Merge tag 'riscv-for-linus-6.10-mw1' of git://git.kernel.org/pub/scm/linux/kernel/git/riscv/linux

Pull RISC-V updates from Palmer Dabbelt:

 - Add byte/half-word compare-and-exchange, emulated via LR/SC loops

 - Support for Rust

 - Support for Zihintpause in hwprobe

 - Add PR_RISCV_SET_ICACHE_FLUSH_CTX prctl()

 - Support lockless lockrefs

* tag 'riscv-for-linus-6.10-mw1' of git://git.kernel.org/pub/scm/linux/kernel/git/riscv/linux: (42 commits)
  riscv: defconfig: Enable CONFIG_CLK_SOPHGO_CV1800
  riscv: select ARCH_HAS_FAST_MULTIPLIER
  riscv: mm: still create swiotlb buffer for kmalloc() bouncing if required
  riscv: Annotate pgtable_l{4,5}_enabled with __ro_after_init
  riscv: Remove redundant CONFIG_64BIT from pgtable_l{4,5}_enabled
  riscv: mm: Always use an ASID to flush mm contexts
  riscv: mm: Preserve global TLB entries when switching contexts
  riscv: mm: Make asid_bits a local variable
  riscv: mm: Use a fixed layout for the MM context ID
  riscv: mm: Introduce cntx2asid/cntx2version helper macros
  riscv: Avoid TLB flush loops when affected by SiFive CIP-1200
  riscv: Apply SiFive CIP-1200 workaround to single-ASID sfence.vma
  riscv: mm: Combine the SMP and UP TLB flush code
  riscv: Only send remote fences when some other CPU is online
  riscv: mm: Broadcast kernel TLB flushes only when needed
  riscv: Use IPIs for remote cache/TLB flushes by default
  riscv: Factor out page table TLB synchronization
  riscv: Flush the instruction cache during SMP bringup
  riscv: hwprobe: export Zihintpause ISA extension
  riscv: misaligned: remove CONFIG_RISCV_M_MODE specific code
  ...

Author: torvalds

Documentation/arch/riscv/cmodx.rst

@@ -0,0 +1,98 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+==============================================================================
+Concurrent Modification and Execution of Instructions (CMODX) for RISC-V Linux
+==============================================================================
+
+CMODX is a programming technique where a program executes instructions that were
+modified by the program itself. Instruction storage and the instruction cache
+(icache) are not guaranteed to be synchronized on RISC-V hardware. Therefore, the
+program must enforce its own synchronization with the unprivileged fence.i
+instruction.
+
+However, the default Linux ABI prohibits the use of fence.i in userspace
+applications. At any point the scheduler may migrate a task onto a new hart. If
+migration occurs after the userspace synchronized the icache and instruction
+storage with fence.i, the icache on the new hart will no longer be clean. This
+is due to the behavior of fence.i only affecting the hart that it is called on.
+Thus, the hart that the task has been migrated to may not have synchronized
+instruction storage and icache.
+
+There are two ways to solve this problem: use the riscv_flush_icache() syscall,
+or use the ``PR_RISCV_SET_ICACHE_FLUSH_CTX`` prctl() and emit fence.i in
+userspace. The syscall performs a one-off icache flushing operation. The prctl
+changes the Linux ABI to allow userspace to emit icache flushing operations.
+
+As an aside, "deferred" icache flushes can sometimes be triggered in the kernel.
+At the time of writing, this only occurs during the riscv_flush_icache() syscall
+and when the kernel uses copy_to_user_page(). These deferred flushes happen only
+when the memory map being used by a hart changes. If the prctl() context caused
+an icache flush, this deferred icache flush will be skipped as it is redundant.
+Therefore, there will be no additional flush when using the riscv_flush_icache()
+syscall inside of the prctl() context.
+
+prctl() Interface
+---------------------
+
+Call prctl() with ``PR_RISCV_SET_ICACHE_FLUSH_CTX`` as the first argument. The
+remaining arguments will be delegated to the riscv_set_icache_flush_ctx
+function detailed below.
+
+.. kernel-doc:: arch/riscv/mm/cacheflush.c
+	:identifiers: riscv_set_icache_flush_ctx
+
+Example usage:
+
+The following files are meant to be compiled and linked with each other. The
+modify_instruction() function replaces an add with 0 with an add with one,
+causing the instruction sequence in get_value() to change from returning a zero
+to returning a one.
+
+cmodx.c::
+
+	#include <stdio.h>
+	#include <sys/prctl.h>
+
+	extern int get_value();
+	extern void modify_instruction();
+
+	int main()
+	{
+		int value = get_value();
+		printf("Value before cmodx: %d\n", value);
+
+		// Call prctl before first fence.i is called inside modify_instruction
+		prctl(PR_RISCV_SET_ICACHE_FLUSH_CTX_ON, PR_RISCV_CTX_SW_FENCEI, PR_RISCV_SCOPE_PER_PROCESS);
+		modify_instruction();
+		// Call prctl after final fence.i is called in process
+		prctl(PR_RISCV_SET_ICACHE_FLUSH_CTX_OFF, PR_RISCV_CTX_SW_FENCEI, PR_RISCV_SCOPE_PER_PROCESS);
+
+		value = get_value();
+		printf("Value after cmodx: %d\n", value);
+		return 0;
+	}
+
+cmodx.S::
+
+	.option norvc
+
+	.text
+	.global modify_instruction
+	modify_instruction:
+	lw a0, new_insn
+	lui a5,%hi(old_insn)
+	sw  a0,%lo(old_insn)(a5)
+	fence.i
+	ret
+
+	.section modifiable, "awx"
+	.global get_value
+	get_value:
+	li a0, 0
+	old_insn:
+	addi a0, a0, 0
+	ret
+
+	.data
+	new_insn:
+	addi a0, a0, 1

Documentation/arch/riscv/hwprobe.rst

@@ -188,6 +188,10 @@ The following keys are defined:
        manual starting from commit 95cf1f9 ("Add changes requested by Ved
        during signoff")
 
+  * :c:macro:`RISCV_HWPROBE_EXT_ZIHINTPAUSE`: The Zihintpause extension is
+       supported as defined in the RISC-V ISA manual starting from commit
+       d8ab5c78c207 ("Zihintpause is ratified").
+
 * :c:macro:`RISCV_HWPROBE_KEY_CPUPERF_0`: A bitmask that contains performance
   information about the selected set of processors.
 

Documentation/arch/riscv/index.rst

@@ -13,6 +13,7 @@ RISC-V architecture
     patch-acceptance
     uabi
     vector
+    cmodx
 
     features
 

Documentation/rust/arch-support.rst

@@ -17,6 +17,7 @@ Architecture   Level of support  Constraints
 =============  ================  ==============================================
 ``arm64``      Maintained        Little Endian only.
 ``loongarch``  Maintained        \-
+``riscv``      Maintained        ``riscv64`` only.
 ``um``         Maintained        ``x86_64`` only.
 ``x86``        Maintained        ``x86_64`` only.
 =============  ================  ==============================================

arch/riscv/Kconfig

@@ -23,6 +23,7 @@ config RISCV
 	select ARCH_HAS_DEBUG_VIRTUAL if MMU
 	select ARCH_HAS_DEBUG_VM_PGTABLE
 	select ARCH_HAS_DEBUG_WX
+	select ARCH_HAS_FAST_MULTIPLIER
 	select ARCH_HAS_FORTIFY_SOURCE
 	select ARCH_HAS_GCOV_PROFILE_ALL
 	select ARCH_HAS_GIGANTIC_PAGE
@@ -57,10 +58,11 @@ config RISCV
 	select ARCH_SUPPORTS_PAGE_TABLE_CHECK if MMU
 	select ARCH_SUPPORTS_PER_VMA_LOCK if MMU
 	select ARCH_SUPPORTS_SHADOW_CALL_STACK if HAVE_SHADOW_CALL_STACK
+	select ARCH_USE_CMPXCHG_LOCKREF if 64BIT
 	select ARCH_USE_MEMTEST
 	select ARCH_USE_QUEUED_RWLOCKS
 	select ARCH_USES_CFI_TRAPS if CFI_CLANG
-	select ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH if SMP && MMU
+	select ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH if MMU
 	select ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT if MMU
 	select ARCH_WANT_FRAME_POINTERS
 	select ARCH_WANT_GENERAL_HUGETLB if !RISCV_ISA_SVNAPOT
@@ -71,7 +73,7 @@ config RISCV
 	select ARCH_WANTS_THP_SWAP if HAVE_ARCH_TRANSPARENT_HUGEPAGE
 	select BINFMT_FLAT_NO_DATA_START_OFFSET if !MMU
 	select BUILDTIME_TABLE_SORT if MMU
-	select CLINT_TIMER if !MMU
+	select CLINT_TIMER if RISCV_M_MODE
 	select CLONE_BACKWARDS
 	select COMMON_CLK
 	select CPU_PM if CPU_IDLE || HIBERNATION || SUSPEND
@@ -155,6 +157,7 @@ config RISCV
 	select HAVE_REGS_AND_STACK_ACCESS_API
 	select HAVE_RETHOOK if !XIP_KERNEL
 	select HAVE_RSEQ
+	select HAVE_RUST if 64BIT
 	select HAVE_SAMPLE_FTRACE_DIRECT
 	select HAVE_SAMPLE_FTRACE_DIRECT_MULTI
 	select HAVE_STACKPROTECTOR
@@ -231,8 +234,12 @@ config ARCH_MMAP_RND_COMPAT_BITS_MAX
 
 # set if we run in machine mode, cleared if we run in supervisor mode
 config RISCV_M_MODE
-	bool
-	default !MMU
+	bool "Build a kernel that runs in machine mode"
+	depends on !MMU
+	default y
+	help
+	  Select this option if you want to run the kernel in M-mode,
+	  without the assistance of any other firmware.
 
 # set if we are running in S-mode and can use SBI calls
 config RISCV_SBI
@@ -249,8 +256,9 @@ config MMU
 
 config PAGE_OFFSET
 	hex
-	default 0xC0000000 if 32BIT && MMU
-	default 0x80000000 if !MMU
+	default 0x80000000 if !MMU && RISCV_M_MODE
+	default 0x80200000 if !MMU
+	default 0xc0000000 if 32BIT
 	default 0xff60000000000000 if 64BIT
 
 config KASAN_SHADOW_OFFSET
@@ -598,7 +606,6 @@ config TOOLCHAIN_HAS_VECTOR_CRYPTO
 config RISCV_ISA_ZBB
 	bool "Zbb extension support for bit manipulation instructions"
 	depends on TOOLCHAIN_HAS_ZBB
-	depends on MMU
 	depends on RISCV_ALTERNATIVE
 	default y
 	help
@@ -630,7 +637,6 @@ config RISCV_ISA_ZICBOM
 
 config RISCV_ISA_ZICBOZ
 	bool "Zicboz extension support for faster zeroing of memory"
-	depends on MMU
 	depends on RISCV_ALTERNATIVE
 	default y
 	help

arch/riscv/Makefile

@@ -34,6 +34,9 @@ ifeq ($(CONFIG_ARCH_RV64I),y)
 	KBUILD_AFLAGS += -mabi=lp64
 
 	KBUILD_LDFLAGS += -melf64lriscv
+
+	KBUILD_RUSTFLAGS += -Ctarget-cpu=generic-rv64 --target=riscv64imac-unknown-none-elf \
+			    -Cno-redzone
 else
 	BITS := 32
 	UTS_MACHINE := riscv32
@@ -68,6 +71,10 @@ riscv-march-$(CONFIG_FPU)		:= $(riscv-march-y)fd
 riscv-march-$(CONFIG_RISCV_ISA_C)	:= $(riscv-march-y)c
 riscv-march-$(CONFIG_RISCV_ISA_V)	:= $(riscv-march-y)v
 
+ifneq ($(CONFIG_RISCV_ISA_C),y)
+	KBUILD_RUSTFLAGS += -Ctarget-feature=-c
+endif
+
 ifdef CONFIG_TOOLCHAIN_NEEDS_OLD_ISA_SPEC
 KBUILD_CFLAGS += -Wa,-misa-spec=2.2
 KBUILD_AFLAGS += -Wa,-misa-spec=2.2
@@ -133,7 +140,15 @@ boot		:= arch/riscv/boot
 ifeq ($(CONFIG_XIP_KERNEL),y)
 KBUILD_IMAGE := $(boot)/xipImage
 else
+ifeq ($(CONFIG_RISCV_M_MODE)$(CONFIG_SOC_CANAAN_K210),yy)
+KBUILD_IMAGE := $(boot)/loader.bin
+else
+ifeq ($(CONFIG_EFI_ZBOOT),)
 KBUILD_IMAGE	:= $(boot)/Image.gz
+else
+KBUILD_IMAGE := $(boot)/vmlinuz.efi
+endif
+endif
 endif
 
 libs-y += arch/riscv/lib/
@@ -153,17 +168,6 @@ endif
 vdso-install-y			+= arch/riscv/kernel/vdso/vdso.so.dbg
 vdso-install-$(CONFIG_COMPAT)	+= arch/riscv/kernel/compat_vdso/compat_vdso.so.dbg
 
-ifneq ($(CONFIG_XIP_KERNEL),y)
-ifeq ($(CONFIG_RISCV_M_MODE)$(CONFIG_SOC_CANAAN_K210),yy)
-KBUILD_IMAGE := $(boot)/loader.bin
-else
-ifeq ($(CONFIG_EFI_ZBOOT),)
-KBUILD_IMAGE := $(boot)/Image.gz
-else
-KBUILD_IMAGE := $(boot)/vmlinuz.efi
-endif
-endif
-endif
 BOOT_TARGETS := Image Image.gz loader loader.bin xipImage vmlinuz.efi
 
 all:	$(notdir $(KBUILD_IMAGE))

arch/riscv/configs/defconfig

@@ -234,6 +234,7 @@ CONFIG_VIRTIO_BALLOON=y
 CONFIG_VIRTIO_INPUT=y
 CONFIG_VIRTIO_MMIO=y
 CONFIG_RENESAS_OSTM=y
+CONFIG_CLK_SOPHGO_CV1800=y
 CONFIG_SUN8I_DE2_CCU=m
 CONFIG_SUN50I_IOMMU=y
 CONFIG_RPMSG_CHAR=y

arch/riscv/errata/sifive/errata.c

@@ -42,6 +42,11 @@ static bool errata_cip_1200_check_func(unsigned long  arch_id, unsigned long imp
 		return false;
 	if ((impid & 0xffffff) > 0x200630 || impid == 0x1200626)
 		return false;
+
+#ifdef CONFIG_MMU
+	tlb_flush_all_threshold = 0;
+#endif
+
 	return true;
 }