RISC-V nommu support v4

RISC-V nommu support v4

[Christoph Hellwig]

Hi all,

below is a series to support nommu mode on RISC-V.  For now this series
just works under qemu with the qemu-virt platform, but Damien has also
been able to get kernel based on this tree with additional driver hacks
to work on the Kendryte KD210, but that will take a while to cleanup
an upstream.

A git tree is available here:

    git://git.infradead.org/users/hch/riscv.git riscv-nommu.4

Gitweb:

    http://git.infradead.org/users/hch/riscv.git/shortlog/refs/heads/riscv-nommu.4

I've also pushed out a builtroot branch that can build a RISC-V nommu
root filesystem here:

   git://git.infradead.org/users/hch/buildroot.git riscv-nommu.2

Gitweb:

   http://git.infradead.org/users/hch/buildroot.git/shortlog/refs/heads/riscv-nommu.2


Changes since v3:
 - improve a few commit message
 - cleanup riscv_cpuid_to_hartid_mask
 - cleanup the timer handling
 - cleanup the IPI handling a little more
 - renamed CONFIG_M_MODE to CONFIG_RISCV_M_MODE
 - split out CONFIG_RISCV_SBI to make some of the ifdefs more obbious
 - use IS_ENABLED wherever possible instead of if ifdefs to make the
   code more readable

Changes since v2:
 - rebased to 5.3-rc
 - remove the EFI image header for nommu builds
 - set ARCH_SLAB_MINALIGN to ensure stack alignment in the flat binary
   loader
 - minor comment improvement
 - use #defines for more CSRs

Changes since v1:
 - fixes so that a kernel with this series still work on builds with an
   IOMMU
 - small clint cleanups
 - the binfmt_flat base and buildroot now don't put arguments on the stack

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[PATCH 01/20] irqchip/sifive-plic: set max threshold for ignored handlers

[Christoph Hellwig]

When running in M-mode, the S-mode plic handlers are still listed in the
device tree.  Ignore them by setting the maximum threshold.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Marc Zyngier <maz@kernel.org>
---
 drivers/irqchip/irq-sifive-plic.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/drivers/irqchip/irq-sifive-plic.c b/drivers/irqchip/irq-sifive-plic.c
index cf755964f2f8..c72c036aea76 100644
--- a/drivers/irqchip/irq-sifive-plic.c
+++ b/drivers/irqchip/irq-sifive-plic.c
@@ -244,6 +244,7 @@ static int __init plic_init(struct device_node *node,
 		struct plic_handler *handler;
 		irq_hw_number_t hwirq;
 		int cpu, hartid;
+		u32 threshold = 0;
 
 		if (of_irq_parse_one(node, i, &parent)) {
 			pr_err("failed to parse parent for context %d.\n", i);
@@ -266,10 +267,16 @@ static int __init plic_init(struct device_node *node,
 			continue;
 		}
 
+		/*
+		 * When running in M-mode we need to ignore the S-mode handler.
+		 * Here we assume it always comes later, but that might be a
+		 * little fragile.
+		 */
 		handler = per_cpu_ptr(&plic_handlers, cpu);
 		if (handler->present) {
 			pr_warn("handler already present for context %d.\n", i);
-			continue;
+			threshold = 0xffffffff;
+			goto done;
 		}
 
 		handler->present = true;
@@ -279,8 +286,9 @@ static int __init plic_init(struct device_node *node,
 		handler->enable_base =
 			plic_regs + ENABLE_BASE + i * ENABLE_PER_HART;
 
+done:
 		/* priority must be > threshold to trigger an interrupt */
-		writel(0, handler->hart_base + CONTEXT_THRESHOLD);
+		writel(threshold, handler->hart_base + CONTEXT_THRESHOLD);
 		for (hwirq = 1; hwirq <= nr_irqs; hwirq++)
 			plic_toggle(handler, hwirq, 0);
 		nr_handlers++;
-- 
2.20.1


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[PATCH 02/20] riscv: refactor the IPI code

[Christoph Hellwig]

This prepares for adding native non-SBI IPI code.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Atish Patra <atish.patra@wdc.com>
---
 arch/riscv/kernel/smp.c | 55 +++++++++++++++++++++++------------------
 1 file changed, 31 insertions(+), 24 deletions(-)

diff --git a/arch/riscv/kernel/smp.c b/arch/riscv/kernel/smp.c
index 5a9834503a2f..8cd730239613 100644
--- a/arch/riscv/kernel/smp.c
+++ b/arch/riscv/kernel/smp.c
@@ -78,13 +78,38 @@ static void ipi_stop(void)
 		wait_for_interrupt();
 }
 
+static void send_ipi_mask(const struct cpumask *mask, enum ipi_message_type op)
+{
+	int cpuid, hartid;
+	struct cpumask hartid_mask;
+
+	cpumask_clear(&hartid_mask);
+	mb();
+	for_each_cpu(cpuid, mask) {
+		set_bit(op, &ipi_data[cpuid].bits);
+		hartid = cpuid_to_hartid_map(cpuid);
+		cpumask_set_cpu(hartid, &hartid_mask);
+	}
+	mb();
+	sbi_send_ipi(cpumask_bits(&hartid_mask));
+}
+
+static void send_ipi_single(int cpu, enum ipi_message_type op)
+{
+	send_ipi_mask(cpumask_of(cpu), op);
+}
+
+static inline void clear_ipi(void)
+{
+	csr_clear(CSR_SIP, SIE_SSIE);
+}
+
 void riscv_software_interrupt(void)
 {
 	unsigned long *pending_ipis = &ipi_data[smp_processor_id()].bits;
 	unsigned long *stats = ipi_data[smp_processor_id()].stats;
 
-	/* Clear pending IPI */
-	csr_clear(CSR_SIP, SIE_SSIE);
+	clear_ipi();
 
 	while (true) {
 		unsigned long ops;
@@ -118,23 +143,6 @@ void riscv_software_interrupt(void)
 	}
 }
 
-static void
-send_ipi_message(const struct cpumask *to_whom, enum ipi_message_type operation)
-{
-	int cpuid, hartid;
-	struct cpumask hartid_mask;
-
-	cpumask_clear(&hartid_mask);
-	mb();
-	for_each_cpu(cpuid, to_whom) {
-		set_bit(operation, &ipi_data[cpuid].bits);
-		hartid = cpuid_to_hartid_map(cpuid);
-		cpumask_set_cpu(hartid, &hartid_mask);
-	}
-	mb();
-	sbi_send_ipi(cpumask_bits(&hartid_mask));
-}
-
 static const char * const ipi_names[] = {
 	[IPI_RESCHEDULE]	= "Rescheduling interrupts",
 	[IPI_CALL_FUNC]		= "Function call interrupts",
@@ -156,12 +164,12 @@ void show_ipi_stats(struct seq_file *p, int prec)
 
 void arch_send_call_function_ipi_mask(struct cpumask *mask)
 {
-	send_ipi_message(mask, IPI_CALL_FUNC);
+	send_ipi_mask(mask, IPI_CALL_FUNC);
 }
 
 void arch_send_call_function_single_ipi(int cpu)
 {
-	send_ipi_message(cpumask_of(cpu), IPI_CALL_FUNC);
+	send_ipi_single(cpu, IPI_CALL_FUNC);
 }
 
 void smp_send_stop(void)
@@ -176,7 +184,7 @@ void smp_send_stop(void)
 
 		if (system_state <= SYSTEM_RUNNING)
 			pr_crit("SMP: stopping secondary CPUs\n");
-		send_ipi_message(&mask, IPI_CPU_STOP);
+		send_ipi_mask(&mask, IPI_CPU_STOP);
 	}
 
 	/* Wait up to one second for other CPUs to stop */
@@ -191,6 +199,5 @@ void smp_send_stop(void)
 
 void smp_send_reschedule(int cpu)
 {
-	send_ipi_message(cpumask_of(cpu), IPI_RESCHEDULE);
+	send_ipi_single(cpu, IPI_RESCHEDULE);
 }
-
-- 
2.20.1


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[PATCH 03/20] riscv: cleanup send_ipi_mask

[Christoph Hellwig]

Use the special barriers for atomic bitops to make the intention
a little more clear, and use riscv_cpuid_to_hartid_mask instead of
open coding it.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Atish Patra <atish.patra@wdc.com>
---
 arch/riscv/kernel/smp.c | 16 +++++++---------
 1 file changed, 7 insertions(+), 9 deletions(-)

diff --git a/arch/riscv/kernel/smp.c b/arch/riscv/kernel/smp.c
index 8cd730239613..2e21669aa068 100644
--- a/arch/riscv/kernel/smp.c
+++ b/arch/riscv/kernel/smp.c
@@ -80,17 +80,15 @@ static void ipi_stop(void)
 
 static void send_ipi_mask(const struct cpumask *mask, enum ipi_message_type op)
 {
-	int cpuid, hartid;
 	struct cpumask hartid_mask;
+	int cpu;
 
-	cpumask_clear(&hartid_mask);
-	mb();
-	for_each_cpu(cpuid, mask) {
-		set_bit(op, &ipi_data[cpuid].bits);
-		hartid = cpuid_to_hartid_map(cpuid);
-		cpumask_set_cpu(hartid, &hartid_mask);
-	}
-	mb();
+	smp_mb__before_atomic();
+	for_each_cpu(cpu, mask)
+		set_bit(op, &ipi_data[cpu].bits);
+	smp_mb__after_atomic();
+
+	riscv_cpuid_to_hartid_mask(mask, &hartid_mask);
 	sbi_send_ipi(cpumask_bits(&hartid_mask));
 }
 
-- 
2.20.1


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[PATCH 04/20] riscv: optimize send_ipi_single

[Christoph Hellwig]

Don't go through send_ipi_mask, but just set the op bit an then pass a
simple generate hartid mask directly to sbi_send_ipi.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Atish Patra <atish.patra@wdc.com>
---
 arch/riscv/kernel/smp.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/arch/riscv/kernel/smp.c b/arch/riscv/kernel/smp.c
index 2e21669aa068..a3715d621f60 100644
--- a/arch/riscv/kernel/smp.c
+++ b/arch/riscv/kernel/smp.c
@@ -94,7 +94,13 @@ static void send_ipi_mask(const struct cpumask *mask, enum ipi_message_type op)
 
 static void send_ipi_single(int cpu, enum ipi_message_type op)
 {
-	send_ipi_mask(cpumask_of(cpu), op);
+	int hartid = cpuid_to_hartid_map(cpu);
+
+	smp_mb__before_atomic();
+	set_bit(op, &ipi_data[cpu].bits);
+	smp_mb__after_atomic();
+
+	sbi_send_ipi(cpumask_bits(cpumask_of(hartid)));
 }
 
 static inline void clear_ipi(void)
-- 
2.20.1


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[PATCH 05/20] riscv: cleanup riscv_cpuid_to_hartid_mask

[Christoph Hellwig]

Move the initial clearing of the mask from the callers to
riscv_cpuid_to_hartid_mask, and remove the unused !CONFIG_SMP stub.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Atish Patra <atish.patra@wdc.com>
---
 arch/riscv/include/asm/smp.h      | 6 ------
 arch/riscv/include/asm/tlbflush.h | 1 -
 arch/riscv/kernel/smp.c           | 1 +
 arch/riscv/mm/cacheflush.c        | 1 -
 4 files changed, 1 insertion(+), 8 deletions(-)

diff --git a/arch/riscv/include/asm/smp.h b/arch/riscv/include/asm/smp.h
index c6ed4d691def..a83451d73a4e 100644
--- a/arch/riscv/include/asm/smp.h
+++ b/arch/riscv/include/asm/smp.h
@@ -61,11 +61,5 @@ static inline unsigned long cpuid_to_hartid_map(int cpu)
 	return boot_cpu_hartid;
 }
 
-static inline void riscv_cpuid_to_hartid_mask(const struct cpumask *in,
-					      struct cpumask *out)
-{
-	cpumask_set_cpu(cpuid_to_hartid_map(0), out);
-}
-
 #endif /* CONFIG_SMP */
 #endif /* _ASM_RISCV_SMP_H */
diff --git a/arch/riscv/include/asm/tlbflush.h b/arch/riscv/include/asm/tlbflush.h
index 4d9bbe8438bf..df31fe2ed09c 100644
--- a/arch/riscv/include/asm/tlbflush.h
+++ b/arch/riscv/include/asm/tlbflush.h
@@ -47,7 +47,6 @@ static inline void remote_sfence_vma(struct cpumask *cmask, unsigned long start,
 {
 	struct cpumask hmask;
 
-	cpumask_clear(&hmask);
 	riscv_cpuid_to_hartid_mask(cmask, &hmask);
 	sbi_remote_sfence_vma(hmask.bits, start, size);
 }
diff --git a/arch/riscv/kernel/smp.c b/arch/riscv/kernel/smp.c
index a3715d621f60..3836760d7aaf 100644
--- a/arch/riscv/kernel/smp.c
+++ b/arch/riscv/kernel/smp.c
@@ -56,6 +56,7 @@ void riscv_cpuid_to_hartid_mask(const struct cpumask *in, struct cpumask *out)
 {
 	int cpu;
 
+	cpumask_clear(out);
 	for_each_cpu(cpu, in)
 		cpumask_set_cpu(cpuid_to_hartid_map(cpu), out);
 }
diff --git a/arch/riscv/mm/cacheflush.c b/arch/riscv/mm/cacheflush.c
index 9ebcff8ba263..3f15938dec89 100644
--- a/arch/riscv/mm/cacheflush.c
+++ b/arch/riscv/mm/cacheflush.c
@@ -47,7 +47,6 @@ void flush_icache_mm(struct mm_struct *mm, bool local)
 	cpumask_andnot(&others, mm_cpumask(mm), cpumask_of(cpu));
 	local |= cpumask_empty(&others);
 	if (mm != current->active_mm || !local) {
-		cpumask_clear(&hmask);
 		riscv_cpuid_to_hartid_mask(&others, &hmask);
 		sbi_remote_fence_i(hmask.bits);
 	} else {
-- 
2.20.1


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[PATCH 06/20] riscv: don't use the rdtime(h) pseudo-instructions

[Christoph Hellwig]

If we just use the CSRs that these map to directly the code is simpler
and doesn't require extra inline assembly code.  Also fix up the top-level
comment in timer-riscv.c to not talk about the cycle count or mention
details of the clocksource interface, of which this file is just a
consumer.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Atish Patra <atish.patra@wdc.com>
---
 arch/riscv/include/asm/timex.h    | 44 +++++++++++++++----------------
 drivers/clocksource/timer-riscv.c | 17 +++---------
 2 files changed, 25 insertions(+), 36 deletions(-)

diff --git a/arch/riscv/include/asm/timex.h b/arch/riscv/include/asm/timex.h
index 6a703ec9d796..c7ef131b9e4c 100644
--- a/arch/riscv/include/asm/timex.h
+++ b/arch/riscv/include/asm/timex.h
@@ -6,43 +6,41 @@
 #ifndef _ASM_RISCV_TIMEX_H
 #define _ASM_RISCV_TIMEX_H
 
-#include <asm/param.h>
+#include <asm/csr.h>
 
 typedef unsigned long cycles_t;
 
-static inline cycles_t get_cycles_inline(void)
+static inline cycles_t get_cycles(void)
 {
-	cycles_t n;
-
-	__asm__ __volatile__ (
-		"rdtime %0"
-		: "=r" (n));
-	return n;
+	return csr_read(CSR_TIME);
 }
-#define get_cycles get_cycles_inline
+#define get_cycles get_cycles
 
 #ifdef CONFIG_64BIT
-static inline uint64_t get_cycles64(void)
+static inline u64 get_cycles64(void)
+{
+	return get_cycles();
+}
+#else /* CONFIG_64BIT */
+static inline u32 get_cycles_hi(void)
 {
-        return get_cycles();
+	return csr_read(CSR_TIMEH);
 }
-#else
-static inline uint64_t get_cycles64(void)
+
+static inline u64 get_cycles64(void)
 {
-	u32 lo, hi, tmp;
-	__asm__ __volatile__ (
-		"1:\n"
-		"rdtimeh %0\n"
-		"rdtime %1\n"
-		"rdtimeh %2\n"
-		"bne %0, %2, 1b"
-		: "=&r" (hi), "=&r" (lo), "=&r" (tmp));
+	u32 hi, lo;
+
+	do {
+		hi = get_cycles_hi();
+		lo = get_cycles();
+	} while (hi != get_cycles_hi());
+
 	return ((u64)hi << 32) | lo;
 }
-#endif
+#endif /* CONFIG_64BIT */
 
 #define ARCH_HAS_READ_CURRENT_TIMER
-
 static inline int read_current_timer(unsigned long *timer_val)
 {
 	*timer_val = get_cycles();
diff --git a/drivers/clocksource/timer-riscv.c b/drivers/clocksource/timer-riscv.c
index 09e031176bc6..470c7ef02ea4 100644
--- a/drivers/clocksource/timer-riscv.c
+++ b/drivers/clocksource/timer-riscv.c
@@ -2,6 +2,10 @@
 /*
  * Copyright (C) 2012 Regents of the University of California
  * Copyright (C) 2017 SiFive
+ *
+ * All RISC-V systems have a timer attached to every hart.  These timers can be
+ * read from the "time" and "timeh" CSRs, and can use the SBI to setup
+ * events.
  */
 #include <linux/clocksource.h>
 #include <linux/clockchips.h>
@@ -12,19 +16,6 @@
 #include <asm/smp.h>
 #include <asm/sbi.h>
 
-/*
- * All RISC-V systems have a timer attached to every hart.  These timers can be
- * read by the 'rdcycle' pseudo instruction, and can use the SBI to setup
- * events.  In order to abstract the architecture-specific timer reading and
- * setting functions away from the clock event insertion code, we provide
- * function pointers to the clockevent subsystem that perform two basic
- * operations: rdtime() reads the timer on the current CPU, and
- * next_event(delta) sets the next timer event to 'delta' cycles in the future.
- * As the timers are inherently a per-cpu resource, these callbacks perform
- * operations on the current hart.  There is guaranteed to be exactly one timer
- * per hart on all RISC-V systems.
- */
-
 static int riscv_clock_next_event(unsigned long delta,
 		struct clock_event_device *ce)
 {
-- 
2.20.1


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[PATCH 07/20] riscv: move the TLB flush logic out of line

[Christoph Hellwig]

The TLB flush logic is going to become more complex.  Start moving
it out of line.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Atish Patra <atish.patra@wdc.com>
---
 arch/riscv/include/asm/tlbflush.h | 37 ++++++-------------------------
 arch/riscv/mm/Makefile            |  3 +++
 arch/riscv/mm/tlbflush.c          | 35 +++++++++++++++++++++++++++++
 3 files changed, 45 insertions(+), 30 deletions(-)
 create mode 100644 arch/riscv/mm/tlbflush.c

diff --git a/arch/riscv/include/asm/tlbflush.h b/arch/riscv/include/asm/tlbflush.h
index df31fe2ed09c..075a784c66c5 100644
--- a/arch/riscv/include/asm/tlbflush.h
+++ b/arch/riscv/include/asm/tlbflush.h
@@ -25,8 +25,13 @@ static inline void local_flush_tlb_page(unsigned long addr)
 	__asm__ __volatile__ ("sfence.vma %0" : : "r" (addr) : "memory");
 }
 
-#ifndef CONFIG_SMP
-
+#ifdef CONFIG_SMP
+void flush_tlb_all(void);
+void flush_tlb_mm(struct mm_struct *mm);
+void flush_tlb_page(struct vm_area_struct *vma, unsigned long addr);
+void flush_tlb_range(struct vm_area_struct *vma, unsigned long start,
+		unsigned long end);
+#else /* CONFIG_SMP */
 #define flush_tlb_all() local_flush_tlb_all()
 #define flush_tlb_page(vma, addr) local_flush_tlb_page(addr)
 
@@ -37,34 +42,6 @@ static inline void flush_tlb_range(struct vm_area_struct *vma,
 }
 
 #define flush_tlb_mm(mm) flush_tlb_all()
-
-#else /* CONFIG_SMP */
-
-#include <asm/sbi.h>
-
-static inline void remote_sfence_vma(struct cpumask *cmask, unsigned long start,
-				     unsigned long size)
-{
-	struct cpumask hmask;
-
-	riscv_cpuid_to_hartid_mask(cmask, &hmask);
-	sbi_remote_sfence_vma(hmask.bits, start, size);
-}
-
-#define flush_tlb_all() sbi_remote_sfence_vma(NULL, 0, -1)
-
-#define flush_tlb_range(vma, start, end) \
-	remote_sfence_vma(mm_cpumask((vma)->vm_mm), start, (end) - (start))
-
-static inline void flush_tlb_page(struct vm_area_struct *vma,
-				  unsigned long addr)
-{
-	flush_tlb_range(vma, addr, addr + PAGE_SIZE);
-}
-
-#define flush_tlb_mm(mm)				\
-	remote_sfence_vma(mm_cpumask(mm), 0, -1)
-
 #endif /* CONFIG_SMP */
 
 /* Flush a range of kernel pages */
diff --git a/arch/riscv/mm/Makefile b/arch/riscv/mm/Makefile
index 74055e1d6f21..9d9a17335686 100644
--- a/arch/riscv/mm/Makefile
+++ b/arch/riscv/mm/Makefile
@@ -13,4 +13,7 @@ obj-y += cacheflush.o
 obj-y += context.o
 obj-y += sifive_l2_cache.o
 
+ifeq ($(CONFIG_MMU),y)
+obj-$(CONFIG_SMP) += tlbflush.o
+endif
 obj-$(CONFIG_HUGETLB_PAGE) += hugetlbpage.o
diff --git a/arch/riscv/mm/tlbflush.c b/arch/riscv/mm/tlbflush.c
new file mode 100644
index 000000000000..df93b26f1b9d
--- /dev/null
+++ b/arch/riscv/mm/tlbflush.c
@@ -0,0 +1,35 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/mm.h>
+#include <linux/smp.h>
+#include <asm/sbi.h>
+
+void flush_tlb_all(void)
+{
+	sbi_remote_sfence_vma(NULL, 0, -1);
+}
+
+static void __sbi_tlb_flush_range(struct cpumask *cmask, unsigned long start,
+		unsigned long size)
+{
+	struct cpumask hmask;
+
+	riscv_cpuid_to_hartid_mask(cmask, &hmask);
+	sbi_remote_sfence_vma(hmask.bits, start, size);
+}
+
+void flush_tlb_mm(struct mm_struct *mm)
+{
+	__sbi_tlb_flush_range(mm_cpumask(mm), 0, -1);
+}
+
+void flush_tlb_page(struct vm_area_struct *vma, unsigned long addr)
+{
+	__sbi_tlb_flush_range(mm_cpumask(vma->vm_mm), addr, PAGE_SIZE);
+}
+
+void flush_tlb_range(struct vm_area_struct *vma, unsigned long start,
+		unsigned long end)
+{
+	__sbi_tlb_flush_range(mm_cpumask(vma->vm_mm), start, end - start);
+}
-- 
2.20.1


_______________________________________________
linux-riscv mailing list
linux-riscv@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-riscv

[PATCH 08/20] riscv: abstract out CSR names for supervisor vs machine mode

[Christoph Hellwig]

Many of the privileged CSRs exist in a supervisor and machine version
that are used very similarly.  Provide a new X-naming layer so that
we don't have to ifdef everywhere for M-mode Linux support.

Contains contributions from Damien Le Moal <Damien.LeMoal@wdc.com>.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Atish Patra <atish.patra@wdc.com>
---
 arch/riscv/Kconfig                 |  4 ++
 arch/riscv/include/asm/asm.h       |  6 +++
 arch/riscv/include/asm/csr.h       | 58 ++++++++++++++++++++++++++--
 arch/riscv/include/asm/irqflags.h  | 12 +++---
 arch/riscv/include/asm/processor.h |  2 +-
 arch/riscv/include/asm/ptrace.h    | 16 ++++----
 arch/riscv/include/asm/switch_to.h | 10 ++---
 arch/riscv/kernel/asm-offsets.c    |  8 ++--
 arch/riscv/kernel/entry.S          | 62 ++++++++++++++++--------------
 arch/riscv/kernel/fpu.S            |  8 ++--
 arch/riscv/kernel/head.S           | 12 +++---
 arch/riscv/kernel/irq.c            |  4 +-
 arch/riscv/kernel/process.c        | 15 ++++----
 arch/riscv/kernel/signal.c         | 21 +++++-----
 arch/riscv/kernel/traps.c          | 16 ++++----
 arch/riscv/lib/uaccess.S           | 12 +++---
 arch/riscv/mm/extable.c            |  4 +-
 arch/riscv/mm/fault.c              |  6 +--
 drivers/clocksource/timer-riscv.c  |  8 ++--
 drivers/irqchip/irq-sifive-plic.c  |  4 +-
 20 files changed, 178 insertions(+), 110 deletions(-)

diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index f392358ad4ea..e4a4bebdbcf3 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -57,6 +57,10 @@ config RISCV
 	select ARCH_WANT_HUGE_PMD_SHARE if 64BIT
 	select SPARSEMEM_STATIC if 32BIT
 
+# set if we run in machine mode, cleared if we run in supervisor mode
+config RISCV_M_MODE
+	bool
+
 config MMU
 	def_bool y
 
diff --git a/arch/riscv/include/asm/asm.h b/arch/riscv/include/asm/asm.h
index 5a02b7d50940..0dfbeeb6fcb4 100644
--- a/arch/riscv/include/asm/asm.h
+++ b/arch/riscv/include/asm/asm.h
@@ -65,4 +65,10 @@
 #error "Unexpected __SIZEOF_SHORT__"
 #endif
 
+#ifdef CONFIG_RISCV_M_MODE
+# define Xret		mret
+#else
+# define Xret		sret
+#endif
+
 #endif /* _ASM_RISCV_ASM_H */
diff --git a/arch/riscv/include/asm/csr.h b/arch/riscv/include/asm/csr.h
index a18923fa23c8..0dae5c361f29 100644
--- a/arch/riscv/include/asm/csr.h
+++ b/arch/riscv/include/asm/csr.h
@@ -11,8 +11,11 @@
 
 /* Status register flags */
 #define SR_SIE		_AC(0x00000002, UL) /* Supervisor Interrupt Enable */
+#define SR_MIE		_AC(0x00000008, UL) /* Machine Interrupt Enable */
 #define SR_SPIE		_AC(0x00000020, UL) /* Previous Supervisor IE */
+#define SR_MPIE		_AC(0x00000080, UL) /* Previous Machine IE */
 #define SR_SPP		_AC(0x00000100, UL) /* Previously Supervisor */
+#define SR_MPP		_AC(0x00001800, UL) /* Previously Machine */
 #define SR_SUM		_AC(0x00040000, UL) /* Supervisor User Memory Access */
 
 #define SR_FS		_AC(0x00006000, UL) /* Floating-point Status */
@@ -44,8 +47,8 @@
 #define SATP_MODE	SATP_MODE_39
 #endif
 
-/* SCAUSE */
-#define SCAUSE_IRQ_FLAG		(_AC(1, UL) << (__riscv_xlen - 1))
+/* *CAUSE */
+#define XCAUSE_IRQ_FLAG		(_AC(1, UL) << (__riscv_xlen - 1))
 
 #define IRQ_U_SOFT		0
 #define IRQ_S_SOFT		1
@@ -67,11 +70,26 @@
 #define EXC_LOAD_PAGE_FAULT	13
 #define EXC_STORE_PAGE_FAULT	15
 
-/* SIE (Interrupt Enable) and SIP (Interrupt Pending) flags */
+/* SIE/SIP (Machine Interrupt Enable/Pending) flags */
+#define MIE_MSIE		(_AC(0x1, UL) << IRQ_M_SOFT)
+#define MIE_MTIE		(_AC(0x1, UL) << IRQ_M_TIMER)
+#define MIE_MEIE		(_AC(0x1, UL) << IRQ_M_EXT)
+
+/* SIE/SIP (Supervisor Interrupt Enable/Pending) flags */
 #define SIE_SSIE		(_AC(0x1, UL) << IRQ_S_SOFT)
 #define SIE_STIE		(_AC(0x1, UL) << IRQ_S_TIMER)
 #define SIE_SEIE		(_AC(0x1, UL) << IRQ_S_EXT)
 
+/* symbolic CSR names: */
+#define CSR_MSTATUS		0x300
+#define CSR_MIE			0x304
+#define CSR_MTVEC		0x305
+#define CSR_MSCRATCH		0x340
+#define CSR_MEPC		0x341
+#define CSR_MCAUSE		0x342
+#define CSR_MTVAL		0x343
+#define CSR_MIP			0x344
+
 #define CSR_CYCLE		0xc00
 #define CSR_TIME		0xc01
 #define CSR_INSTRET		0xc02
@@ -89,6 +107,40 @@
 #define CSR_TIMEH		0xc81
 #define CSR_INSTRETH		0xc82
 
+#ifdef CONFIG_RISCV_M_MODE
+# define CSR_XSTATUS	CSR_MSTATUS
+# define CSR_XIE	CSR_MIE
+# define CSR_XTVEC	CSR_MTVEC
+# define CSR_XSCRATCH	CSR_MSCRATCH
+# define CSR_XEPC	CSR_MEPC
+# define CSR_XCAUSE	CSR_MCAUSE
+# define CSR_XTVAL	CSR_MTVAL
+# define CSR_XIP	CSR_MIP
+
+# define SR_XIE		SR_MIE
+# define SR_XPIE	SR_MPIE
+# define SR_XPP		SR_MPP
+
+# define XIE_XTIE	MIE_MTIE
+# define XIE_XEIE	MIE_MEIE
+#else /* CONFIG_RISCV_M_MODE */
+# define CSR_XSTATUS	CSR_SSTATUS
+# define CSR_XIE	CSR_SIE
+# define CSR_XTVEC	CSR_STVEC
+# define CSR_XSCRATCH	CSR_SSCRATCH
+# define CSR_XEPC	CSR_SEPC
+# define CSR_XCAUSE	CSR_SCAUSE
+# define CSR_XTVAL	CSR_STVAL
+# define CSR_XIP	CSR_SIP
+
+# define SR_XIE		SR_SIE
+# define SR_XPIE	SR_SPIE
+# define SR_XPP		SR_SPP
+
+# define XIE_XTIE	SIE_STIE
+# define XIE_XEIE	SIE_SEIE
+#endif /* CONFIG_RISCV_M_MODE */
+
 #ifndef __ASSEMBLY__
 
 #define csr_swap(csr, val)					\
diff --git a/arch/riscv/include/asm/irqflags.h b/arch/riscv/include/asm/irqflags.h
index e70f647ce3b7..ba2828a37d72 100644
--- a/arch/riscv/include/asm/irqflags.h
+++ b/arch/riscv/include/asm/irqflags.h
@@ -13,31 +13,31 @@
 /* read interrupt enabled status */
 static inline unsigned long arch_local_save_flags(void)
 {
-	return csr_read(CSR_SSTATUS);
+	return csr_read(CSR_XSTATUS);
 }
 
 /* unconditionally enable interrupts */
 static inline void arch_local_irq_enable(void)
 {
-	csr_set(CSR_SSTATUS, SR_SIE);
+	csr_set(CSR_XSTATUS, SR_XIE);
 }
 
 /* unconditionally disable interrupts */
 static inline void arch_local_irq_disable(void)
 {
-	csr_clear(CSR_SSTATUS, SR_SIE);
+	csr_clear(CSR_XSTATUS, SR_XIE);
 }
 
 /* get status and disable interrupts */
 static inline unsigned long arch_local_irq_save(void)
 {
-	return csr_read_clear(CSR_SSTATUS, SR_SIE);
+	return csr_read_clear(CSR_XSTATUS, SR_XIE);
 }
 
 /* test flags */
 static inline int arch_irqs_disabled_flags(unsigned long flags)
 {
-	return !(flags & SR_SIE);
+	return !(flags & SR_XIE);
 }
 
 /* test hardware interrupt enable bit */
@@ -49,7 +49,7 @@ static inline int arch_irqs_disabled(void)
 /* set interrupt enabled status */
 static inline void arch_local_irq_restore(unsigned long flags)
 {
-	csr_set(CSR_SSTATUS, flags & SR_SIE);
+	csr_set(CSR_XSTATUS, flags & SR_XIE);
 }
 
 #endif /* _ASM_RISCV_IRQFLAGS_H */
diff --git a/arch/riscv/include/asm/processor.h b/arch/riscv/include/asm/processor.h
index f539149d04c2..46f825e34575 100644
--- a/arch/riscv/include/asm/processor.h
+++ b/arch/riscv/include/asm/processor.h
@@ -42,7 +42,7 @@ struct thread_struct {
 	((struct pt_regs *)(task_stack_page(tsk) + THREAD_SIZE		\
 			    - ALIGN(sizeof(struct pt_regs), STACK_ALIGN)))
 
-#define KSTK_EIP(tsk)		(task_pt_regs(tsk)->sepc)
+#define KSTK_EIP(tsk)		(task_pt_regs(tsk)->xepc)
 #define KSTK_ESP(tsk)		(task_pt_regs(tsk)->sp)
 
 
diff --git a/arch/riscv/include/asm/ptrace.h b/arch/riscv/include/asm/ptrace.h
index d48d1e13973c..7684d81d0e84 100644
--- a/arch/riscv/include/asm/ptrace.h
+++ b/arch/riscv/include/asm/ptrace.h
@@ -12,7 +12,7 @@
 #ifndef __ASSEMBLY__
 
 struct pt_regs {
-	unsigned long sepc;
+	unsigned long xepc;
 	unsigned long ra;
 	unsigned long sp;
 	unsigned long gp;
@@ -44,10 +44,10 @@ struct pt_regs {
 	unsigned long t4;
 	unsigned long t5;
 	unsigned long t6;
-	/* Supervisor CSRs */
-	unsigned long sstatus;
-	unsigned long sbadaddr;
-	unsigned long scause;
+	/* Supervisor/Machine CSRs */
+	unsigned long xstatus;
+	unsigned long xbadaddr;
+	unsigned long xcause;
 	/* a0 value before the syscall */
 	unsigned long orig_a0;
 };
@@ -58,18 +58,18 @@ struct pt_regs {
 #define REG_FMT "%08lx"
 #endif
 
-#define user_mode(regs) (((regs)->sstatus & SR_SPP) == 0)
+#define user_mode(regs) (((regs)->xstatus & SR_XPP) == 0)
 
 
 /* Helpers for working with the instruction pointer */
 static inline unsigned long instruction_pointer(struct pt_regs *regs)
 {
-	return regs->sepc;
+	return regs->xepc;
 }
 static inline void instruction_pointer_set(struct pt_regs *regs,
 					   unsigned long val)
 {
-	regs->sepc = val;
+	regs->xepc = val;
 }
 
 #define profile_pc(regs) instruction_pointer(regs)
diff --git a/arch/riscv/include/asm/switch_to.h b/arch/riscv/include/asm/switch_to.h
index f0227bdce0f0..77593105b367 100644
--- a/arch/riscv/include/asm/switch_to.h
+++ b/arch/riscv/include/asm/switch_to.h
@@ -16,19 +16,19 @@ extern void __fstate_restore(struct task_struct *restore_from);
 
 static inline void __fstate_clean(struct pt_regs *regs)
 {
-	regs->sstatus = (regs->sstatus & ~SR_FS) | SR_FS_CLEAN;
+	regs->xstatus = (regs->xstatus & ~SR_FS) | SR_FS_CLEAN;
 }
 
 static inline void fstate_off(struct task_struct *task,
 			      struct pt_regs *regs)
 {
-	regs->sstatus = (regs->sstatus & ~SR_FS) | SR_FS_OFF;
+	regs->xstatus = (regs->xstatus & ~SR_FS) | SR_FS_OFF;
 }
 
 static inline void fstate_save(struct task_struct *task,
 			       struct pt_regs *regs)
 {
-	if ((regs->sstatus & SR_FS) == SR_FS_DIRTY) {
+	if ((regs->xstatus & SR_FS) == SR_FS_DIRTY) {
 		__fstate_save(task);
 		__fstate_clean(regs);
 	}
@@ -37,7 +37,7 @@ static inline void fstate_save(struct task_struct *task,
 static inline void fstate_restore(struct task_struct *task,
 				  struct pt_regs *regs)
 {
-	if ((regs->sstatus & SR_FS) != SR_FS_OFF) {
+	if ((regs->xstatus & SR_FS) != SR_FS_OFF) {
 		__fstate_restore(task);
 		__fstate_clean(regs);
 	}
@@ -49,7 +49,7 @@ static inline void __switch_to_aux(struct task_struct *prev,
 	struct pt_regs *regs;
 
 	regs = task_pt_regs(prev);
-	if (unlikely(regs->sstatus & SR_SD))
+	if (unlikely(regs->xstatus & SR_SD))
 		fstate_save(prev, regs);
 	fstate_restore(next, task_pt_regs(next));
 }
diff --git a/arch/riscv/kernel/asm-offsets.c b/arch/riscv/kernel/asm-offsets.c
index 9f5628c38ac9..d631ad41917b 100644
--- a/arch/riscv/kernel/asm-offsets.c
+++ b/arch/riscv/kernel/asm-offsets.c
@@ -71,7 +71,7 @@ void asm_offsets(void)
 	OFFSET(TASK_THREAD_FCSR, task_struct, thread.fstate.fcsr);
 
 	DEFINE(PT_SIZE, sizeof(struct pt_regs));
-	OFFSET(PT_SEPC, pt_regs, sepc);
+	OFFSET(PT_XEPC, pt_regs, xepc);
 	OFFSET(PT_RA, pt_regs, ra);
 	OFFSET(PT_FP, pt_regs, s0);
 	OFFSET(PT_S0, pt_regs, s0);
@@ -105,9 +105,9 @@ void asm_offsets(void)
 	OFFSET(PT_T6, pt_regs, t6);
 	OFFSET(PT_GP, pt_regs, gp);
 	OFFSET(PT_ORIG_A0, pt_regs, orig_a0);
-	OFFSET(PT_SSTATUS, pt_regs, sstatus);
-	OFFSET(PT_SBADADDR, pt_regs, sbadaddr);
-	OFFSET(PT_SCAUSE, pt_regs, scause);
+	OFFSET(PT_XSTATUS, pt_regs, xstatus);
+	OFFSET(PT_XBADADDR, pt_regs, xbadaddr);
+	OFFSET(PT_XCAUSE, pt_regs, xcause);
 
 	/*
 	 * THREAD_{F,X}* might be larger than a S-type offset can handle, but
diff --git a/arch/riscv/kernel/entry.S b/arch/riscv/kernel/entry.S
index 74ccfd464071..2c0513f8b62f 100644
--- a/arch/riscv/kernel/entry.S
+++ b/arch/riscv/kernel/entry.S
@@ -26,14 +26,14 @@
 
 	/*
 	 * If coming from userspace, preserve the user thread pointer and load
-	 * the kernel thread pointer.  If we came from the kernel, sscratch
-	 * will contain 0, and we should continue on the current TP.
+	 * the kernel thread pointer.  If we came from the kernel, the scratch
+	 * register will contain 0, and we should continue on the current TP.
 	 */
-	csrrw tp, CSR_SSCRATCH, tp
+	csrrw tp, CSR_XSCRATCH, tp
 	bnez tp, _save_context
 
 _restore_kernel_tpsp:
-	csrr tp, CSR_SSCRATCH
+	csrr tp, CSR_XSCRATCH
 	REG_S sp, TASK_TI_KERNEL_SP(tp)
 _save_context:
 	REG_S sp, TASK_TI_USER_SP(tp)
@@ -79,16 +79,16 @@ _save_context:
 	li t0, SR_SUM | SR_FS
 
 	REG_L s0, TASK_TI_USER_SP(tp)
-	csrrc s1, CSR_SSTATUS, t0
-	csrr s2, CSR_SEPC
-	csrr s3, CSR_STVAL
-	csrr s4, CSR_SCAUSE
-	csrr s5, CSR_SSCRATCH
+	csrrc s1, CSR_XSTATUS, t0
+	csrr s2, CSR_XEPC
+	csrr s3, CSR_XTVAL
+	csrr s4, CSR_XCAUSE
+	csrr s5, CSR_XSCRATCH
 	REG_S s0, PT_SP(sp)
-	REG_S s1, PT_SSTATUS(sp)
-	REG_S s2, PT_SEPC(sp)
-	REG_S s3, PT_SBADADDR(sp)
-	REG_S s4, PT_SCAUSE(sp)
+	REG_S s1, PT_XSTATUS(sp)
+	REG_S s2, PT_XEPC(sp)
+	REG_S s3, PT_XBADADDR(sp)
+	REG_S s4, PT_XCAUSE(sp)
 	REG_S s5, PT_TP(sp)
 	.endm
 
@@ -97,10 +97,10 @@ _save_context:
  * registers from the stack.
  */
 	.macro RESTORE_ALL
-	REG_L a0, PT_SSTATUS(sp)
-	REG_L a2, PT_SEPC(sp)
-	csrw CSR_SSTATUS, a0
-	csrw CSR_SEPC, a2
+	REG_L a0, PT_XSTATUS(sp)
+	REG_L a2, PT_XEPC(sp)
+	csrw CSR_XSTATUS, a0
+	csrw CSR_XEPC, a2
 
 	REG_L x1,  PT_RA(sp)
 	REG_L x3,  PT_GP(sp)
@@ -144,10 +144,10 @@ ENTRY(handle_exception)
 	SAVE_ALL
 
 	/*
-	 * Set sscratch register to 0, so that if a recursive exception
+	 * Set the scratch register to 0, so that if a recursive exception
 	 * occurs, the exception vector knows it came from the kernel
 	 */
-	csrw CSR_SSCRATCH, x0
+	csrw CSR_XSCRATCH, x0
 
 	/* Load the global pointer */
 .option push
@@ -167,7 +167,7 @@ ENTRY(handle_exception)
 	tail do_IRQ
 1:
 	/* Exceptions run with interrupts enabled */
-	csrs CSR_SSTATUS, SR_SIE
+	csrs CSR_XSTATUS, SR_XIE
 
 	/* Handle syscalls */
 	li t0, EXC_SYSCALL
@@ -194,7 +194,7 @@ handle_syscall:
 	 * scall instruction on sret
 	 */
 	addi s2, s2, 0x4
-	REG_S s2, PT_SEPC(sp)
+	REG_S s2, PT_XEPC(sp)
 	/* Trace syscalls, but only if requested by the user. */
 	REG_L t0, TASK_TI_FLAGS(tp)
 	andi t0, t0, _TIF_SYSCALL_WORK
@@ -221,9 +221,15 @@ ret_from_syscall:
 	bnez t0, handle_syscall_trace_exit
 
 ret_from_exception:
-	REG_L s0, PT_SSTATUS(sp)
-	csrc CSR_SSTATUS, SR_SIE
+	REG_L s0, PT_XSTATUS(sp)
+	csrc CSR_XSTATUS, SR_XIE
+#ifdef CONFIG_RISCV_M_MODE
+	/* the MPP value is too large to be used as an immediate arg for addi */
+	li t0, SR_MPP
+	and s0, s0, t0
+#else
 	andi s0, s0, SR_SPP
+#endif
 	bnez s0, resume_kernel
 
 resume_userspace:
@@ -237,14 +243,14 @@ resume_userspace:
 	REG_S s0, TASK_TI_KERNEL_SP(tp)
 
 	/*
-	 * Save TP into sscratch, so we can find the kernel data structures
-	 * again.
+	 * Save TP into the scratch register , so we can find the kernel data
+	 * structures again.
 	 */
-	csrw CSR_SSCRATCH, tp
+	csrw CSR_XSCRATCH, tp
 
 restore_all:
 	RESTORE_ALL
-	sret
+	Xret
 
 #if IS_ENABLED(CONFIG_PREEMPT)
 resume_kernel:
@@ -265,7 +271,7 @@ work_pending:
 	bnez s1, work_resched
 work_notifysig:
 	/* Handle pending signals and notify-resume requests */
-	csrs CSR_SSTATUS, SR_SIE /* Enable interrupts for do_notify_resume() */
+	csrs CSR_XSTATUS, SR_XIE /* Enable interrupts for do_notify_resume() */
 	move a0, sp /* pt_regs */
 	move a1, s0 /* current_thread_info->flags */
 	tail do_notify_resume
diff --git a/arch/riscv/kernel/fpu.S b/arch/riscv/kernel/fpu.S
index 631d31540660..1dade31f4564 100644
--- a/arch/riscv/kernel/fpu.S
+++ b/arch/riscv/kernel/fpu.S
@@ -23,7 +23,7 @@ ENTRY(__fstate_save)
 	li  a2,  TASK_THREAD_F0
 	add a0, a0, a2
 	li t1, SR_FS
-	csrs CSR_SSTATUS, t1
+	csrs CSR_XSTATUS, t1
 	frcsr t0
 	fsd f0,  TASK_THREAD_F0_F0(a0)
 	fsd f1,  TASK_THREAD_F1_F0(a0)
@@ -58,7 +58,7 @@ ENTRY(__fstate_save)
 	fsd f30, TASK_THREAD_F30_F0(a0)
 	fsd f31, TASK_THREAD_F31_F0(a0)
 	sw t0, TASK_THREAD_FCSR_F0(a0)
-	csrc CSR_SSTATUS, t1
+	csrc CSR_XSTATUS, t1
 	ret
 ENDPROC(__fstate_save)
 
@@ -67,7 +67,7 @@ ENTRY(__fstate_restore)
 	add a0, a0, a2
 	li t1, SR_FS
 	lw t0, TASK_THREAD_FCSR_F0(a0)
-	csrs CSR_SSTATUS, t1
+	csrs CSR_XSTATUS, t1
 	fld f0,  TASK_THREAD_F0_F0(a0)
 	fld f1,  TASK_THREAD_F1_F0(a0)
 	fld f2,  TASK_THREAD_F2_F0(a0)
@@ -101,6 +101,6 @@ ENTRY(__fstate_restore)
 	fld f30, TASK_THREAD_F30_F0(a0)
 	fld f31, TASK_THREAD_F31_F0(a0)
 	fscsr t0
-	csrc CSR_SSTATUS, t1
+	csrc CSR_XSTATUS, t1
 	ret
 ENDPROC(__fstate_restore)
diff --git a/arch/riscv/kernel/head.S b/arch/riscv/kernel/head.S
index 86049aed8251..bb96bb7b95d2 100644
--- a/arch/riscv/kernel/head.S
+++ b/arch/riscv/kernel/head.S
@@ -47,8 +47,8 @@ ENTRY(_start)
 .global _start_kernel
 _start_kernel:
 	/* Mask all interrupts */
-	csrw CSR_SIE, zero
-	csrw CSR_SIP, zero
+	csrw CSR_XIE, zero
+	csrw CSR_XIP, zero
 
 	/* Load the global pointer */
 .option push
@@ -61,7 +61,7 @@ _start_kernel:
 	 * floating point in kernel space
 	 */
 	li t0, SR_FS
-	csrc CSR_SSTATUS, t0
+	csrc CSR_XSTATUS, t0
 
 	/* Pick one hart to run the main boot sequence */
 	la a3, hart_lottery
@@ -111,7 +111,7 @@ relocate:
 	/* Point stvec to virtual address of intruction after satp write */
 	la a2, 1f
 	add a2, a2, a1
-	csrw CSR_STVEC, a2
+	csrw CSR_XTVEC, a2
 
 	/* Compute satp for kernel page tables, but don't load it yet */
 	srl a2, a0, PAGE_SHIFT
@@ -133,7 +133,7 @@ relocate:
 1:
 	/* Set trap vector to spin forever to help debug */
 	la a0, .Lsecondary_park
-	csrw CSR_STVEC, a0
+	csrw CSR_XTVEC, a0
 
 	/* Reload the global pointer */
 .option push
@@ -159,7 +159,7 @@ relocate:
 
 	/* Set trap vector to spin forever to help debug */
 	la a3, .Lsecondary_park
-	csrw CSR_STVEC, a3
+	csrw CSR_XTVEC, a3
 
 	slli a3, a0, LGREG
 	la a1, __cpu_up_stack_pointer
diff --git a/arch/riscv/kernel/irq.c b/arch/riscv/kernel/irq.c
index 6d8659388c49..804ff70bb853 100644
--- a/arch/riscv/kernel/irq.c
+++ b/arch/riscv/kernel/irq.c
@@ -29,7 +29,7 @@ asmlinkage void __irq_entry do_IRQ(struct pt_regs *regs)
 	struct pt_regs *old_regs = set_irq_regs(regs);
 
 	irq_enter();
-	switch (regs->scause & ~SCAUSE_IRQ_FLAG) {
+	switch (regs->xcause & ~XCAUSE_IRQ_FLAG) {
 	case INTERRUPT_CAUSE_TIMER:
 		riscv_timer_interrupt();
 		break;
@@ -46,7 +46,7 @@ asmlinkage void __irq_entry do_IRQ(struct pt_regs *regs)
 		handle_arch_irq(regs);
 		break;
 	default:
-		pr_alert("unexpected interrupt cause 0x%lx", regs->scause);
+		pr_alert("unexpected interrupt cause 0x%lx", regs->xcause);
 		BUG();
 	}
 	irq_exit();
diff --git a/arch/riscv/kernel/process.c b/arch/riscv/kernel/process.c
index fb3a082362eb..853af1b7837b 100644
--- a/arch/riscv/kernel/process.c
+++ b/arch/riscv/kernel/process.c
@@ -34,7 +34,7 @@ void show_regs(struct pt_regs *regs)
 	show_regs_print_info(KERN_DEFAULT);
 
 	pr_cont("sepc: " REG_FMT " ra : " REG_FMT " sp : " REG_FMT "\n",
-		regs->sepc, regs->ra, regs->sp);
+		regs->xepc, regs->ra, regs->sp);
 	pr_cont(" gp : " REG_FMT " tp : " REG_FMT " t0 : " REG_FMT "\n",
 		regs->gp, regs->tp, regs->t0);
 	pr_cont(" t1 : " REG_FMT " t2 : " REG_FMT " s0 : " REG_FMT "\n",
@@ -56,23 +56,23 @@ void show_regs(struct pt_regs *regs)
 	pr_cont(" t5 : " REG_FMT " t6 : " REG_FMT "\n",
 		regs->t5, regs->t6);
 
-	pr_cont("sstatus: " REG_FMT " sbadaddr: " REG_FMT " scause: " REG_FMT "\n",
-		regs->sstatus, regs->sbadaddr, regs->scause);
+	pr_cont("status: " REG_FMT " badaddr: " REG_FMT " cause: " REG_FMT "\n",
+		regs->xstatus, regs->xbadaddr, regs->xcause);
 }
 
 void start_thread(struct pt_regs *regs, unsigned long pc,
 	unsigned long sp)
 {
-	regs->sstatus = SR_SPIE;
+	regs->xstatus = SR_SPIE;
 	if (has_fpu) {
-		regs->sstatus |= SR_FS_INITIAL;
+		regs->xstatus |= SR_FS_INITIAL;
 		/*
 		 * Restore the initial value to the FP register
 		 * before starting the user program.
 		 */
 		fstate_restore(current, regs);
 	}
-	regs->sepc = pc;
+	regs->xepc = pc;
 	regs->sp = sp;
 	set_fs(USER_DS);
 }
@@ -108,7 +108,8 @@ int copy_thread(unsigned long clone_flags, unsigned long usp,
 		const register unsigned long gp __asm__ ("gp");
 		memset(childregs, 0, sizeof(struct pt_regs));
 		childregs->gp = gp;
-		childregs->sstatus = SR_SPP | SR_SPIE; /* Supervisor, irqs on */
+		/* Supervisor/Machine, irqs on: */
+		childregs->xstatus = SR_XPP | SR_XPIE;
 
 		p->thread.ra = (unsigned long)ret_from_kernel_thread;
 		p->thread.s[0] = usp; /* fn */
diff --git a/arch/riscv/kernel/signal.c b/arch/riscv/kernel/signal.c
index b14d7647d800..e1a2cee340f7 100644
--- a/arch/riscv/kernel/signal.c
+++ b/arch/riscv/kernel/signal.c
@@ -124,7 +124,7 @@ SYSCALL_DEFINE0(rt_sigreturn)
 		pr_info_ratelimited(
 			"%s[%d]: bad frame in %s: frame=%p pc=%p sp=%p\n",
 			task->comm, task_pid_nr(task), __func__,
-			frame, (void *)regs->sepc, (void *)regs->sp);
+			frame, (void *)regs->xepc, (void *)regs->sp);
 	}
 	force_sig(SIGSEGV);
 	return 0;
@@ -199,7 +199,7 @@ static int setup_rt_frame(struct ksignal *ksig, sigset_t *set,
 	 * We always pass siginfo and mcontext, regardless of SA_SIGINFO,
 	 * since some things rely on this (e.g. glibc's debug/segfault.c).
 	 */
-	regs->sepc = (unsigned long)ksig->ka.sa.sa_handler;
+	regs->xepc = (unsigned long)ksig->ka.sa.sa_handler;
 	regs->sp = (unsigned long)frame;
 	regs->a0 = ksig->sig;                     /* a0: signal number */
 	regs->a1 = (unsigned long)(&frame->info); /* a1: siginfo pointer */
@@ -208,7 +208,7 @@ static int setup_rt_frame(struct ksignal *ksig, sigset_t *set,
 #if DEBUG_SIG
 	pr_info("SIG deliver (%s:%d): sig=%d pc=%p ra=%p sp=%p\n",
 		current->comm, task_pid_nr(current), ksig->sig,
-		(void *)regs->sepc, (void *)regs->ra, frame);
+		(void *)regs->xepc, (void *)regs->ra, frame);
 #endif
 
 	return 0;
@@ -220,10 +220,9 @@ static void handle_signal(struct ksignal *ksig, struct pt_regs *regs)
 	int ret;
 
 	/* Are we from a system call? */
-	if (regs->scause == EXC_SYSCALL) {
+	if (regs->xcause == EXC_SYSCALL) {
 		/* Avoid additional syscall restarting via ret_from_exception */
-		regs->scause = -1UL;
-
+		regs->xcause = -1UL;
 		/* If so, check system call restarting.. */
 		switch (regs->a0) {
 		case -ERESTART_RESTARTBLOCK:
@@ -239,7 +238,7 @@ static void handle_signal(struct ksignal *ksig, struct pt_regs *regs)
 			/* fallthrough */
 		case -ERESTARTNOINTR:
                         regs->a0 = regs->orig_a0;
-			regs->sepc -= 0x4;
+			regs->xepc -= 0x4;
 			break;
 		}
 	}
@@ -261,9 +260,9 @@ static void do_signal(struct pt_regs *regs)
 	}
 
 	/* Did we come from a system call? */
-	if (regs->scause == EXC_SYSCALL) {
+	if (regs->xcause == EXC_SYSCALL) {
 		/* Avoid additional syscall restarting via ret_from_exception */
-		regs->scause = -1UL;
+		regs->xcause = -1UL;
 
 		/* Restart the system call - no handlers present */
 		switch (regs->a0) {
@@ -271,12 +270,12 @@ static void do_signal(struct pt_regs *regs)
 		case -ERESTARTSYS:
 		case -ERESTARTNOINTR:
                         regs->a0 = regs->orig_a0;
-			regs->sepc -= 0x4;
+			regs->xepc -= 0x4;
 			break;
 		case -ERESTART_RESTARTBLOCK:
                         regs->a0 = regs->orig_a0;
 			regs->a7 = __NR_restart_syscall;
-			regs->sepc -= 0x4;
+			regs->xepc -= 0x4;
 			break;
 		}
 	}
diff --git a/arch/riscv/kernel/traps.c b/arch/riscv/kernel/traps.c
index 424eb72d56b1..86b05780c1d9 100644
--- a/arch/riscv/kernel/traps.c
+++ b/arch/riscv/kernel/traps.c
@@ -40,7 +40,7 @@ void die(struct pt_regs *regs, const char *str)
 	print_modules();
 	show_regs(regs);
 
-	ret = notify_die(DIE_OOPS, str, regs, 0, regs->scause, SIGSEGV);
+	ret = notify_die(DIE_OOPS, str, regs, 0, regs->xcause, SIGSEGV);
 
 	bust_spinlocks(0);
 	add_taint(TAINT_DIE, LOCKDEP_NOW_UNRELIABLE);
@@ -85,7 +85,7 @@ static void do_trap_error(struct pt_regs *regs, int signo, int code,
 #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_trap_error(regs, signo, code, regs->xepc, "Oops - " str);	\
 }
 
 DO_ERROR_INFO(do_trap_unknown,
@@ -128,12 +128,12 @@ asmlinkage void do_trap_break(struct pt_regs *regs)
 	if (!user_mode(regs)) {
 		enum bug_trap_type type;
 
-		type = report_bug(regs->sepc, regs);
+		type = report_bug(regs->xepc, regs);
 		switch (type) {
 		case BUG_TRAP_TYPE_NONE:
 			break;
 		case BUG_TRAP_TYPE_WARN:
-			regs->sepc += get_break_insn_length(regs->sepc);
+			regs->xepc += get_break_insn_length(regs->xepc);
 			break;
 		case BUG_TRAP_TYPE_BUG:
 			die(regs, "Kernel BUG");
@@ -141,7 +141,7 @@ asmlinkage void do_trap_break(struct pt_regs *regs)
 	}
 #endif /* CONFIG_GENERIC_BUG */
 
-	force_sig_fault(SIGTRAP, TRAP_BRKPT, (void __user *)(regs->sepc));
+	force_sig_fault(SIGTRAP, TRAP_BRKPT, (void __user *)(regs->xepc));
 }
 
 #ifdef CONFIG_GENERIC_BUG
@@ -166,9 +166,9 @@ 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(CSR_SSCRATCH, 0);
+	csr_write(CSR_XSCRATCH, 0);
 	/* Set the exception vector address */
-	csr_write(CSR_STVEC, &handle_exception);
+	csr_write(CSR_XTVEC, &handle_exception);
 	/* Enable all interrupts */
-	csr_write(CSR_SIE, -1);
+	csr_write(CSR_XIE, -1);
 }
diff --git a/arch/riscv/lib/uaccess.S b/arch/riscv/lib/uaccess.S
index ed2696c0143d..f47a2ea4dc89 100644
--- a/arch/riscv/lib/uaccess.S
+++ b/arch/riscv/lib/uaccess.S
@@ -18,7 +18,7 @@ ENTRY(__asm_copy_from_user)
 
 	/* Enable access to user memory */
 	li t6, SR_SUM
-	csrs CSR_SSTATUS, t6
+	csrs CSR_XSTATUS, t6
 
 	add a3, a1, a2
 	/* Use word-oriented copy only if low-order bits match */
@@ -47,7 +47,7 @@ ENTRY(__asm_copy_from_user)
 
 3:
 	/* Disable access to user memory */
-	csrc CSR_SSTATUS, t6
+	csrc CSR_XSTATUS, t6
 	li a0, 0
 	ret
 4: /* Edge case: unalignment */
@@ -72,7 +72,7 @@ ENTRY(__clear_user)
 
 	/* Enable access to user memory */
 	li t6, SR_SUM
-	csrs CSR_SSTATUS, t6
+	csrs CSR_XSTATUS, t6
 
 	add a3, a0, a1
 	addi t0, a0, SZREG-1
@@ -94,7 +94,7 @@ ENTRY(__clear_user)
 
 3:
 	/* Disable access to user memory */
-	csrc CSR_SSTATUS, t6
+	csrc CSR_XSTATUS, t6
 	li a0, 0
 	ret
 4: /* Edge case: unalignment */
@@ -114,11 +114,11 @@ ENDPROC(__clear_user)
 	/* Fixup code for __copy_user(10) and __clear_user(11) */
 10:
 	/* Disable access to user memory */
-	csrs CSR_SSTATUS, t6
+	csrs CSR_XSTATUS, t6
 	mv a0, a2
 	ret
 11:
-	csrs CSR_SSTATUS, t6
+	csrs CSR_XSTATUS, t6
 	mv a0, a1
 	ret
 	.previous
diff --git a/arch/riscv/mm/extable.c b/arch/riscv/mm/extable.c
index 7aed9178d365..e0659deeb16b 100644
--- a/arch/riscv/mm/extable.c
+++ b/arch/riscv/mm/extable.c
@@ -15,9 +15,9 @@ int fixup_exception(struct pt_regs *regs)
 {
 	const struct exception_table_entry *fixup;
 
-	fixup = search_exception_tables(regs->sepc);
+	fixup = search_exception_tables(regs->xepc);
 	if (fixup) {
-		regs->sepc = fixup->fixup;
+		regs->xepc = fixup->fixup;
 		return 1;
 	}
 	return 0;
diff --git a/arch/riscv/mm/fault.c b/arch/riscv/mm/fault.c
index 96add1427a75..10a8ce38ac7a 100644
--- a/arch/riscv/mm/fault.c
+++ b/arch/riscv/mm/fault.c
@@ -32,8 +32,8 @@ asmlinkage void do_page_fault(struct pt_regs *regs)
 	int code = SEGV_MAPERR;
 	vm_fault_t fault;
 
-	cause = regs->scause;
-	addr = regs->sbadaddr;
+	cause = regs->xcause;
+	addr = regs->xbadaddr;
 
 	tsk = current;
 	mm = tsk->mm;
@@ -51,7 +51,7 @@ asmlinkage void do_page_fault(struct pt_regs *regs)
 		goto vmalloc_fault;
 
 	/* Enable interrupts if they were enabled in the parent context. */
-	if (likely(regs->sstatus & SR_SPIE))
+	if (likely(regs->xstatus & SR_XPIE))
 		local_irq_enable();
 
 	/*
diff --git a/drivers/clocksource/timer-riscv.c b/drivers/clocksource/timer-riscv.c
index 470c7ef02ea4..5d2fdc3e28a9 100644
--- a/drivers/clocksource/timer-riscv.c
+++ b/drivers/clocksource/timer-riscv.c
@@ -19,7 +19,7 @@
 static int riscv_clock_next_event(unsigned long delta,
 		struct clock_event_device *ce)
 {
-	csr_set(sie, SIE_STIE);
+	csr_set(CSR_XIE, XIE_XTIE);
 	sbi_set_timer(get_cycles64() + delta);
 	return 0;
 }
@@ -61,13 +61,13 @@ static int riscv_timer_starting_cpu(unsigned int cpu)
 	ce->cpumask = cpumask_of(cpu);
 	clockevents_config_and_register(ce, riscv_timebase, 100, 0x7fffffff);
 
-	csr_set(sie, SIE_STIE);
+	csr_set(CSR_XIE, XIE_XTIE);
 	return 0;
 }
 
 static int riscv_timer_dying_cpu(unsigned int cpu)
 {
-	csr_clear(sie, SIE_STIE);
+	csr_clear(CSR_XIE, XIE_XTIE);
 	return 0;
 }
 
@@ -76,7 +76,7 @@ void riscv_timer_interrupt(void)
 {
 	struct clock_event_device *evdev = this_cpu_ptr(&riscv_clock_event);
 
-	csr_clear(sie, SIE_STIE);
+	csr_clear(CSR_XIE, XIE_XTIE);
 	evdev->event_handler(evdev);
 }
 
diff --git a/drivers/irqchip/irq-sifive-plic.c b/drivers/irqchip/irq-sifive-plic.c
index c72c036aea76..4ee96ac90ea4 100644
--- a/drivers/irqchip/irq-sifive-plic.c
+++ b/drivers/irqchip/irq-sifive-plic.c
@@ -179,7 +179,7 @@ static void plic_handle_irq(struct pt_regs *regs)
 
 	WARN_ON_ONCE(!handler->present);
 
-	csr_clear(sie, SIE_SEIE);
+	csr_clear(CSR_XIE, XIE_XEIE);
 	while ((hwirq = readl(claim))) {
 		int irq = irq_find_mapping(plic_irqdomain, hwirq);
 
@@ -190,7 +190,7 @@ static void plic_handle_irq(struct pt_regs *regs)
 			generic_handle_irq(irq);
 		writel(hwirq, claim);
 	}
-	csr_set(sie, SIE_SEIE);
+	csr_set(CSR_XIE, XIE_XEIE);
 }
 
 /*
-- 
2.20.1


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[PATCH 09/20] riscv: don't allow selecting SBI based drivers for M-mode

[Christoph Hellwig]

From: Damien Le Moal <damien.lemoal@wdc.com>

When running in M-mode we can't use SBI based drivers.  Add a new
CONFIG_RISCV_SBI that drivers that do SBI calls can depend on
instead.

Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 arch/riscv/Kconfig         | 6 ++++++
 drivers/tty/hvc/Kconfig    | 2 +-
 drivers/tty/serial/Kconfig | 2 +-
 3 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index e4a4bebdbcf3..86fcf608f193 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -61,6 +61,12 @@ config RISCV
 config RISCV_M_MODE
 	bool
 
+# set if we are running in S-mode and can use SBI calls
+config RISCV_SBI
+	bool
+	depends on !RISCV_M_MODE
+	default y
+
 config MMU
 	def_bool y
 
diff --git a/drivers/tty/hvc/Kconfig b/drivers/tty/hvc/Kconfig
index 4d22b911111f..4487a6b9acc8 100644
--- a/drivers/tty/hvc/Kconfig
+++ b/drivers/tty/hvc/Kconfig
@@ -89,7 +89,7 @@ config HVC_DCC
 
 config HVC_RISCV_SBI
 	bool "RISC-V SBI console support"
-	depends on RISCV
+	depends on RISCV_SBI
 	select HVC_DRIVER
 	help
 	  This enables support for console output via RISC-V SBI calls, which
diff --git a/drivers/tty/serial/Kconfig b/drivers/tty/serial/Kconfig
index 3083dbae35f7..530cb966092f 100644
--- a/drivers/tty/serial/Kconfig
+++ b/drivers/tty/serial/Kconfig
@@ -88,7 +88,7 @@ config SERIAL_EARLYCON_ARM_SEMIHOST
 
 config SERIAL_EARLYCON_RISCV_SBI
 	bool "Early console using RISC-V SBI"
-	depends on RISCV
+	depends on RISCV_SBI
 	select SERIAL_CORE
 	select SERIAL_CORE_CONSOLE
 	select SERIAL_EARLYCON
-- 
2.20.1


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[PATCH 10/20] riscv: poison SBI calls for M-mode

[Christoph Hellwig]

There is no SBI when we run in M-mode, so fail the compile for any code
trying to use SBI calls.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 arch/riscv/include/asm/sbi.h | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/arch/riscv/include/asm/sbi.h b/arch/riscv/include/asm/sbi.h
index 21134b3ef404..b167af3e7470 100644
--- a/arch/riscv/include/asm/sbi.h
+++ b/arch/riscv/include/asm/sbi.h
@@ -8,6 +8,7 @@
 
 #include <linux/types.h>
 
+#ifdef CONFIG_RISCV_SBI
 #define SBI_SET_TIMER 0
 #define SBI_CONSOLE_PUTCHAR 1
 #define SBI_CONSOLE_GETCHAR 2
@@ -93,5 +94,5 @@ static inline void sbi_remote_sfence_vma_asid(const unsigned long *hart_mask,
 {
 	SBI_CALL_4(SBI_REMOTE_SFENCE_VMA_ASID, hart_mask, start, size, asid);
 }
-
-#endif
+#endif /* CONFIG_RISCV_SBI */
+#endif /* _ASM_RISCV_SBI_H */
-- 
2.20.1


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[PATCH 11/20] riscv: cleanup the default power off implementation

[Christoph Hellwig]

Move the sbi poweroff to a separate function and file that is only
compiled if CONFIG_SBI is set.  Provide a new default fallback
power off that just sits in a wfi loop to save some power.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Atish Patra <atish.patra@wdc.com>
---
 arch/riscv/kernel/Makefile |  1 +
 arch/riscv/kernel/reset.c  |  5 ++---
 arch/riscv/kernel/sbi.c    | 17 +++++++++++++++++
 3 files changed, 20 insertions(+), 3 deletions(-)
 create mode 100644 arch/riscv/kernel/sbi.c

diff --git a/arch/riscv/kernel/Makefile b/arch/riscv/kernel/Makefile
index 2420d37d96de..21a8d09c298c 100644
--- a/arch/riscv/kernel/Makefile
+++ b/arch/riscv/kernel/Makefile
@@ -39,5 +39,6 @@ obj-$(CONFIG_FUNCTION_TRACER)	+= mcount.o ftrace.o
 obj-$(CONFIG_DYNAMIC_FTRACE)	+= mcount-dyn.o
 
 obj-$(CONFIG_PERF_EVENTS)      += perf_event.o
+obj-$(CONFIG_RISCV_SBI)		+= sbi.o
 
 clean:
diff --git a/arch/riscv/kernel/reset.c b/arch/riscv/kernel/reset.c
index d0fe623bfb8f..5e4e69859af1 100644
--- a/arch/riscv/kernel/reset.c
+++ b/arch/riscv/kernel/reset.c
@@ -4,12 +4,11 @@
  */
 
 #include <linux/reboot.h>
-#include <asm/sbi.h>
 
 static void default_power_off(void)
 {
-	sbi_shutdown();
-	while (1);
+	while (1)
+		wait_for_interrupt();
 }
 
 void (*pm_power_off)(void) = default_power_off;
diff --git a/arch/riscv/kernel/sbi.c b/arch/riscv/kernel/sbi.c
new file mode 100644
index 000000000000..f6c7c3e82d28
--- /dev/null
+++ b/arch/riscv/kernel/sbi.c
@@ -0,0 +1,17 @@
+// SPDX-License-Identifier: GPL-2.0-only
+
+#include <linux/init.h>
+#include <linux/pm.h>
+#include <asm/sbi.h>
+
+static void sbi_power_off(void)
+{
+	sbi_shutdown();
+}
+
+static int __init sbi_init(void)
+{
+	pm_power_off = sbi_power_off;
+	return 0;
+}
+early_initcall(sbi_init);
-- 
2.20.1


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[PATCH 12/20] riscv: implement remote sfence.i using IPIs

[Christoph Hellwig]

The RISC-V ISA only supports flushing the instruction cache for the
local CPU core.  Currently we always offload the remote TLB flushing to
the SBI, which then issues an IPI under the hoods.  But with M-mode
we do not have an SBI so we have to do it ourselves.   IPI to the
other nodes using the existing kernel helpers instead if we have
native clint support and thus can IPI directly from the kernel.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 arch/riscv/include/asm/sbi.h |  3 +++
 arch/riscv/mm/cacheflush.c   | 24 ++++++++++++++++++------
 2 files changed, 21 insertions(+), 6 deletions(-)

diff --git a/arch/riscv/include/asm/sbi.h b/arch/riscv/include/asm/sbi.h
index b167af3e7470..0cb74eccc73f 100644
--- a/arch/riscv/include/asm/sbi.h
+++ b/arch/riscv/include/asm/sbi.h
@@ -94,5 +94,8 @@ static inline void sbi_remote_sfence_vma_asid(const unsigned long *hart_mask,
 {
 	SBI_CALL_4(SBI_REMOTE_SFENCE_VMA_ASID, hart_mask, start, size, asid);
 }
+#else /* CONFIG_RISCV_SBI */
+/* stub to for code is only reachable under IS_ENABLED(CONFIG_RISCV_SBI): */
+void sbi_remote_fence_i(const unsigned long *hart_mask);
 #endif /* CONFIG_RISCV_SBI */
 #endif /* _ASM_RISCV_SBI_H */
diff --git a/arch/riscv/mm/cacheflush.c b/arch/riscv/mm/cacheflush.c
index 3f15938dec89..794c9ab256eb 100644
--- a/arch/riscv/mm/cacheflush.c
+++ b/arch/riscv/mm/cacheflush.c
@@ -10,9 +10,17 @@
 
 #include <asm/sbi.h>
 
+static void ipi_remote_fence_i(void *info)
+{
+	return local_flush_icache_all();
+}
+
 void flush_icache_all(void)
 {
-	sbi_remote_fence_i(NULL);
+	if (IS_ENABLED(CONFIG_RISCV_SBI))
+		sbi_remote_fence_i(NULL);
+	else
+		on_each_cpu(ipi_remote_fence_i, NULL, 1);
 }
 
 /*
@@ -28,7 +36,7 @@ void flush_icache_all(void)
 void flush_icache_mm(struct mm_struct *mm, bool local)
 {
 	unsigned int cpu;
-	cpumask_t others, hmask, *mask;
+	cpumask_t others, *mask;
 
 	preempt_disable();
 
@@ -46,10 +54,7 @@ void flush_icache_mm(struct mm_struct *mm, bool local)
 	 */
 	cpumask_andnot(&others, mm_cpumask(mm), cpumask_of(cpu));
 	local |= cpumask_empty(&others);
-	if (mm != current->active_mm || !local) {
-		riscv_cpuid_to_hartid_mask(&others, &hmask);
-		sbi_remote_fence_i(hmask.bits);
-	} else {
+	if (mm == current->active_mm && local) {
 		/*
 		 * It's assumed that at least one strongly ordered operation is
 		 * performed on this hart between setting a hart's cpumask bit
@@ -59,6 +64,13 @@ void flush_icache_mm(struct mm_struct *mm, bool local)
 		 * with flush_icache_deferred().
 		 */
 		smp_mb();
+	} else if (IS_ENABLED(CONFIG_RISCV_SBI)) {
+		cpumask_t hartid_mask;
+
+		riscv_cpuid_to_hartid_mask(&others, &hartid_mask);
+		sbi_remote_fence_i(cpumask_bits(&hartid_mask));
+	} else {
+		on_each_cpu_mask(&others, ipi_remote_fence_i, NULL, 1);
 	}
 
 	preempt_enable();
-- 
2.20.1


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[PATCH 13/20] riscv: add support for MMIO access to the timer registers

[Christoph Hellwig]

When running in M-mode we can't use the SBI to set the timer, and
don't have access to the time CSR as that usually is emulated by
M-mode.  Instead provide code that directly accesses the MMIO for
the timer.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 arch/riscv/include/asm/sbi.h      |  3 ++-
 arch/riscv/include/asm/timex.h    | 19 +++++++++++++++++--
 drivers/clocksource/timer-riscv.c | 21 +++++++++++++++++----
 3 files changed, 36 insertions(+), 7 deletions(-)

diff --git a/arch/riscv/include/asm/sbi.h b/arch/riscv/include/asm/sbi.h
index 0cb74eccc73f..a4774bafe033 100644
--- a/arch/riscv/include/asm/sbi.h
+++ b/arch/riscv/include/asm/sbi.h
@@ -95,7 +95,8 @@ static inline void sbi_remote_sfence_vma_asid(const unsigned long *hart_mask,
 	SBI_CALL_4(SBI_REMOTE_SFENCE_VMA_ASID, hart_mask, start, size, asid);
 }
 #else /* CONFIG_RISCV_SBI */
-/* stub to for code is only reachable under IS_ENABLED(CONFIG_RISCV_SBI): */
+/* stubs to for code is only reachable under IS_ENABLED(CONFIG_RISCV_SBI): */
+void sbi_set_timer(uint64_t stime_value);
 void sbi_remote_fence_i(const unsigned long *hart_mask);
 #endif /* CONFIG_RISCV_SBI */
 #endif /* _ASM_RISCV_SBI_H */
diff --git a/arch/riscv/include/asm/timex.h b/arch/riscv/include/asm/timex.h
index c7ef131b9e4c..e17837d61667 100644
--- a/arch/riscv/include/asm/timex.h
+++ b/arch/riscv/include/asm/timex.h
@@ -7,12 +7,25 @@
 #define _ASM_RISCV_TIMEX_H
 
 #include <asm/csr.h>
+#include <asm/io.h>
 
 typedef unsigned long cycles_t;
 
+extern u64 __iomem *riscv_time_val;
+extern u64 __iomem *riscv_time_cmp;
+
+#ifdef CONFIG_64BIT
+#define mmio_get_cycles()	readq_relaxed(riscv_time_val)
+#else
+#define mmio_get_cycles()	readl_relaxed(riscv_time_val)
+#define mmio_get_cycles_hi()	readl_relaxed(((u32 *)riscv_time_val) + 1)
+#endif
+
 static inline cycles_t get_cycles(void)
 {
-	return csr_read(CSR_TIME);
+	if (IS_ENABLED(CONFIG_RISCV_SBI))
+		return csr_read(CSR_TIME);
+	return mmio_get_cycles();
 }
 #define get_cycles get_cycles
 
@@ -24,7 +37,9 @@ static inline u64 get_cycles64(void)
 #else /* CONFIG_64BIT */
 static inline u32 get_cycles_hi(void)
 {
-	return csr_read(CSR_TIMEH);
+	if (IS_ENABLED(CONFIG_RISCV_SBI))
+		return csr_read(CSR_TIMEH);
+	return mmio_get_cycles_hi();
 }
 
 static inline u64 get_cycles64(void)
diff --git a/drivers/clocksource/timer-riscv.c b/drivers/clocksource/timer-riscv.c
index 5d2fdc3e28a9..2b9fbc4ebe49 100644
--- a/drivers/clocksource/timer-riscv.c
+++ b/drivers/clocksource/timer-riscv.c
@@ -3,9 +3,9 @@
  * Copyright (C) 2012 Regents of the University of California
  * Copyright (C) 2017 SiFive
  *
- * All RISC-V systems have a timer attached to every hart.  These timers can be
- * read from the "time" and "timeh" CSRs, and can use the SBI to setup
- * events.
+ * All RISC-V systems have a timer attached to every hart.  These timers can
+ * either be read from the "time" and "timeh" CSRs, and can use the SBI to
+ * setup events, or directly accessed using MMIO registers.
  */
 #include <linux/clocksource.h>
 #include <linux/clockchips.h>
@@ -13,14 +13,27 @@
 #include <linux/delay.h>
 #include <linux/irq.h>
 #include <linux/sched_clock.h>
+#include <linux/io-64-nonatomic-lo-hi.h>
 #include <asm/smp.h>
 #include <asm/sbi.h>
 
+u64 __iomem *riscv_time_cmp;
+u64 __iomem *riscv_time_val;
+
+static inline void mmio_set_timer(u64 val)
+{
+	writeq_relaxed(val,
+		riscv_time_cmp + cpuid_to_hartid_map(smp_processor_id()));
+}
+
 static int riscv_clock_next_event(unsigned long delta,
 		struct clock_event_device *ce)
 {
 	csr_set(CSR_XIE, XIE_XTIE);
-	sbi_set_timer(get_cycles64() + delta);
+	if (IS_ENABLED(CONFIG_RISCV_SBI))
+		sbi_set_timer(get_cycles64() + delta);
+	else
+		mmio_set_timer(get_cycles64() + delta);
 	return 0;
 }
 
-- 
2.20.1


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[PATCH 14/20] riscv: provide native clint access for M-mode

[Christoph Hellwig]

RISC-V has the concept of a cpu level interrupt controller.  The
interface for it is split between a standardized part that is exposed
as bits in the mstatus/sstatus register and the mie/mip/sie/sip
CRS.  But the bit to actually trigger IPIs is not standardized and
just mentioned as implementable using MMIO.

Add support for IPIs using MMIO using the SiFive clint layout (which is
also shared by Ariane, Kendrye and the Qemu virt platform).  Additional
the MMIO block also support the time value and timer compare registers,
so they are also set up using the same OF node.  Support for other
layouts should also be relatively easy to add in the future.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 arch/riscv/include/asm/clint.h | 39 ++++++++++++++++++++++++++++++
 arch/riscv/include/asm/sbi.h   |  2 ++
 arch/riscv/kernel/Makefile     |  1 +
 arch/riscv/kernel/clint.c      | 44 ++++++++++++++++++++++++++++++++++
 arch/riscv/kernel/setup.c      |  2 ++
 arch/riscv/kernel/smp.c        | 16 ++++++++++---
 arch/riscv/kernel/smpboot.c    |  4 ++++
 7 files changed, 105 insertions(+), 3 deletions(-)
 create mode 100644 arch/riscv/include/asm/clint.h
 create mode 100644 arch/riscv/kernel/clint.c

diff --git a/arch/riscv/include/asm/clint.h b/arch/riscv/include/asm/clint.h
new file mode 100644
index 000000000000..02a26b68f21d
--- /dev/null
+++ b/arch/riscv/include/asm/clint.h
@@ -0,0 +1,39 @@
+// SPDX-License-Identifier: GPL-2.0
+#ifndef _ASM_CLINT_H
+#define _ASM_CLINT_H 1
+
+#include <linux/io.h>
+#include <linux/smp.h>
+
+#ifdef CONFIG_RISCV_M_MODE
+extern u32 __iomem *clint_ipi_base;
+
+void clint_init_boot_cpu(void);
+
+static inline void clint_send_ipi_single(unsigned long hartid)
+{
+	writel(1, clint_ipi_base + hartid);
+}
+
+static inline void clint_send_ipi_mask(const struct cpumask *hartid_mask)
+{
+	int hartid;
+
+	for_each_cpu(hartid, hartid_mask)
+		clint_send_ipi_single(hartid);
+}
+
+static inline void clint_clear_ipi(unsigned long hartid)
+{
+	writel(0, clint_ipi_base + hartid);
+}
+#else /* CONFIG_RISCV_M_MODE */
+#define clint_init_boot_cpu()	do { } while (0)
+
+/* stubs to for code is only reachable under IS_ENABLED(CONFIG_RISCV_M_MODE): */
+void clint_send_ipi_single(unsigned long hartid);
+void clint_send_ipi_mask(const struct cpumask *hartid_mask);
+void clint_clear_ipi(unsigned long hartid);
+#endif /* CONFIG_RISCV_M_MODE */
+
+#endif /* _ASM_CLINT_H */
diff --git a/arch/riscv/include/asm/sbi.h b/arch/riscv/include/asm/sbi.h
index a4774bafe033..407d1024f9eb 100644
--- a/arch/riscv/include/asm/sbi.h
+++ b/arch/riscv/include/asm/sbi.h
@@ -97,6 +97,8 @@ static inline void sbi_remote_sfence_vma_asid(const unsigned long *hart_mask,
 #else /* CONFIG_RISCV_SBI */
 /* stubs to for code is only reachable under IS_ENABLED(CONFIG_RISCV_SBI): */
 void sbi_set_timer(uint64_t stime_value);
+void sbi_clear_ipi(void);
+void sbi_send_ipi(const unsigned long *hart_mask);
 void sbi_remote_fence_i(const unsigned long *hart_mask);
 #endif /* CONFIG_RISCV_SBI */
 #endif /* _ASM_RISCV_SBI_H */
diff --git a/arch/riscv/kernel/Makefile b/arch/riscv/kernel/Makefile
index 21a8d09c298c..b4bfeb62d28a 100644
--- a/arch/riscv/kernel/Makefile
+++ b/arch/riscv/kernel/Makefile
@@ -29,6 +29,7 @@ obj-y	+= vdso.o
 obj-y	+= cacheinfo.o
 obj-y	+= vdso/
 
+obj-$(CONFIG_RISCV_M_MODE)	+= clint.o
 obj-$(CONFIG_FPU)		+= fpu.o
 obj-$(CONFIG_SMP)		+= smpboot.o
 obj-$(CONFIG_SMP)		+= smp.o
diff --git a/arch/riscv/kernel/clint.c b/arch/riscv/kernel/clint.c
new file mode 100644
index 000000000000..3647980d14c3
--- /dev/null
+++ b/arch/riscv/kernel/clint.c
@@ -0,0 +1,44 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (c) 2019 Christoph Hellwig.
+ */
+
+#include <linux/io.h>
+#include <linux/of_address.h>
+#include <linux/types.h>
+#include <asm/clint.h>
+#include <asm/csr.h>
+#include <asm/timex.h>
+#include <asm/smp.h>
+
+/*
+ * This is the layout used by the SiFive clint, which is also shared by the qemu
+ * virt platform, and the Kendryte KD210 at least.
+ */
+#define CLINT_IPI_OFF		0
+#define CLINT_TIME_CMP_OFF	0x4000
+#define CLINT_TIME_VAL_OFF	0xbff8
+
+u32 __iomem *clint_ipi_base;
+
+void clint_init_boot_cpu(void)
+{
+	struct device_node *np;
+	void __iomem *base;
+
+	np = of_find_compatible_node(NULL, NULL, "riscv,clint0");
+	if (!np) {
+		panic("clint not found");
+		return;
+	}
+
+	base = of_iomap(np, 0);
+	if (!base)
+		panic("could not map CLINT");
+
+	clint_ipi_base = base + CLINT_IPI_OFF;
+	riscv_time_cmp = base + CLINT_TIME_CMP_OFF;
+	riscv_time_val = base + CLINT_TIME_VAL_OFF;
+
+	clint_clear_ipi(boot_cpu_hartid);
+}
diff --git a/arch/riscv/kernel/setup.c b/arch/riscv/kernel/setup.c
index a990a6cb184f..f4ba71b66c73 100644
--- a/arch/riscv/kernel/setup.c
+++ b/arch/riscv/kernel/setup.c
@@ -17,6 +17,7 @@
 #include <linux/sched/task.h>
 #include <linux/swiotlb.h>
 
+#include <asm/clint.h>
 #include <asm/setup.h>
 #include <asm/sections.h>
 #include <asm/pgtable.h>
@@ -65,6 +66,7 @@ void __init setup_arch(char **cmdline_p)
 	setup_bootmem();
 	paging_init();
 	unflatten_device_tree();
+	clint_init_boot_cpu();
 
 #ifdef CONFIG_SWIOTLB
 	swiotlb_init(1);
diff --git a/arch/riscv/kernel/smp.c b/arch/riscv/kernel/smp.c
index 3836760d7aaf..006084463b76 100644
--- a/arch/riscv/kernel/smp.c
+++ b/arch/riscv/kernel/smp.c
@@ -14,6 +14,7 @@
 #include <linux/seq_file.h>
 #include <linux/delay.h>
 
+#include <asm/clint.h>
 #include <asm/sbi.h>
 #include <asm/tlbflush.h>
 #include <asm/cacheflush.h>
@@ -90,7 +91,10 @@ static void send_ipi_mask(const struct cpumask *mask, enum ipi_message_type op)
 	smp_mb__after_atomic();
 
 	riscv_cpuid_to_hartid_mask(mask, &hartid_mask);
-	sbi_send_ipi(cpumask_bits(&hartid_mask));
+	if (IS_ENABLED(CONFIG_RISCV_SBI))
+		sbi_send_ipi(cpumask_bits(&hartid_mask));
+	else
+		clint_send_ipi_mask(&hartid_mask);
 }
 
 static void send_ipi_single(int cpu, enum ipi_message_type op)
@@ -101,12 +105,18 @@ static void send_ipi_single(int cpu, enum ipi_message_type op)
 	set_bit(op, &ipi_data[cpu].bits);
 	smp_mb__after_atomic();
 
-	sbi_send_ipi(cpumask_bits(cpumask_of(hartid)));
+	if (IS_ENABLED(CONFIG_RISCV_SBI))
+		sbi_send_ipi(cpumask_bits(cpumask_of(hartid)));
+	else
+		clint_send_ipi_single(hartid);
 }
 
 static inline void clear_ipi(void)
 {
-	csr_clear(CSR_SIP, SIE_SSIE);
+	if (IS_ENABLED(CONFIG_RISCV_SBI))
+		csr_clear(CSR_SIP, SIE_SSIE);
+	else
+		clint_clear_ipi(cpuid_to_hartid_map(smp_processor_id()));
 }
 
 void riscv_software_interrupt(void)
diff --git a/arch/riscv/kernel/smpboot.c b/arch/riscv/kernel/smpboot.c
index 18ae6da5115e..6300b09f1d1d 100644
--- a/arch/riscv/kernel/smpboot.c
+++ b/arch/riscv/kernel/smpboot.c
@@ -24,6 +24,7 @@
 #include <linux/of.h>
 #include <linux/sched/task_stack.h>
 #include <linux/sched/mm.h>
+#include <asm/clint.h>
 #include <asm/irq.h>
 #include <asm/mmu_context.h>
 #include <asm/tlbflush.h>
@@ -134,6 +135,9 @@ asmlinkage void __init smp_callin(void)
 {
 	struct mm_struct *mm = &init_mm;
 
+	if (!IS_ENABLED(CONFIG_RISCV_SBI))
+		clint_clear_ipi(cpuid_to_hartid_map(smp_processor_id()));
+
 	/* All kernel threads share the same mm context.  */
 	mmgrab(mm);
 	current->active_mm = mm;
-- 
2.20.1


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[PATCH 15/20] riscv: read the hart ID from mhartid on boot

[Christoph Hellwig]

From: Damien Le Moal <Damien.LeMoal@wdc.com>

When in M-Mode, we can use the mhartid CSR to get the ID of the running
HART. Doing so, direct M-Mode boot without firmware is possible.

Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Atish Patra <atish.patra@wdc.com>
---
 arch/riscv/include/asm/csr.h | 1 +
 arch/riscv/kernel/head.S     | 8 ++++++++
 2 files changed, 9 insertions(+)

diff --git a/arch/riscv/include/asm/csr.h b/arch/riscv/include/asm/csr.h
index 0dae5c361f29..d0b5113e1a54 100644
--- a/arch/riscv/include/asm/csr.h
+++ b/arch/riscv/include/asm/csr.h
@@ -81,6 +81,7 @@
 #define SIE_SEIE		(_AC(0x1, UL) << IRQ_S_EXT)
 
 /* symbolic CSR names: */
+#define CSR_MHARTID		0xf14
 #define CSR_MSTATUS		0x300
 #define CSR_MIE			0x304
 #define CSR_MTVEC		0x305
diff --git a/arch/riscv/kernel/head.S b/arch/riscv/kernel/head.S
index bb96bb7b95d2..e0350499d7a4 100644
--- a/arch/riscv/kernel/head.S
+++ b/arch/riscv/kernel/head.S
@@ -50,6 +50,14 @@ _start_kernel:
 	csrw CSR_XIE, zero
 	csrw CSR_XIP, zero
 
+#ifdef CONFIG_RISCV_M_MODE
+	/*
+	 * The hartid in a0 is expected later on, and we have no firmware
+	 * to hand it to us.
+	 */
+	csrr a0, CSR_MHARTID
+#endif
+
 	/* Load the global pointer */
 .option push
 .option norelax
-- 
2.20.1


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[PATCH 16/20] riscv: use the correct interrupt levels for M-mode

[Christoph Hellwig]

The numerical levels for External/Timer/Software interrupts differ
between S-mode and M-mode.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 arch/riscv/kernel/irq.c | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/arch/riscv/kernel/irq.c b/arch/riscv/kernel/irq.c
index 804ff70bb853..dbd1fd7c22e4 100644
--- a/arch/riscv/kernel/irq.c
+++ b/arch/riscv/kernel/irq.c
@@ -14,9 +14,15 @@
 /*
  * Possible interrupt causes:
  */
-#define INTERRUPT_CAUSE_SOFTWARE	IRQ_S_SOFT
-#define INTERRUPT_CAUSE_TIMER		IRQ_S_TIMER
-#define INTERRUPT_CAUSE_EXTERNAL	IRQ_S_EXT
+#ifdef CONFIG_RISCV_M_MODE
+# define INTERRUPT_CAUSE_SOFTWARE	IRQ_M_SOFT
+# define INTERRUPT_CAUSE_TIMER		IRQ_M_TIMER
+# define INTERRUPT_CAUSE_EXTERNAL	IRQ_M_EXT
+#else
+# define INTERRUPT_CAUSE_SOFTWARE	IRQ_S_SOFT
+# define INTERRUPT_CAUSE_TIMER		IRQ_S_TIMER
+# define INTERRUPT_CAUSE_EXTERNAL	IRQ_S_EXT
+#endif /* CONFIG_RISCV_M_MODE */
 
 int arch_show_interrupts(struct seq_file *p, int prec)
 {
-- 
2.20.1


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[PATCH 17/20] riscv: clear the instruction cache and all registers when booting

[Christoph Hellwig]

When we get booted we want a clear slate without any leaks from previous
supervisors or the firmware.  Flush the instruction cache and then clear
all registers to known good values.  This is really important for the
upcoming nommu support that runs on M-mode, but can't really harm when
running in S-mode either.  Vaguely based on the concepts from opensbi.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 arch/riscv/include/asm/csr.h |  1 +
 arch/riscv/kernel/head.S     | 88 +++++++++++++++++++++++++++++++++++-
 2 files changed, 88 insertions(+), 1 deletion(-)

diff --git a/arch/riscv/include/asm/csr.h b/arch/riscv/include/asm/csr.h
index d0b5113e1a54..ee0101278608 100644
--- a/arch/riscv/include/asm/csr.h
+++ b/arch/riscv/include/asm/csr.h
@@ -83,6 +83,7 @@
 /* symbolic CSR names: */
 #define CSR_MHARTID		0xf14
 #define CSR_MSTATUS		0x300
+#define CSR_MISA		0x301
 #define CSR_MIE			0x304
 #define CSR_MTVEC		0x305
 #define CSR_MSCRATCH		0x340
diff --git a/arch/riscv/kernel/head.S b/arch/riscv/kernel/head.S
index e0350499d7a4..93b369342042 100644
--- a/arch/riscv/kernel/head.S
+++ b/arch/riscv/kernel/head.S
@@ -11,6 +11,7 @@
 #include <asm/thread_info.h>
 #include <asm/page.h>
 #include <asm/csr.h>
+#include <asm/hwcap.h>
 #include <asm/image.h>
 
 __INIT
@@ -51,12 +52,18 @@ _start_kernel:
 	csrw CSR_XIP, zero
 
 #ifdef CONFIG_RISCV_M_MODE
+	/* flush the instruction cache */
+	fence.i
+
+	/* Reset all registers except ra, a0, a1 */
+	call reset_regs
+
 	/*
 	 * The hartid in a0 is expected later on, and we have no firmware
 	 * to hand it to us.
 	 */
 	csrr a0, CSR_MHARTID
-#endif
+#endif /* CONFIG_RISCV_M_MODE */
 
 	/* Load the global pointer */
 .option push
@@ -201,6 +208,85 @@ relocate:
 	j .Lsecondary_park
 END(_start)
 
+#ifdef CONFIG_RISCV_M_MODE
+ENTRY(reset_regs)
+	li	sp, 0
+	li	gp, 0
+	li	tp, 0
+	li	t0, 0
+	li	t1, 0
+	li	t2, 0
+	li	s0, 0
+	li	s1, 0
+	li	a2, 0
+	li	a3, 0
+	li	a4, 0
+	li	a5, 0
+	li	a6, 0
+	li	a7, 0
+	li	s2, 0
+	li	s3, 0
+	li	s4, 0
+	li	s5, 0
+	li	s6, 0
+	li	s7, 0
+	li	s8, 0
+	li	s9, 0
+	li	s10, 0
+	li	s11, 0
+	li	t3, 0
+	li	t4, 0
+	li	t5, 0
+	li	t6, 0
+	csrw	sscratch, 0
+
+#ifdef CONFIG_FPU
+	csrr	t0, CSR_MISA
+	andi	t0, t0, (COMPAT_HWCAP_ISA_F | COMPAT_HWCAP_ISA_D)
+	bnez	t0, .Lreset_regs_done
+
+	li	t1, SR_FS
+	csrs	CSR_XSTATUS, t1
+	fmv.s.x	f0, zero
+	fmv.s.x	f1, zero
+	fmv.s.x	f2, zero
+	fmv.s.x	f3, zero
+	fmv.s.x	f4, zero
+	fmv.s.x	f5, zero
+	fmv.s.x	f6, zero
+	fmv.s.x	f7, zero
+	fmv.s.x	f8, zero
+	fmv.s.x	f9, zero
+	fmv.s.x	f10, zero
+	fmv.s.x	f11, zero
+	fmv.s.x	f12, zero
+	fmv.s.x	f13, zero
+	fmv.s.x	f14, zero
+	fmv.s.x	f15, zero
+	fmv.s.x	f16, zero
+	fmv.s.x	f17, zero
+	fmv.s.x	f18, zero
+	fmv.s.x	f19, zero
+	fmv.s.x	f20, zero
+	fmv.s.x	f21, zero
+	fmv.s.x	f22, zero
+	fmv.s.x	f23, zero
+	fmv.s.x	f24, zero
+	fmv.s.x	f25, zero
+	fmv.s.x	f26, zero
+	fmv.s.x	f27, zero
+	fmv.s.x	f28, zero
+	fmv.s.x	f29, zero
+	fmv.s.x	f30, zero
+	fmv.s.x	f31, zero
+	csrw	fcsr, 0
+	/* note that the caller must clear SR_FS */
+#endif /* CONFIG_FPU */
+.Lreset_regs_done:
+	ret
+END(reset_regs)
+#endif /* CONFIG_RISCV_M_MODE */
+
 __PAGE_ALIGNED_BSS
 	/* Empty zero page */
 	.balign PAGE_SIZE
-- 
2.20.1


_______________________________________________
linux-riscv mailing list
linux-riscv@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-riscv

[PATCH 18/20] riscv: add nommu support

[Christoph Hellwig]

The kernel runs in M-mode without using page tables, and thus can't run
bare metal without help from additional firmware.

Most of the patch is just stubbing out code not needed without page
tables, but there is an interesting detail in the signals implementation:

 - The normal RISC-V syscall ABI only implements rt_sigreturn as VDSO
   entry point, but the ELF VDSO is not supported for nommu Linux.
   We instead copy the code to call the syscall onto the stack.

In addition to enabling the nommu code a new defconfig for a small
kernel image that can run in nommu mode on qemu is also provided, to run
a kernel in qemu you can use the following command line:

qemu-system-riscv64 -smp 2 -m 64 -machine virt -nographic \
	-kernel arch/riscv/boot/loader \
	-drive file=rootfs.ext2,format=raw,id=hd0 \
	-device virtio-blk-device,drive=hd0

Contains contributions from Damien Le Moal <Damien.LeMoal@wdc.com>.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 arch/riscv/Kconfig                      | 24 +++++---
 arch/riscv/configs/nommu_virt_defconfig | 78 +++++++++++++++++++++++++
 arch/riscv/include/asm/cache.h          |  8 +++
 arch/riscv/include/asm/elf.h            |  4 +-
 arch/riscv/include/asm/fixmap.h         |  2 +
 arch/riscv/include/asm/futex.h          |  6 ++
 arch/riscv/include/asm/io.h             |  4 ++
 arch/riscv/include/asm/mmu.h            |  3 +
 arch/riscv/include/asm/page.h           | 10 +++-
 arch/riscv/include/asm/pgalloc.h        |  2 +
 arch/riscv/include/asm/pgtable.h        | 60 +++++++++++--------
 arch/riscv/include/asm/tlbflush.h       | 12 +++-
 arch/riscv/include/asm/uaccess.h        |  4 ++
 arch/riscv/kernel/Makefile              |  3 +-
 arch/riscv/kernel/entry.S               | 11 ++++
 arch/riscv/kernel/head.S                |  6 ++
 arch/riscv/kernel/signal.c              | 17 +++++-
 arch/riscv/lib/Makefile                 | 11 ++--
 arch/riscv/mm/Makefile                  |  3 +-
 arch/riscv/mm/cacheflush.c              |  2 +
 arch/riscv/mm/context.c                 |  2 +
 arch/riscv/mm/init.c                    | 13 ++++-
 22 files changed, 233 insertions(+), 52 deletions(-)
 create mode 100644 arch/riscv/configs/nommu_virt_defconfig

diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index 86fcf608f193..7f708ba23f5a 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -26,13 +26,13 @@ config RISCV
 	select GENERIC_IRQ_SHOW
 	select GENERIC_PCI_IOMAP
 	select GENERIC_SCHED_CLOCK
-	select GENERIC_STRNCPY_FROM_USER
-	select GENERIC_STRNLEN_USER
+	select GENERIC_STRNCPY_FROM_USER if MMU
+	select GENERIC_STRNLEN_USER if MMU
 	select GENERIC_SMP_IDLE_THREAD
 	select GENERIC_ATOMIC64 if !64BIT
 	select HAVE_ARCH_AUDITSYSCALL
 	select HAVE_MEMBLOCK_NODE_MAP
-	select HAVE_DMA_CONTIGUOUS
+	select HAVE_DMA_CONTIGUOUS if MMU
 	select HAVE_FUTEX_CMPXCHG if FUTEX
 	select HAVE_PERF_EVENTS
 	select HAVE_SYSCALL_TRACEPOINTS
@@ -47,6 +47,7 @@ config RISCV
 	select PCI_DOMAINS_GENERIC if PCI
 	select PCI_MSI if PCI
 	select RISCV_TIMER
+	select UACCESS_MEMCPY if !MMU
 	select GENERIC_IRQ_MULTI_HANDLER
 	select GENERIC_ARCH_TOPOLOGY if SMP
 	select ARCH_HAS_PTE_SPECIAL
@@ -60,6 +61,7 @@ config RISCV
 # set if we run in machine mode, cleared if we run in supervisor mode
 config RISCV_M_MODE
 	bool
+	default !MMU
 
 # set if we are running in S-mode and can use SBI calls
 config RISCV_SBI
@@ -68,7 +70,11 @@ config RISCV_SBI
 	default y
 
 config MMU
-	def_bool y
+	bool "MMU-based Paged Memory Management Support"
+	default y
+	help
+	  Select if you want MMU-based virtualised addressing space
+	  support by paged memory management. If unsure, say 'Y'.
 
 config ZONE_DMA32
 	bool
@@ -87,6 +93,7 @@ config PA_BITS
 config PAGE_OFFSET
 	hex
 	default 0xC0000000 if 32BIT && MAXPHYSMEM_2GB
+	default 0x80000000 if 64BIT && !MMU
 	default 0xffffffff80000000 if 64BIT && MAXPHYSMEM_2GB
 	default 0xffffffe000000000 if 64BIT && MAXPHYSMEM_128GB
 
@@ -130,7 +137,7 @@ config GENERIC_HWEIGHT
 	def_bool y
 
 config FIX_EARLYCON_MEM
-	def_bool y
+	def_bool CONFIG_MMU
 
 config PGTABLE_LEVELS
 	int
@@ -155,6 +162,7 @@ config ARCH_RV32I
 	select GENERIC_LIB_ASHRDI3
 	select GENERIC_LIB_LSHRDI3
 	select GENERIC_LIB_UCMPDI2
+	select MMU
 
 config ARCH_RV64I
 	bool "RV64I"
@@ -163,9 +171,9 @@ config ARCH_RV64I
 	select HAVE_FUNCTION_TRACER
 	select HAVE_FUNCTION_GRAPH_TRACER
 	select HAVE_FTRACE_MCOUNT_RECORD
-	select HAVE_DYNAMIC_FTRACE
-	select HAVE_DYNAMIC_FTRACE_WITH_REGS
-	select SWIOTLB
+	select HAVE_DYNAMIC_FTRACE if MMU
+	select HAVE_DYNAMIC_FTRACE_WITH_REGS if HAVE_DYNAMIC_FTRACE
+	select SWIOTLB if MMU
 
 endchoice
 
diff --git a/arch/riscv/configs/nommu_virt_defconfig b/arch/riscv/configs/nommu_virt_defconfig
new file mode 100644
index 000000000000..cf74e179bf90
--- /dev/null
+++ b/arch/riscv/configs/nommu_virt_defconfig
@@ -0,0 +1,78 @@
+# CONFIG_CPU_ISOLATION is not set
+CONFIG_LOG_BUF_SHIFT=16
+CONFIG_PRINTK_SAFE_LOG_BUF_SHIFT=12
+CONFIG_BLK_DEV_INITRD=y
+# CONFIG_RD_BZIP2 is not set
+# CONFIG_RD_LZMA is not set
+# CONFIG_RD_XZ is not set
+# CONFIG_RD_LZO is not set
+# CONFIG_RD_LZ4 is not set
+CONFIG_CC_OPTIMIZE_FOR_SIZE=y
+CONFIG_EXPERT=y
+# CONFIG_SYSFS_SYSCALL is not set
+# CONFIG_FHANDLE is not set
+# CONFIG_BASE_FULL is not set
+# CONFIG_EPOLL is not set
+# CONFIG_SIGNALFD is not set
+# CONFIG_TIMERFD is not set
+# CONFIG_EVENTFD is not set
+# CONFIG_AIO is not set
+# CONFIG_IO_URING is not set
+# CONFIG_ADVISE_SYSCALLS is not set
+# CONFIG_MEMBARRIER is not set
+# CONFIG_KALLSYMS is not set
+# CONFIG_VM_EVENT_COUNTERS is not set
+# CONFIG_COMPAT_BRK is not set
+CONFIG_SLOB=y
+# CONFIG_SLAB_MERGE_DEFAULT is not set
+# CONFIG_MMU is not set
+CONFIG_MAXPHYSMEM_2GB=y
+CONFIG_SMP=y
+CONFIG_CMDLINE="root=/dev/vda rw earlycon=uart8250,mmio,0x10000000,115200n8 console=ttyS0"
+CONFIG_CMDLINE_FORCE=y
+# CONFIG_BLK_DEV_BSG is not set
+CONFIG_PARTITION_ADVANCED=y
+# CONFIG_MSDOS_PARTITION is not set
+# CONFIG_EFI_PARTITION is not set
+# CONFIG_MQ_IOSCHED_DEADLINE is not set
+# CONFIG_MQ_IOSCHED_KYBER is not set
+CONFIG_BINFMT_FLAT=y
+# CONFIG_COREDUMP is not set
+CONFIG_DEVTMPFS=y
+CONFIG_DEVTMPFS_MOUNT=y
+# CONFIG_FW_LOADER is not set
+# CONFIG_ALLOW_DEV_COREDUMP is not set
+CONFIG_VIRTIO_BLK=y
+# CONFIG_INPUT_KEYBOARD is not set
+# CONFIG_INPUT_MOUSE is not set
+# CONFIG_SERIO is not set
+# CONFIG_LEGACY_PTYS is not set
+# CONFIG_LDISC_AUTOLOAD is not set
+# CONFIG_DEVMEM is not set
+CONFIG_SERIAL_8250=y
+# CONFIG_SERIAL_8250_DEPRECATED_OPTIONS is not set
+CONFIG_SERIAL_8250_CONSOLE=y
+CONFIG_SERIAL_8250_NR_UARTS=1
+CONFIG_SERIAL_8250_RUNTIME_UARTS=1
+CONFIG_SERIAL_OF_PLATFORM=y
+# CONFIG_HW_RANDOM is not set
+# CONFIG_HWMON is not set
+# CONFIG_LCD_CLASS_DEVICE is not set
+# CONFIG_BACKLIGHT_CLASS_DEVICE is not set
+# CONFIG_VGA_CONSOLE is not set
+# CONFIG_HID is not set
+# CONFIG_USB_SUPPORT is not set
+CONFIG_VIRTIO_MMIO=y
+CONFIG_VIRTIO_MMIO_CMDLINE_DEVICES=y
+CONFIG_SIFIVE_PLIC=y
+# CONFIG_VALIDATE_FS_PARSER is not set
+CONFIG_EXT2_FS=y
+# CONFIG_DNOTIFY is not set
+# CONFIG_INOTIFY_USER is not set
+# CONFIG_MISC_FILESYSTEMS is not set
+CONFIG_LSM="[]"
+CONFIG_PRINTK_TIME=y
+# CONFIG_SCHED_DEBUG is not set
+# CONFIG_RCU_TRACE is not set
+# CONFIG_FTRACE is not set
+# CONFIG_RUNTIME_TESTING_MENU is not set
diff --git a/arch/riscv/include/asm/cache.h b/arch/riscv/include/asm/cache.h
index bfd523e8f0b2..9b58b104559e 100644
--- a/arch/riscv/include/asm/cache.h
+++ b/arch/riscv/include/asm/cache.h
@@ -11,4 +11,12 @@
 
 #define L1_CACHE_BYTES		(1 << L1_CACHE_SHIFT)
 
+/*
+ * RISC-V requires the stack pointer to be 16-byte aligned, so ensure that
+ * the flat loader aligns it accordingly.
+ */
+#ifndef CONFIG_MMU
+#define ARCH_SLAB_MINALIGN	16
+#endif
+
 #endif /* _ASM_RISCV_CACHE_H */
diff --git a/arch/riscv/include/asm/elf.h b/arch/riscv/include/asm/elf.h
index ef04084bf0de..d83a4efd052b 100644
--- a/arch/riscv/include/asm/elf.h
+++ b/arch/riscv/include/asm/elf.h
@@ -56,16 +56,16 @@ extern unsigned long elf_hwcap;
  */
 #define ELF_PLATFORM	(NULL)
 
+#ifdef CONFIG_MMU
 #define ARCH_DLINFO						\
 do {								\
 	NEW_AUX_ENT(AT_SYSINFO_EHDR,				\
 		(elf_addr_t)current->mm->context.vdso);		\
 } while (0)
-
-
 #define ARCH_HAS_SETUP_ADDITIONAL_PAGES
 struct linux_binprm;
 extern int arch_setup_additional_pages(struct linux_binprm *bprm,
 	int uses_interp);
+#endif /* CONFIG_MMU */
 
 #endif /* _ASM_RISCV_ELF_H */
diff --git a/arch/riscv/include/asm/fixmap.h b/arch/riscv/include/asm/fixmap.h
index 161f28d04a07..42d2c42f3cc9 100644
--- a/arch/riscv/include/asm/fixmap.h
+++ b/arch/riscv/include/asm/fixmap.h
@@ -11,6 +11,7 @@
 #include <asm/page.h>
 #include <asm/pgtable.h>
 
+#ifdef CONFIG_MMU
 /*
  * Here we define all the compile-time 'special' virtual addresses.
  * The point is to have a constant address at compile time, but to
@@ -42,4 +43,5 @@ extern void __set_fixmap(enum fixed_addresses idx,
 
 #include <asm-generic/fixmap.h>
 
+#endif /* CONFIG_MMU */
 #endif /* _ASM_RISCV_FIXMAP_H */
diff --git a/arch/riscv/include/asm/futex.h b/arch/riscv/include/asm/futex.h
index 4ad6409c4647..418564b96dc4 100644
--- a/arch/riscv/include/asm/futex.h
+++ b/arch/riscv/include/asm/futex.h
@@ -12,6 +12,12 @@
 #include <linux/errno.h>
 #include <asm/asm.h>
 
+/* We don't even really need the extable code, but for now keep it simple */
+#ifndef CONFIG_MMU
+#define __enable_user_access()		do { } while (0)
+#define __disable_user_access()		do { } while (0)
+#endif
+
 #define __futex_atomic_op(insn, ret, oldval, uaddr, oparg)	\
 {								\
 	uintptr_t tmp;						\
diff --git a/arch/riscv/include/asm/io.h b/arch/riscv/include/asm/io.h
index fc1189ad3777..d39a8f03e85e 100644
--- a/arch/riscv/include/asm/io.h
+++ b/arch/riscv/include/asm/io.h
@@ -14,6 +14,7 @@
 #include <linux/types.h>
 #include <asm/mmiowb.h>
 
+#ifdef CONFIG_MMU
 extern void __iomem *ioremap(phys_addr_t offset, unsigned long size);
 
 /*
@@ -26,6 +27,9 @@ extern void __iomem *ioremap(phys_addr_t offset, unsigned long size);
 #define ioremap_wt(addr, size) ioremap((addr), (size))
 
 extern void iounmap(volatile void __iomem *addr);
+#else
+#define pgprot_noncached(x)	(x)
+#endif /* CONFIG_MMU */
 
 /* Generic IO read/write.  These perform native-endian accesses. */
 #define __raw_writeb __raw_writeb
diff --git a/arch/riscv/include/asm/mmu.h b/arch/riscv/include/asm/mmu.h
index 151476fb58cb..967eacb01ab5 100644
--- a/arch/riscv/include/asm/mmu.h
+++ b/arch/riscv/include/asm/mmu.h
@@ -10,6 +10,9 @@
 #ifndef __ASSEMBLY__
 
 typedef struct {
+#ifndef CONFIG_MMU
+	unsigned long	end_brk;
+#endif
 	void *vdso;
 #ifdef CONFIG_SMP
 	/* A local icache flush is needed before user execution can resume. */
diff --git a/arch/riscv/include/asm/page.h b/arch/riscv/include/asm/page.h
index 3db261c4810f..ac699246ae7e 100644
--- a/arch/riscv/include/asm/page.h
+++ b/arch/riscv/include/asm/page.h
@@ -88,8 +88,14 @@ typedef struct page *pgtable_t;
 #define PTE_FMT "%08lx"
 #endif
 
+#ifdef CONFIG_MMU
 extern unsigned long va_pa_offset;
 extern unsigned long pfn_base;
+#define ARCH_PFN_OFFSET		(pfn_base)
+#else
+#define va_pa_offset		0
+#define ARCH_PFN_OFFSET		(PAGE_OFFSET >> PAGE_SHIFT)
+#endif /* CONFIG_MMU */
 
 extern unsigned long max_low_pfn;
 extern unsigned long min_low_pfn;
@@ -112,11 +118,9 @@ extern unsigned long min_low_pfn;
 
 #ifdef CONFIG_FLATMEM
 #define pfn_valid(pfn) \
-	(((pfn) >= pfn_base) && (((pfn)-pfn_base) < max_mapnr))
+	(((pfn) >= ARCH_PFN_OFFSET) && (((pfn) - ARCH_PFN_OFFSET) < max_mapnr))
 #endif
 
-#define ARCH_PFN_OFFSET		(pfn_base)
-
 #endif /* __ASSEMBLY__ */
 
 #define virt_addr_valid(vaddr)	(pfn_valid(virt_to_pfn(vaddr)))
diff --git a/arch/riscv/include/asm/pgalloc.h b/arch/riscv/include/asm/pgalloc.h
index 56a67d66f72f..d810b9e7476f 100644
--- a/arch/riscv/include/asm/pgalloc.h
+++ b/arch/riscv/include/asm/pgalloc.h
@@ -10,6 +10,7 @@
 #include <linux/mm.h>
 #include <asm/tlb.h>
 
+#ifdef CONFIG_MMU
 #include <asm-generic/pgalloc.h>	/* for pte_{alloc,free}_one */
 
 static inline void pmd_populate_kernel(struct mm_struct *mm,
@@ -81,6 +82,7 @@ do {                                    \
 	pgtable_page_dtor(pte);         \
 	tlb_remove_page((tlb), pte);    \
 } while (0)
+#endif /* CONFIG_MMU */
 
 static inline void check_pgt_cache(void)
 {
diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/pgtable.h
index 80905b27ee98..616c0a742492 100644
--- a/arch/riscv/include/asm/pgtable.h
+++ b/arch/riscv/include/asm/pgtable.h
@@ -24,6 +24,7 @@
 #include <asm/pgtable-32.h>
 #endif /* CONFIG_64BIT */
 
+#ifdef CONFIG_MMU
 /* Number of entries in the page global directory */
 #define PTRS_PER_PGD    (PAGE_SIZE / sizeof(pgd_t))
 /* Number of entries in the page table */
@@ -31,7 +32,6 @@
 
 /* Number of PGD entries that a user-mode program can use */
 #define USER_PTRS_PER_PGD   (TASK_SIZE / PGDIR_SIZE)
-#define FIRST_USER_ADDRESS  0
 
 /* Page protection bits */
 #define _PAGE_BASE	(_PAGE_PRESENT | _PAGE_ACCESSED | _PAGE_USER)
@@ -96,13 +96,6 @@ extern pgd_t swapper_pg_dir[];
 
 #define vmemmap		((struct page *)VMEMMAP_START)
 
-/*
- * ZERO_PAGE is a global shared page that is always zero,
- * used for zero-mapped memory areas, etc.
- */
-extern unsigned long empty_zero_page[PAGE_SIZE / sizeof(unsigned long)];
-#define ZERO_PAGE(vaddr) (virt_to_page(empty_zero_page))
-
 static inline int pmd_present(pmd_t pmd)
 {
 	return (pmd_val(pmd) & (_PAGE_PRESENT | _PAGE_PROT_NONE));
@@ -416,22 +409,9 @@ static inline int ptep_clear_flush_young(struct vm_area_struct *vma,
 #define __pte_to_swp_entry(pte)	((swp_entry_t) { pte_val(pte) })
 #define __swp_entry_to_pte(x)	((pte_t) { (x).val })
 
-#ifdef CONFIG_FLATMEM
-#define kern_addr_valid(addr)   (1) /* FIXME */
-#endif
-
-extern void *dtb_early_va;
-extern void setup_bootmem(void);
-extern void paging_init(void);
-
-static inline void pgtable_cache_init(void)
-{
-	/* No page table caches to initialize */
-}
-
-#define VMALLOC_SIZE     (KERN_VIRT_SIZE >> 1)
-#define VMALLOC_END      (PAGE_OFFSET - 1)
-#define VMALLOC_START    (PAGE_OFFSET - VMALLOC_SIZE)
+#define VMALLOC_SIZE		(KERN_VIRT_SIZE >> 1)
+#define VMALLOC_END		(PAGE_OFFSET - 1)
+#define VMALLOC_START		(PAGE_OFFSET - VMALLOC_SIZE)
 
 #define FIXADDR_TOP      VMALLOC_START
 #ifdef CONFIG_64BIT
@@ -451,6 +431,38 @@ static inline void pgtable_cache_init(void)
 #define TASK_SIZE FIXADDR_START
 #endif
 
+#else /* CONFIG_MMU */
+
+#define PAGE_KERNEL		__pgprot(0)
+#define swapper_pg_dir		NULL
+#define VMALLOC_START		0
+
+#define TASK_SIZE 0xffffffffUL
+
+#endif /* !CONFIG_MMU */
+
+#ifdef CONFIG_FLATMEM
+#define kern_addr_valid(addr)   (1) /* FIXME */
+#endif
+
+extern void *dtb_early_va;
+extern void setup_bootmem(void);
+extern void paging_init(void);
+
+static inline void pgtable_cache_init(void)
+{
+	/* No page table caches to initialize */
+}
+
+#define FIRST_USER_ADDRESS  0
+
+/*
+ * ZERO_PAGE is a global shared page that is always zero,
+ * used for zero-mapped memory areas, etc.
+ */
+extern unsigned long empty_zero_page[PAGE_SIZE / sizeof(unsigned long)];
+#define ZERO_PAGE(vaddr) (virt_to_page(empty_zero_page))
+
 #include <asm-generic/pgtable.h>
 
 #endif /* !__ASSEMBLY__ */
diff --git a/arch/riscv/include/asm/tlbflush.h b/arch/riscv/include/asm/tlbflush.h
index 075a784c66c5..b912456310b0 100644
--- a/arch/riscv/include/asm/tlbflush.h
+++ b/arch/riscv/include/asm/tlbflush.h
@@ -10,6 +10,7 @@
 #include <linux/mm_types.h>
 #include <asm/smp.h>
 
+#ifdef CONFIG_MMU
 /*
  * Flush entire local TLB.  'sfence.vma' implicitly fences with the instruction
  * cache as well, so a 'fence.i' is not necessary.
@@ -24,14 +25,19 @@ static inline void local_flush_tlb_page(unsigned long addr)
 {
 	__asm__ __volatile__ ("sfence.vma %0" : : "r" (addr) : "memory");
 }
+#else /* CONFIG_MMU */
+#define local_flush_tlb_all()			do { } while (0)
+#define local_flush_tlb_page(addr)		do { } while (0)
+#endif /* CONFIG_MMU */
 
-#ifdef CONFIG_SMP
+#if defined(CONFIG_SMP) && defined(CONFIG_MMU)
 void flush_tlb_all(void);
 void flush_tlb_mm(struct mm_struct *mm);
 void flush_tlb_page(struct vm_area_struct *vma, unsigned long addr);
 void flush_tlb_range(struct vm_area_struct *vma, unsigned long start,
 		unsigned long end);
-#else /* CONFIG_SMP */
+#else /* CONFIG_SMP && CONFIG_MMU */
+
 #define flush_tlb_all() local_flush_tlb_all()
 #define flush_tlb_page(vma, addr) local_flush_tlb_page(addr)
 
@@ -42,7 +48,7 @@ static inline void flush_tlb_range(struct vm_area_struct *vma,
 }
 
 #define flush_tlb_mm(mm) flush_tlb_all()
-#endif /* CONFIG_SMP */
+#endif /* !CONFIG_SMP || !CONFIG_MMU */
 
 /* Flush a range of kernel pages */
 static inline void flush_tlb_kernel_range(unsigned long start,
diff --git a/arch/riscv/include/asm/uaccess.h b/arch/riscv/include/asm/uaccess.h
index e076437cfafe..f462a183a9c2 100644
--- a/arch/riscv/include/asm/uaccess.h
+++ b/arch/riscv/include/asm/uaccess.h
@@ -11,6 +11,7 @@
 /*
  * User space memory access functions
  */
+#ifdef CONFIG_MMU
 #include <linux/errno.h>
 #include <linux/compiler.h>
 #include <linux/thread_info.h>
@@ -475,4 +476,7 @@ unsigned long __must_check clear_user(void __user *to, unsigned long n)
 	__ret;							\
 })
 
+#else /* CONFIG_MMU */
+#include <asm-generic/uaccess.h>
+#endif /* CONFIG_MMU */
 #endif /* _ASM_RISCV_UACCESS_H */
diff --git a/arch/riscv/kernel/Makefile b/arch/riscv/kernel/Makefile
index b4bfeb62d28a..158784871a08 100644
--- a/arch/riscv/kernel/Makefile
+++ b/arch/riscv/kernel/Makefile
@@ -25,9 +25,8 @@ obj-y	+= time.o
 obj-y	+= traps.o
 obj-y	+= riscv_ksyms.o
 obj-y	+= stacktrace.o
-obj-y	+= vdso.o
 obj-y	+= cacheinfo.o
-obj-y	+= vdso/
+obj-$(CONFIG_MMU) += vdso.o vdso/
 
 obj-$(CONFIG_RISCV_M_MODE)	+= clint.o
 obj-$(CONFIG_FPU)		+= fpu.o
diff --git a/arch/riscv/kernel/entry.S b/arch/riscv/kernel/entry.S
index 2c0513f8b62f..6a9693e1cf89 100644
--- a/arch/riscv/kernel/entry.S
+++ b/arch/riscv/kernel/entry.S
@@ -370,6 +370,10 @@ ENTRY(__switch_to)
 	ret
 ENDPROC(__switch_to)
 
+#ifndef CONFIG_MMU
+#define do_page_fault do_trap_unknown
+#endif
+
 	.section ".rodata"
 	/* Exception vector table */
 ENTRY(excp_vect_table)
@@ -391,3 +395,10 @@ ENTRY(excp_vect_table)
 	RISCV_PTR do_page_fault   /* store page fault */
 excp_vect_table_end:
 END(excp_vect_table)
+
+#ifndef CONFIG_MMU
+ENTRY(__user_rt_sigreturn)
+	li a7, __NR_rt_sigreturn
+	scall
+END(__user_rt_sigreturn)
+#endif
diff --git a/arch/riscv/kernel/head.S b/arch/riscv/kernel/head.S
index 93b369342042..102520e4bdc8 100644
--- a/arch/riscv/kernel/head.S
+++ b/arch/riscv/kernel/head.S
@@ -104,8 +104,10 @@ clear_bss_done:
 	la sp, init_thread_union + THREAD_SIZE
 	mv a0, s1
 	call setup_vm
+#ifdef CONFIG_MMU
 	la a0, early_pg_dir
 	call relocate
+#endif /* CONFIG_MMU */
 
 	/* Restore C environment */
 	la tp, init_task
@@ -116,6 +118,7 @@ clear_bss_done:
 	call parse_dtb
 	tail start_kernel
 
+#ifdef CONFIG_MMU
 relocate:
 	/* Relocate return address */
 	li a1, PAGE_OFFSET
@@ -166,6 +169,7 @@ relocate:
 	sfence.vma
 
 	ret
+#endif /* CONFIG_MMU */
 
 .Lsecondary_start:
 #ifdef CONFIG_SMP
@@ -194,9 +198,11 @@ relocate:
 	beqz tp, .Lwait_for_cpu_up
 	fence
 
+#ifdef CONFIG_MMU
 	/* Enable virtual memory and relocate to virtual address */
 	la a0, swapper_pg_dir
 	call relocate
+#endif
 
 	tail smp_callin
 #endif
diff --git a/arch/riscv/kernel/signal.c b/arch/riscv/kernel/signal.c
index e1a2cee340f7..eb8ba201feff 100644
--- a/arch/riscv/kernel/signal.c
+++ b/arch/riscv/kernel/signal.c
@@ -17,11 +17,16 @@
 #include <asm/switch_to.h>
 #include <asm/csr.h>
 
+extern u32 __user_rt_sigreturn[2];
+
 #define DEBUG_SIG 0
 
 struct rt_sigframe {
 	struct siginfo info;
 	struct ucontext uc;
+#ifndef CONFIG_MMU
+	u32 sigreturn_code[2];
+#endif
 };
 
 #ifdef CONFIG_FPU
@@ -166,7 +171,6 @@ static inline void __user *get_sigframe(struct ksignal *ksig,
 	return (void __user *)sp;
 }
 
-
 static int setup_rt_frame(struct ksignal *ksig, sigset_t *set,
 	struct pt_regs *regs)
 {
@@ -189,8 +193,19 @@ static int setup_rt_frame(struct ksignal *ksig, sigset_t *set,
 		return -EFAULT;
 
 	/* Set up to return from userspace. */
+#ifdef CONFIG_MMU
 	regs->ra = (unsigned long)VDSO_SYMBOL(
 		current->mm->context.vdso, rt_sigreturn);
+#else
+	/*
+	 * For the nommu case we don't have a VDSO.  Instead we push two
+	 * instructions to call the rt_sigreturn syscall onto the user stack.
+	 */
+	if (copy_to_user(&frame->sigreturn_code, __user_rt_sigreturn,
+			sizeof(frame->sigreturn_code)))
+		return -EFAULT;
+	regs->ra = (unsigned long)&frame->sigreturn_code;;
+#endif /* CONFIG_MMU */
 
 	/*
 	 * Set up registers for signal handler.
diff --git a/arch/riscv/lib/Makefile b/arch/riscv/lib/Makefile
index 267feaa10f6a..47e7a8204460 100644
--- a/arch/riscv/lib/Makefile
+++ b/arch/riscv/lib/Makefile
@@ -1,7 +1,6 @@
 # SPDX-License-Identifier: GPL-2.0-only
-lib-y	+= delay.o
-lib-y	+= memcpy.o
-lib-y	+= memset.o
-lib-y	+= uaccess.o
-
-lib-$(CONFIG_64BIT) += tishift.o
+lib-y			+= delay.o
+lib-y			+= memcpy.o
+lib-y			+= memset.o
+lib-$(CONFIG_MMU)	+= uaccess.o
+lib-$(CONFIG_64BIT)	+= tishift.o
diff --git a/arch/riscv/mm/Makefile b/arch/riscv/mm/Makefile
index 9d9a17335686..44ab8f28c3fa 100644
--- a/arch/riscv/mm/Makefile
+++ b/arch/riscv/mm/Makefile
@@ -6,9 +6,8 @@ CFLAGS_REMOVE_init.o = -pg
 endif
 
 obj-y += init.o
-obj-y += fault.o
 obj-y += extable.o
-obj-y += ioremap.o
+obj-$(CONFIG_MMU) += fault.o ioremap.o
 obj-y += cacheflush.o
 obj-y += context.o
 obj-y += sifive_l2_cache.o
diff --git a/arch/riscv/mm/cacheflush.c b/arch/riscv/mm/cacheflush.c
index 794c9ab256eb..8f1900686640 100644
--- a/arch/riscv/mm/cacheflush.c
+++ b/arch/riscv/mm/cacheflush.c
@@ -78,6 +78,7 @@ void flush_icache_mm(struct mm_struct *mm, bool local)
 
 #endif /* CONFIG_SMP */
 
+#ifdef CONFIG_MMU
 void flush_icache_pte(pte_t pte)
 {
 	struct page *page = pte_page(pte);
@@ -85,3 +86,4 @@ void flush_icache_pte(pte_t pte)
 	if (!test_and_set_bit(PG_dcache_clean, &page->flags))
 		flush_icache_all();
 }
+#endif /* CONFIG_MMU */
diff --git a/arch/riscv/mm/context.c b/arch/riscv/mm/context.c
index beeb5d7f92ea..073ff12a838a 100644
--- a/arch/riscv/mm/context.c
+++ b/arch/riscv/mm/context.c
@@ -57,8 +57,10 @@ void switch_mm(struct mm_struct *prev, struct mm_struct *next,
 	cpumask_clear_cpu(cpu, mm_cpumask(prev));
 	cpumask_set_cpu(cpu, mm_cpumask(next));
 
+#ifdef CONFIG_MMU
 	csr_write(CSR_SATP, virt_to_pfn(next->pgd) | SATP_MODE);
 	local_flush_tlb_all();
+#endif
 
 	flush_icache_deferred(next);
 }
diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
index f0ba71304b6e..2bc0a9fa4269 100644
--- a/arch/riscv/mm/init.c
+++ b/arch/riscv/mm/init.c
@@ -23,6 +23,7 @@ unsigned long empty_zero_page[PAGE_SIZE / sizeof(unsigned long)]
 EXPORT_SYMBOL(empty_zero_page);
 
 extern char _start[];
+void *dtb_early_va;
 
 static void __init zone_sizes_init(void)
 {
@@ -132,12 +133,12 @@ void __init setup_bootmem(void)
 	}
 }
 
+#ifdef CONFIG_MMU
 unsigned long va_pa_offset;
 EXPORT_SYMBOL(va_pa_offset);
 unsigned long pfn_base;
 EXPORT_SYMBOL(pfn_base);
 
-void *dtb_early_va;
 pgd_t swapper_pg_dir[PTRS_PER_PGD] __page_aligned_bss;
 pgd_t trampoline_pg_dir[PTRS_PER_PGD] __page_aligned_bss;
 pte_t fixmap_pte[PTRS_PER_PTE] __page_aligned_bss;
@@ -438,6 +439,16 @@ static void __init setup_vm_final(void)
 	csr_write(CSR_SATP, PFN_DOWN(__pa(swapper_pg_dir)) | SATP_MODE);
 	local_flush_tlb_all();
 }
+#else
+asmlinkage void __init setup_vm(uintptr_t dtb_pa)
+{
+	dtb_early_va = (void *)dtb_pa;
+}
+
+static inline void setup_vm_final(void)
+{
+}
+#endif /* CONFIG_MMU */
 
 void __init paging_init(void)
 {
-- 
2.20.1


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[PATCH 19/20] riscv: provide a flat image loader

[Christoph Hellwig]

This allows just loading the kernel at a pre-set address without
qemu going bonkers trying to map the ELF file.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 arch/riscv/Makefile        | 13 +++++++++----
 arch/riscv/boot/Makefile   |  7 ++++++-
 arch/riscv/boot/loader.S   |  8 ++++++++
 arch/riscv/boot/loader.lds | 14 ++++++++++++++
 4 files changed, 37 insertions(+), 5 deletions(-)
 create mode 100644 arch/riscv/boot/loader.S
 create mode 100644 arch/riscv/boot/loader.lds

diff --git a/arch/riscv/Makefile b/arch/riscv/Makefile
index a73659e30f8d..bdad38beda78 100644
--- a/arch/riscv/Makefile
+++ b/arch/riscv/Makefile
@@ -80,13 +80,18 @@ PHONY += vdso_install
 vdso_install:
 	$(Q)$(MAKE) $(build)=arch/riscv/kernel/vdso $@
 
-all: Image.gz
+ifeq ($(CONFIG_RISCV_M_MODE),y)
+KBUILD_IMAGE := $(boot)/loader
+else
+KBUILD_IMAGE := $(boot)/Image.gz
+endif
+BOOT_TARGETS := Image Image.gz loader
 
-Image: vmlinux
-	$(Q)$(MAKE) $(build)=$(boot) $(boot)/$@
+all:	$(notdir $(KBUILD_IMAGE))
 
-Image.%: Image
+$(BOOT_TARGETS): vmlinux
 	$(Q)$(MAKE) $(build)=$(boot) $(boot)/$@
+	@$(kecho) '  Kernel: $(boot)/$@ is ready'
 
 zinstall install:
 	$(Q)$(MAKE) $(build)=$(boot) $@
diff --git a/arch/riscv/boot/Makefile b/arch/riscv/boot/Makefile
index 0990a9fdbe5d..32d2addeddba 100644
--- a/arch/riscv/boot/Makefile
+++ b/arch/riscv/boot/Makefile
@@ -16,7 +16,7 @@
 
 OBJCOPYFLAGS_Image :=-O binary -R .note -R .note.gnu.build-id -R .comment -S
 
-targets := Image
+targets := Image loader
 
 $(obj)/Image: vmlinux FORCE
 	$(call if_changed,objcopy)
@@ -24,6 +24,11 @@ $(obj)/Image: vmlinux FORCE
 $(obj)/Image.gz: $(obj)/Image FORCE
 	$(call if_changed,gzip)
 
+loader.o: $(src)/loader.S $(obj)/Image
+
+$(obj)/loader: $(obj)/loader.o $(obj)/Image FORCE
+	$(Q)$(LD) -T $(src)/loader.lds -o $@ $(obj)/loader.o
+
 install:
 	$(CONFIG_SHELL) $(srctree)/$(src)/install.sh $(KERNELRELEASE) \
 	$(obj)/Image System.map "$(INSTALL_PATH)"
diff --git a/arch/riscv/boot/loader.S b/arch/riscv/boot/loader.S
new file mode 100644
index 000000000000..5586e2610dbb
--- /dev/null
+++ b/arch/riscv/boot/loader.S
@@ -0,0 +1,8 @@
+// SPDX-License-Identifier: GPL-2.0
+
+	.align 4
+	.section .payload, "ax", %progbits
+	.globl _start
+_start:
+	.incbin "arch/riscv/boot/Image"
+
diff --git a/arch/riscv/boot/loader.lds b/arch/riscv/boot/loader.lds
new file mode 100644
index 000000000000..da9efd57bf44
--- /dev/null
+++ b/arch/riscv/boot/loader.lds
@@ -0,0 +1,14 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+OUTPUT_ARCH(riscv)
+ENTRY(_start)
+
+SECTIONS
+{
+	. = 0x80000000;
+
+	.payload : {
+		*(.payload)
+		. = ALIGN(8);
+	}
+}
-- 
2.20.1


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[PATCH 20/20] riscv: disable the EFI PECOFF header for M-mode

[Christoph Hellwig]

No point in bloating the kernel image with a bootloader header if
we run bare metal.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 arch/riscv/kernel/head.S | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/riscv/kernel/head.S b/arch/riscv/kernel/head.S
index 102520e4bdc8..5a36c36bc823 100644
--- a/arch/riscv/kernel/head.S
+++ b/arch/riscv/kernel/head.S
@@ -16,6 +16,7 @@
 
 __INIT
 ENTRY(_start)
+#ifndef CONFIG_RISCV_M_MODE
 	/*
 	 * Image header expected by Linux boot-loaders. The image header data
 	 * structure is described in asm/image.h.
@@ -47,6 +48,7 @@ ENTRY(_start)
 
 .global _start_kernel
 _start_kernel:
+#endif /* CONFIG_RISCV_M_MODE */
 	/* Mask all interrupts */
 	csrw CSR_XIE, zero
 	csrw CSR_XIP, zero
-- 
2.20.1


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Re: [PATCH 08/20] riscv: abstract out CSR names for supervisor vs machine mode

[Paul Walmsley]

On Tue, 3 Sep 2019, Christoph Hellwig wrote:

> Many of the privileged CSRs exist in a supervisor and machine version
> that are used very similarly.  Provide a new X-naming layer so that
> we don't have to ifdef everywhere for M-mode Linux support.
> 
> Contains contributions from Damien Le Moal <Damien.LeMoal@wdc.com>.
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> Reviewed-by: Atish Patra <atish.patra@wdc.com>

[ ... ]

> diff --git a/arch/riscv/kernel/process.c b/arch/riscv/kernel/process.c
> index fb3a082362eb..853af1b7837b 100644
> --- a/arch/riscv/kernel/process.c
> +++ b/arch/riscv/kernel/process.c
> @@ -56,23 +56,23 @@ void show_regs(struct pt_regs *regs)
>  	pr_cont(" t5 : " REG_FMT " t6 : " REG_FMT "\n",
>  		regs->t5, regs->t6);
>  
> -	pr_cont("sstatus: " REG_FMT " sbadaddr: " REG_FMT " scause: " REG_FMT "\n",
> -		regs->sstatus, regs->sbadaddr, regs->scause);
> +	pr_cont("status: " REG_FMT " badaddr: " REG_FMT " cause: " REG_FMT "\n",
> +		regs->xstatus, regs->xbadaddr, regs->xcause);
>  }
>  
>  void start_thread(struct pt_regs *regs, unsigned long pc,
>  	unsigned long sp)
>  {
> -	regs->sstatus = SR_SPIE;
> +	regs->xstatus = SR_SPIE;

Looks like this should be "regs->xstatus = SR_PIE;"

Will update it here.  Let me know if you don't agree -


- Paul

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Re: [PATCH 08/20] riscv: abstract out CSR names for supervisor vs machine mode

[Christoph Hellwig]

On Tue, Oct 15, 2019 at 07:07:17PM -0700, Paul Walmsley wrote:
> >  void start_thread(struct pt_regs *regs, unsigned long pc,
> >  	unsigned long sp)
> >  {
> > -	regs->sstatus = SR_SPIE;
> > +	regs->xstatus = SR_SPIE;
> 
> Looks like this should be "regs->xstatus = SR_PIE;"
> 
> Will update it here.  Let me know if you don't agree -

there is no SR_PIE, do you mean SR_XPІE?  Good catch in that case,
but please let me resend the whole thing.  I have some minor updates,
and I'd also like to do the rebase myself.

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