From 775215234e0e02ad2eaf6939c50253537a16625a Mon Sep 17 00:00:00 2001
From: Joel Granados <joel.granados@kernel.org>
Date: Wed, 11 Jun 2025 09:58:48 +0200
Subject: [PATCH 01/12] nixvm: Allways run a kernel setup function

The path is ready for when we need to run an imageless nixvm without a
-k. But for now it will always fail.

Signed-off-by: Joel Granados <joel.granados@kernel.org>
---
 cmd/run       |  4 +++-
 lib/qemu/kern | 43 +++++++++++++++++++++++++++++--------------
 lib/qemu/nix  | 34 ++++++++++++++++++++--------------
 3 files changed, 52 insertions(+), 29 deletions(-)

diff --git a/cmd/run b/cmd/run
index 81b087a..c5ae39a 100644
--- a/cmd/run
+++ b/cmd/run
@@ -145,7 +145,9 @@ _run() {
   QEMU_PARAMS+=("-pidfile" "${VMROOT}/run/${VMNAME}/pidfile")
 
   if [[ -v kernel_dir ]]; then
-    qemu_kern_add_custom --kernel-dir "${kernel_dir}"
+    qemu_kernel_setup --kernel-dir "${kernel_dir}"
+  else
+    qemu_kernel_setup
   fi
 
   if [[ -v do_background ]]; then
diff --git a/lib/qemu/kern b/lib/qemu/kern
index 333f012..7e1ad20 100644
--- a/lib/qemu/kern
+++ b/lib/qemu/kern
@@ -36,9 +36,15 @@ _qemu_kern_img_add() {
   QEMU_PARAMS+=("-append" "$cmdline")
 }
 
-qemu_kern_add_custom() {
-  local cmdline_extra=""
-  local mod_share="9p"
+_qemu_check_kern_globs() {
+  for var in GUEST_KERNEL_IMAGE GUEST_KERNEL_CONSOLE; do
+    if [[ ! -v ${var} ]]; then
+      _fatal 1 "${FUNCNAME[0]} Missing var ${var}. Add it to ${VMCONFIG}"
+    fi
+  done
+}
+
+qemu_kernel_setup() {
   local long="kernel-dir:,cmdline-extra:,mod-share:"
 
   if ! tmp=$(getopt -o "" --long "$long" -n "${FUNCNAME[0]}" -- "$@"); then
@@ -69,24 +75,33 @@ qemu_kern_add_custom() {
   done
 
   if [[ ! -v kernel_dir ]]; then
-    _fatal 1 "${FUNCNAME[0]} Missing required --kernel-dir argument"
+    # Yes!; Do nothing with image-backed
+    if [[ -v NIX_STORE_PATH ]]; then
+      _qemu_check_kern_globs
+      qemu_nix_add_noimgnix
+    fi
+    return
   fi
 
-  for var in GUEST_KERNEL_IMAGE GUEST_KERNEL_CONSOLE; do
-    if [[ ! -v ${var} ]]; then
-      _fatal 1 "${FUNCNAME[0]} Missing var ${var}. Add it to ${VMCONFIG}"
-    fi
-  done
+  _qemu_check_kern_globs
 
-  if [[ -v NIX_STORE_PATH ]]; then
-    qemu_nix_add_noimgnix
-  else
-    _qemu_kern_img_add "${cmdline_extra}"
+  if [[ ! -v mod_share ]]; then
+    local mod_share="9p"
   fi
 
   local kernel_tag="kernel_dir"
   qemu_share_add --shared-dir "${kernel_dir}" \
     --tag "${kernel_tag}" \
     --share-type "${mod_share}"
-}
 
+  if [[ ! -v cmdline_extra ]]; then
+    local cmdline_extra=""
+  fi
+
+  if [[ -v NIX_STORE_PATH ]]; then
+    qemu_nix_add_noimgnix --kernel-dir "${kernel_dir}"
+  else
+    _qemu_kern_img_add "${cmdline_extra}"
+  fi
+
+}
diff --git a/lib/qemu/nix b/lib/qemu/nix
index 200e1e1..0431656 100644
--- a/lib/qemu/nix
+++ b/lib/qemu/nix
@@ -67,8 +67,11 @@ qemu_nix_add_noimgnix () {
   _require_program nix
   _require_path "${NIX_STORE_PATH}"
 
-  local long="cmd-line-extra:"
+  if [[ ! -v VMSTATE ]]; then
+    _fatal 1 "${FUNCNAME[0]}: VMSTATE global var is not set"
+  fi
 
+  local long="cmd-line-extra:,kernel-dir:"
   if ! tmp=$(getopt -o "" --long "$long" -n "${FUNCNAME[0]}" -- "$@"); then
     exit 1
   fi
@@ -82,6 +85,9 @@ qemu_nix_add_noimgnix () {
       '--cmd-line-extra' )
         cmd_line_extra="$2"; shift 2
         ;;
+      '--kernel-dir' )
+        local kernel_dir="$2"; shift 2
+        ;;
       '--' )
         shift; break
         ;;
@@ -91,25 +97,28 @@ qemu_nix_add_noimgnix () {
     esac
   done
 
-  if [[ ! -v VMSTATE ]]; then
-    _fatal 1 "${FUNCNAME[0]}: VMSTATE global var is not set"
-  fi
-
-  local dst_path="${VMSTATE}/nixsys"
+  local nixsys_path="${VMSTATE}/nixsys"
   : "${NIX_SYS_BUILD_FORCE:="no"}" # defaults to "no" if not set
-  if [[ ${NIX_SYS_BUILD_FORCE} == "yes" || ! -h ${dst_path} ]]; then
-    _qemu_nix_create_nix_sys "${dst_path}"
+  if [[ ${NIX_SYS_BUILD_FORCE} == "yes" || ! -h ${nixsys_path} ]]; then
+    _qemu_nix_create_nix_sys "${nixsys_path}"
   fi
 
-  _qemu_nix_create_nix_init "${VMSTATE}"
-
   qemu_share_add --shared-dir "${NIX_STORE_PATH}" \
       --tag "nixstore" \
       --share-type "virtiofs" \
       --vm-dir "/nix/store"
 
+  _qemu_nix_create_nix_init "${VMSTATE}"
+
+  if [[ -v kernel_dir ]]; then
+    QEMU_PARAMS+=("-kernel" "${kernel_dir}/${GUEST_KERNEL_IMAGE}")
+    QEMU_PARAMS+=("-initrd" "${VMSTATE}/init.img")
+  else
+    _fatal 1 "${FUNCNAME[0]}: Running a nixvm without a kernel is unsupported"
+  fi
+
   local nix_init_path=""
-  nix_init_path="$(readlink "${dst_path}")/init"
+  nix_init_path="$(readlink "${nixsys_path}")/init"
   local cmd_line="root=/dev/ram0 console=${GUEST_KERNEL_CONSOLE}"
   if [[ -v GUEST_KERNEL_APPEND_EXTRA ]]; then
     cmd_line="${cmd_line} ${GUEST_KERNEL_APPEND_EXTRA}"
@@ -122,8 +131,5 @@ qemu_nix_add_noimgnix () {
     done
   fi
 
-  QEMU_PARAMS+=("-kernel" "${kernel_dir}/${GUEST_KERNEL_IMAGE}")
   QEMU_PARAMS+=("-append" "${cmd_line}")
-  QEMU_PARAMS+=("-initrd" "${VMSTATE}/init.img")
-
 }

From f5d2645bebe7e086b6ed15f4134ad4986af9f663 Mon Sep 17 00:00:00 2001
From: Joel Granados <joel.granados@kernel.org>
Date: Tue, 17 Jun 2025 08:40:00 +0200
Subject: [PATCH 02/12] nixvm: separate nix sys result link from result path

Signed-off-by: Joel Granados <joel.granados@kernel.org>
---
 lib/qemu/nix | 11 +++++------
 1 file changed, 5 insertions(+), 6 deletions(-)

diff --git a/lib/qemu/nix b/lib/qemu/nix
index 0431656..c9fd417 100644
--- a/lib/qemu/nix
+++ b/lib/qemu/nix
@@ -97,10 +97,11 @@ qemu_nix_add_noimgnix () {
     esac
   done
 
-  local nixsys_path="${VMSTATE}/nixsys"
+  local nixsys_link="${VMSTATE}/nixsys"
+  local nixsys_path=""; nixsys_path="$(readlink "${nixsys_link}")"
   : "${NIX_SYS_BUILD_FORCE:="no"}" # defaults to "no" if not set
-  if [[ ${NIX_SYS_BUILD_FORCE} == "yes" || ! -h ${nixsys_path} ]]; then
-    _qemu_nix_create_nix_sys "${nixsys_path}"
+  if [[ ${NIX_SYS_BUILD_FORCE} == "yes" || ! -h ${nixsys_link} ]]; then
+    _qemu_nix_create_nix_sys "${nixsys_link}"
   fi
 
   qemu_share_add --shared-dir "${NIX_STORE_PATH}" \
@@ -117,14 +118,12 @@ qemu_nix_add_noimgnix () {
     _fatal 1 "${FUNCNAME[0]}: Running a nixvm without a kernel is unsupported"
   fi
 
-  local nix_init_path=""
-  nix_init_path="$(readlink "${nixsys_path}")/init"
   local cmd_line="root=/dev/ram0 console=${GUEST_KERNEL_CONSOLE}"
   if [[ -v GUEST_KERNEL_APPEND_EXTRA ]]; then
     cmd_line="${cmd_line} ${GUEST_KERNEL_APPEND_EXTRA}"
   fi
   cmd_line="${cmd_line} ${cmd_line_extra}"
-  cmd_line="${cmd_line} -- --init-path ${nix_init_path}"
+  cmd_line="${cmd_line} -- --init-path ${nixsys_path}/init"
   if [[ -v NIX_MOUNTS ]]; then
     for nmount in "${NIX_MOUNTS[@]}"; do
       cmd_line="${cmd_line} --mount ${nmount}"

From e0737fa1aabccda46264e2c1902a2a042db0fa6c Mon Sep 17 00:00:00 2001
From: Joel Granados <joel.granados@kernel.org>
Date: Tue, 17 Jun 2025 21:22:22 +0200
Subject: [PATCH 03/12] nixvm: always share kernel_dir when -k is used

Signed-off-by: Joel Granados <joel.granados@kernel.org>
---
 lib/qemu/kern | 19 ++++++-------------
 1 file changed, 6 insertions(+), 13 deletions(-)

diff --git a/lib/qemu/kern b/lib/qemu/kern
index 7e1ad20..b86215f 100644
--- a/lib/qemu/kern
+++ b/lib/qemu/kern
@@ -45,7 +45,7 @@ _qemu_check_kern_globs() {
 }
 
 qemu_kernel_setup() {
-  local long="kernel-dir:,cmdline-extra:,mod-share:"
+  local long="kernel-dir:,cmdline-extra:"
 
   if ! tmp=$(getopt -o "" --long "$long" -n "${FUNCNAME[0]}" -- "$@"); then
     exit 1
@@ -62,9 +62,6 @@ qemu_kernel_setup() {
       '--cmdline-extra' )
         cmdline_extra="${cmdline_extra} $2"; shift 2
         ;;
-      'mod-share' )
-        mod_share="$2"; shift 2
-        ;;
       '--' )
         shift; break
         ;;
@@ -85,23 +82,19 @@ qemu_kernel_setup() {
 
   _qemu_check_kern_globs
 
-  if [[ ! -v mod_share ]]; then
-    local mod_share="9p"
-  fi
-
-  local kernel_tag="kernel_dir"
-  qemu_share_add --shared-dir "${kernel_dir}" \
-    --tag "${kernel_tag}" \
-    --share-type "${mod_share}"
-
   if [[ ! -v cmdline_extra ]]; then
     local cmdline_extra=""
   fi
 
   if [[ -v NIX_STORE_PATH ]]; then
     qemu_nix_add_noimgnix --kernel-dir "${kernel_dir}"
+    local mod_share="9p"
   else
     _qemu_kern_img_add "${cmdline_extra}"
+    local mod_share="virtiofs"
   fi
 
+  qemu_share_add --shared-dir "${kernel_dir}" \
+    --tag "kernel_dir" \
+    --share-type "${mod_share}"
 }

From e43ab466e8fadcacff967af9c403ad2a9ad89100 Mon Sep 17 00:00:00 2001
From: Joel Granados <joel.granados@kernel.org>
Date: Fri, 20 Jun 2025 09:41:11 +0200
Subject: [PATCH 04/12] kern: Pass custom kernel path with a GLOB

Signed-off-by: Joel Granados <joel.granados@kernel.org>
---
 cmd/run       | 12 ++++--------
 lib/qemu/kern | 17 +++++++----------
 lib/qemu/nix  |  9 +++------
 3 files changed, 14 insertions(+), 24 deletions(-)

diff --git a/cmd/run b/cmd/run
index c5ae39a..00f2fce 100644
--- a/cmd/run
+++ b/cmd/run
@@ -49,10 +49,10 @@ _run() {
   while true; do
     case "$1" in
       '-k' | '--kernel-dir' )
-        local kernel_dir="$2"; shift 2
+        GUEST_KERNEL_CUSTOM_DIR="$2"; shift 2
 
-        if [[ ! -d "$kernel_dir" ]]; then
-          _fatal 1 "no such directory: '$kernel_dir'"
+        if [[ ! -d "${GUEST_KERNEL_CUSTOM_DIR}" ]]; then
+          _fatal 1 "no such directory: '${GUEST_KERNEL_CUSTOM_DIR}'"
         fi
         ;;
 
@@ -144,11 +144,7 @@ _run() {
 
   QEMU_PARAMS+=("-pidfile" "${VMROOT}/run/${VMNAME}/pidfile")
 
-  if [[ -v kernel_dir ]]; then
-    qemu_kernel_setup --kernel-dir "${kernel_dir}"
-  else
-    qemu_kernel_setup
-  fi
+  qemu_kernel_setup
 
   if [[ -v do_background ]]; then
     QEMU_PARAMS+=("-daemonize")
diff --git a/lib/qemu/kern b/lib/qemu/kern
index b86215f..b3a99e4 100644
--- a/lib/qemu/kern
+++ b/lib/qemu/kern
@@ -32,7 +32,7 @@ _qemu_kern_img_add() {
     cmdline="$cmdline ${GUEST_KERNEL_APPEND_EXTRA}"
   fi
 
-  QEMU_PARAMS+=("-kernel" "${kernel_dir}/${GUEST_KERNEL_IMAGE}")
+  QEMU_PARAMS+=("-kernel" "${GUEST_KERNEL_CUSTOM_DIR}/${GUEST_KERNEL_IMAGE}")
   QEMU_PARAMS+=("-append" "$cmdline")
 }
 
@@ -45,7 +45,7 @@ _qemu_check_kern_globs() {
 }
 
 qemu_kernel_setup() {
-  local long="kernel-dir:,cmdline-extra:"
+  local long="cmdline-extra:"
 
   if ! tmp=$(getopt -o "" --long "$long" -n "${FUNCNAME[0]}" -- "$@"); then
     exit 1
@@ -56,9 +56,6 @@ qemu_kernel_setup() {
 
   while true; do
     case "$1" in
-      '--kernel-dir' )
-        local kernel_dir="$2"; shift 2
-        ;;
       '--cmdline-extra' )
         cmdline_extra="${cmdline_extra} $2"; shift 2
         ;;
@@ -71,7 +68,7 @@ qemu_kernel_setup() {
     esac
   done
 
-  if [[ ! -v kernel_dir ]]; then
+  if [[ ! -v GUEST_KERNEL_CUSTOM_DIR ]]; then
     # Yes!; Do nothing with image-backed
     if [[ -v NIX_STORE_PATH ]]; then
       _qemu_check_kern_globs
@@ -87,14 +84,14 @@ qemu_kernel_setup() {
   fi
 
   if [[ -v NIX_STORE_PATH ]]; then
-    qemu_nix_add_noimgnix --kernel-dir "${kernel_dir}"
-    local mod_share="9p"
+    qemu_nix_add_noimgnix
+    local mod_share="virtiofs"
   else
     _qemu_kern_img_add "${cmdline_extra}"
-    local mod_share="virtiofs"
+    local mod_share="9p"
   fi
 
-  qemu_share_add --shared-dir "${kernel_dir}" \
+  qemu_share_add --shared-dir "${GUEST_KERNEL_CUSTOM_DIR}" \
     --tag "kernel_dir" \
     --share-type "${mod_share}"
 }
diff --git a/lib/qemu/nix b/lib/qemu/nix
index c9fd417..e8d63b9 100644
--- a/lib/qemu/nix
+++ b/lib/qemu/nix
@@ -71,7 +71,7 @@ qemu_nix_add_noimgnix () {
     _fatal 1 "${FUNCNAME[0]}: VMSTATE global var is not set"
   fi
 
-  local long="cmd-line-extra:,kernel-dir:"
+  local long="cmd-line-extra:"
   if ! tmp=$(getopt -o "" --long "$long" -n "${FUNCNAME[0]}" -- "$@"); then
     exit 1
   fi
@@ -85,9 +85,6 @@ qemu_nix_add_noimgnix () {
       '--cmd-line-extra' )
         cmd_line_extra="$2"; shift 2
         ;;
-      '--kernel-dir' )
-        local kernel_dir="$2"; shift 2
-        ;;
       '--' )
         shift; break
         ;;
@@ -111,8 +108,8 @@ qemu_nix_add_noimgnix () {
 
   _qemu_nix_create_nix_init "${VMSTATE}"
 
-  if [[ -v kernel_dir ]]; then
-    QEMU_PARAMS+=("-kernel" "${kernel_dir}/${GUEST_KERNEL_IMAGE}")
+  if [[ -v GUEST_KERNEL_CUSTOM_DIR ]]; then
+    QEMU_PARAMS+=("-kernel" "${GUEST_KERNEL_CUSTOM_DIR}/${GUEST_KERNEL_IMAGE}")
     QEMU_PARAMS+=("-initrd" "${VMSTATE}/init.img")
   else
     _fatal 1 "${FUNCNAME[0]}: Running a nixvm without a kernel is unsupported"

From ac270d1b24e52e3d3cbf77a5c885dd133352143e Mon Sep 17 00:00:00 2001
From: Joel Granados <joel.granados@kernel.org>
Date: Fri, 20 Jun 2025 09:59:20 +0200
Subject: [PATCH 05/12] kern: consolidate all kern extra cmdline in
 GUEST_KERNEL_APPEND_EXTRA

Signed-off-by: Joel Granados <joel.granados@kernel.org>
---
 lib/qemu/kern | 39 +++------------------------------------
 lib/qemu/nix  | 28 +---------------------------
 2 files changed, 4 insertions(+), 63 deletions(-)

diff --git a/lib/qemu/kern b/lib/qemu/kern
index b3a99e4..3e9cdc4 100644
--- a/lib/qemu/kern
+++ b/lib/qemu/kern
@@ -5,8 +5,6 @@
 # Written by Joel Granados <joel.granados@kernel.org>
 
 _qemu_kern_img_add() {
-  local cmdline_extra="$1"
-
   for var in GUEST_BOOT GUEST_BOOT_BASE; do
     if [[ ! -v ${var} ]]; then
       _fatal 1 "${FUNCNAME[0]} Missing var ${var}. Add it to ${VMCONFIG}"
@@ -27,13 +25,9 @@ _qemu_kern_img_add() {
     GUEST_KERNEL_BOOTDEV="/dev/vda1"
   fi
 
-  local cmdline="root=${GUEST_KERNEL_BOOTDEV} console=${GUEST_KERNEL_CONSOLE} ${cmdline_extra}"
-  if [[ -v GUEST_KERNEL_APPEND_EXTRA ]]; then
-    cmdline="$cmdline ${GUEST_KERNEL_APPEND_EXTRA}"
-  fi
-
   QEMU_PARAMS+=("-kernel" "${GUEST_KERNEL_CUSTOM_DIR}/${GUEST_KERNEL_IMAGE}")
-  QEMU_PARAMS+=("-append" "$cmdline")
+  QEMU_PARAMS+=("-append" \
+    "root=${GUEST_KERNEL_BOOTDEV} console=${GUEST_KERNEL_CONSOLE} ${GUEST_KERNEL_APPEND_EXTRA}")
 }
 
 _qemu_check_kern_globs() {
@@ -45,29 +39,6 @@ _qemu_check_kern_globs() {
 }
 
 qemu_kernel_setup() {
-  local long="cmdline-extra:"
-
-  if ! tmp=$(getopt -o "" --long "$long" -n "${FUNCNAME[0]}" -- "$@"); then
-    exit 1
-  fi
-
-  eval set -- "$tmp"
-  unset tmp
-
-  while true; do
-    case "$1" in
-      '--cmdline-extra' )
-        cmdline_extra="${cmdline_extra} $2"; shift 2
-        ;;
-      '--' )
-        shift; break
-        ;;
-      * )
-        _fatal 1 "unknown argument '$1'"
-        ;;
-    esac
-  done
-
   if [[ ! -v GUEST_KERNEL_CUSTOM_DIR ]]; then
     # Yes!; Do nothing with image-backed
     if [[ -v NIX_STORE_PATH ]]; then
@@ -79,15 +50,11 @@ qemu_kernel_setup() {
 
   _qemu_check_kern_globs
 
-  if [[ ! -v cmdline_extra ]]; then
-    local cmdline_extra=""
-  fi
-
   if [[ -v NIX_STORE_PATH ]]; then
     qemu_nix_add_noimgnix
     local mod_share="virtiofs"
   else
-    _qemu_kern_img_add "${cmdline_extra}"
+    _qemu_kern_img_add
     local mod_share="9p"
   fi
 
diff --git a/lib/qemu/nix b/lib/qemu/nix
index e8d63b9..0d01bd7 100644
--- a/lib/qemu/nix
+++ b/lib/qemu/nix
@@ -71,29 +71,6 @@ qemu_nix_add_noimgnix () {
     _fatal 1 "${FUNCNAME[0]}: VMSTATE global var is not set"
   fi
 
-  local long="cmd-line-extra:"
-  if ! tmp=$(getopt -o "" --long "$long" -n "${FUNCNAME[0]}" -- "$@"); then
-    exit 1
-  fi
-
-  eval set -- "$tmp"
-  unset tmp
-
-  local cmd_line_extra=""
-  while true; do
-    case "$1" in
-      '--cmd-line-extra' )
-        cmd_line_extra="$2"; shift 2
-        ;;
-      '--' )
-        shift; break
-        ;;
-      * )
-        _fatal 1 "unknown argument '$1'"
-        ;;
-    esac
-  done
-
   local nixsys_link="${VMSTATE}/nixsys"
   local nixsys_path=""; nixsys_path="$(readlink "${nixsys_link}")"
   : "${NIX_SYS_BUILD_FORCE:="no"}" # defaults to "no" if not set
@@ -116,10 +93,7 @@ qemu_nix_add_noimgnix () {
   fi
 
   local cmd_line="root=/dev/ram0 console=${GUEST_KERNEL_CONSOLE}"
-  if [[ -v GUEST_KERNEL_APPEND_EXTRA ]]; then
-    cmd_line="${cmd_line} ${GUEST_KERNEL_APPEND_EXTRA}"
-  fi
-  cmd_line="${cmd_line} ${cmd_line_extra}"
+  cmd_line="${cmd_line} ${GUEST_KERNEL_APPEND_EXTRA}"
   cmd_line="${cmd_line} -- --init-path ${nixsys_path}/init"
   if [[ -v NIX_MOUNTS ]]; then
     for nmount in "${NIX_MOUNTS[@]}"; do

From 04846849abd0e5a147df4fd6347e4b49fe62ff45 Mon Sep 17 00:00:00 2001
From: Joel Granados <joel.granados@kernel.org>
Date: Mon, 23 Jun 2025 19:56:56 +0200
Subject: [PATCH 06/12] treewide: generalize checking for globals in common

Signed-off-by: Joel Granados <joel.granados@kernel.org>
---
 common/rc      |  8 ++++++++
 lib/qemu/kern  | 18 +++---------------
 lib/qemu/nix   |  5 +----
 lib/qemu/share |  4 +---
 4 files changed, 13 insertions(+), 22 deletions(-)

diff --git a/common/rc b/common/rc
index 3222a5a..1a38436 100644
--- a/common/rc
+++ b/common/rc
@@ -137,6 +137,14 @@ _require_path() {
   fi
 }
 
+_require_vars() {
+  for var in $1; do
+    if [[ ! -v ${var} ]]; then
+      _fatal 1 "${FUNCNAME[0]} Missing var ${var}. Missing in ${VMCONFIG}?"
+    fi
+  done
+}
+
 _is_running() {
   if [[ -f "${VMRUN}/pidfile" ]]; then
     return 0
diff --git a/lib/qemu/kern b/lib/qemu/kern
index 3e9cdc4..c99f7ba 100644
--- a/lib/qemu/kern
+++ b/lib/qemu/kern
@@ -5,11 +5,7 @@
 # Written by Joel Granados <joel.granados@kernel.org>
 
 _qemu_kern_img_add() {
-  for var in GUEST_BOOT GUEST_BOOT_BASE; do
-    if [[ ! -v ${var} ]]; then
-      _fatal 1 "${FUNCNAME[0]} Missing var ${var}. Add it to ${VMCONFIG}"
-    fi
-  done
+  _require_vars "GUEST_BOOT GUEST_BOOT_BASE"
 
   if [[ ! -f "${VMROOT}/$GUEST_BOOT" ]]; then
     if [[ ! -f "${VMROOT}/$GUEST_BOOT_BASE" ]]; then
@@ -30,25 +26,17 @@ _qemu_kern_img_add() {
     "root=${GUEST_KERNEL_BOOTDEV} console=${GUEST_KERNEL_CONSOLE} ${GUEST_KERNEL_APPEND_EXTRA}")
 }
 
-_qemu_check_kern_globs() {
-  for var in GUEST_KERNEL_IMAGE GUEST_KERNEL_CONSOLE; do
-    if [[ ! -v ${var} ]]; then
-      _fatal 1 "${FUNCNAME[0]} Missing var ${var}. Add it to ${VMCONFIG}"
-    fi
-  done
-}
-
 qemu_kernel_setup() {
   if [[ ! -v GUEST_KERNEL_CUSTOM_DIR ]]; then
     # Yes!; Do nothing with image-backed
     if [[ -v NIX_STORE_PATH ]]; then
-      _qemu_check_kern_globs
+      _require_vars "GUEST_KERNEL_IMAGE GUEST_KERNEL_CONSOLE"
       qemu_nix_add_noimgnix
     fi
     return
   fi
 
-  _qemu_check_kern_globs
+  _require_vars "GUEST_KERNEL_IMAGE GUEST_KERNEL_CONSOLE"
 
   if [[ -v NIX_STORE_PATH ]]; then
     qemu_nix_add_noimgnix
diff --git a/lib/qemu/nix b/lib/qemu/nix
index 0d01bd7..89ee688 100644
--- a/lib/qemu/nix
+++ b/lib/qemu/nix
@@ -66,10 +66,7 @@ _qemu_nix_create_nix_init () {
 qemu_nix_add_noimgnix () {
   _require_program nix
   _require_path "${NIX_STORE_PATH}"
-
-  if [[ ! -v VMSTATE ]]; then
-    _fatal 1 "${FUNCNAME[0]}: VMSTATE global var is not set"
-  fi
+  _require_vars "VMSTATE"
 
   local nixsys_link="${VMSTATE}/nixsys"
   local nixsys_path=""; nixsys_path="$(readlink "${nixsys_link}")"
diff --git a/lib/qemu/share b/lib/qemu/share
index 4cb375f..b2d15df 100644
--- a/lib/qemu/share
+++ b/lib/qemu/share
@@ -6,9 +6,7 @@
 
 _qemu_share_force_memshare() {
   # memshare for virtiofs https://virtio-fs.gitlab.io/howto-qemu.html
-  if [[ ! -v GUEST_MEMORY ]]; then
-    _fatal 1 "${FUNCNAME[0]}: GUEST_MEMORY variable is undefined"
-  fi
+  _require_vars "GUEST_MEMORY"
 
   if [[ "${QEMU_PARAMS[*]}" != *"memory-backend-file"* ]]; then
     QEMU_PARAMS+=("-object" "memory-backend-file,id=mem,size=${GUEST_MEMORY},mem-path=/dev/shm,share=on")

From 7747f4fb76dacb75b5f473abe614958a639c5741 Mon Sep 17 00:00:00 2001
From: Joel Granados <joel.granados@kernel.org>
Date: Mon, 23 Jun 2025 20:09:55 +0200
Subject: [PATCH 07/12] nixvm: Add all the nix commands to VMPRE

Signed-off-by: Joel Granados <joel.granados@kernel.org>
---
 lib/qemu/nix | 27 +++++++--------------------
 1 file changed, 7 insertions(+), 20 deletions(-)

diff --git a/lib/qemu/nix b/lib/qemu/nix
index 89ee688..80660a1 100644
--- a/lib/qemu/nix
+++ b/lib/qemu/nix
@@ -15,18 +15,12 @@ _qemu_nix_create_nix_sys () {
     _fatal 1 "${FUNCNAME[0]}: File not found (${NIX_FLAKE_PATH})"
   fi
 
-  if ! cp -f "${NIX_FLAKE_PATH}" "${flake_dst_path}"; then
-    _fatal 1 "${FUNCNAME[0]}: Error copying \
-      src:(${NIX_FLAKE_PATH}) dest:(${flake_dst_path})"
-  fi
+  _add_pre_cmd "cp -f \"${NIX_FLAKE_PATH}\" \"${flake_dst_path}\""
 
-  local nix_build_cmd="nix build \
+  _add_pre_cmd "nix build \
     'path:${flake_dst_dir}#${flake_attr_path}' \
     -o \"${dst_path}\" \
     --no-write-lock-file"
-  if ! eval "${nix_build_cmd}"; then
-    _fatal 1 "${FUNCNAME[0]}: Error running '${nix_build_cmd}'"
-  fi
 }
 
 _qemu_nix_create_nix_init () {
@@ -41,26 +35,19 @@ _qemu_nix_create_nix_init () {
 
   local make_path="${state_dir}/Makefile"
   if [[ ! -f ${make_path} ]]; then
-    if ! ln -s "${BASEDIR}/contrib/nix/Makefile" "${make_path}"; then
-      _fatal 1 "${FUNCNAME[0]}: Error creating sym link for ${make_path}"
-    fi
+    _add_pre_cmd "ln -s \"${BASEDIR}/contrib/nix/Makefile\" \"${make_path}\""
   fi
 
   local c_init_path="${state_dir}/vmctl_init.c"
   if [[ ! -f ${c_init_path} ]]; then
-    if ! ln -s "${BASEDIR}/contrib/nix/vmctl_init.c" "${c_init_path}"; then
-      _fatal 1 "${FUNCNAME[0]}: Error creating sym link for ${c_init_path}"
-    fi
+    _add_pre_cmd "ln -s \"${BASEDIR}/contrib/nix/vmctl_init.c\" \"${c_init_path}\""
   fi
 
   if [[ ${NIX_INIT_REBUILD} == "yes" ]]; then
-    if ! make -C "${state_dir}" clean; then
-      _fatal 1 "${FUNCNAME[0]}: Error cleaning ${c_init_path}"
-    fi
-  fi
-  if ! make -C "${state_dir}" all; then
-    _fatal 1 "${FUNCNAME[0]}: Error compiling ${c_init_path}"
+    _add_pre_cmd "make -C \"${state_dir}\" clean"
   fi
+
+  _add_pre_cmd "make -C \"${state_dir}\" all"
 }
 
 qemu_nix_add_noimgnix () {

From fa6be13d2f1c964861ac9de85b6b26181859c3b9 Mon Sep 17 00:00:00 2001
From: Joel Granados <joel.granados@kernel.org>
Date: Mon, 23 Jun 2025 20:27:30 +0200
Subject: [PATCH 08/12] treewide: use _require_path for path check that fail
 when missing

Signed-off-by: Joel Granados <joel.granados@kernel.org>
---
 cmd/env        | 4 +---
 cmd/run        | 5 +----
 common/rc      | 2 +-
 lib/qemu/share | 4 +---
 vmctl          | 5 +----
 5 files changed, 5 insertions(+), 15 deletions(-)

diff --git a/cmd/env b/cmd/env
index cb27fc3..08b0fa3 100644
--- a/cmd/env
+++ b/cmd/env
@@ -52,9 +52,7 @@ _env() {
     _require_program socat
 
     exampledir="${BASEDIR}/examples/vm"
-    if [[ ! -d ${exampledir} ]]; then
-      _fatal 1 "Example dir (${exampledir}) not found."
-    fi
+    _require_path "${exampledir}"
 
     if [ ! -d "${bootstrap_dir}" ]; then
       if ! mkdir --parent ${verbose} "${bootstrap_dir}"; then
diff --git a/cmd/run b/cmd/run
index 00f2fce..491b6a3 100644
--- a/cmd/run
+++ b/cmd/run
@@ -50,10 +50,7 @@ _run() {
     case "$1" in
       '-k' | '--kernel-dir' )
         GUEST_KERNEL_CUSTOM_DIR="$2"; shift 2
-
-        if [[ ! -d "${GUEST_KERNEL_CUSTOM_DIR}" ]]; then
-          _fatal 1 "no such directory: '${GUEST_KERNEL_CUSTOM_DIR}'"
-        fi
+        _require_path "${GUEST_KERNEL_CUSTOM_DIR}"
         ;;
 
       '-c' | '--cloud-init' )
diff --git a/common/rc b/common/rc
index 1a38436..5c1c7f7 100644
--- a/common/rc
+++ b/common/rc
@@ -130,7 +130,7 @@ _require_program() {
 }
 
 _require_path() {
-  local rpath="$1"; shift
+  local rpath="$1"
 
   if [[ ! -d "${rpath}" ]]; then
     _fatal 1 "Path not found (${rpath}). $*"
diff --git a/lib/qemu/share b/lib/qemu/share
index b2d15df..5d21276 100644
--- a/lib/qemu/share
+++ b/lib/qemu/share
@@ -77,9 +77,7 @@ qemu_share_add() {
     _fatal 1 "${FUNCNAME[0]}: missing required '--shared-dir' argument"
   fi
 
-  if [[ ! -d ${shared_dir} ]]; then
-    _fatal 1 "${FUNCNAME[0]}: ${shared_dir} does not exist"
-  fi
+  _require_path "${shared_dir}"
 
   if [[ ! -v tag ]]; then
     _fatal 1 "${FUNCNAME[0]}: missing required '--tag' argument"
diff --git a/vmctl b/vmctl
index 8b6b94f..262f1b5 100755
--- a/vmctl
+++ b/vmctl
@@ -73,11 +73,8 @@ _main() {
         ;;
 
       '-b' | '--basedir' )
-        if [[ ! -d "$2" ]]; then
-          _fatal 1 "invalid base directory '$2'"
-        fi
-
         VMCTL_VMROOT="$2"; shift 2
+        _require_path "${VMCTL_VMROOT}"
         ;;
 
       '-h' | '--help' )

From d6ac4019362cd984aa73d785c98508b3da00f23d Mon Sep 17 00:00:00 2001
From: Joel Granados <joel.granados@kernel.org>
Date: Thu, 26 Jun 2025 11:54:31 +0200
Subject: [PATCH 09/12] kern: Move kernel path check to qemu_kernel_setup

Signed-off-by: Joel Granados <joel.granados@kernel.org>
---
 cmd/run       | 1 -
 lib/qemu/kern | 1 +
 2 files changed, 1 insertion(+), 1 deletion(-)

diff --git a/cmd/run b/cmd/run
index 491b6a3..25199ee 100644
--- a/cmd/run
+++ b/cmd/run
@@ -50,7 +50,6 @@ _run() {
     case "$1" in
       '-k' | '--kernel-dir' )
         GUEST_KERNEL_CUSTOM_DIR="$2"; shift 2
-        _require_path "${GUEST_KERNEL_CUSTOM_DIR}"
         ;;
 
       '-c' | '--cloud-init' )
diff --git a/lib/qemu/kern b/lib/qemu/kern
index c99f7ba..6e8dde3 100644
--- a/lib/qemu/kern
+++ b/lib/qemu/kern
@@ -36,6 +36,7 @@ qemu_kernel_setup() {
     return
   fi
 
+  _require_path "${GUEST_KERNEL_CUSTOM_DIR}"
   _require_vars "GUEST_KERNEL_IMAGE GUEST_KERNEL_CONSOLE"
 
   if [[ -v NIX_STORE_PATH ]]; then

From 858b6db7117f696fef0c883cffb3b570557f57f1 Mon Sep 17 00:00:00 2001
From: Joel Granados <joel.granados@kernel.org>
Date: Thu, 26 Jun 2025 11:55:02 +0200
Subject: [PATCH 10/12] nixvm: create a nixstage staging dir to avoid nix build
 errors

Signed-off-by: Joel Granados <joel.granados@kernel.org>
---
 lib/qemu/nix | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/lib/qemu/nix b/lib/qemu/nix
index 80660a1..0bddfeb 100644
--- a/lib/qemu/nix
+++ b/lib/qemu/nix
@@ -7,7 +7,7 @@
 _qemu_nix_create_nix_sys () {
   local dst_path="$1"
   local flake_attr_path="nixosConfigurations.vm.config.system.build.toplevel"
-  local flake_dst_dir="${VMSTATE}"
+  local flake_dst_dir="${VMSTATE}/nixstage"
   local flake_dst_path="${flake_dst_dir}/flake.nix"
 
   : "${NIX_FLAKE_PATH:="${BASEDIR}/contrib/nix/x86_64-noimgnix-base.nix"}"
@@ -15,6 +15,7 @@ _qemu_nix_create_nix_sys () {
     _fatal 1 "${FUNCNAME[0]}: File not found (${NIX_FLAKE_PATH})"
   fi
 
+  _add_pre_cmd "mkdir -p \"${flake_dst_dir}\""
   _add_pre_cmd "cp -f \"${NIX_FLAKE_PATH}\" \"${flake_dst_path}\""
 
   _add_pre_cmd "nix build \
@@ -56,7 +57,7 @@ qemu_nix_add_noimgnix () {
   _require_vars "VMSTATE"
 
   local nixsys_link="${VMSTATE}/nixsys"
-  local nixsys_path=""; nixsys_path="$(readlink "${nixsys_link}")"
+  local nixsys_path=""; nixsys_path="$(readlink -f "${nixsys_link}")"
   : "${NIX_SYS_BUILD_FORCE:="no"}" # defaults to "no" if not set
   if [[ ${NIX_SYS_BUILD_FORCE} == "yes" || ! -h ${nixsys_link} ]]; then
     _qemu_nix_create_nix_sys "${nixsys_link}"

From 6cb071a93b00921c6df9bf19ae27767e6735e65b Mon Sep 17 00:00:00 2001
From: Joel Granados <joel.granados@kernel.org>
Date: Mon, 30 Jun 2025 14:07:55 +0200
Subject: [PATCH 11/12] kern: Replace the kernel dir after we source the config
 file

Signed-off-by: Joel Granados <joel.granados@kernel.org>
---
 cmd/run | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/cmd/run b/cmd/run
index 25199ee..2951f20 100644
--- a/cmd/run
+++ b/cmd/run
@@ -49,7 +49,7 @@ _run() {
   while true; do
     case "$1" in
       '-k' | '--kernel-dir' )
-        GUEST_KERNEL_CUSTOM_DIR="$2"; shift 2
+        local kernel_dir="$2" ; shift 2
         ;;
 
       '-c' | '--cloud-init' )
@@ -140,6 +140,9 @@ _run() {
 
   QEMU_PARAMS+=("-pidfile" "${VMROOT}/run/${VMNAME}/pidfile")
 
+  if [[ -v kernel_dir ]]; then
+    GUEST_KERNEL_CUSTOM_DIR="${kernel_dir}"
+  fi
   qemu_kernel_setup
 
   if [[ -v do_background ]]; then

From e68b90e7bdef298617ca83e04db1b9fe58bdf06f Mon Sep 17 00:00:00 2001
From: Joel Granados <joel.granados@kernel.org>
Date: Wed, 2 Jul 2025 21:42:17 +0200
Subject: [PATCH 12/12] shellcheck: silence GUEST_KERNEL_CUSTOM_DIR

Signed-off-by: Joel Granados <joel.granados@kernel.org>
---
 common/shellcheck | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/common/shellcheck b/common/shellcheck
index 73629e8..c585dfb 100644
--- a/common/shellcheck
+++ b/common/shellcheck
@@ -6,5 +6,9 @@
 
 # suppress unused global variable warnings
 _silence_sc2034() {
-  echo "$QEMU_SYSTEM_BINARY $QEMU_TRACE_EVENTS ${GUEST_KERNEL_CMDLINE[*]} $RESET" > /dev/null
+  echo "$QEMU_SYSTEM_BINARY \
+    $QEMU_TRACE_EVENTS \
+    ${GUEST_KERNEL_CMDLINE[*]} \
+    $RESET \
+    $GUEST_KERNEL_CUSTOM_DIR " > /dev/null
 }