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References: <20220430090518.3127980-1-chenhuacai@loongson.cn>
 <20220430090518.3127980-6-chenhuacai@loongson.cn> <3f46aa25-ef45-fff8-dba5-5db1034b38d9@xen0n.name>
In-Reply-To: <3f46aa25-ef45-fff8-dba5-5db1034b38d9@xen0n.name>
From:   Huacai Chen <chenhuacai@gmail.com>
Date:   Sun, 1 May 2022 20:41:46 +0800
Message-ID: <CAAhV-H7xR_4ib29Kaw3jBX5P=Mu70Lbts26hiPoht94Ouumh=g@mail.gmail.com>
Subject: Re: [PATCH V9 05/24] LoongArch: Add build infrastructure
To:     WANG Xuerui <kernel@xen0n.name>
Cc:     Huacai Chen <chenhuacai@loongson.cn>,
        Arnd Bergmann <arnd@arndb.de>,
        Andy Lutomirski <luto@kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Peter Zijlstra <peterz@infradead.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        David Airlie <airlied@linux.ie>,
        Jonathan Corbet <corbet@lwn.net>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        linux-arch <linux-arch@vger.kernel.org>,
        "open list:DOCUMENTATION" <linux-doc@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Xuefeng Li <lixuefeng@loongson.cn>,
        Yanteng Si <siyanteng@loongson.cn>,
        Guo Ren <guoren@kernel.org>,
        Jiaxun Yang <jiaxun.yang@flygoat.com>
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

Hi, Xuerui,

On Sun, May 1, 2022 at 6:09 PM WANG Xuerui <kernel@xen0n.name> wrote:
>
>
> On 4/30/22 17:04, Huacai Chen wrote:
> > This patch adds Kbuild, Makefile, Kconfig and link script for LoongArch
> > build infrastructure.
> >
> > Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
> > ---
> >   arch/loongarch/.gitignore              |   9 +
> >   arch/loongarch/Kbuild                  |   3 +
> >   arch/loongarch/Kconfig                 | 351 +++++++++++++++++++++++++
> >   arch/loongarch/Kconfig.debug           |   0
> >   arch/loongarch/Makefile                |  99 +++++++
> >   arch/loongarch/include/asm/Kbuild      |  29 ++
> >   arch/loongarch/include/uapi/asm/Kbuild |   2 +
> >   arch/loongarch/kernel/Makefile         |  22 ++
> >   arch/loongarch/kernel/vmlinux.lds.S    | 100 +++++++
> >   arch/loongarch/lib/Makefile            |   7 +
> >   arch/loongarch/mm/Makefile             |   9 +
> >   arch/loongarch/pci/Makefile            |   7 +
> >   scripts/subarch.include                |   2 +-
> >   13 files changed, 639 insertions(+), 1 deletion(-)
> >   create mode 100644 arch/loongarch/.gitignore
> >   create mode 100644 arch/loongarch/Kbuild
> >   create mode 100644 arch/loongarch/Kconfig
> >   create mode 100644 arch/loongarch/Kconfig.debug
> >   create mode 100644 arch/loongarch/Makefile
> >   create mode 100644 arch/loongarch/include/asm/Kbuild
> >   create mode 100644 arch/loongarch/include/uapi/asm/Kbuild
> >   create mode 100644 arch/loongarch/kernel/Makefile
> >   create mode 100644 arch/loongarch/kernel/vmlinux.lds.S
> >   create mode 100644 arch/loongarch/lib/Makefile
> >   create mode 100644 arch/loongarch/mm/Makefile
> >   create mode 100644 arch/loongarch/pci/Makefile
> >
> > diff --git a/arch/loongarch/.gitignore b/arch/loongarch/.gitignore
> > new file mode 100644
> > index 000000000000..fd88d21e7172
> > --- /dev/null
> > +++ b/arch/loongarch/.gitignore
> > @@ -0,0 +1,9 @@
> > +*.lds
> > +*.raw
> > +calc_vmlinuz_load_addr
> > +elf-entry
> > +relocs
> > +vmlinux*
> > +vmlinuz*
> > +
> > +!kernel/vmlinux.lds.S
> This exclude entry is unnecessary?
> > diff --git a/arch/loongarch/Kbuild b/arch/loongarch/Kbuild
> > new file mode 100644
> > index 000000000000..1ad35aabdd16
> > --- /dev/null
> > +++ b/arch/loongarch/Kbuild
> > @@ -0,0 +1,3 @@
> > +obj-y += kernel/
> > +obj-y += mm/
> > +obj-y += vdso/
> > diff --git a/arch/loongarch/Kconfig b/arch/loongarch/Kconfig
> > new file mode 100644
> > index 000000000000..44b763046893
> > --- /dev/null
> > +++ b/arch/loongarch/Kconfig
> > @@ -0,0 +1,351 @@
> > +# SPDX-License-Identifier: GPL-2.0
> > +config LOONGARCH
> > +     bool
> > +     default y
> > +     select ACPI_MCFG if ACPI
> > +     select ACPI_SYSTEM_POWER_STATES_SUPPORT if ACPI
> > +     select ARCH_BINFMT_ELF_STATE
> > +     select ARCH_ENABLE_MEMORY_HOTPLUG
> > +     select ARCH_ENABLE_MEMORY_HOTREMOVE
> > +     select ARCH_HAS_ACPI_TABLE_UPGRADE      if ACPI
> > +     select ARCH_HAS_PTE_SPECIAL
> > +     select ARCH_HAS_TICK_BROADCAST if GENERIC_CLOCKEVENTS_BROADCAST
> > +     select ARCH_INLINE_READ_LOCK if !PREEMPTION
> > +     select ARCH_INLINE_READ_LOCK_BH if !PREEMPTION
> > +     select ARCH_INLINE_READ_LOCK_IRQ if !PREEMPTION
> > +     select ARCH_INLINE_READ_LOCK_IRQSAVE if !PREEMPTION
> > +     select ARCH_INLINE_READ_UNLOCK if !PREEMPTION
> > +     select ARCH_INLINE_READ_UNLOCK_BH if !PREEMPTION
> > +     select ARCH_INLINE_READ_UNLOCK_IRQ if !PREEMPTION
> > +     select ARCH_INLINE_READ_UNLOCK_IRQRESTORE if !PREEMPTION
> > +     select ARCH_INLINE_WRITE_LOCK if !PREEMPTION
> > +     select ARCH_INLINE_WRITE_LOCK_BH if !PREEMPTION
> > +     select ARCH_INLINE_WRITE_LOCK_IRQ if !PREEMPTION
> > +     select ARCH_INLINE_WRITE_LOCK_IRQSAVE if !PREEMPTION
> > +     select ARCH_INLINE_WRITE_UNLOCK if !PREEMPTION
> > +     select ARCH_INLINE_WRITE_UNLOCK_BH if !PREEMPTION
> > +     select ARCH_INLINE_WRITE_UNLOCK_IRQ if !PREEMPTION
> > +     select ARCH_INLINE_WRITE_UNLOCK_IRQRESTORE if !PREEMPTION
> > +     select ARCH_INLINE_SPIN_TRYLOCK if !PREEMPTION
> > +     select ARCH_INLINE_SPIN_TRYLOCK_BH if !PREEMPTION
> > +     select ARCH_INLINE_SPIN_LOCK if !PREEMPTION
> > +     select ARCH_INLINE_SPIN_LOCK_BH if !PREEMPTION
> > +     select ARCH_INLINE_SPIN_LOCK_IRQ if !PREEMPTION
> > +     select ARCH_INLINE_SPIN_LOCK_IRQSAVE if !PREEMPTION
> > +     select ARCH_INLINE_SPIN_UNLOCK if !PREEMPTION
> > +     select ARCH_INLINE_SPIN_UNLOCK_BH if !PREEMPTION
> > +     select ARCH_INLINE_SPIN_UNLOCK_IRQ if !PREEMPTION
> > +     select ARCH_INLINE_SPIN_UNLOCK_IRQRESTORE if !PREEMPTION
> > +     select ARCH_MIGHT_HAVE_PC_PARPORT
> > +     select ARCH_MIGHT_HAVE_PC_SERIO
> > +     select ARCH_SPARSEMEM_ENABLE
> > +     select ARCH_SUPPORTS_ACPI
> > +     select ARCH_SUPPORTS_ATOMIC_RMW
> > +     select ARCH_SUPPORTS_HUGETLBFS
> > +     select ARCH_USE_BUILTIN_BSWAP
> > +     select ARCH_USE_CMPXCHG_LOCKREF
> > +     select ARCH_USE_QUEUED_RWLOCKS
> > +     select ARCH_USE_QUEUED_SPINLOCKS
> > +     select ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT
> > +     select ARCH_WANTS_NO_INSTR
> > +     select BUILDTIME_TABLE_SORT
> > +     select COMMON_CLK
> > +     select GENERIC_CLOCKEVENTS
> > +     select GENERIC_CMOS_UPDATE
> > +     select GENERIC_CPU_AUTOPROBE
> > +     select GENERIC_ENTRY
> > +     select GENERIC_FIND_FIRST_BIT
> > +     select GENERIC_GETTIMEOFDAY
> > +     select GENERIC_IRQ_MULTI_HANDLER
> > +     select GENERIC_IRQ_PROBE
> > +     select GENERIC_IRQ_SHOW
> > +     select GENERIC_LIB_ASHLDI3
> > +     select GENERIC_LIB_ASHRDI3
> > +     select GENERIC_LIB_CMPDI2
> > +     select GENERIC_LIB_LSHRDI3
> > +     select GENERIC_LIB_UCMPDI2
> > +     select GENERIC_PCI_IOMAP
> > +     select GENERIC_SCHED_CLOCK
> > +     select GENERIC_TIME_VSYSCALL
> > +     select GPIOLIB
> > +     select HAVE_ARCH_AUDITSYSCALL
> > +     select HAVE_ARCH_COMPILER_H
> > +     select HAVE_ARCH_MMAP_RND_BITS if MMU
> > +     select HAVE_ARCH_SECCOMP_FILTER
> > +     select HAVE_ARCH_TRACEHOOK
> > +     select HAVE_ARCH_TRANSPARENT_HUGEPAGE
> > +     select HAVE_ASM_MODVERSIONS
> > +     select HAVE_CONTEXT_TRACKING
> > +     select HAVE_COPY_THREAD_TLS
> > +     select HAVE_DEBUG_KMEMLEAK
> > +     select HAVE_DEBUG_STACKOVERFLOW
> > +     select HAVE_DMA_CONTIGUOUS
> > +     select HAVE_EXIT_THREAD
> > +     select HAVE_FAST_GUP
> > +     select HAVE_GENERIC_VDSO
> > +     select HAVE_IOREMAP_PROT
> > +     select HAVE_IRQ_EXIT_ON_IRQ_STACK
> > +     select HAVE_IRQ_TIME_ACCOUNTING
> > +     select HAVE_MEMBLOCK
> > +     select HAVE_MEMBLOCK_NODE_MAP
> > +     select HAVE_MOD_ARCH_SPECIFIC
> > +     select HAVE_NMI
> > +     select HAVE_PCI
> > +     select HAVE_PERF_EVENTS
> > +     select HAVE_REGS_AND_STACK_ACCESS_API
> > +     select HAVE_RSEQ
> > +     select HAVE_SYSCALL_TRACEPOINTS
> > +     select HAVE_TIF_NOHZ
> > +     select HAVE_VIRT_CPU_ACCOUNTING_GEN
> > +     select IRQ_FORCED_THREADING
> > +     select IRQ_LOONGARCH_CPU
> > +     select MODULES_USE_ELF_RELA if MODULES
> > +     select PCI
> > +     select PCI_DOMAINS_GENERIC
> > +     select PCI_ECAM if ACPI
> > +     select PCI_MSI_ARCH_FALLBACKS
> > +     select PERF_USE_VMALLOC
> > +     select RTC_LIB
> > +     select SPARSE_IRQ
> > +     select SYSCTL_EXCEPTION_TRACE
> > +     select SWIOTLB
> > +     select TRACE_IRQFLAGS_SUPPORT
> > +     select ZONE_DMA32
> > +
> > +config 32BIT
> > +     bool
> > +
> > +config 64BIT
> > +     def_bool y
> > +
> > +config CPU_HAS_FPU
> > +     bool
> > +     default y
> > +
> > +config CPU_HAS_PREFETCH
> > +     bool
> > +     default y
> > +
> > +config GENERIC_CALIBRATE_DELAY
> > +     def_bool y
> > +
> > +config GENERIC_CSUM
> > +     def_bool y
> > +
> > +config GENERIC_HWEIGHT
> > +     def_bool y
> > +
> > +config L1_CACHE_SHIFT
> > +     int
> > +     default "6"
> > +
> > +config LOCKDEP_SUPPORT
> > +     bool
> > +     default y
> > +
> > +config MACH_LOONGSON32
> > +     def_bool 32BIT
> > +
> > +config MACH_LOONGSON64
> > +     def_bool 64BIT
> These two config symbols are not used anywhere in arch/loongarch, but
> from a quick grep it seems they're sharing the names of the MIPS config
> symbols, on purpose, maybe for sharing code between the MIPS-era
> Loongson models and the LoongArch models. If so, a comment explaining
> this could be beneficial.
> > +
> > +config PAGE_SIZE_4KB
> > +     bool
> > +
> > +config PAGE_SIZE_16KB
> > +     bool
> > +
> > +config PAGE_SIZE_64KB
> > +     bool
> > +
> > +config PGTABLE_2LEVEL
> > +     bool
> > +
> > +config PGTABLE_3LEVEL
> > +     bool
> > +
> > +config PGTABLE_4LEVEL
> > +     bool
> > +
> > +config PGTABLE_LEVELS
> > +     int
> > +     default 2 if PGTABLE_2LEVEL
> > +     default 3 if PGTABLE_3LEVEL
> > +     default 4 if PGTABLE_4LEVEL
> > +
> > +config SCHED_OMIT_FRAME_POINTER
> > +     bool
> > +     default y
> > +
> > +menu "Kernel type"
> > +
> > +source "kernel/Kconfig.hz"
> > +
> > +choice
> > +     prompt "Page Table Layout"
> > +     default 16KB_2LEVEL if 32BIT
> > +     default 16KB_3LEVEL if 64BIT
> > +     help
> > +       Allows choosing the page table layout, which is a combination
> > +       of page size and page table levels. The virtual memory address
> > +       space bits are determined by the page table layout.
> "The size of virtual memory address space"?
> > +
> > +config 4KB_3LEVEL
> > +     bool "4KB with 3 levels"
> > +     select PAGE_SIZE_4KB
> > +     select PGTABLE_3LEVEL
> > +     help
> > +       This option selects 4KB page size with 3 level page tables, which
> > +       support a maximum 39 bits of application virtual memory.
> "a maximum of XX bits" -- similarly for all occurrences below.
OK, most of your suggestions will be taken.

Huacai
> > +
> > +config 4KB_4LEVEL
> > +     bool "4KB with 4 levels"
> > +     select PAGE_SIZE_4KB
> > +     select PGTABLE_4LEVEL
> > +     help
> > +       This option selects 4KB page size with 4 level page tables, which
> > +       support a maximum 48 bits of application virtual memory.
> > +
> > +config 16KB_2LEVEL
> > +     bool "16KB with 2 levels"
> > +     select PAGE_SIZE_16KB
> > +     select PGTABLE_2LEVEL
> > +     help
> > +       This option selects 16KB page size with 2 level page tables, which
> > +       support a maximum 36 bits of application virtual memory.
> > +
> > +config 16KB_3LEVEL
> > +     bool "16KB with 3 levels"
> > +     select PAGE_SIZE_16KB
> > +     select PGTABLE_3LEVEL
> > +     help
> > +       This option selects 16KB page size with 3 level page tables, which
> > +       support a maximum 47 bits of application virtual memory.
> > +
> > +config 64KB_2LEVEL
> > +     bool "64KB with 2 levels"
> > +     select PAGE_SIZE_64KB
> > +     select PGTABLE_2LEVEL
> > +     help
> > +       This option selects 64KB page size with 2 level page tables, which
> > +       support a maximum 42 bits of application virtual memory.
> > +
> > +config 64KB_3LEVEL
> > +     bool "64KB with 3 levels"
> > +     select PAGE_SIZE_64KB
> > +     select PGTABLE_3LEVEL
> > +     help
> > +       This option selects 64KB page size with 3 level page tables, which
> > +       support a maximum 55 bits of application virtual memory.
> > +
> > +endchoice
> > +
> > +config DMI
> > +     bool "Enable DMI scanning"
> > +     select DMI_SCAN_MACHINE_NON_EFI_FALLBACK
> > +     default y
> > +     help
> > +       Enabled scanning of DMI to identify machine quirks. Say Y
> Should be "Enable scanning ..." but the arch/x86 and arch/mips versions
> of this text all have this typo. Might be wise to fix here... then fix
> the other two later.
> > +       here unless you have verified that your setup is not
> > +       affected by entries in the DMI blacklist. Required by PNP
> > +       BIOS code.
> Do we have a "PNP BIOS"? I know this is also copied text, but we may
> tweak it to suit our platform.
> > +
> > +config EFI
> > +     bool "EFI runtime service support"
> > +     select UCS2_STRING
> > +     select EFI_RUNTIME_WRAPPERS
> > +     help
> > +       This enables the kernel to use EFI runtime services that are
> > +       available (such as the EFI variable services).
> > +
> > +       This option is only useful on systems that have EFI firmware.
> > +       In addition, you should use the latest ELILO loader available
> > +       at <http://elilo.sourceforge.net> in order to take advantage
> > +       of EFI runtime services. However, even with this option, the
> Remove mention of ELILO?
> > +       resultant kernel should continue to boot on existing non-EFI
> > +       platforms.
> > +
> > +config FORCE_MAX_ZONEORDER
> > +     int "Maximum zone order"
> > +     range 14 64 if PAGE_SIZE_64KB
> > +     default "14" if PAGE_SIZE_64KB
> > +     range 12 64 if PAGE_SIZE_16KB
> > +     default "12" if PAGE_SIZE_16KB
> > +     range 11 64
> > +     default "11"
> > +     help
> > +       The kernel memory allocator divides physically contiguous memory
> > +       blocks into "zones", where each zone is a power of two number of
> > +       pages.  This option selects the largest power of two that the kernel
> > +       keeps in the memory allocator.  If you need to allocate very large
> > +       blocks of physically contiguous memory, then you may need to
> > +       increase this value.
> > +
> > +       This config option is actually maximum order plus one. For example,
> > +       a value of 11 means that the largest free memory block is 2^10 pages.
> > +
> > +       The page size is not necessarily 4KB.  Keep this in mind
> > +       when choosing a value for this option.
> > +
> > +config SECCOMP
> > +     bool "Enable seccomp to safely compute untrusted bytecode"
> > +     depends on PROC_FS
> > +     default y
> > +     help
> > +       This kernel feature is useful for number crunching applications
> > +       that may need to compute untrusted bytecode during their
> > +       execution. By using pipes or other transports made available to
> > +       the process as file descriptors supporting the read/write
> > +       syscalls, it's possible to isolate those applications in
> > +       their own address space using seccomp. Once seccomp is
> > +       enabled via /proc/<pid>/seccomp, it cannot be disabled
> > +       and the task is only allowed to execute a few safe syscalls
> > +       defined by each seccomp mode.
> > +
> > +       If unsure, say Y. Only embedded should say N here.
> > +
> > +endmenu
> > +
> > +config ARCH_SELECT_MEMORY_MODEL
> > +     def_bool y
> > +
> > +config ARCH_FLATMEM_ENABLE
> > +     def_bool y
> > +
> > +config ARCH_SPARSEMEM_ENABLE
> > +     def_bool y
> > +     help
> > +       Say Y to support efficient handling of sparse physical memory,
> > +       for architectures which are either NUMA (Non-Uniform Memory Access)
> > +       or have huge holes in the physical address space for other reasons.
> > +       See <file:Documentation/vm/numa.rst> for more.
> > +
> > +config ARCH_ENABLE_THP_MIGRATION
> > +     def_bool y
> > +     depends on TRANSPARENT_HUGEPAGE
> > +
> > +config ARCH_MEMORY_PROBE
> > +     def_bool y
> > +     depends on MEMORY_HOTPLUG
> > +
> > +config MMU
> > +     bool
> > +     default y
> > +
> > +config ARCH_MMAP_RND_BITS_MIN
> > +     default 12
> > +
> > +config ARCH_MMAP_RND_BITS_MAX
> > +     default 18
> > +
> > +menu "Bus options"
> > +
> > +endmenu
> > +
> > +menu "Power management options"
> > +
> > +source "drivers/acpi/Kconfig"
> > +
> > +endmenu
> > +
> > +source "drivers/firmware/Kconfig"
> > diff --git a/arch/loongarch/Kconfig.debug b/arch/loongarch/Kconfig.debug
> > new file mode 100644
> > index 000000000000..e69de29bb2d1
> > diff --git a/arch/loongarch/Makefile b/arch/loongarch/Makefile
> > new file mode 100644
> > index 000000000000..0a40e79b3265
> > --- /dev/null
> > +++ b/arch/loongarch/Makefile
> > @@ -0,0 +1,99 @@
> > +# SPDX-License-Identifier: GPL-2.0
> > +#
> > +# Author: Huacai Chen <chenhuacai@loongson.cn>
> > +# Copyright (C) 2020-2022 Loongson Technology Corporation Limited
> > +
> > +#
> > +# Select the object file format to substitute into the linker script.
> > +#
> > +64bit-tool-archpref  = loongarch64
> > +32bit-bfd            = elf32-loongarch
> > +64bit-bfd            = elf64-loongarch
> > +32bit-emul           = elf32loongarch
> > +64bit-emul           = elf64loongarch
> > +
> > +ifdef CONFIG_64BIT
> > +tool-archpref                = $(64bit-tool-archpref)
> > +UTS_MACHINE          := loongarch64
> > +endif
> > +
> > +ifneq ($(SUBARCH),$(ARCH))
> > +  ifeq ($(CROSS_COMPILE),)
> > +    CROSS_COMPILE := $(call cc-cross-prefix, $(tool-archpref)-linux-  $(tool-archpref)-linux-gnu-  $(tool-archpref)-unknown-linux-gnu-)
> > +  endif
> > +endif
> > +
> > +cflags-y += $(call cc-option, -mno-check-zero-division)
> > +
> > +ifdef CONFIG_64BIT
> > +ld-emul                      = $(64bit-emul)
> > +cflags-y             += -mabi=lp64s
> > +endif
> > +
> > +all-y                        := vmlinux
> > +
> > +#
> > +# GCC uses -G0 -mabicalls -fpic as default.  We don't want PIC in the kernel
> > +# code since it only slows down the whole thing.  At some point we might make
> > +# use of global pointer optimizations but their use of $r2 conflicts with
> > +# the current pointer optimization.
> LoongArch doesn't have any notion of "abicalls", please remove the whole
> MIPS legacy... or at least replace with something suitable for LoongArch.
> > +#
> > +cflags-y                     += -G0 -pipe
> > +cflags-y                     += -msoft-float
> > +LDFLAGS_vmlinux                      += -G0 -static -n -nostdlib
> > +KBUILD_AFLAGS_KERNEL         += -Wa,-mla-global-with-pcrel
> > +KBUILD_CFLAGS_KERNEL         += -Wa,-mla-global-with-pcrel
> > +KBUILD_AFLAGS_MODULE         += -Wa,-mla-global-with-abs
> > +KBUILD_CFLAGS_MODULE         += -fplt -Wa,-mla-global-with-abs,-mla-local-with-abs
> These switches are the ones that should receive more love via
> comments... they are here to tell the assembler to emit the "la.global"
> and "la.local" pseudo-insns in a particular "flavor". Why not simply use
> the default? This needs explanation!
> > +
> > +cflags-y += -ffreestanding
> > +cflags-y += $(call as-option,-Wa$(comma)-mno-fix-loongson3-llsc,)
> Unfortunately we're still working around the LL/SC hardware issue even
> after migrating to LoongArch... might be better to add a comment too.
> (something along the line of "we work around the issue manually in the
> handwritten assembly, so no automatic workarounds should kick in")
> > +
> > +load-y               = 0x9000000000200000
> > +bootvars-y   = VMLINUX_LOAD_ADDRESS=$(load-y)
> > +
> > +drivers-$(CONFIG_PCI)                += arch/loongarch/pci/
> > +
> > +KBUILD_AFLAGS        += $(cflags-y)
> > +KBUILD_CFLAGS        += $(cflags-y)
> > +KBUILD_CPPFLAGS += -DVMLINUX_LOAD_ADDRESS=$(load-y)
> > +
> > +# This is required to get dwarf unwinding tables into .debug_frame
> > +# instead of .eh_frame so we don't discard them.
> > +KBUILD_CFLAGS += -fno-asynchronous-unwind-tables
> > +KBUILD_CFLAGS += -isystem $(shell $(CC) -print-file-name=include)
> > +KBUILD_CFLAGS += $(call cc-option,-mstrict-align)
> Explain reason of this -mstrict-align request -- it's because not all
> LoongArch cores support unaligned accesses, and as kernel we can't rely
> on others to provide emulation for these accesses.
> > +
> > +KBUILD_LDFLAGS       += -m $(ld-emul)
> > +
> > +ifdef CONFIG_LOONGARCH
> > +CHECKFLAGS += $(shell $(CC) $(KBUILD_CFLAGS) -dM -E -x c /dev/null | \
> > +     egrep -vw '__GNUC_(MINOR_|PATCHLEVEL_)?_' | \
> > +     sed -e "s/^\#define /-D'/" -e "s/ /'='/" -e "s/$$/'/" -e 's/\$$/&&/g')
> > +endif
> > +
> > +head-y := arch/loongarch/kernel/head.o
> > +
> > +libs-y += arch/loongarch/lib/
> > +
> > +prepare: vdso_prepare
> > +vdso_prepare: prepare0
> > +     $(Q)$(MAKE) $(build)=arch/loongarch/vdso include/generated/vdso-offsets.h
> > +
> > +PHONY += vdso_install
> > +vdso_install:
> > +     $(Q)$(MAKE) $(build)=arch/loongarch/vdso $@
> > +
> > +all: $(all-y)
> > +
> > +CLEAN_FILES += vmlinux
> > +
> > +install:
> > +     $(Q)install -D -m 755 vmlinux $(INSTALL_PATH)/vmlinux-$(KERNELRELEASE)
> > +     $(Q)install -D -m 644 .config $(INSTALL_PATH)/config-$(KERNELRELEASE)
> > +     $(Q)install -D -m 644 System.map $(INSTALL_PATH)/System.map-$(KERNELRELEASE)
> > +
> > +define archhelp
> > +     echo '  install              - install kernel into $(INSTALL_PATH)'
> > +     echo
> > +endef
> > diff --git a/arch/loongarch/include/asm/Kbuild b/arch/loongarch/include/asm/Kbuild
> > new file mode 100644
> > index 000000000000..a0eed6076c79
> > --- /dev/null
> > +++ b/arch/loongarch/include/asm/Kbuild
> > @@ -0,0 +1,29 @@
> > +# SPDX-License-Identifier: GPL-2.0
> > +generic-y += dma-contiguous.h
> > +generic-y += export.h
> > +generic-y += mcs_spinlock.h
> > +generic-y += parport.h
> > +generic-y += early_ioremap.h
> > +generic-y += qrwlock.h
> > +generic-y += qspinlock.h
> > +generic-y += rwsem.h
> > +generic-y += segment.h
> > +generic-y += user.h
> > +generic-y += stat.h
> > +generic-y += fcntl.h
> > +generic-y += ioctl.h
> > +generic-y += ioctls.h
> > +generic-y += mman.h
> > +generic-y += msgbuf.h
> > +generic-y += sembuf.h
> > +generic-y += shmbuf.h
> > +generic-y += statfs.h
> > +generic-y += socket.h
> > +generic-y += sockios.h
> > +generic-y += termios.h
> > +generic-y += termbits.h
> > +generic-y += poll.h
> > +generic-y += param.h
> > +generic-y += posix_types.h
> > +generic-y += resource.h
> > +generic-y += kvm_para.h
> > diff --git a/arch/loongarch/include/uapi/asm/Kbuild b/arch/loongarch/include/uapi/asm/Kbuild
> > new file mode 100644
> > index 000000000000..4aa680ca2e5f
> > --- /dev/null
> > +++ b/arch/loongarch/include/uapi/asm/Kbuild
> > @@ -0,0 +1,2 @@
> > +# SPDX-License-Identifier: GPL-2.0
> > +generic-y += kvm_para.h
> > diff --git a/arch/loongarch/kernel/Makefile b/arch/loongarch/kernel/Makefile
> > new file mode 100644
> > index 000000000000..ead27a11e8e0
> > --- /dev/null
> > +++ b/arch/loongarch/kernel/Makefile
> > @@ -0,0 +1,22 @@
> > +# SPDX-License-Identifier: GPL-2.0
> > +#
> > +# Makefile for the Linux/LoongArch kernel.
> > +#
> > +
> > +extra-y              := head.o vmlinux.lds
> > +
> > +obj-y                += cpu-probe.o cacheinfo.o cmdline.o env.o setup.o entry.o genex.o \
> > +                traps.o irq.o idle.o process.o dma.o mem.o io.o reset.o switch.o \
> > +                elf.o rtc.o syscall.o signal.o time.o topology.o cmpxchg.o \
> > +                inst.o ptrace.o vdso.o
> > +
> > +obj-$(CONFIG_ACPI)           += acpi.o
> > +obj-$(CONFIG_EFI)            += efi.o
> > +
> > +obj-$(CONFIG_CPU_HAS_FPU)    += fpu.o
> > +
> > +obj-$(CONFIG_MODULES)                += module.o module-sections.o
> > +
> > +obj-$(CONFIG_PROC_FS)                += proc.o
> > +
> > +CPPFLAGS_vmlinux.lds         := $(KBUILD_CFLAGS)
> > diff --git a/arch/loongarch/kernel/vmlinux.lds.S b/arch/loongarch/kernel/vmlinux.lds.S
> > new file mode 100644
> > index 000000000000..02abfaaa4892
> > --- /dev/null
> > +++ b/arch/loongarch/kernel/vmlinux.lds.S
> > @@ -0,0 +1,100 @@
> > +/* SPDX-License-Identifier: GPL-2.0 */
> > +#include <linux/sizes.h>
> > +#include <asm/asm-offsets.h>
> > +#include <asm/thread_info.h>
> > +
> > +#define PAGE_SIZE _PAGE_SIZE
> > +
> > +/*
> > + * Put .bss..swapper_pg_dir as the first thing in .bss. This will
> > + * ensure that it has .bss alignment (64K).
> > + */
> > +#define BSS_FIRST_SECTIONS *(.bss..swapper_pg_dir)
> > +
> > +#include <asm-generic/vmlinux.lds.h>
> > +
> > +OUTPUT_ARCH(loongarch)
> > +ENTRY(kernel_entry)
> > +PHDRS {
> > +     text PT_LOAD FLAGS(7);  /* RWX */
> > +     note PT_NOTE FLAGS(4);  /* R__ */
> > +}
> > +
> > +jiffies       = jiffies_64;
> > +
> > +SECTIONS
> > +{
> > +     . = VMLINUX_LOAD_ADDRESS;
> > +
> > +     _text = .;
> > +     .text : {
> > +             TEXT_TEXT
> > +             SCHED_TEXT
> > +             CPUIDLE_TEXT
> > +             LOCK_TEXT
> > +             KPROBES_TEXT
> > +             IRQENTRY_TEXT
> > +             SOFTIRQENTRY_TEXT
> > +             *(.fixup)
> > +             *(.gnu.warning)
> > +     } :text = 0
> > +     _etext = .;
> > +
> > +     EXCEPTION_TABLE(16)
> > +
> > +     . = ALIGN(PAGE_SIZE);
> > +     __init_begin = .;
> > +     __inittext_begin = .;
> > +
> > +     INIT_TEXT_SECTION(PAGE_SIZE)
> > +     .exit.text : {
> > +             EXIT_TEXT
> > +     }
> > +
> > +     __inittext_end = .;
> > +
> > +     __initdata_begin = .;
> > +
> > +     INIT_DATA_SECTION(16)
> > +     .exit.data : {
> > +             EXIT_DATA
> > +     }
> > +
> > +     __initdata_end = .;
> > +
> > +     __init_end = .;
> > +
> > +     _sdata = .;
> > +     RO_DATA(4096)
> > +     RW_DATA(1 << CONFIG_L1_CACHE_SHIFT, PAGE_SIZE, THREAD_SIZE)
> > +
> > +     .sdata : {
> > +             *(.sdata)
> > +     }
> > +
> > +     . = ALIGN(SZ_64K);
> > +     _edata =  .;
> > +
> > +     BSS_SECTION(0, SZ_64K, 8)
> > +
> > +     _end = .;
> > +
> > +     STABS_DEBUG
> > +     DWARF_DEBUG
> > +
> > +     .gptab.sdata : {
> > +             *(.gptab.data)
> > +             *(.gptab.sdata)
> > +     }
> > +     .gptab.sbss : {
> > +             *(.gptab.bss)
> > +             *(.gptab.sbss)
> > +     }
> > +
> > +     DISCARDS
> > +     /DISCARD/ : {
> > +             *(.gnu.attributes)
> > +             *(.options)
> > +             *(.eh_frame)
> > +     }
> > +}
> > diff --git a/arch/loongarch/lib/Makefile b/arch/loongarch/lib/Makefile
> > new file mode 100644
> > index 000000000000..7f32f3e4a6ec
> > --- /dev/null
> > +++ b/arch/loongarch/lib/Makefile
> > @@ -0,0 +1,7 @@
> > +# SPDX-License-Identifier: GPL-2.0
> > +#
> > +# Makefile for LoongArch-specific library files..
> One extra period at end of line.
> > +#
> > +
> > +lib-y        += delay.o memset.o memcpy.o memmove.o \
> > +        clear_user.o copy_user.o dump_tlb.o
> > diff --git a/arch/loongarch/mm/Makefile b/arch/loongarch/mm/Makefile
> > new file mode 100644
> > index 000000000000..8ffc6383f836
> > --- /dev/null
> > +++ b/arch/loongarch/mm/Makefile
> > @@ -0,0 +1,9 @@
> > +# SPDX-License-Identifier: GPL-2.0
> > +#
> > +# Makefile for the Linux/LoongArch-specific parts of the memory manager.
> > +#
> > +
> > +obj-y                                += init.o cache.o tlb.o tlbex.o extable.o \
> > +                                fault.o ioremap.o maccess.o mmap.o pgtable.o page.o
> > +
> > +obj-$(CONFIG_HUGETLB_PAGE)   += hugetlbpage.o
> > diff --git a/arch/loongarch/pci/Makefile b/arch/loongarch/pci/Makefile
> > new file mode 100644
> > index 000000000000..8101ef3df71c
> > --- /dev/null
> > +++ b/arch/loongarch/pci/Makefile
> > @@ -0,0 +1,7 @@
> > +# SPDX-License-Identifier: GPL-2.0
> > +#
> > +# Makefile for the PCI specific kernel interface routines under Linux.
> > +#
> > +
> > +obj-y                                += pci.o
> > +obj-$(CONFIG_ACPI)           += acpi.o
> > diff --git a/scripts/subarch.include b/scripts/subarch.include
> > index 776849a3c500..4bd327d0ae42 100644
> > --- a/scripts/subarch.include
> > +++ b/scripts/subarch.include
> > @@ -10,4 +10,4 @@ SUBARCH := $(shell uname -m | sed -e s/i.86/x86/ -e s/x86_64/x86/ \
> >                                 -e s/s390x/s390/ \
> >                                 -e s/ppc.*/powerpc/ -e s/mips.*/mips/ \
> >                                 -e s/sh[234].*/sh/ -e s/aarch64.*/arm64/ \
> > -                               -e s/riscv.*/riscv/)
> > +                               -e s/riscv.*/riscv/ -e s/loongarch.*/loongarch/)