configs/qemu_riscv64_nommu_virt_defconfig: new defconfig

Add RISC-V 64-bit nommu defconfig for QEMU virt machine with MMU
disabled.

Unlike qemu_riscv64_virt, qemu_riscv64_nommu_virt does not use OpenSBI,
since the kernel is running in machine mode (M-mode).

After the build is complete, you can start QEMU using the launcher
script:
$ output/images/start-qemu.sh

Signed-off-by: Niklas Cassel <niklas.cassel@wdc.com>
Signed-off-by: Damien Le Moal <damien.lemoal@opensource.wdc.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

DEVELOPERS

@@ -2153,6 +2153,9 @@ N:	Nicolas Serafini <nicolas.serafini@ik.me>
 F:	package/exiv2/
 F:	package/ofono/
 
+N:	Niklas Cassel <niklas.cassel@wdc.com>
+F:	configs/qemu_riscv64_nommu_virt_defconfig
+
 N:	Nikolay Dimitrov <nikolay.dimitrov@retrohub.org>
 F:	board/embest/riotboard/
 F:	configs/riotboard_defconfig

board/qemu/riscv64-virt/readme.txt

@@ -2,4 +2,6 @@ Run Linux in emulation with:
 
   qemu-system-riscv64 -M virt -bios output/images/fw_jump.elf -kernel output/images/Image -append "rootwait root=/dev/vda ro" -drive file=output/images/rootfs.ext2,format=raw,id=hd0 -device virtio-blk-device,drive=hd0 -netdev user,id=net0 -device virtio-net-device,netdev=net0 -nographic # qemu_riscv64_virt_defconfig
 
+  qemu-system-riscv64 -M virt -bios none -kernel output/images/Image -append "rootwait root=/dev/vda ro" -drive file=output/images/rootfs.ext2,format=raw,id=hd0 -device virtio-blk-device,drive=hd0 -nographic -cpu rv64,mmu=off # qemu_riscv64_nommu_virt_defconfig
+
 The login prompt will appear in the terminal that started Qemu.

configs/qemu_riscv64_nommu_virt_defconfig

@@ -0,0 +1,37 @@
+# Architecture
+BR2_riscv=y
+BR2_RISCV_64=y
+
+# Patches
+BR2_GLOBAL_PATCH_DIR="board/riscv/nommu/patches"
+
+# Toolchain
+BR2_PACKAGE_HOST_ELF2FLT=y
+# BR2_USE_MMU is not set
+
+# Busybox with hush
+BR2_PACKAGE_BUSYBOX_CONFIG="package/busybox/busybox-minimal.config"
+
+# System
+BR2_TARGET_GENERIC_GETTY=y
+
+# Filesystem
+BR2_TARGET_ROOTFS_EXT2=y
+
+# Image
+BR2_ROOTFS_POST_IMAGE_SCRIPT="board/qemu/post-image.sh"
+BR2_ROOTFS_POST_SCRIPT_ARGS="$(BR2_DEFCONFIG)"
+
+# Kernel
+BR2_LINUX_KERNEL=y
+BR2_LINUX_KERNEL_CUSTOM_VERSION=y
+BR2_LINUX_KERNEL_CUSTOM_VERSION_VALUE="5.18"
+BR2_LINUX_KERNEL_DEFCONFIG="nommu_virt"
+BR2_LINUX_KERNEL_IMAGE=y
+
+# Disable network scripts
+# BR2_PACKAGE_IFUPDOWN_SCRIPTS is not set
+
+# host-qemu for gitlab testing
+BR2_PACKAGE_HOST_QEMU=y
+BR2_PACKAGE_HOST_QEMU_SYSTEM_MODE=y