore fv18 garmin garmintxt gpsclock greis isync itrax navcom oceanserver oncore rtcm104v2 rtcm104v3 sirf skytraq superstar2 tsip tripmate tnt ublox" GRUB_PLATFORMS="pc" GUILE_SINGLE_TARGET="3-0" GUILE_TARGETS="3-0" INPUT_DEVICES="libinput wacom" KERNEL="linux" LCD_DEVICES="bayrad cfontz glk hd44780 lb216 lcdm001 mtxorb text" LLVM_TARGETS="X86" LUA_SINGLE_TARGET="lua5-1" LUA_TARGETS="lua5-1" OFFICE_IMPLEMENTATION="libreoffice" PHP_TARGETS="php8-3" POSTGRES_TARGETS="postgres17" PYTHON_SINGLE_TARGET="python3_13" PYTHON_TARGETS="python3_13" RUBY_TARGETS="ruby32 ruby33" VIDEO_CARDS="nvidia" XTABLES_ADDONS="quota2 psd pknock lscan length2 ipv4options ipp2p iface geoip fuzzy condition tarpit sysrq proto logmark ipmark dhcpmac delude chaos account"
Unset:  ADDR2LINE, AR, ARFLAGS, AS, ASFLAGS, CC, CCLD, CONFIG_SHELL, CPP, CPPFLAGS, CTARGET, CXX, CXXFILT, ELFEDIT, EMERGE_DEFAULT_OPTS, EXTRA_ECONF, F77FLAGS, FC, GCOV, GPROF, LC_ALL, LD, LFLAGS, LIBTOOL, LINGUAS, MAKE, MAKEFLAGS, NM, OBJCOPY, OBJDUMP, PORTAGE_BINHOST, PORTAGE_BUNZIP2_COMMAND, PORTAGE_COMPRESS_FLAGS, PORTAGE_RSYNC_EXTRA_OPTS, PYTHONPATH, RANLIB, READELF, RUSTFLAGS, SIZE, STRINGS, STRIP, YACC, YFLAGS

Post by **Banana** » Tue Feb 24, 2026 8:11 am

irets wrote:Afterwards I copied .config.old over current .config so I should be back at the starting position, right? But no.

And did what exactly after that? Maybe there is something you missed.

irets · Post by **irets** » Tue Feb 24, 2026 8:14 am

Hi, Banana.

Afterwards I ran make -j7 + make install + make modules_install + emerge @module-rebuild.

I was able to get back into my system using the .old variant of the kernel but now that's also overwritten with the non-functioning one.
There still was 6.12.41 available in GRUB so I can use my computer to troubleshoot my latest kernel.

irets · Post by **irets** » Tue Feb 24, 2026 8:38 am

I went through make clean and repeating the compiling process and now boots again without a clue why.

Wish I knew further as to why all of this happened and how it got fixed but I can close this thread now and carry on.

New at Gentoo · Post by **pietinger** » Tue Feb 24, 2026 12:28 pm

irets wrote:[...] Wish I knew further as to why all of this happened and how it got fixed but I can close this thread now and carry on.

->

irets wrote:[...] Afterwards I copied .config.old over current .config so I should be back at the starting position, right? But no.

Have you done a "make oldconfig" after copying the .config file?

If not, then this is the answer to your question.

irets · Post by **irets** » Tue Feb 24, 2026 3:08 pm

pietinger,
The .config.old was already within /usr/src/linux.
I executed cp .config.old .config and rebuilt the kernel.
Was make oldconfig really required here? I never ran that at any point.

New at Gentoo · Post by **pietinger** » Tue Feb 24, 2026 3:42 pm

irets wrote:I executed cp .config.old .config and rebuilt the kernel.
Was make oldconfig really required here? [...]

Yes.

Another way is of course to delete any old stuff with "make clean".

(Generally speaking: Whenever you copy a .config file to /usr/src/linux that has different settings than the existing kernel configuration, you should first apply it with "make oldconfig". before doing the "make". The "make" is a "make all" which does a "make vmlinux"+"make modules", OR (on x86) "make bzImage"+"make modules", but no "make oldonfig". See also in "make help".)