bak

README.adoc

@@ -1295,7 +1295,24 @@ In the background, it uses `BR2_TARGET_ROOTFS_INITRAMFS`, and this makes the ker
 
 http://nairobi-embedded.org/initramfs_tutorial.html shows a full manual setup.
 
-== ftrace
+== Linux kernel
+
+=== Use your own .config
+
+By default, we use a `.config` that is a mixture of:
+
+* Buildroot's minimal per machine `.config`, which has the minimal options needed to boot
+* our link:kernel_config_fragment[] which enables options we want to play with
+
+If you want to just use your own exact `.config` instead, do:
+
+....
+./build -K myconfig
+....
+
+Beware that Buildroot can `sed` override some of the configurations we make no matter what, e.g. it forces `CONFIG_BLK_DEV_INITRD=y` when `BR2_TARGET_ROOTFS_CPIO` is on.
+
+=== ftrace
 
 Trace a single function:
 
@@ -1390,7 +1407,11 @@ TODO: what do `+` and `!` mean?
 
 Each `enable` under the `events/` tree enables a certain set of functions, the higher the `enable` more functions are enabled.
 
-== Snapshot
+== QEMU
+
+Some QEMU specific features to play with and limitations to cry over.
+
+=== Snapshot
 
 https://stackoverflow.com/questions/40227651/does-qemu-emulator-have-checkpoint-function/48724371#48724371
 
@@ -1467,10 +1488,6 @@ This is useful to learn:
 
 To get started, have a look at the "Hardware device drivers" section under link:kernel_module/README.adoc[], and try to run those modules, and then grep the QEMU source code.
 
-== QEMU
-
-Some QEMU specific features to play with and limitations to cry over.
-
 === 9P
 
 This protocol allows sharing a mountable filesystem between guest and host.
@@ -1479,7 +1496,7 @@ With networking, it's boring, we can just use any of the old tools like sshfs an
 
 https://superuser.com/questions/628169/how-to-share-a-directory-with-the-host-without-networking-in-qemu
 
-One advantage of this method over NFS is that can run without `sudo` on host, or having to pass host cretendials on guest for sshfs.
+One advantage of this method over NFS is that can run without `sudo` on host, or having to pass host credentials on guest for sshfs.
 
 TODO performance compared to NFS.
 
@@ -1541,8 +1558,15 @@ and on `aarch64`:
 mount: mounting host0 on /mnt/my9p failed: Invalid argument
 ....
 
+and dmesg gives:
+
+....
+9pnet_virtio: no channels available for device
+....
+
 A few hits:
 
+* https://lists.gnu.org/archive/html/qemu-devel/2013-08/msg00044.html
 * https://superuser.com/questions/502205/libvirt-9p-kvm-mount-in-fstab-fails-to-mount-at-boot-time
 
 ==== 9P gem5

build

@@ -8,10 +8,11 @@ config_fragments='buildroot_config_fragment buildroot_config_fragment_cli'
 extra_make_args=''
 gem5=false
 j="$(($(nproc) - 2))"
+linux_kernel_custom_config_file=''
 post_script_args=''
 qemu_sdl='--enable-sdl --with-sdlabi=2.0'
 v=0
-while getopts 'a:c:Cgj:i:klp:qS:v' OPT; do
+while getopts 'a:c:Cgj:i:kK:lp:qS:v' OPT; do
   case "$OPT" in
     a)
       arch="$OPTARG"
@@ -34,6 +35,9 @@ while getopts 'a:c:Cgj:i:klp:qS:v' OPT; do
     k)
       extra_make_args="$extra_make_args kernel_module-reconfigure"
     ;;
+    K)
+      linux_kernel_custom_config_file="$OPTARG"
+    ;;
     l)
       extra_make_args="$extra_make_args linux-reconfigure"
     ;;
@@ -96,20 +100,26 @@ BR2_JLEVEL=$j
 BR2_ROOTFS_POST_SCRIPT_ARGS=\"$post_script_args\"
 " >> "${config_file}"
   if "$gem5"; then
-    printf "\
-BR2_LINUX_KERNEL_CUSTOM_CONFIG_FILE=\"../kernel_config_${arch_dir}\"
-BR2_PACKAGE_GEM5=y
-" >> "${config_file}"
+    if [ -z "$linux_kernel_custom_config_file" ]; then
+      printf "BR2_LINUX_KERNEL_CUSTOM_CONFIG_FILE=\"../kernel_config_${arch_dir}\"" >> "${config_file}"
+    fi
+    printf "BR2_PACKAGE_GEM5=\"../kernel_config_${arch_dir}\"" >> "${config_file}"
   else
-    printf "\
-BR2_LINUX_KERNEL_CONFIG_FRAGMENT_FILES=\"../kernel_config_fragment\"
-" >> "${config_file}"
+    if [ -z "$linux_kernel_custom_config_file" ]; then
+      printf "BR2_LINUX_KERNEL_CONFIG_FRAGMENT_FILES=\"../kernel_config_fragment\"" >> "${config_file}"
+    fi
   fi
   if [ "$arch" = 'mips64' ]; then
     # Workaround for:
     # http://lists.busybox.net/pipermail/buildroot/2017-August/201053.html
     sed -Ei 's/^BR2_PACKAGE_LINUX_TOOLS_GPIO/BR2_PACKAGE_LINUX_TOOLS_GPIO=n/' "${config_file}"
   fi
+  # TODO why is this needed. Otherwise kernel .config does not change, even though Buildroot
+  # .config did due to -K. even if we are running linux-kernel-reconfigure!
+  rm -f "${out_dir}/build/linux-custom/.config"
+  if [ -n "$linux_kernel_custom_config_file" ]; then
+    printf "BR2_LINUX_KERNEL_CUSTOM_CONFIG_FILE=\"../${linux_kernel_custom_config_file}\"" >> "${config_file}"
+  fi
   make O="$out_dir" olddefconfig
 fi
 

kernel_config_fragment

@@ -1,8 +1,5 @@
 # Changes to this file are automatically trigger kernel reconfigures
 # even without using the linux-reconfigure target.
-#
-# Beware that buildroot can override some of the configurations we make, e.g.
-# it forces CONFIG_BLK_DEV_INITRD=y when BR2_TARGET_ROOTFS_CPIO is on.
 
 CONFIG_MODULE_SRCVERSION_ALL=y
 CONFIG_BLK_DEV_INITRD=y
@@ -69,13 +66,16 @@ CONFIG_NET_9P=y
 CONFIG_NET_9P_DEBUG=y
 CONFIG_NET_9P_VIRTIO=y
 
-## Virtio. TODO: aarch64 hangs before boot if I do all of these.
+## Virtio
+CONFIG_VIRTIO_PCI=y
+CONFIG_VFIO_PCI_INTX=y
+CONFIG_VFIO_PCI_MMAP=y
+# TODO: aarch64 hangs before boot if I do all of these.
 #CONFIG_RPMSG_VIRTIO=y
 #CONFIG_VIRTIO_BALLOON=y
 #CONFIG_VIRTIO_BLK=y
 #CONFIG_VIRTIO_BLK_SCSI=y
 #CONFIG_VIRTIO_INPUT=y
-#CONFIG_VIRTIO_PCI=y
 #CONFIG_VIRTIO_VSOCKETS=y
 
 ## Networking

rootfs_overlay/etc/init.d/S98

@@ -1,6 +1,7 @@
 #!/bin/sh
 echo "hello S98"
 if [ -n "$lkmc_eval" ]; then
+	echo "$lkmc_eval"
   eval "$lkmc_eval"
 fi
 exit 0