Re: [PATCH v8 10/18] RISC-V: Init and Halt Code

Re: [PATCH v8 10/18] RISC-V: Init and Halt Code

[Palmer Dabbelt]

On Wed, 13 Sep 2017 08:20:42 PDT (-0700), Arnd Bergmann wrote:
> On Tue, Sep 12, 2017 at 11:57 PM, Palmer Dabbelt <palmer@dabbelt.com> wrote:
>> This contains the various __init C functions, the initial assembly
>> kernel entry point, and the code to reset the system.  When a file was
>> init-related this patch contains the entire file.
>
> One minor comment:
>
>> +       /*
>> +        * This hart didn't win the lottery, so we wait for the winning hart to
>> +        * get far enough along the boot process that it should continue.
>> +        */
>> +.Lwait_for_cpu_up:
>> +       REG_L sp, (a1)
>> +       REG_L tp, (a2)
>> +       beqz sp, .Lwait_for_cpu_up
>> +       beqz tp, .Lwait_for_cpu_up
>> +       fence
>
> We usually discourage having the CPUs spin in a busy-loop while
> waiting to be started up, at least on ARM platforms. It seems that
> you could however just have them wait for an interrupt before checking
> the sp/tp values. Would that guarantee to put the CPUs in a low
> power state?

There's no way to _force_ a core to go into a low power state, but putting a
WFI (Wait For Interrupt) in there would at least allow implementations that
care to save power.  We already have some WFIs elsewhere, so it's the right
thing to do here.

There's a few sticky bits here:
* WFI can be implemented as a noop, so this could race with other IPI handling.
  I think it's safe: our IPI is just a "maybe there's a new message" signal, so
  if there's a spurious one it's ignored.
* Interrupts are disabled at this time, though since there's no trap vector it
  should be safe to enable them with a local trap vector here.

I added a FIXME for now, I'll fix it by the v9.

diff --git a/arch/riscv/kernel/head.S b/arch/riscv/kernel/head.S
index 1c50fe3765b1..76af908f87c1 100644
--- a/arch/riscv/kernel/head.S
+++ b/arch/riscv/kernel/head.S
@@ -130,6 +130,7 @@ relocate:
         * get far enough along the boot process that it should continue.
         */
 .Lwait_for_cpu_up:
+       /* FIXME: We should WFI to save some energy here. */
        REG_L sp, (a1)
        REG_L tp, (a2)
        beqz sp, .Lwait_for_cpu_up

Re: [PATCH v8 10/18] RISC-V: Init and Halt Code

[Dmitriy Cherkasov]

On 09/16/2017 06:28 AM, Daniel Lezcano wrote:
> On 16/09/2017 08:23, Dmitriy Cherkasov wrote:
>> On 09/13/2017 11:15 AM, Daniel Lezcano wrote:

>>>
>>> Where is get_cycles64() ?
>>
>> This is in asm/timex.h. Should this be split into a separate asm header
>> ala arm64?
> 
> No, it is fine but may be it is get_cycles(), no get_cycles64(), right?
> 

get_cycles() returns a 32 or 64-bit value depending on machine register width, 
using one assembly instruction to retrieve it.

get_cycles64() always returns a 64-bit value at the expense of a few more 
instructions on 32-bit systems.

Re: [PATCH v8 10/18] RISC-V: Init and Halt Code

[Daniel Lezcano]

On 16/09/2017 08:23, Dmitriy Cherkasov wrote:
> On 09/13/2017 11:15 AM, Daniel Lezcano wrote:
>>
>> All this code must go in the timer side and use the TIMER_OF_DECLARE
>> macro with the proper wrappers.
> 
> Hi, thanks for the feedback.
> 
> Agreed. I'll clean this up.
> 
>>
>> Where is the request_per_cpu_interrupt()?
>>
>> What is this riscv_timer_interrupt() signature?
> 
> This arch defines a separate exception type for local timer interrupts.
> Currently the interrupt controller driver checks the trap cause
> register, determines that it's a timer, and calls the handler directly.
> To make this go through the interrupt subsystem, this driver would need
> to be reworked.
> 
>>
>> Where is get_cycles64() ?
> 
> This is in asm/timex.h. Should this be split into a separate asm header
> ala arm64?

No, it is fine but may be it is get_cycles(), no get_cycles64(), right?

>> The timer driver should be self-contained and not spread across
>> different places, it is very difficult to review it.
>>
>> [ ... ]
>>
> 
> Agreed, thanks again for reviewing it anyway :)

Ok, thanks.

  -- Daniel

-- 
 <http://www.linaro.org/> Linaro.org │ Open source software for ARM SoCs

Follow Linaro:  <http://www.facebook.com/pages/Linaro> Facebook |
<http://twitter.com/#!/linaroorg> Twitter |
<http://www.linaro.org/linaro-blog/> Blog

Re: [PATCH v8 10/18] RISC-V: Init and Halt Code

[Dmitriy Cherkasov]

On 09/13/2017 11:15 AM, Daniel Lezcano wrote:
> 
> All this code must go in the timer side and use the TIMER_OF_DECLARE
> macro with the proper wrappers.

Hi, thanks for the feedback.

Agreed. I'll clean this up.

> 
> Where is the request_per_cpu_interrupt()?
> 
> What is this riscv_timer_interrupt() signature?

This arch defines a separate exception type for local timer interrupts. 
Currently the interrupt controller driver checks the trap cause register, 
determines that it's a timer, and calls the handler directly. To make this go 
through the interrupt subsystem, this driver would need to be reworked.

> 
> Where is get_cycles64() ?

This is in asm/timex.h. Should this be split into a separate asm header ala arm64?

> 
> The timer driver should be self-contained and not spread across
> different places, it is very difficult to review it.
> 
> [ ... ]
> 

Agreed, thanks again for reviewing it anyway :)

Re: [PATCH v8 10/18] RISC-V: Init and Halt Code

[Daniel Lezcano]

On 12/09/2017 23:57, Palmer Dabbelt wrote:
> This contains the various __init C functions, the initial assembly
> kernel entry point, and the code to reset the system.  When a file was
> init-related this patch contains the entire file.
> 
> Signed-off-by: Palmer Dabbelt <palmer@dabbelt.com>
> ---

[ ... ]

> diff --git a/arch/riscv/kernel/time.c b/arch/riscv/kernel/time.c
> new file mode 100644
> index 000000000000..8362a0e17a1a
> --- /dev/null
> +++ b/arch/riscv/kernel/time.c
> @@ -0,0 +1,78 @@
> +/*
> + * Copyright (C) 2012 Regents of the University of California
> + * Copyright (C) 2017 SiFive
> + *
> + *   This program is free software; you can redistribute it and/or
> + *   modify it under the terms of the GNU General Public License
> + *   as published by the Free Software Foundation, version 2.
> + *
> + *   This program is distributed in the hope that it will be useful,
> + *   but WITHOUT ANY WARRANTY; without even the implied warranty of
> + *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> + *   GNU General Public License for more details.
> + */
> +
> +#include <linux/clocksource.h>
> +#include <linux/clockchips.h>
> +#include <linux/delay.h>
> +#include <linux/timer_riscv.h>
> +
> +#include <asm/sbi.h>
> +
> +unsigned long riscv_timebase;
> +
> +DECLARE_PER_CPU(struct clock_event_device, riscv_clock_event);
> +
> +static int next_event(unsigned long delta, struct clock_event_device *ce)
> +{
> +	/*
> +	 * time_init() allocates a timer for each CPU.  Since we're writing the
> +	 * timer comparison register here we can't allow the timers to cross
> +	 * harts.
> +	 */
> +	BUG_ON(ce != this_cpu_ptr(&riscv_clock_event));
> +	sbi_set_timer(get_cycles64() + delta);
> +	return 0;
> +}
> +
> +static unsigned long long rdtime(struct clocksource *cs)
> +{
> +	/*
> +	 * It's guarnteed that all the timers across all the harts are
> +	 * synchronized within one tick of each other, so while this could
> +	 * technically go backwards when hopping between CPUs, practically it
> +	 * won't happen.
> +	 */
> +	return get_cycles64();
> +}
> +
> +void riscv_timer_interrupt(void)
> +{
> +	struct clock_event_device *evdev = this_cpu_ptr(&riscv_clock_event);
> +
> +	evdev->event_handler(evdev);
> +}
> +
> +void __init init_clockevent(void)
> +{
> +	int cpu_id = smp_processor_id();
> +
> +	timer_riscv_init(cpu_id, riscv_timebase, &next_event);
> +	csr_set(sie, SIE_STIE);
> +}
> +
> +void __init time_init(void)
> +{
> +	struct device_node *cpu;
> +	u32 prop;
> +
> +	cpu = of_find_node_by_path("/cpus");
> +	if (!cpu || of_property_read_u32(cpu, "timebase-frequency", &prop))
> +		panic(KERN_WARNING "RISC-V system with no 'timebase-frequency' in DTS\n");
> +	riscv_timebase = prop;
> +
> +	lpj_fine = riscv_timebase / HZ;
> +
> +	clocksource_riscv_init(&rdtime);
> +	init_clockevent();
> +}

All this code must go in the timer side and use the TIMER_OF_DECLARE
macro with the proper wrappers.

Where is the request_per_cpu_interrupt()?

What is this riscv_timer_interrupt() signature?

Where is get_cycles64() ?

The timer driver should be self-contained and not spread across
different places, it is very difficult to review it.

[ ... ]

-- 
 <http://www.linaro.org/> Linaro.org │ Open source software for ARM SoCs

Follow Linaro:  <http://www.facebook.com/pages/Linaro> Facebook |
<http://twitter.com/#!/linaroorg> Twitter |
<http://www.linaro.org/linaro-blog/> Blog

[PATCH v8 10/18] RISC-V: Init and Halt Code

[Palmer Dabbelt]

This contains the various __init C functions, the initial assembly
kernel entry point, and the code to reset the system.  When a file was
init-related this patch contains the entire file.

Signed-off-by: Palmer Dabbelt <palmer@dabbelt.com>
---
 arch/riscv/include/asm/bug.h   |  88 ++++++++++++++
 arch/riscv/include/asm/cache.h |  22 ++++
 arch/riscv/include/asm/smp.h   |  52 +++++++++
 arch/riscv/kernel/cacheinfo.c  | 105 +++++++++++++++++
 arch/riscv/kernel/cpu.c        | 108 ++++++++++++++++++
 arch/riscv/kernel/head.S       | 156 +++++++++++++++++++++++++
 arch/riscv/kernel/irq.c        |  20 ++++
 arch/riscv/kernel/reset.c      |  36 ++++++
 arch/riscv/kernel/setup.c      | 254 +++++++++++++++++++++++++++++++++++++++++
 arch/riscv/kernel/smp.c        | 110 ++++++++++++++++++
 arch/riscv/kernel/smpboot.c    | 114 ++++++++++++++++++
 arch/riscv/kernel/time.c       |  78 +++++++++++++
 arch/riscv/kernel/traps.c      | 180 +++++++++++++++++++++++++++++
 arch/riscv/kernel/vdso.c       | 125 ++++++++++++++++++++
 arch/riscv/mm/init.c           |  70 ++++++++++++
 15 files changed, 1518 insertions(+)
 create mode 100644 arch/riscv/include/asm/bug.h
 create mode 100644 arch/riscv/include/asm/cache.h
 create mode 100644 arch/riscv/include/asm/smp.h
 create mode 100644 arch/riscv/kernel/cacheinfo.c
 create mode 100644 arch/riscv/kernel/cpu.c
 create mode 100644 arch/riscv/kernel/head.S
 create mode 100644 arch/riscv/kernel/irq.c
 create mode 100644 arch/riscv/kernel/reset.c
 create mode 100644 arch/riscv/kernel/setup.c
 create mode 100644 arch/riscv/kernel/smp.c
 create mode 100644 arch/riscv/kernel/smpboot.c
 create mode 100644 arch/riscv/kernel/time.c
 create mode 100644 arch/riscv/kernel/traps.c
 create mode 100644 arch/riscv/kernel/vdso.c
 create mode 100644 arch/riscv/mm/init.c

diff --git a/arch/riscv/include/asm/bug.h b/arch/riscv/include/asm/bug.h
new file mode 100644
index 000000000000..c3e13764a943
--- /dev/null
+++ b/arch/riscv/include/asm/bug.h
@@ -0,0 +1,88 @@
+/*
+ * Copyright (C) 2012 Regents of the University of California
+ *
+ *   This program is free software; you can redistribute it and/or
+ *   modify it under the terms of the GNU General Public License
+ *   as published by the Free Software Foundation, version 2.
+ *
+ *   This program is distributed in the hope that it will be useful,
+ *   but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *   GNU General Public License for more details.
+ */
+
+#ifndef _ASM_RISCV_BUG_H
+#define _ASM_RISCV_BUG_H
+
+#include <linux/compiler.h>
+#include <linux/const.h>
+#include <linux/types.h>
+
+#include <asm/asm.h>
+
+#ifdef CONFIG_GENERIC_BUG
+#define __BUG_INSN	_AC(0x00100073, UL) /* ebreak */
+
+#ifndef __ASSEMBLY__
+typedef u32 bug_insn_t;
+
+#ifdef CONFIG_GENERIC_BUG_RELATIVE_POINTERS
+#define __BUG_ENTRY_ADDR	INT " 1b - 2b"
+#define __BUG_ENTRY_FILE	INT " %0 - 2b"
+#else
+#define __BUG_ENTRY_ADDR	RISCV_PTR " 1b"
+#define __BUG_ENTRY_FILE	RISCV_PTR " %0"
+#endif
+
+#ifdef CONFIG_DEBUG_BUGVERBOSE
+#define __BUG_ENTRY			\
+	__BUG_ENTRY_ADDR "\n\t"		\
+	__BUG_ENTRY_FILE "\n\t"		\
+	SHORT " %1"
+#else
+#define __BUG_ENTRY			\
+	__BUG_ENTRY_ADDR
+#endif
+
+#define BUG()							\
+do {								\
+	__asm__ __volatile__ (					\
+		"1:\n\t"					\
+			"ebreak\n"				\
+			".pushsection __bug_table,\"a\"\n\t"	\
+		"2:\n\t"					\
+			__BUG_ENTRY "\n\t"			\
+			".org 2b + %2\n\t"			\
+			".popsection"				\
+		:						\
+		: "i" (__FILE__), "i" (__LINE__),		\
+		  "i" (sizeof(struct bug_entry)));		\
+	unreachable();						\
+} while (0)
+#endif /* !__ASSEMBLY__ */
+#else /* CONFIG_GENERIC_BUG */
+#ifndef __ASSEMBLY__
+#define BUG()							\
+do {								\
+	__asm__ __volatile__ ("ebreak\n");			\
+	unreachable();						\
+} while (0)
+#endif /* !__ASSEMBLY__ */
+#endif /* CONFIG_GENERIC_BUG */
+
+#define HAVE_ARCH_BUG
+
+#include <asm-generic/bug.h>
+
+#ifndef __ASSEMBLY__
+
+struct pt_regs;
+struct task_struct;
+
+extern void die(struct pt_regs *regs, const char *str);
+extern void do_trap(struct pt_regs *regs, int signo, int code,
+	unsigned long addr, struct task_struct *tsk);
+
+#endif /* !__ASSEMBLY__ */
+
+#endif /* _ASM_RISCV_BUG_H */
diff --git a/arch/riscv/include/asm/cache.h b/arch/riscv/include/asm/cache.h
new file mode 100644
index 000000000000..e8f0d1110d74
--- /dev/null
+++ b/arch/riscv/include/asm/cache.h
@@ -0,0 +1,22 @@
+/*
+ * Copyright (C) 2017 Chen Liqin <liqin.chen@sunplusct.com>
+ * Copyright (C) 2012 Regents of the University of California
+ *
+ *   This program is free software; you can redistribute it and/or
+ *   modify it under the terms of the GNU General Public License
+ *   as published by the Free Software Foundation, version 2.
+ *
+ *   This program is distributed in the hope that it will be useful,
+ *   but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *   GNU General Public License for more details.
+ */
+
+#ifndef _ASM_RISCV_CACHE_H
+#define _ASM_RISCV_CACHE_H
+
+#define L1_CACHE_SHIFT		6
+
+#define L1_CACHE_BYTES		(1 << L1_CACHE_SHIFT)
+
+#endif /* _ASM_RISCV_CACHE_H */
diff --git a/arch/riscv/include/asm/smp.h b/arch/riscv/include/asm/smp.h
new file mode 100644
index 000000000000..85e4220839b0
--- /dev/null
+++ b/arch/riscv/include/asm/smp.h
@@ -0,0 +1,52 @@
+/*
+ * Copyright (C) 2012 Regents of the University of California
+ *
+ *   This program is free software; you can redistribute it and/or
+ *   modify it under the terms of the GNU General Public License
+ *   as published by the Free Software Foundation, version 2.
+ *
+ *   This program is distributed in the hope that it will be useful,
+ *   but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *   GNU General Public License for more details.
+ */
+
+#ifndef _ASM_RISCV_SMP_H
+#define _ASM_RISCV_SMP_H
+
+/* This both needs asm-offsets.h and is used when generating it. */
+#ifndef GENERATING_ASM_OFFSETS
+#include <asm/asm-offsets.h>
+#endif
+
+#include <linux/cpumask.h>
+#include <linux/irqreturn.h>
+
+#ifdef CONFIG_SMP
+
+/* SMP initialization hook for setup_arch */
+void __init init_clockevent(void);
+
+/* SMP initialization hook for setup_arch */
+void __init setup_smp(void);
+
+/* Hook for the generic smp_call_function_many() routine. */
+void arch_send_call_function_ipi_mask(struct cpumask *mask);
+
+/* Hook for the generic smp_call_function_single() routine. */
+void arch_send_call_function_single_ipi(int cpu);
+
+/*
+ * This is particularly ugly: it appears we can't actually get the definition
+ * of task_struct here, but we need access to the CPU this task is running on.
+ * Instead of using C we're using asm-offsets.h to get the current processor
+ * ID.
+ */
+#define raw_smp_processor_id() (*((int*)((char*)get_current() + TASK_TI_CPU)))
+
+/* Interprocessor interrupt handler */
+irqreturn_t handle_ipi(void);
+
+#endif /* CONFIG_SMP */
+
+#endif /* _ASM_RISCV_SMP_H */
diff --git a/arch/riscv/kernel/cacheinfo.c b/arch/riscv/kernel/cacheinfo.c
new file mode 100644
index 000000000000..10ed2749e246
--- /dev/null
+++ b/arch/riscv/kernel/cacheinfo.c
@@ -0,0 +1,105 @@
+/*
+ * Copyright (C) 2017 SiFive
+ *
+ *   This program is free software; you can redistribute it and/or
+ *   modify it under the terms of the GNU General Public License
+ *   as published by the Free Software Foundation, version 2.
+ *
+ *   This program is distributed in the hope that it will be useful,
+ *   but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *   GNU General Public License for more details.
+ */
+
+#include <linux/cacheinfo.h>
+#include <linux/cpu.h>
+#include <linux/of.h>
+#include <linux/of_device.h>
+
+static void ci_leaf_init(struct cacheinfo *this_leaf,
+			 struct device_node *node,
+			 enum cache_type type, unsigned int level)
+{
+	this_leaf->of_node = node;
+	this_leaf->level = level;
+	this_leaf->type = type;
+	/* not a sector cache */
+	this_leaf->physical_line_partition = 1;
+	/* TODO: Add to DTS */
+	this_leaf->attributes =
+		CACHE_WRITE_BACK
+		| CACHE_READ_ALLOCATE
+		| CACHE_WRITE_ALLOCATE;
+}
+
+static int __init_cache_level(unsigned int cpu)
+{
+	struct cpu_cacheinfo *this_cpu_ci = get_cpu_cacheinfo(cpu);
+	struct device_node *np = of_cpu_device_node_get(cpu);
+	int levels = 0, leaves = 0, level;
+
+	if (of_property_read_bool(np, "cache-size"))
+		++leaves;
+	if (of_property_read_bool(np, "i-cache-size"))
+		++leaves;
+	if (of_property_read_bool(np, "d-cache-size"))
+		++leaves;
+	if (leaves > 0)
+		levels = 1;
+
+	while ((np = of_find_next_cache_node(np))) {
+		if (!of_device_is_compatible(np, "cache"))
+			break;
+		if (of_property_read_u32(np, "cache-level", &level))
+			break;
+		if (level <= levels)
+			break;
+		if (of_property_read_bool(np, "cache-size"))
+			++leaves;
+		if (of_property_read_bool(np, "i-cache-size"))
+			++leaves;
+		if (of_property_read_bool(np, "d-cache-size"))
+			++leaves;
+		levels = level;
+	}
+
+	this_cpu_ci->num_levels = levels;
+	this_cpu_ci->num_leaves = leaves;
+	return 0;
+}
+
+static int __populate_cache_leaves(unsigned int cpu)
+{
+	struct cpu_cacheinfo *this_cpu_ci = get_cpu_cacheinfo(cpu);
+	struct cacheinfo *this_leaf = this_cpu_ci->info_list;
+	struct device_node *np = of_cpu_device_node_get(cpu);
+	int levels = 1, level = 1;
+
+	if (of_property_read_bool(np, "cache-size"))
+		ci_leaf_init(this_leaf++, np, CACHE_TYPE_UNIFIED, level);
+	if (of_property_read_bool(np, "i-cache-size"))
+		ci_leaf_init(this_leaf++, np, CACHE_TYPE_INST, level);
+	if (of_property_read_bool(np, "d-cache-size"))
+		ci_leaf_init(this_leaf++, np, CACHE_TYPE_DATA, level);
+
+	while ((np = of_find_next_cache_node(np))) {
+		if (!of_device_is_compatible(np, "cache"))
+			break;
+		if (of_property_read_u32(np, "cache-level", &level))
+			break;
+		if (level <= levels)
+			break;
+		if (of_property_read_bool(np, "cache-size"))
+			ci_leaf_init(this_leaf++, np, CACHE_TYPE_UNIFIED, level);
+		if (of_property_read_bool(np, "i-cache-size"))
+			ci_leaf_init(this_leaf++, np, CACHE_TYPE_INST, level);
+		if (of_property_read_bool(np, "d-cache-size"))
+			ci_leaf_init(this_leaf++, np, CACHE_TYPE_DATA, level);
+		levels = level;
+	}
+
+	return 0;
+}
+
+DEFINE_SMP_CALL_CACHE_FUNCTION(init_cache_level)
+DEFINE_SMP_CALL_CACHE_FUNCTION(populate_cache_leaves)
diff --git a/arch/riscv/kernel/cpu.c b/arch/riscv/kernel/cpu.c
new file mode 100644
index 000000000000..ca6c81e54e37
--- /dev/null
+++ b/arch/riscv/kernel/cpu.c
@@ -0,0 +1,108 @@
+/*
+ * Copyright (C) 2012 Regents of the University of California
+ *
+ *   This program is free software; you can redistribute it and/or
+ *   modify it under the terms of the GNU General Public License
+ *   as published by the Free Software Foundation, version 2.
+ *
+ *   This program is distributed in the hope that it will be useful,
+ *   but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *   GNU General Public License for more details.
+ */
+
+#include <linux/init.h>
+#include <linux/seq_file.h>
+#include <linux/of.h>
+
+/* Return -1 if not a valid hart */
+int riscv_of_processor_hart(struct device_node *node)
+{
+	const char *isa, *status;
+	u32 hart;
+
+	if (!of_device_is_compatible(node, "riscv")) {
+		pr_warn("Found incompatible CPU\n");
+		return -(ENODEV);
+	}
+
+	if (of_property_read_u32(node, "reg", &hart)) {
+		pr_warn("Found CPU without hart ID\n");
+		return -(ENODEV);
+	}
+	if (hart >= NR_CPUS) {
+		pr_info("Found hart ID %d, which is above NR_CPUs.  Disabling this hart\n", hart);
+		return -(ENODEV);
+	}
+
+	if (of_property_read_string(node, "status", &status)) {
+		pr_warn("CPU with hartid=%d has no \"status\" property\n", hart);
+		return -(ENODEV);
+	}
+	if (strcmp(status, "okay")) {
+		pr_info("CPU with hartid=%d has a non-okay status of \"%s\"\n", hart, status);
+		return -(ENODEV);
+	}
+
+	if (of_property_read_string(node, "riscv,isa", &isa)) {
+		pr_warn("CPU with hartid=%d has no \"riscv,isa\" property\n", hart);
+		return -(ENODEV);
+	}
+	if (isa[0] != 'r' || isa[1] != 'v') {
+		pr_warn("CPU with hartid=%d has an invalid ISA of \"%s\"\n", hart, isa);
+		return -(ENODEV);
+	}
+
+	return hart;
+}
+
+#ifdef CONFIG_PROC_FS
+
+static void *c_start(struct seq_file *m, loff_t *pos)
+{
+	*pos = cpumask_next(*pos - 1, cpu_online_mask);
+	if ((*pos) < nr_cpu_ids)
+		return (void *)(uintptr_t)(1 + *pos);
+	return NULL;
+}
+
+static void *c_next(struct seq_file *m, void *v, loff_t *pos)
+{
+	(*pos)++;
+	return c_start(m, pos);
+}
+
+static void c_stop(struct seq_file *m, void *v)
+{
+}
+
+static int c_show(struct seq_file *m, void *v)
+{
+	unsigned long hart_id = (unsigned long)v - 1;
+	struct device_node *node = of_get_cpu_node(hart_id, NULL);
+	const char *compat, *isa, *mmu;
+
+	seq_printf(m, "hart\t: %lu\n", hart_id);
+	if (!of_property_read_string(node, "riscv,isa", &isa)
+	    && isa[0] == 'r'
+	    && isa[1] == 'v')
+		seq_printf(m, "isa\t: %s\n", isa);
+	if (!of_property_read_string(node, "mmu-type", &mmu)
+	    && !strncmp(mmu, "riscv,", 6))
+		seq_printf(m, "mmu\t: %s\n", mmu+6);
+	if (!of_property_read_string(node, "compatible", &compat)
+	    && strcmp(compat, "riscv"))
+		seq_printf(m, "uarch\t: %s\n", compat);
+	seq_puts(m, "\n");
+
+	return 0;
+}
+
+const struct seq_operations cpuinfo_op = {
+	.start	= c_start,
+	.next	= c_next,
+	.stop	= c_stop,
+	.show	= c_show
+};
+
+#endif /* CONFIG_PROC_FS */
diff --git a/arch/riscv/kernel/head.S b/arch/riscv/kernel/head.S
new file mode 100644
index 000000000000..1c50fe3765b1
--- /dev/null
+++ b/arch/riscv/kernel/head.S
@@ -0,0 +1,156 @@
+/*
+ * Copyright (C) 2012 Regents of the University of California
+ *
+ *   This program is free software; you can redistribute it and/or
+ *   modify it under the terms of the GNU General Public License
+ *   as published by the Free Software Foundation, version 2.
+ *
+ *   This program is distributed in the hope that it will be useful,
+ *   but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *   GNU General Public License for more details.
+ */
+
+#include <asm/thread_info.h>
+#include <asm/asm-offsets.h>
+#include <asm/asm.h>
+#include <linux/init.h>
+#include <linux/linkage.h>
+#include <asm/thread_info.h>
+#include <asm/page.h>
+#include <asm/csr.h>
+
+__INIT
+ENTRY(_start)
+	/* Mask all interrupts */
+	csrw sie, zero
+
+	/* Load the global pointer */
+.option push
+.option norelax
+	la gp, __global_pointer$
+.option pop
+
+	/*
+	 * Disable FPU to detect illegal usage of
+	 * floating point in kernel space
+	 */
+	li t0, SR_FS
+	csrc sstatus, t0
+
+	/* Pick one hart to run the main boot sequence */
+	la a3, hart_lottery
+	li a2, 1
+	amoadd.w a3, a2, (a3)
+	bnez a3, .Lsecondary_start
+
+	/* Save hart ID and DTB physical address */
+	mv s0, a0
+	mv s1, a1
+
+	/* Initialize page tables and relocate to virtual addresses */
+	la sp, init_thread_union + THREAD_SIZE
+	call setup_vm
+	call relocate
+
+	/* Restore C environment */
+	la tp, init_task
+	sw s0, TASK_TI_CPU(tp)
+
+	la sp, init_thread_union
+	li a0, ASM_THREAD_SIZE
+	add sp, sp, a0
+
+	/* Start the kernel */
+	mv a0, s0
+	mv a1, s1
+	call sbi_save
+	tail start_kernel
+
+relocate:
+	/* Relocate return address */
+	li a1, PAGE_OFFSET
+	la a0, _start
+	sub a1, a1, a0
+	add ra, ra, a1
+
+	/* Point stvec to virtual address of intruction after sptbr write */
+	la a0, 1f
+	add a0, a0, a1
+	csrw stvec, a0
+
+	/* Compute sptbr for kernel page tables, but don't load it yet */
+	la a2, swapper_pg_dir
+	srl a2, a2, PAGE_SHIFT
+	li a1, SPTBR_MODE
+	or a2, a2, a1
+
+	/*
+	 * Load trampoline page directory, which will cause us to trap to
+	 * stvec if VA != PA, or simply fall through if VA == PA
+	 */
+	la a0, trampoline_pg_dir
+	srl a0, a0, PAGE_SHIFT
+	or a0, a0, a1
+	sfence.vma
+	csrw sptbr, a0
+1:
+	/* Set trap vector to spin forever to help debug */
+	la a0, .Lsecondary_park
+	csrw stvec, a0
+
+	/* Reload the global pointer */
+.option push
+.option norelax
+	la gp, __global_pointer$
+.option pop
+
+	/* Switch to kernel page tables */
+	csrw sptbr, a2
+
+	ret
+
+.Lsecondary_start:
+#ifdef CONFIG_SMP
+	li a1, CONFIG_NR_CPUS
+	bgeu a0, a1, .Lsecondary_park
+
+	/* Set trap vector to spin forever to help debug */
+	la a3, .Lsecondary_park
+	csrw stvec, a3
+
+	slli a3, a0, LGREG
+	la a1, __cpu_up_stack_pointer
+	la a2, __cpu_up_task_pointer
+	add a1, a3, a1
+	add a2, a3, a2
+
+	/*
+	 * This hart didn't win the lottery, so we wait for the winning hart to
+	 * get far enough along the boot process that it should continue.
+	 */
+.Lwait_for_cpu_up:
+	REG_L sp, (a1)
+	REG_L tp, (a2)
+	beqz sp, .Lwait_for_cpu_up
+	beqz tp, .Lwait_for_cpu_up
+	fence
+
+	/* Enable virtual memory and relocate to virtual address */
+	call relocate
+
+	tail smp_callin
+#endif
+
+.Lsecondary_park:
+	/* We lack SMP support or have too many harts, so park this hart */
+	wfi
+	j .Lsecondary_park
+END(_start)
+
+__PAGE_ALIGNED_BSS
+	/* Empty zero page */
+	.balign PAGE_SIZE
+ENTRY(empty_zero_page)
+	.fill (empty_zero_page + PAGE_SIZE) - ., 1, 0x00
+END(empty_zero_page)
diff --git a/arch/riscv/kernel/irq.c b/arch/riscv/kernel/irq.c
new file mode 100644
index 000000000000..737d7cce2c6d
--- /dev/null
+++ b/arch/riscv/kernel/irq.c
@@ -0,0 +1,20 @@
+/*
+ * Copyright (C) 2012 Regents of the University of California
+ * Copyright (C) 2017 SiFive
+ *
+ *   This program is free software; you can redistribute it and/or
+ *   modify it under the terms of the GNU General Public License
+ *   as published by the Free Software Foundation, version 2.
+ *
+ *   This program is distributed in the hope that it will be useful,
+ *   but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *   GNU General Public License for more details.
+ */
+
+#include <linux/irqchip.h>
+
+void __init init_IRQ(void)
+{
+	irqchip_init();
+}
diff --git a/arch/riscv/kernel/reset.c b/arch/riscv/kernel/reset.c
new file mode 100644
index 000000000000..2a53d26ffdd6
--- /dev/null
+++ b/arch/riscv/kernel/reset.c
@@ -0,0 +1,36 @@
+/*
+ * Copyright (C) 2012 Regents of the University of California
+ *
+ *   This program is free software; you can redistribute it and/or
+ *   modify it under the terms of the GNU General Public License
+ *   as published by the Free Software Foundation, version 2.
+ *
+ *   This program is distributed in the hope that it will be useful,
+ *   but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *   GNU General Public License for more details.
+ */
+
+#include <linux/reboot.h>
+#include <linux/export.h>
+#include <asm/sbi.h>
+
+void (*pm_power_off)(void) = machine_power_off;
+EXPORT_SYMBOL(pm_power_off);
+
+void machine_restart(char *cmd)
+{
+	do_kernel_restart(cmd);
+	while (1);
+}
+
+void machine_halt(void)
+{
+	machine_power_off();
+}
+
+void machine_power_off(void)
+{
+	sbi_shutdown();
+	while (1);
+}
diff --git a/arch/riscv/kernel/setup.c b/arch/riscv/kernel/setup.c
new file mode 100644
index 000000000000..4753b8105e22
--- /dev/null
+++ b/arch/riscv/kernel/setup.c
@@ -0,0 +1,254 @@
+/*
+ * Copyright (C) 2009 Sunplus Core Technology Co., Ltd.
+ *  Chen Liqin <liqin.chen@sunplusct.com>
+ *  Lennox Wu <lennox.wu@sunplusct.com>
+ * Copyright (C) 2012 Regents of the University of California
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see the file COPYING, or write
+ * to the Free Software Foundation, Inc.,
+ */
+
+#include <linux/init.h>
+#include <linux/mm.h>
+#include <linux/memblock.h>
+#include <linux/sched.h>
+#include <linux/initrd.h>
+#include <linux/console.h>
+#include <linux/screen_info.h>
+#include <linux/of_fdt.h>
+#include <linux/of_platform.h>
+#include <linux/sched/task.h>
+
+#include <asm/setup.h>
+#include <asm/sections.h>
+#include <asm/pgtable.h>
+#include <asm/smp.h>
+#include <asm/sbi.h>
+#include <asm/tlbflush.h>
+#include <asm/thread_info.h>
+#include <asm/hvc_riscv_sbi.h>
+
+#ifdef CONFIG_DUMMY_CONSOLE
+struct screen_info screen_info = {
+	.orig_video_lines	= 30,
+	.orig_video_cols	= 80,
+	.orig_video_mode	= 0,
+	.orig_video_ega_bx	= 0,
+	.orig_video_isVGA	= 1,
+	.orig_video_points	= 8
+};
+#endif
+
+#ifdef CONFIG_CMDLINE_BOOL
+static char __initdata builtin_cmdline[COMMAND_LINE_SIZE] = CONFIG_CMDLINE;
+#endif /* CONFIG_CMDLINE_BOOL */
+
+unsigned long va_pa_offset;
+unsigned long pfn_base;
+
+/* The lucky hart to first increment this variable will boot the other cores */
+atomic_t hart_lottery;
+
+#ifdef CONFIG_BLK_DEV_INITRD
+static void __init setup_initrd(void)
+{
+	extern char __initramfs_start[];
+	extern unsigned long __initramfs_size;
+	unsigned long size;
+
+	if (__initramfs_size > 0) {
+		initrd_start = (unsigned long)(&__initramfs_start);
+		initrd_end = initrd_start + __initramfs_size;
+	}
+
+	if (initrd_start >= initrd_end) {
+		printk(KERN_INFO "initrd not found or empty");
+		goto disable;
+	}
+	if (__pa(initrd_end) > PFN_PHYS(max_low_pfn)) {
+		printk(KERN_ERR "initrd extends beyond end of memory");
+		goto disable;
+	}
+
+	size =  initrd_end - initrd_start;
+	memblock_reserve(__pa(initrd_start), size);
+	initrd_below_start_ok = 1;
+
+	printk(KERN_INFO "Initial ramdisk at: 0x%p (%lu bytes)\n",
+		(void *)(initrd_start), size);
+	return;
+disable:
+	pr_cont(" - disabling initrd\n");
+	initrd_start = 0;
+	initrd_end = 0;
+}
+#endif /* CONFIG_BLK_DEV_INITRD */
+
+pgd_t swapper_pg_dir[PTRS_PER_PGD] __page_aligned_bss;
+pgd_t trampoline_pg_dir[PTRS_PER_PGD] __initdata __aligned(PAGE_SIZE);
+
+#ifndef __PAGETABLE_PMD_FOLDED
+#define NUM_SWAPPER_PMDS ((uintptr_t)-PAGE_OFFSET >> PGDIR_SHIFT)
+pmd_t swapper_pmd[PTRS_PER_PMD*((-PAGE_OFFSET)/PGDIR_SIZE)] __page_aligned_bss;
+pmd_t trampoline_pmd[PTRS_PER_PGD] __initdata __aligned(PAGE_SIZE);
+#endif
+
+asmlinkage void __init setup_vm(void)
+{
+	extern char _start;
+	uintptr_t i;
+	uintptr_t pa = (uintptr_t) &_start;
+	pgprot_t prot = __pgprot(pgprot_val(PAGE_KERNEL) | _PAGE_EXEC);
+
+	va_pa_offset = PAGE_OFFSET - pa;
+	pfn_base = PFN_DOWN(pa);
+
+	/* Sanity check alignment and size */
+	BUG_ON((PAGE_OFFSET % PGDIR_SIZE) != 0);
+	BUG_ON((pa % (PAGE_SIZE * PTRS_PER_PTE)) != 0);
+
+#ifndef __PAGETABLE_PMD_FOLDED
+	trampoline_pg_dir[(PAGE_OFFSET >> PGDIR_SHIFT) % PTRS_PER_PGD] =
+		pfn_pgd(PFN_DOWN((uintptr_t)trampoline_pmd),
+			__pgprot(_PAGE_TABLE));
+	trampoline_pmd[0] = pfn_pmd(PFN_DOWN(pa), prot);
+
+	for (i = 0; i < (-PAGE_OFFSET)/PGDIR_SIZE; ++i) {
+		size_t o = (PAGE_OFFSET >> PGDIR_SHIFT) % PTRS_PER_PGD + i;
+		swapper_pg_dir[o] =
+			pfn_pgd(PFN_DOWN((uintptr_t)swapper_pmd) + i,
+				__pgprot(_PAGE_TABLE));
+	}
+	for (i = 0; i < ARRAY_SIZE(swapper_pmd); i++)
+		swapper_pmd[i] = pfn_pmd(PFN_DOWN(pa + i * PMD_SIZE), prot);
+#else
+	trampoline_pg_dir[(PAGE_OFFSET >> PGDIR_SHIFT) % PTRS_PER_PGD] =
+		pfn_pgd(PFN_DOWN(pa), prot);
+
+	for (i = 0; i < (-PAGE_OFFSET)/PGDIR_SIZE; ++i) {
+		size_t o = (PAGE_OFFSET >> PGDIR_SHIFT) % PTRS_PER_PGD + i;
+		swapper_pg_dir[o] =
+			pfn_pgd(PFN_DOWN(pa + i * PGDIR_SIZE), prot);
+	}
+#endif
+}
+
+void __init sbi_save(unsigned int hartid, void *dtb)
+{
+	early_init_dt_scan(__va(dtb));
+}
+
+/*
+ * Allow the user to manually add a memory region (in case DTS is broken);
+ * "mem_end=nn[KkMmGg]"
+ */
+static int __init mem_end_override(char *p)
+{
+	resource_size_t base, end;
+
+	if (!p)
+		return -EINVAL;
+	base = (uintptr_t) __pa(PAGE_OFFSET);
+	end = memparse(p, &p) & PMD_MASK;
+	if (end == 0)
+		return -EINVAL;
+	memblock_add(base, end - base);
+	return 0;
+}
+early_param("mem_end", mem_end_override);
+
+static void __init setup_bootmem(void)
+{
+	struct memblock_region *reg;
+	phys_addr_t mem_size = 0;
+
+	/* Find the memory region containing the kernel */
+	for_each_memblock(memory, reg) {
+		phys_addr_t vmlinux_end = __pa(_end);
+		phys_addr_t end = reg->base + reg->size;
+
+		if (reg->base <= vmlinux_end && vmlinux_end <= end) {
+			/*
+			 * Reserve from the start of the region to the end of
+			 * the kernel
+			 */
+			memblock_reserve(reg->base, vmlinux_end - reg->base);
+			mem_size = min(reg->size, (phys_addr_t)-PAGE_OFFSET);
+		}
+	}
+	BUG_ON(mem_size == 0);
+
+	set_max_mapnr(PFN_DOWN(mem_size));
+	max_low_pfn = pfn_base + PFN_DOWN(mem_size);
+
+#ifdef CONFIG_BLK_DEV_INITRD
+	setup_initrd();
+#endif /* CONFIG_BLK_DEV_INITRD */
+
+	early_init_fdt_reserve_self();
+	early_init_fdt_scan_reserved_mem();
+	memblock_allow_resize();
+	memblock_dump_all();
+}
+
+void __init setup_arch(char **cmdline_p)
+{
+#if defined(CONFIG_HVC_RISCV_SBI)
+	if (likely(early_console == NULL)) {
+		early_console = &riscv_sbi_early_console_dev;
+		register_console(early_console);
+	}
+#endif
+
+#ifdef CONFIG_CMDLINE_BOOL
+#ifdef CONFIG_CMDLINE_OVERRIDE
+	strlcpy(boot_command_line, builtin_cmdline, COMMAND_LINE_SIZE);
+#else
+	if (builtin_cmdline[0] != '\0') {
+		/* Append bootloader command line to built-in */
+		strlcat(builtin_cmdline, " ", COMMAND_LINE_SIZE);
+		strlcat(builtin_cmdline, boot_command_line, COMMAND_LINE_SIZE);
+		strlcpy(boot_command_line, builtin_cmdline, COMMAND_LINE_SIZE);
+	}
+#endif /* CONFIG_CMDLINE_OVERRIDE */
+#endif /* CONFIG_CMDLINE_BOOL */
+	*cmdline_p = boot_command_line;
+
+	parse_early_param();
+
+	init_mm.start_code = (unsigned long) _stext;
+	init_mm.end_code   = (unsigned long) _etext;
+	init_mm.end_data   = (unsigned long) _edata;
+	init_mm.brk        = (unsigned long) _end;
+
+	setup_bootmem();
+	paging_init();
+	unflatten_device_tree();
+
+#ifdef CONFIG_SMP
+	setup_smp();
+#endif
+
+#ifdef CONFIG_DUMMY_CONSOLE
+	conswitchp = &dummy_con;
+#endif
+
+	riscv_fill_hwcap();
+}
+
+static int __init riscv_device_init(void)
+{
+	return of_platform_populate(NULL, of_default_bus_match_table, NULL, NULL);
+}
+subsys_initcall_sync(riscv_device_init);
diff --git a/arch/riscv/kernel/smp.c b/arch/riscv/kernel/smp.c
new file mode 100644
index 000000000000..b4a71ec5906f
--- /dev/null
+++ b/arch/riscv/kernel/smp.c
@@ -0,0 +1,110 @@
+/*
+ * SMP initialisation and IPI support
+ * Based on arch/arm64/kernel/smp.c
+ *
+ * Copyright (C) 2012 ARM Ltd.
+ * Copyright (C) 2015 Regents of the University of California
+ * Copyright (C) 2017 SiFive
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <linux/interrupt.h>
+#include <linux/smp.h>
+#include <linux/sched.h>
+
+#include <asm/sbi.h>
+#include <asm/tlbflush.h>
+#include <asm/cacheflush.h>
+
+/* A collection of single bit ipi messages.  */
+static struct {
+	unsigned long bits ____cacheline_aligned;
+} ipi_data[NR_CPUS] __cacheline_aligned;
+
+enum ipi_message_type {
+	IPI_RESCHEDULE,
+	IPI_CALL_FUNC,
+	IPI_MAX
+};
+
+irqreturn_t handle_ipi(void)
+{
+	unsigned long *pending_ipis = &ipi_data[smp_processor_id()].bits;
+
+	/* Clear pending IPI */
+	csr_clear(sip, SIE_SSIE);
+
+	while (true) {
+		unsigned long ops;
+
+		/* Order bit clearing and data access. */
+		mb();
+
+		ops = xchg(pending_ipis, 0);
+		if (ops == 0)
+			return IRQ_HANDLED;
+
+		if (ops & (1 << IPI_RESCHEDULE))
+			scheduler_ipi();
+
+		if (ops & (1 << IPI_CALL_FUNC))
+			generic_smp_call_function_interrupt();
+
+		BUG_ON((ops >> IPI_MAX) != 0);
+
+		/* Order data access and bit testing. */
+		mb();
+	}
+
+	return IRQ_HANDLED;
+}
+
+static void
+send_ipi_message(const struct cpumask *to_whom, enum ipi_message_type operation)
+{
+	int i;
+
+	mb();
+	for_each_cpu(i, to_whom)
+		set_bit(operation, &ipi_data[i].bits);
+
+	mb();
+	sbi_send_ipi(cpumask_bits(to_whom));
+}
+
+void arch_send_call_function_ipi_mask(struct cpumask *mask)
+{
+	send_ipi_message(mask, IPI_CALL_FUNC);
+}
+
+void arch_send_call_function_single_ipi(int cpu)
+{
+	send_ipi_message(cpumask_of(cpu), IPI_CALL_FUNC);
+}
+
+static void ipi_stop(void *unused)
+{
+	while (1)
+		wait_for_interrupt();
+}
+
+void smp_send_stop(void)
+{
+	on_each_cpu(ipi_stop, NULL, 1);
+}
+
+void smp_send_reschedule(int cpu)
+{
+	send_ipi_message(cpumask_of(cpu), IPI_RESCHEDULE);
+}
diff --git a/arch/riscv/kernel/smpboot.c b/arch/riscv/kernel/smpboot.c
new file mode 100644
index 000000000000..f741458c5a3f
--- /dev/null
+++ b/arch/riscv/kernel/smpboot.c
@@ -0,0 +1,114 @@
+/*
+ * SMP initialisation and IPI support
+ * Based on arch/arm64/kernel/smp.c
+ *
+ * Copyright (C) 2012 ARM Ltd.
+ * Copyright (C) 2015 Regents of the University of California
+ * Copyright (C) 2017 SiFive
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/mm.h>
+#include <linux/sched.h>
+#include <linux/kernel_stat.h>
+#include <linux/notifier.h>
+#include <linux/cpu.h>
+#include <linux/percpu.h>
+#include <linux/delay.h>
+#include <linux/err.h>
+#include <linux/irq.h>
+#include <linux/of.h>
+#include <linux/sched/task_stack.h>
+#include <asm/irq.h>
+#include <asm/mmu_context.h>
+#include <asm/tlbflush.h>
+#include <asm/sections.h>
+#include <asm/sbi.h>
+
+void *__cpu_up_stack_pointer[NR_CPUS];
+void *__cpu_up_task_pointer[NR_CPUS];
+
+void __init smp_prepare_boot_cpu(void)
+{
+}
+
+void __init smp_prepare_cpus(unsigned int max_cpus)
+{
+}
+
+void __init setup_smp(void)
+{
+	struct device_node *dn = NULL;
+	int hart, im_okay_therefore_i_am = 0;
+
+	while ((dn = of_find_node_by_type(dn, "cpu"))) {
+		hart = riscv_of_processor_hart(dn);
+		if (hart >= 0) {
+			set_cpu_possible(hart, true);
+			set_cpu_present(hart, true);
+			if (hart == smp_processor_id()) {
+				BUG_ON(im_okay_therefore_i_am);
+				im_okay_therefore_i_am = 1;
+			}
+		}
+	}
+
+	BUG_ON(!im_okay_therefore_i_am);
+}
+
+int __cpu_up(unsigned int cpu, struct task_struct *tidle)
+{
+	tidle->thread_info.cpu = cpu;
+
+	/*
+	 * On RISC-V systems, all harts boot on their own accord.  Our _start
+	 * selects the first hart to boot the kernel and causes the remainder
+	 * of the harts to spin in a loop waiting for their stack pointer to be
+	 * setup by that main hart.  Writing __cpu_up_stack_pointer signals to
+	 * the spinning harts that they can continue the boot process.
+	 */
+	smp_mb();
+	__cpu_up_stack_pointer[cpu] = task_stack_page(tidle) + THREAD_SIZE;
+	__cpu_up_task_pointer[cpu] = tidle;
+
+	while (!cpu_online(cpu))
+		cpu_relax();
+
+	return 0;
+}
+
+void __init smp_cpus_done(unsigned int max_cpus)
+{
+}
+
+/*
+ * C entry point for a secondary processor.
+ */
+asmlinkage void __init smp_callin(void)
+{
+	struct mm_struct *mm = &init_mm;
+
+	/* All kernel threads share the same mm context.  */
+	atomic_inc(&mm->mm_count);
+	current->active_mm = mm;
+
+	trap_init();
+	init_clockevent();
+	notify_cpu_starting(smp_processor_id());
+	set_cpu_online(smp_processor_id(), 1);
+	local_flush_tlb_all();
+	local_irq_enable();
+	preempt_disable();
+	cpu_startup_entry(CPUHP_AP_ONLINE_IDLE);
+}
diff --git a/arch/riscv/kernel/time.c b/arch/riscv/kernel/time.c
new file mode 100644
index 000000000000..8362a0e17a1a
--- /dev/null
+++ b/arch/riscv/kernel/time.c
@@ -0,0 +1,78 @@
+/*
+ * Copyright (C) 2012 Regents of the University of California
+ * Copyright (C) 2017 SiFive
+ *
+ *   This program is free software; you can redistribute it and/or
+ *   modify it under the terms of the GNU General Public License
+ *   as published by the Free Software Foundation, version 2.
+ *
+ *   This program is distributed in the hope that it will be useful,
+ *   but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *   GNU General Public License for more details.
+ */
+
+#include <linux/clocksource.h>
+#include <linux/clockchips.h>
+#include <linux/delay.h>
+#include <linux/timer_riscv.h>
+
+#include <asm/sbi.h>
+
+unsigned long riscv_timebase;
+
+DECLARE_PER_CPU(struct clock_event_device, riscv_clock_event);
+
+static int next_event(unsigned long delta, struct clock_event_device *ce)
+{
+	/*
+	 * time_init() allocates a timer for each CPU.  Since we're writing the
+	 * timer comparison register here we can't allow the timers to cross
+	 * harts.
+	 */
+	BUG_ON(ce != this_cpu_ptr(&riscv_clock_event));
+	sbi_set_timer(get_cycles64() + delta);
+	return 0;
+}
+
+static unsigned long long rdtime(struct clocksource *cs)
+{
+	/*
+	 * It's guarnteed that all the timers across all the harts are
+	 * synchronized within one tick of each other, so while this could
+	 * technically go backwards when hopping between CPUs, practically it
+	 * won't happen.
+	 */
+	return get_cycles64();
+}
+
+void riscv_timer_interrupt(void)
+{
+	struct clock_event_device *evdev = this_cpu_ptr(&riscv_clock_event);
+
+	evdev->event_handler(evdev);
+}
+
+void __init init_clockevent(void)
+{
+	int cpu_id = smp_processor_id();
+
+	timer_riscv_init(cpu_id, riscv_timebase, &next_event);
+	csr_set(sie, SIE_STIE);
+}
+
+void __init time_init(void)
+{
+	struct device_node *cpu;
+	u32 prop;
+
+	cpu = of_find_node_by_path("/cpus");
+	if (!cpu || of_property_read_u32(cpu, "timebase-frequency", &prop))
+		panic(KERN_WARNING "RISC-V system with no 'timebase-frequency' in DTS\n");
+	riscv_timebase = prop;
+
+	lpj_fine = riscv_timebase / HZ;
+
+	clocksource_riscv_init(&rdtime);
+	init_clockevent();
+}
diff --git a/arch/riscv/kernel/traps.c b/arch/riscv/kernel/traps.c
new file mode 100644
index 000000000000..93132cb59184
--- /dev/null
+++ b/arch/riscv/kernel/traps.c
@@ -0,0 +1,180 @@
+/*
+ * Copyright (C) 2012 Regents of the University of California
+ *
+ *   This program is free software; you can redistribute it and/or
+ *   modify it under the terms of the GNU General Public License
+ *   as published by the Free Software Foundation, version 2.
+ *
+ *   This program is distributed in the hope that it will be useful,
+ *   but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *   GNU General Public License for more details.
+ */
+
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/sched.h>
+#include <linux/sched/debug.h>
+#include <linux/sched/signal.h>
+#include <linux/signal.h>
+#include <linux/kdebug.h>
+#include <linux/uaccess.h>
+#include <linux/mm.h>
+#include <linux/module.h>
+#include <linux/irq.h>
+
+#include <asm/processor.h>
+#include <asm/ptrace.h>
+#include <asm/csr.h>
+
+int show_unhandled_signals = 1;
+
+extern asmlinkage void handle_exception(void);
+
+static DEFINE_SPINLOCK(die_lock);
+
+void die(struct pt_regs *regs, const char *str)
+{
+	static int die_counter;
+	int ret;
+
+	oops_enter();
+
+	spin_lock_irq(&die_lock);
+	console_verbose();
+	bust_spinlocks(1);
+
+	pr_emerg("%s [#%d]\n", str, ++die_counter);
+	print_modules();
+	show_regs(regs);
+
+	ret = notify_die(DIE_OOPS, str, regs, 0, regs->scause, SIGSEGV);
+
+	bust_spinlocks(0);
+	add_taint(TAINT_DIE, LOCKDEP_NOW_UNRELIABLE);
+	spin_unlock_irq(&die_lock);
+	oops_exit();
+
+	if (in_interrupt())
+		panic("Fatal exception in interrupt");
+	if (panic_on_oops)
+		panic("Fatal exception");
+	if (ret != NOTIFY_STOP)
+		do_exit(SIGSEGV);
+}
+
+static inline void do_trap_siginfo(int signo, int code,
+	unsigned long addr, struct task_struct *tsk)
+{
+	siginfo_t info;
+
+	info.si_signo = signo;
+	info.si_errno = 0;
+	info.si_code = code;
+	info.si_addr = (void __user *)addr;
+	force_sig_info(signo, &info, tsk);
+}
+
+void do_trap(struct pt_regs *regs, int signo, int code,
+	unsigned long addr, struct task_struct *tsk)
+{
+	if (show_unhandled_signals && unhandled_signal(tsk, signo)
+	    && printk_ratelimit()) {
+		pr_info("%s[%d]: unhandled signal %d code 0x%x at 0x" REG_FMT,
+			tsk->comm, task_pid_nr(tsk), signo, code, addr);
+		print_vma_addr(KERN_CONT " in ", GET_IP(regs));
+		pr_cont("\n");
+		show_regs(regs);
+	}
+
+	do_trap_siginfo(signo, code, addr, tsk);
+}
+
+static void do_trap_error(struct pt_regs *regs, int signo, int code,
+	unsigned long addr, const char *str)
+{
+	if (user_mode(regs)) {
+		do_trap(regs, signo, code, addr, current);
+	} else {
+		if (!fixup_exception(regs))
+			die(regs, str);
+	}
+}
+
+#define DO_ERROR_INFO(name, signo, code, str)				\
+asmlinkage void name(struct pt_regs *regs)				\
+{									\
+	do_trap_error(regs, signo, code, regs->sepc, "Oops - " str);	\
+}
+
+DO_ERROR_INFO(do_trap_unknown,
+	SIGILL, ILL_ILLTRP, "unknown exception");
+DO_ERROR_INFO(do_trap_insn_misaligned,
+	SIGBUS, BUS_ADRALN, "instruction address misaligned");
+DO_ERROR_INFO(do_trap_insn_fault,
+	SIGSEGV, SEGV_ACCERR, "instruction access fault");
+DO_ERROR_INFO(do_trap_insn_illegal,
+	SIGILL, ILL_ILLOPC, "illegal instruction");
+DO_ERROR_INFO(do_trap_load_misaligned,
+	SIGBUS, BUS_ADRALN, "load address misaligned");
+DO_ERROR_INFO(do_trap_load_fault,
+	SIGSEGV, SEGV_ACCERR, "load access fault");
+DO_ERROR_INFO(do_trap_store_misaligned,
+	SIGBUS, BUS_ADRALN, "store (or AMO) address misaligned");
+DO_ERROR_INFO(do_trap_store_fault,
+	SIGSEGV, SEGV_ACCERR, "store (or AMO) access fault");
+DO_ERROR_INFO(do_trap_ecall_u,
+	SIGILL, ILL_ILLTRP, "environment call from U-mode");
+DO_ERROR_INFO(do_trap_ecall_s,
+	SIGILL, ILL_ILLTRP, "environment call from S-mode");
+DO_ERROR_INFO(do_trap_ecall_m,
+	SIGILL, ILL_ILLTRP, "environment call from M-mode");
+
+asmlinkage void do_trap_break(struct pt_regs *regs)
+{
+#ifdef CONFIG_GENERIC_BUG
+	if (!user_mode(regs)) {
+		enum bug_trap_type type;
+
+		type = report_bug(regs->sepc, regs);
+		switch (type) {
+		case BUG_TRAP_TYPE_NONE:
+			break;
+		case BUG_TRAP_TYPE_WARN:
+			regs->sepc += sizeof(bug_insn_t);
+			return;
+		case BUG_TRAP_TYPE_BUG:
+			die(regs, "Kernel BUG");
+		}
+	}
+#endif /* CONFIG_GENERIC_BUG */
+
+	do_trap_siginfo(SIGTRAP, TRAP_BRKPT, regs->sepc, current);
+	regs->sepc += 0x4;
+}
+
+#ifdef CONFIG_GENERIC_BUG
+int is_valid_bugaddr(unsigned long pc)
+{
+	bug_insn_t insn;
+
+	if (pc < PAGE_OFFSET)
+		return 0;
+	if (probe_kernel_address((bug_insn_t __user *)pc, insn))
+		return 0;
+	return (insn == __BUG_INSN);
+}
+#endif /* CONFIG_GENERIC_BUG */
+
+void __init trap_init(void)
+{
+	/*
+	 * Set sup0 scratch register to 0, indicating to exception vector
+	 * that we are presently executing in the kernel
+	 */
+	csr_write(sscratch, 0);
+	/* Set the exception vector address */
+	csr_write(stvec, &handle_exception);
+	/* Enable all interrupts */
+	csr_write(sie, -1);
+}
diff --git a/arch/riscv/kernel/vdso.c b/arch/riscv/kernel/vdso.c
new file mode 100644
index 000000000000..e8a178df8144
--- /dev/null
+++ b/arch/riscv/kernel/vdso.c
@@ -0,0 +1,125 @@
+/*
+ * Copyright (C) 2004 Benjamin Herrenschmidt, IBM Corp.
+ *                    <benh@kernel.crashing.org>
+ * Copyright (C) 2012 ARM Limited
+ * Copyright (C) 2015 Regents of the University of California
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <linux/mm.h>
+#include <linux/slab.h>
+#include <linux/binfmts.h>
+#include <linux/err.h>
+
+#include <asm/vdso.h>
+
+extern char vdso_start[], vdso_end[];
+
+static unsigned int vdso_pages;
+static struct page **vdso_pagelist;
+
+/*
+ * The vDSO data page.
+ */
+static union {
+	struct vdso_data	data;
+	u8			page[PAGE_SIZE];
+} vdso_data_store __page_aligned_data;
+struct vdso_data *vdso_data = &vdso_data_store.data;
+
+static int __init vdso_init(void)
+{
+	unsigned int i;
+
+	vdso_pages = (vdso_end - vdso_start) >> PAGE_SHIFT;
+	vdso_pagelist =
+		kcalloc(vdso_pages + 1, sizeof(struct page *), GFP_KERNEL);
+	if (unlikely(vdso_pagelist == NULL)) {
+		pr_err("vdso: pagelist allocation failed\n");
+		return -ENOMEM;
+	}
+
+	for (i = 0; i < vdso_pages; i++) {
+		struct page *pg;
+
+		pg = virt_to_page(vdso_start + (i << PAGE_SHIFT));
+		ClearPageReserved(pg);
+		vdso_pagelist[i] = pg;
+	}
+	vdso_pagelist[i] = virt_to_page(vdso_data);
+
+	return 0;
+}
+arch_initcall(vdso_init);
+
+int arch_setup_additional_pages(struct linux_binprm *bprm,
+	int uses_interp)
+{
+	struct mm_struct *mm = current->mm;
+	unsigned long vdso_base, vdso_len;
+	int ret;
+
+	vdso_len = (vdso_pages + 1) << PAGE_SHIFT;
+
+	down_write(&mm->mmap_sem);
+	vdso_base = get_unmapped_area(NULL, 0, vdso_len, 0, 0);
+	if (unlikely(IS_ERR_VALUE(vdso_base))) {
+		ret = vdso_base;
+		goto end;
+	}
+
+	/*
+	 * Put vDSO base into mm struct. We need to do this before calling
+	 * install_special_mapping or the perf counter mmap tracking code
+	 * will fail to recognise it as a vDSO (since arch_vma_name fails).
+	 */
+	mm->context.vdso = (void *)vdso_base;
+
+	ret = install_special_mapping(mm, vdso_base, vdso_len,
+		(VM_READ | VM_EXEC | VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC),
+		vdso_pagelist);
+
+	if (unlikely(ret))
+		mm->context.vdso = NULL;
+
+end:
+	up_write(&mm->mmap_sem);
+	return ret;
+}
+
+const char *arch_vma_name(struct vm_area_struct *vma)
+{
+	if (vma->vm_mm && (vma->vm_start == (long)vma->vm_mm->context.vdso))
+		return "[vdso]";
+	return NULL;
+}
+
+/*
+ * Function stubs to prevent linker errors when AT_SYSINFO_EHDR is defined
+ */
+
+int in_gate_area_no_mm(unsigned long addr)
+{
+	return 0;
+}
+
+int in_gate_area(struct mm_struct *mm, unsigned long addr)
+{
+	return 0;
+}
+
+struct vm_area_struct *get_gate_vma(struct mm_struct *mm)
+{
+	return NULL;
+}
diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
new file mode 100644
index 000000000000..9f4bee5e51fd
--- /dev/null
+++ b/arch/riscv/mm/init.c
@@ -0,0 +1,70 @@
+/*
+ * Copyright (C) 2012 Regents of the University of California
+ *
+ *   This program is free software; you can redistribute it and/or
+ *   modify it under the terms of the GNU General Public License
+ *   as published by the Free Software Foundation, version 2.
+ *
+ *   This program is distributed in the hope that it will be useful,
+ *   but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *   GNU General Public License for more details.
+ */
+
+#include <linux/init.h>
+#include <linux/mm.h>
+#include <linux/bootmem.h>
+#include <linux/initrd.h>
+#include <linux/memblock.h>
+#include <linux/swap.h>
+
+#include <asm/tlbflush.h>
+#include <asm/sections.h>
+#include <asm/pgtable.h>
+#include <asm/io.h>
+
+static void __init zone_sizes_init(void)
+{
+	unsigned long zones_size[MAX_NR_ZONES];
+
+	memset(zones_size, 0, sizeof(zones_size));
+	zones_size[ZONE_NORMAL] = max_mapnr;
+	free_area_init_node(0, zones_size, pfn_base, NULL);
+}
+
+void setup_zero_page(void)
+{
+	memset((void *)empty_zero_page, 0, PAGE_SIZE);
+}
+
+void __init paging_init(void)
+{
+	init_mm.pgd = (pgd_t *)pfn_to_virt(csr_read(sptbr));
+
+	setup_zero_page();
+	local_flush_tlb_all();
+	zone_sizes_init();
+}
+
+void __init mem_init(void)
+{
+#ifdef CONFIG_FLATMEM
+	BUG_ON(!mem_map);
+#endif /* CONFIG_FLATMEM */
+
+	high_memory = (void *)(__va(PFN_PHYS(max_low_pfn)));
+	free_all_bootmem();
+
+	mem_init_print_info(NULL);
+}
+
+void free_initmem(void)
+{
+	free_initmem_default(0);
+}
+
+#ifdef CONFIG_BLK_DEV_INITRD
+void free_initrd_mem(unsigned long start, unsigned long end)
+{
+}
+#endif /* CONFIG_BLK_DEV_INITRD */
-- 
2.13.5