fix: NVIDIA fix on Limine edits the existing cmdline line; early modules only when every kernel has them

Found by running it in a VM: the appended += line became literal text on the
kernel command line, and a kernel without the modules made limine-mkinitcpio
skip its boot entry.

CHANGELOG.md

@@ -9,6 +9,7 @@ one per merged pull request.
 
 - **feat: the SteamOS conversion fixes a corrupted gaming mode screen with an NVIDIA GPU: nvidia-drm.modeset=1 and fbdev=1 on the kernel command line, NVIDIA modules in the initramfs (lib/nvidia.sh)**
 - **test: tests/nvidia-test.sh runs the NVIDIA fix against a fake RTX 5080 beside an iGPU, a stub modinfo and temp copies of the Limine, systemd-boot and GRUB files (no root, VM or hardware); NVIDIA_DRM_DIR points detection at a fake sysfs tree**
+- **fix: NVIDIA fix on Limine edits the KERNEL_CMDLINE[default] line (an appended += line ended up as literal text on the kernel command line, found in a VM); the modules are only loaded early when every installed kernel has them, and a Limine boot entry without the parameters is an error**
 
 ## 2.9.6 - 2026-09-30
 

TECHNICAL.md

@@ -216,7 +216,12 @@ its driver installed (`lib/nvidia.sh`), the SteamOS conversion adds
 systemd-boot or GRUB; the file is backed up first) and
 `/etc/mkinitcpio.conf.d/90-steamify-nvidia.conf` (`MODULES+=(nvidia
 nvidia_modeset nvidia_uvm nvidia_drm)`), then rebuilds the initramfs and boot
-entries. Only what's missing is changed; it applies after a reboot. Turning
+entries. The early-load drop-in is only written when every installed kernel
+has the NVIDIA modules (mkinitcpio fails on a missing module, and
+`limine-mkinitcpio` then skips that kernel's boot entry, parameters included).
+On Limine the parameters go into the existing `KERNEL_CMDLINE[default]="..."`
+line: an extra appended `+=` line is pasted into the command line as text.
+Only what's missing is changed; it applies after a reboot. Turning
 the conversion off removes both. Untested on hardware so far.
 
 ## HDMI-CEC

lib/nvidia.sh

@@ -9,7 +9,6 @@
 
 NVIDIA_PARAMS="nvidia-drm.modeset=1 nvidia-drm.fbdev=1"
 NVIDIA_INITRAMFS_CONF=/etc/mkinitcpio.conf.d/90-steamify-nvidia.conf
-NVIDIA_MARK="# steamify-nvidia"
 # The DRM devices in sysfs; the tests point this at a fake tree.
 NVIDIA_DRM_DIR=${NVIDIA_DRM_DIR:-/sys/class/drm}
 
@@ -46,6 +45,19 @@ nvidia_initramfs_ok() {
     [[ -f "$NVIDIA_INITRAMFS_CONF" ]] || grep -qE '^MODULES=.*nvidia_drm' /etc/mkinitcpio.conf 2>/dev/null
 }
 
+nvidia_modules_everywhere() {
+    # 0 when every installed kernel has the nvidia_drm module: mkinitcpio fails
+    # on a MODULES entry a kernel lacks, and limine-mkinitcpio then skips that
+    # kernel's initramfs and boot entry, so the parameters never reach it.
+    local k found=0
+    for k in "${NVIDIA_MODULES_DIR:-/usr/lib/modules}"/*/; do
+        [[ -f "$k/pkgbase" || -d "$k/kernel" || -d "$k/updates" || -d "$k/extramodules" ]] || continue
+        find "$k" -name 'nvidia-drm.ko*' -print -quit 2>/dev/null | grep -q . || return 1
+        found=1
+    done
+    [[ $found == 1 ]]
+}
+
 nvidia_rebuild_boot() {
     local f; f="$(nvidia_boot_file)"
     info "Rebuilding the initramfs and boot entries..."
@@ -68,7 +80,7 @@ nvidia_enable() {
             backup_file "$f"
             case "$f" in
                 */limine)
-                    printf 'KERNEL_CMDLINE[default]+=" %s" %s\n' "$NVIDIA_PARAMS" "$NVIDIA_MARK" | sudo tee -a "$f" >/dev/null ;;
+                    sudo sed -i -E "s/^(KERNEL_CMDLINE\[default\]=\"[^\"]*)\"/\1 $NVIDIA_PARAMS\"/" "$f" ;;
                 */sdboot-manage.conf)
                     sudo sed -i -E "s/^(LINUX_OPTIONS=\"[^\"]*)\"/\1 $NVIDIA_PARAMS\"/" "$f" ;;
                 */grub)
@@ -77,13 +89,20 @@ nvidia_enable() {
             changed=1
         fi
     fi
-    if ! nvidia_initramfs_ok; then
+    if ! nvidia_initramfs_ok && ! nvidia_modules_everywhere; then
+        warn "Not every installed kernel has the NVIDIA modules: skipping loading them early (the kernel parameters still apply)."
+    elif ! nvidia_initramfs_ok; then
         info "Loading the NVIDIA modules early (initramfs)..."
         printf 'MODULES+=(nvidia nvidia_modeset nvidia_uvm nvidia_drm)\n' |
             sudo install -Dm644 /dev/stdin "$NVIDIA_INITRAMFS_CONF" && changed=1
     fi
     if [[ $changed == 1 ]]; then
         nvidia_rebuild_boot || { err "Rebuilding the boot entries failed."; return 1; }
+        if [[ "$f" == */limine && -f "${NVIDIA_LIMINE_CONF:-/boot/limine.conf}" ]] &&
+            ! grep -q 'nvidia-drm.modeset=1' "${NVIDIA_LIMINE_CONF:-/boot/limine.conf}"; then
+            err "The boot entries don't have the NVIDIA parameters: the initramfs build failed (see above)."
+            return 1
+        fi
         ok "NVIDIA gaming mode fix applied; it takes effect after a reboot."
     fi
     return 0
@@ -92,10 +111,7 @@ nvidia_enable() {
 nvidia_disable() {
     local f changed=0; f="$(nvidia_boot_file)"
     if [[ -n "$f" ]] && grep -q "$NVIDIA_PARAMS" "$f" 2>/dev/null; then
-        case "$f" in
+        sudo sed -i "s/ \?$NVIDIA_PARAMS//" "$f"
-            */limine) sudo sed -i "/$NVIDIA_MARK\$/d" "$f" ;;
-            *) sudo sed -i "s/ \?$NVIDIA_PARAMS//" "$f" ;;
-        esac
         changed=1
     fi
     [[ -f "$NVIDIA_INITRAMFS_CONF" ]] && { sudo rm -f "$NVIDIA_INITRAMFS_CONF"; changed=1; }

tests/nvidia-test.sh

@@ -19,6 +19,8 @@ echo 0x8086 > "$T/drm/card0/device/vendor"; echo 0x030000 > "$T/drm/card0/device
 echo 0x10de > "$T/drm/card1/device/vendor"; echo 0x030000 > "$T/drm/card1/device/class"
 echo 0x2c02 > "$T/drm/card1/device/device"
 NVIDIA_DRM_DIR="$T/drm"
+mkdir -p "$T/mods/6.1.0-cachyos/kernel"; : > "$T/mods/6.1.0-cachyos/kernel/nvidia-drm.ko.zst"
+NVIDIA_MODULES_DIR="$T/mods"
 
 FAKE_DRIVER=1; check "finds the NVIDIA card as card1 beside an iGPU" nvidia_present
 FAKE_DRIVER=0; check "skips when the driver isn't installed" '! nvidia_present'
@@ -43,6 +45,11 @@ for loader in limine sdboot grub; do
     check "$loader: disable restores the file and drops the drop-in" '[[ "$(cat "$F")" == "$ORIG" && ! -f "$NVIDIA_INITRAMFS_CONF" ]]'
 done
 
+# A second kernel without the NVIDIA modules: no early-load drop-in, parameters still set.
+mkdir -p "$T/mods/6.6.0-lts/kernel"; F="$T/sdboot-manage.conf"; printf 'LINUX_OPTIONS="quiet"\n' > "$F"
+nvidia_boot_file() { echo "$F"; }; rm -f "$NVIDIA_INITRAMFS_CONF"; REBUILDS=0; nvidia_enable
+check "kernel without nvidia modules: no drop-in, parameters set" '[[ ! -f "$NVIDIA_INITRAMFS_CONF" ]] && grep -q "nvidia-drm.fbdev=1" "$F"'
+rm -rf "$T/mods/6.6.0-lts"
 FAKE_DRIVER=0; printf 'LINUX_OPTIONS="quiet"\n' > "$T/sdboot"; F="$T/sdboot"; REBUILDS=0; nvidia_enable
 check "no NVIDIA driver: nothing touched" '[[ "$(cat "$F")" == "LINUX_OPTIONS=\"quiet\"" && $REBUILDS == 0 ]]'
 exit $fail