RISC-V nommu support v2

RISC-V nommu support v2

[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.

To be useful this series also require the RISC-V binfmt_flat support,
which I've sent out separately.

A branch that includes this series and the binfmt_flat support is
available here:

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

Gitweb:

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

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 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

[PATCH 01/17] mm: provide a print_vma_addr stub for !CONFIG_MMU

[Christoph Hellwig]

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Vladimir Murzin <vladimir.murzin@arm.com>
---
 include/linux/mm.h | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index dd0b5f4e1e45..69843ee0c5f8 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -2756,7 +2756,13 @@ extern int randomize_va_space;
 #endif
 
 const char * arch_vma_name(struct vm_area_struct *vma);
+#ifdef CONFIG_MMU
 void print_vma_addr(char *prefix, unsigned long rip);
+#else
+static inline void print_vma_addr(char *prefix, unsigned long rip)
+{
+}
+#endif
 
 void *sparse_buffer_alloc(unsigned long size);
 struct page *sparse_mem_map_populate(unsigned long pnum, int nid,
-- 
2.20.1

[PATCH 02/17] mm: stub out all of swapops.h for !CONFIG_MMU

[Christoph Hellwig]

The whole header file deals with swap entries and PTEs, none of which
can exist for nommu builds.

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

diff --git a/include/linux/swapops.h b/include/linux/swapops.h
index 4d961668e5fc..b02922556846 100644
--- a/include/linux/swapops.h
+++ b/include/linux/swapops.h
@@ -6,6 +6,8 @@
 #include <linux/bug.h>
 #include <linux/mm_types.h>
 
+#ifdef CONFIG_MMU
+
 /*
  * swapcache pages are stored in the swapper_space radix tree.  We want to
  * get good packing density in that tree, so the index should be dense in
@@ -50,13 +52,11 @@ static inline pgoff_t swp_offset(swp_entry_t entry)
 	return entry.val & SWP_OFFSET_MASK;
 }
 
-#ifdef CONFIG_MMU
 /* check whether a pte points to a swap entry */
 static inline int is_swap_pte(pte_t pte)
 {
 	return !pte_none(pte) && !pte_present(pte);
 }
-#endif
 
 /*
  * Convert the arch-dependent pte representation of a swp_entry_t into an
@@ -375,4 +375,5 @@ static inline int non_swap_entry(swp_entry_t entry)
 }
 #endif
 
+#endif /* CONFIG_MMU */
 #endif /* _LINUX_SWAPOPS_H */
-- 
2.20.1

[PATCH 03/17] mm/nommu: fix the MAP_UNINITIALIZED flag

[Christoph Hellwig]

We can't expose UAPI symbols differently based on CONFIG_ symbols, as
userspace won't have them available.  Instead always define the flag,
but only respect it based on the config option.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Vladimir Murzin <vladimir.murzin@arm.com>
---
 arch/xtensa/include/uapi/asm/mman.h    | 6 +-----
 include/uapi/asm-generic/mman-common.h | 8 +++-----
 mm/nommu.c                             | 4 +++-
 3 files changed, 7 insertions(+), 11 deletions(-)

diff --git a/arch/xtensa/include/uapi/asm/mman.h b/arch/xtensa/include/uapi/asm/mman.h
index be726062412b..ebbb48842190 100644
--- a/arch/xtensa/include/uapi/asm/mman.h
+++ b/arch/xtensa/include/uapi/asm/mman.h
@@ -56,12 +56,8 @@
 #define MAP_STACK	0x40000		/* give out an address that is best suited for process/thread stacks */
 #define MAP_HUGETLB	0x80000		/* create a huge page mapping */
 #define MAP_FIXED_NOREPLACE 0x100000	/* MAP_FIXED which doesn't unmap underlying mapping */
-#ifdef CONFIG_MMAP_ALLOW_UNINITIALIZED
-# define MAP_UNINITIALIZED 0x4000000	/* For anonymous mmap, memory could be
+#define MAP_UNINITIALIZED 0x4000000	/* For anonymous mmap, memory could be
 					 * uninitialized */
-#else
-# define MAP_UNINITIALIZED 0x0		/* Don't support this flag */
-#endif
 
 /*
  * Flags for msync
diff --git a/include/uapi/asm-generic/mman-common.h b/include/uapi/asm-generic/mman-common.h
index abd238d0f7a4..cb556b430e71 100644
--- a/include/uapi/asm-generic/mman-common.h
+++ b/include/uapi/asm-generic/mman-common.h
@@ -19,15 +19,13 @@
 #define MAP_TYPE	0x0f		/* Mask for type of mapping */
 #define MAP_FIXED	0x10		/* Interpret addr exactly */
 #define MAP_ANONYMOUS	0x20		/* don't use a file */
-#ifdef CONFIG_MMAP_ALLOW_UNINITIALIZED
-# define MAP_UNINITIALIZED 0x4000000	/* For anonymous mmap, memory could be uninitialized */
-#else
-# define MAP_UNINITIALIZED 0x0		/* Don't support this flag */
-#endif
 
 /* 0x0100 - 0x80000 flags are defined in asm-generic/mman.h */
 #define MAP_FIXED_NOREPLACE	0x100000	/* MAP_FIXED which doesn't unmap underlying mapping */
 
+#define MAP_UNINITIALIZED 0x4000000	/* For anonymous mmap, memory could be
+					 * uninitialized */
+
 /*
  * Flags for mlock
  */
diff --git a/mm/nommu.c b/mm/nommu.c
index d8c02fbe03b5..ec75a0dffd4f 100644
--- a/mm/nommu.c
+++ b/mm/nommu.c
@@ -1349,7 +1349,9 @@ unsigned long do_mmap(struct file *file,
 	add_nommu_region(region);
 
 	/* clear anonymous mappings that don't ask for uninitialized data */
-	if (!vma->vm_file && !(flags & MAP_UNINITIALIZED))
+	if (!vma->vm_file &&
+	    (!IS_ENABLED(CONFIG_MMAP_ALLOW_UNINITIALIZED) ||
+	     !(flags & MAP_UNINITIALIZED)))
 		memset((void *)region->vm_start, 0,
 		       region->vm_end - region->vm_start);
 
-- 
2.20.1

[PATCH 04/17] irqchip/sifive-plic: set max threshold for ignored handlers

[Christoph Hellwig]

When running in M-mode we still the S-mode plic handlers in the DT.
Ignore them by setting the maximum threshold.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 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

[PATCH 05/17] riscv: use CSR_SATP instead of the legacy sptbr name in switch_mm

[Christoph Hellwig]

Switch to our own constant for the satp register instead of using
the old name from a legacy version of the privileged spec.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 arch/riscv/mm/context.c | 7 +------
 1 file changed, 1 insertion(+), 6 deletions(-)

diff --git a/arch/riscv/mm/context.c b/arch/riscv/mm/context.c
index 89ceb3cbe218..beeb5d7f92ea 100644
--- a/arch/riscv/mm/context.c
+++ b/arch/riscv/mm/context.c
@@ -57,12 +57,7 @@ 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));
 
-	/*
-	 * Use the old spbtr name instead of using the current satp
-	 * name to support binutils 2.29 which doesn't know about the
-	 * privileged ISA 1.10 yet.
-	 */
-	csr_write(sptbr, virt_to_pfn(next->pgd) | SATP_MODE);
+	csr_write(CSR_SATP, virt_to_pfn(next->pgd) | SATP_MODE);
 	local_flush_tlb_all();
 
 	flush_icache_deferred(next);
-- 
2.20.1

[PATCH 06/17] riscv: refactor the IPI code

[Christoph Hellwig]

This prepare for adding native non-SBI IPI code.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 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

[PATCH 07/17] 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>
---
 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 |  8 ++--
 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, 177 insertions(+), 109 deletions(-)

diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index 2c19baa8d6c3..2185481d1589 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -52,6 +52,10 @@ config RISCV
 	select ARCH_HAS_MMIOWB
 	select HAVE_EBPF_JIT if 64BIT
 
+# set if we run in machine mode, cleared if we run in supervisor mode
+config 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..14604f01e9f8 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_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..026a761835b7 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 */
+/* MIE / MIP 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 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_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_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_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 853b65ef656d..4cbe33bb5dd7 100644
--- a/arch/riscv/include/asm/switch_to.h
+++ b/arch/riscv/include/asm/switch_to.h
@@ -16,13 +16,13 @@ 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_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);
 	}
@@ -31,7 +31,7 @@ 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);
 	}
@@ -43,7 +43,7 @@ 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 bc7a56e1ca6f..b722ce20dc20 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 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 sstatus, SR_SIE
+	REG_L s0, PT_XSTATUS(sp)
+	csrc CSR_XSTATUS, SR_XIE
+#ifdef CONFIG_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 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 1defb0618aff..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 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 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 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 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 4e46f31072da..e5fa5481aa99 100644
--- a/arch/riscv/kernel/head.S
+++ b/arch/riscv/kernel/head.S
@@ -15,8 +15,8 @@
 __INIT
 ENTRY(_start)
 	/* 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
@@ -29,7 +29,7 @@ ENTRY(_start)
 	 * floating point in kernel space
 	 */
 	li t0, SR_FS
-	csrc sstatus, t0
+	csrc CSR_XSTATUS, t0
 
 	/* Pick one hart to run the main boot sequence */
 	la a3, hart_lottery
@@ -78,7 +78,7 @@ relocate:
 	/* Point stvec to virtual address of intruction after satp write */
 	la a0, 1f
 	add a0, a0, a1
-	csrw CSR_STVEC, a0
+	csrw CSR_XTVEC, a0
 
 	/* Compute satp for kernel page tables, but don't load it yet */
 	la a2, swapper_pg_dir
@@ -101,7 +101,7 @@ 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
@@ -127,7 +127,7 @@ 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 f23794bd1e90..1f03920d07d3 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",
@@ -56,17 +56,17 @@ 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_XPIE;
 	if (has_fpu)
-		regs->sstatus |= SR_FS_INITIAL;
-	regs->sepc = pc;
+		regs->xstatus |= SR_FS_INITIAL;
+	regs->xepc = pc;
 	regs->sp = sp;
 	set_fs(USER_DS);
 }
@@ -101,7 +101,8 @@ 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 1fe1b02e44d0..dfb26b64e17a 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, task);
 	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 6b32190ba73c..e028276928f8 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);
@@ -84,7 +84,7 @@ 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,
@@ -127,12 +127,12 @@ 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");
@@ -140,7 +140,7 @@ asmlinkage void do_trap_break(struct pt_regs *regs)
 	}
 #endif /* CONFIG_GENERIC_BUG */
 
-	force_sig_fault(SIGTRAP, TRAP_BRKPT, (void __user *)(regs->sepc), current);
+	force_sig_fault(SIGTRAP, TRAP_BRKPT, (void __user *)(regs->xepc), current);
 }
 
 #ifdef CONFIG_GENERIC_BUG
@@ -165,9 +165,9 @@ 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 399e6f0c2d98..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 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 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 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 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 sstatus, t6
+	csrs CSR_XSTATUS, t6
 	mv a0, a2
 	ret
 11:
-	csrs 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 3e2708c626a8..377248e45bba 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 5e6038fbf115..2e2d363faabf 100644
--- a/drivers/clocksource/timer-riscv.c
+++ b/drivers/clocksource/timer-riscv.c
@@ -28,7 +28,7 @@
 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;
 }
@@ -70,13 +70,13 @@ 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;
 }
 
@@ -85,7 +85,7 @@ 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

[PATCH 08/17] riscv: improve the default power off implementation

[Christoph Hellwig]

Only call the SBI code if we are not running in M mode, and if we didn't
do the SBI call, or it didn't succeed call wfi in a loop to at least
save some power.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 arch/riscv/kernel/reset.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/arch/riscv/kernel/reset.c b/arch/riscv/kernel/reset.c
index d0fe623bfb8f..2f5ca379747e 100644
--- a/arch/riscv/kernel/reset.c
+++ b/arch/riscv/kernel/reset.c
@@ -8,8 +8,11 @@
 
 static void default_power_off(void)
 {
+#ifndef CONFIG_M_MODE
 	sbi_shutdown();
-	while (1);
+#endif
+	while (1)
+		wait_for_interrupt();
 }
 
 void (*pm_power_off)(void) = default_power_off;
-- 
2.20.1

[PATCH 09/17] riscv: provide a flat entry 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 6b0741c9f348..69dbb6cb72f3 100644
--- a/arch/riscv/Makefile
+++ b/arch/riscv/Makefile
@@ -84,13 +84,18 @@ PHONY += vdso_install
 vdso_install:
 	$(Q)$(MAKE) $(build)=arch/riscv/kernel/vdso $@
 
-all: Image.gz
+ifeq ($(CONFIG_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

[PATCH 10/17] 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>
---
 arch/riscv/kernel/head.S | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/arch/riscv/kernel/head.S b/arch/riscv/kernel/head.S
index e5fa5481aa99..a4c170e41a34 100644
--- a/arch/riscv/kernel/head.S
+++ b/arch/riscv/kernel/head.S
@@ -18,6 +18,14 @@ ENTRY(_start)
 	csrw CSR_XIE, zero
 	csrw CSR_XIP, zero
 
+#ifdef CONFIG_M_MODE
+	/*
+	 * The hartid in a0 is expected later on, and we have no firmware
+	 * to hand it to us.
+	 */
+	csrr a0, mhartid
+#endif
+
 	/* Load the global pointer */
 .option push
 .option norelax
-- 
2.20.1

[PATCH 11/17] riscv: provide native clint access for M-mode

[Christoph Hellwig]

RISC-V has the concept of a cpu level interrupt controller.  Part of it
is expose as bits in the status registers, and 2 new CSRs per privilege
level in the instruction set, but the machanisms to trigger IPIs and
timer events, as well as reading the actual timer value are not
specified in the RISC-V spec but usually delegated to a block of MMIO
registers.  This patch adds support for those MMIO registers in the
timer and IPI code.  For now only the SiFive layout also supported by
a few other implementations is supported, but the code should be
easily extensible to others in the future.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 arch/riscv/include/asm/clint.h    | 40 +++++++++++++++++++++++++++
 arch/riscv/include/asm/timex.h    | 17 ++++++++++++
 arch/riscv/kernel/Makefile        |  1 +
 arch/riscv/kernel/clint.c         | 45 +++++++++++++++++++++++++++++++
 arch/riscv/kernel/setup.c         |  2 ++
 arch/riscv/kernel/smp.c           | 24 +++++++++++++++++
 arch/riscv/kernel/smpboot.c       |  3 +++
 drivers/clocksource/timer-riscv.c | 16 ++++++++---
 8 files changed, 144 insertions(+), 4 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..46d182d9a4db
--- /dev/null
+++ b/arch/riscv/include/asm/clint.h
@@ -0,0 +1,40 @@
+// SPDX-License-Identifier: GPL-2.0
+#ifndef _ASM_CLINT_H
+#define _ASM_CLINT_H 1
+
+#include <linux/smp.h>
+
+#ifdef CONFIG_M_MODE
+extern u32 __iomem *clint_ipi_base;
+extern u64 __iomem *clint_time_val;
+extern u64 __iomem *clint_time_cmp;
+
+void clint_init_boot_cpu(void);
+
+static inline void clint_send_ipi(unsigned long hartid)
+{
+	writel(1, clint_ipi_base + hartid);
+}
+
+static inline void clint_clear_ipi(unsigned long hartid)
+{
+	writel(0, clint_ipi_base + hartid);
+}
+
+static inline u64 clint_read_timer(void)
+{
+	return readq_relaxed(clint_time_val);
+}
+
+static inline void clint_set_timer(unsigned long delta)
+{
+	writeq_relaxed(clint_read_timer() + delta,
+		clint_time_cmp + cpuid_to_hartid_map(smp_processor_id()));
+}
+
+#else
+#define clint_init_boot_cpu()	do { } while (0)
+#define clint_clear_ipi(hartid)	do { } while (0)
+#endif /* CONFIG_M_MODE */
+
+#endif /* _ASM_CLINT_H */
diff --git a/arch/riscv/include/asm/timex.h b/arch/riscv/include/asm/timex.h
index 6a703ec9d796..bf907997f107 100644
--- a/arch/riscv/include/asm/timex.h
+++ b/arch/riscv/include/asm/timex.h
@@ -10,6 +10,22 @@
 
 typedef unsigned long cycles_t;
 
+#ifdef CONFIG_M_MODE
+
+#include <linux/io-64-nonatomic-lo-hi.h>
+#include <asm/clint.h>
+
+static inline cycles_t get_cycles(void)
+{
+#ifdef CONFIG_64BIT
+	return readq_relaxed(clint_time_val);
+#else
+	return readl_relaxed(clint_time_val);
+#endif
+}
+#define get_cycles	get_cycles
+
+#else /* CONFIG_M_MODE */
 static inline cycles_t get_cycles_inline(void)
 {
 	cycles_t n;
@@ -40,6 +56,7 @@ static inline uint64_t get_cycles64(void)
 	return ((u64)hi << 32) | lo;
 }
 #endif
+#endif /* CONFIG_M_MODE */
 
 #define ARCH_HAS_READ_CURRENT_TIMER
 
diff --git a/arch/riscv/kernel/Makefile b/arch/riscv/kernel/Makefile
index 2420d37d96de..f933c04f89db 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-$(CONFIG_M_MODE)		+= clint.o
 obj-$(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..15b9e7fa5416
--- /dev/null
+++ b/arch/riscv/kernel/clint.c
@@ -0,0 +1,45 @@
+// 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/csr.h>
+#include <asm/irq.h>
+#include <asm/timex.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_VAL_OFF	0xbff8
+#define CLINT_TIME_CMP_OFF	0x4000;
+
+u32 __iomem *clint_ipi_base;
+u64 __iomem *clint_time_val;
+u64 __iomem *clint_time_cmp;
+
+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;
+	clint_time_val = base + CLINT_TIME_VAL_OFF;
+	clint_time_cmp = base + CLINT_TIME_CMP_OFF;
+
+	clint_clear_ipi(boot_cpu_hartid);
+}
diff --git a/arch/riscv/kernel/setup.c b/arch/riscv/kernel/setup.c
index b92e6831d1ec..2892d82f474c 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>
@@ -67,6 +68,7 @@ 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 8cd730239613..ee8599a7ca48 100644
--- a/arch/riscv/kernel/smp.c
+++ b/arch/riscv/kernel/smp.c
@@ -13,7 +13,9 @@
 #include <linux/sched.h>
 #include <linux/seq_file.h>
 #include <linux/delay.h>
+#include <linux/io.h>
 
+#include <asm/clint.h>
 #include <asm/sbi.h>
 #include <asm/tlbflush.h>
 #include <asm/cacheflush.h>
@@ -78,6 +80,27 @@ static void ipi_stop(void)
 		wait_for_interrupt();
 }
 
+#ifdef CONFIG_M_MODE
+static inline void send_ipi_single(int cpu, enum ipi_message_type op)
+{
+	set_bit(op, &ipi_data[cpu].bits);
+	clint_send_ipi(cpuid_to_hartid_map(cpu));
+}
+
+static inline void send_ipi_mask(const struct cpumask *mask,
+		enum ipi_message_type op)
+{
+	int cpu;
+
+	for_each_cpu(cpu, mask)
+		send_ipi_single(cpu, op);
+}
+
+static inline void clear_ipi(void)
+{
+	clint_clear_ipi(cpuid_to_hartid_map(smp_processor_id()));
+}
+#else /* CONFIG_M_MODE */
 static void send_ipi_mask(const struct cpumask *mask, enum ipi_message_type op)
 {
 	int cpuid, hartid;
@@ -103,6 +126,7 @@ static inline void clear_ipi(void)
 {
 	csr_clear(CSR_SIP, SIE_SSIE);
 }
+#endif /* CONFIG_M_MODE */
 
 void riscv_software_interrupt(void)
 {
diff --git a/arch/riscv/kernel/smpboot.c b/arch/riscv/kernel/smpboot.c
index 7462a44304fe..1b7678d86ec8 100644
--- a/arch/riscv/kernel/smpboot.c
+++ b/arch/riscv/kernel/smpboot.c
@@ -23,6 +23,7 @@
 #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>
@@ -132,6 +133,8 @@ asmlinkage void __init smp_callin(void)
 {
 	struct mm_struct *mm = &init_mm;
 
+	clint_clear_ipi(cpuid_to_hartid_map(smp_processor_id()));
+
 	/* All kernel threads share the same mm context.  */
 	mmgrab(mm);
 	current->active_mm = mm;
diff --git a/drivers/clocksource/timer-riscv.c b/drivers/clocksource/timer-riscv.c
index 2e2d363faabf..008af21611d9 100644
--- a/drivers/clocksource/timer-riscv.c
+++ b/drivers/clocksource/timer-riscv.c
@@ -24,12 +24,16 @@
  * 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)
 {
 	csr_set(CSR_XIE, XIE_XTIE);
+
+#ifdef CONFIG_M_MODE
+	clint_set_timer(delta);
+#else
 	sbi_set_timer(get_cycles64() + delta);
+#endif
 	return 0;
 }
 
@@ -45,14 +49,18 @@ static DEFINE_PER_CPU(struct clock_event_device, riscv_clock_event) = {
  * within one tick of each other, so while this could technically go
  * backwards when hopping between CPUs, practically it won't happen.
  */
-static unsigned long long riscv_clocksource_rdtime(struct clocksource *cs)
+static u64 riscv_sched_clock(void)
 {
+#ifdef CONFIG_M_MODE
+	return clint_read_timer();
+#else
 	return get_cycles64();
+#endif
 }
 
-static u64 riscv_sched_clock(void)
+static unsigned long long riscv_clocksource_rdtime(struct clocksource *cs)
 {
-	return get_cycles64();
+	return riscv_sched_clock();
 }
 
 static DEFINE_PER_CPU(struct clocksource, riscv_clocksource) = {
-- 
2.20.1

[PATCH 12/17] riscv: implement remote sfence.i natively for M-mode

[Christoph Hellwig]

The RISC-V ISA only supports flushing the instruction cache for the local
CPU core.  For normal S-mode Linux remote flushing is offloaded to
machine mode using ecalls, but for M-mode Linux we'll have to do it
ourselves.  Use the same implementation as all the existing open source
SBI implementations by just doing an IPI to all remote cores to execute
th sfence.i instruction on every live core.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 arch/riscv/mm/cacheflush.c | 31 +++++++++++++++++++++++++++----
 1 file changed, 27 insertions(+), 4 deletions(-)

diff --git a/arch/riscv/mm/cacheflush.c b/arch/riscv/mm/cacheflush.c
index 9ebcff8ba263..10875ea1065e 100644
--- a/arch/riscv/mm/cacheflush.c
+++ b/arch/riscv/mm/cacheflush.c
@@ -10,10 +10,35 @@
 
 #include <asm/sbi.h>
 
+#ifdef CONFIG_M_MODE
+static void ipi_remote_fence_i(void *info)
+{
+	return local_flush_icache_all();
+}
+
+void flush_icache_all(void)
+{
+	on_each_cpu(ipi_remote_fence_i, NULL, 1);
+}
+
+static void flush_icache_cpumask(const cpumask_t *mask)
+{
+	on_each_cpu_mask(mask, ipi_remote_fence_i, NULL, 1);
+}
+#else /* CONFIG_M_MODE */
 void flush_icache_all(void)
 {
 	sbi_remote_fence_i(NULL);
 }
+static void flush_icache_cpumask(const cpumask_t *mask)
+{
+	cpumask_t hmask;
+
+	cpumask_clear(&hmask);
+	riscv_cpuid_to_hartid_mask(mask, &hmask);
+	sbi_remote_fence_i(hmask.bits);
+}
+#endif /* CONFIG_M_MODE */
 
 /*
  * Performs an icache flush for the given MM context.  RISC-V has no direct
@@ -28,7 +53,7 @@ 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();
 
@@ -47,9 +72,7 @@ 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) {
-		cpumask_clear(&hmask);
-		riscv_cpuid_to_hartid_mask(&others, &hmask);
-		sbi_remote_fence_i(hmask.bits);
+		flush_icache_cpumask(&others);
 	} else {
 		/*
 		 * It's assumed that at least one strongly ordered operation is
-- 
2.20.1

[PATCH 13/17] 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 | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/arch/riscv/include/asm/sbi.h b/arch/riscv/include/asm/sbi.h
index 21134b3ef404..1e17f07eadaf 100644
--- a/arch/riscv/include/asm/sbi.h
+++ b/arch/riscv/include/asm/sbi.h
@@ -8,6 +8,7 @@
 
 #include <linux/types.h>
 
+#ifndef CONFIG_M_MODE
 #define SBI_SET_TIMER 0
 #define SBI_CONSOLE_PUTCHAR 1
 #define SBI_CONSOLE_GETCHAR 2
@@ -94,4 +95,5 @@ 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_M_MODE */
+#endif /* _ASM_RISCV_SBI_H */
-- 
2.20.1

[PATCH 14/17] riscv: don't allow selecting SBI-based drivers for M-mode

[Christoph Hellwig]

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

Do not allow selecting SBI related options with MMU option not set.

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

diff --git a/drivers/tty/hvc/Kconfig b/drivers/tty/hvc/Kconfig
index 4d22b911111f..5a1ab6b536ff 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 && !M_MODE
 	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 0d31251e04cc..59dba9f9e466 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 && !M_MODE
 	select SERIAL_CORE
 	select SERIAL_CORE_CONSOLE
 	select SERIAL_EARLYCON
-- 
2.20.1

[PATCH 15/17] 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..9566aabbe50b 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_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_M_MODE */
 
 int arch_show_interrupts(struct seq_file *p, int prec)
 {
-- 
2.20.1

[PATCH 16/17] 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/kernel/head.S | 85 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 85 insertions(+)

diff --git a/arch/riscv/kernel/head.S b/arch/riscv/kernel/head.S
index a4c170e41a34..74feb17737b4 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>
 
 __INIT
 ENTRY(_start)
@@ -19,6 +20,12 @@ ENTRY(_start)
 	csrw CSR_XIP, zero
 
 #ifdef CONFIG_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.
@@ -168,6 +175,84 @@ relocate:
 	j .Lsecondary_park
 END(_start)
 
+#ifdef CONFIG_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, misa
+	andi	t0, t0, (COMPAT_HWCAP_ISA_F | COMPAT_HWCAP_ISA_D)
+	bnez	t0, .Lreset_regs_done
+
+	li	t1, SR_FS
+	csrs	sstatus, 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
+#endif /* CONFIG_FPU */
+.Lreset_regs_done:
+	ret
+END(reset_regs)
+#endif /* CONFIG_M_MODE */
+
 __PAGE_ALIGNED_BSS
 	/* Empty zero page */
 	.balign PAGE_SIZE
-- 
2.20.1

[PATCH 17/17] 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/elf.h            |  4 +-
 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           | 12 +++-
 arch/riscv/include/asm/pgalloc.h        |  2 +
 arch/riscv/include/asm/pgtable.h        | 38 ++++++++----
 arch/riscv/include/asm/tlbflush.h       |  7 ++-
 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                 |  8 +--
 arch/riscv/mm/Makefile                  |  3 +-
 arch/riscv/mm/cacheflush.c              |  2 +
 arch/riscv/mm/context.c                 |  2 +
 arch/riscv/mm/init.c                    |  2 +
 20 files changed, 200 insertions(+), 36 deletions(-)
 create mode 100644 arch/riscv/configs/nommu_virt_defconfig

diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index 2185481d1589..f36f337c7570 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 ARCH_HAS_PTE_SPECIAL
 	select ARCH_HAS_MMIOWB
@@ -55,9 +56,14 @@ config RISCV
 # set if we run in machine mode, cleared if we run in supervisor mode
 config M_MODE
 	bool
+	default y if !MMU
 
 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
@@ -66,6 +72,7 @@ config ZONE_DMA32
 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
 
@@ -93,7 +100,7 @@ config GENERIC_HWEIGHT
 	def_bool y
 
 config FIX_EARLYCON_MEM
-	def_bool y
+	def_bool CONFIG_MMU
 
 config PGTABLE_LEVELS
 	int
@@ -116,6 +123,7 @@ config ARCH_RV32I
 	select GENERIC_LIB_ASHRDI3
 	select GENERIC_LIB_LSHRDI3
 	select GENERIC_LIB_UCMPDI2
+	select MMU
 
 config ARCH_RV64I
 	bool "RV64I"
@@ -124,9 +132,9 @@ 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/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/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 8ddb6c7fedac..df0256a9a965 100644
--- a/arch/riscv/include/asm/page.h
+++ b/arch/riscv/include/asm/page.h
@@ -78,8 +78,14 @@ 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;
@@ -101,9 +107,7 @@ extern unsigned long min_low_pfn;
 #define phys_to_page(paddr)	(pfn_to_page(phys_to_pfn(paddr)))
 
 #define pfn_valid(pfn) \
-	(((pfn) >= pfn_base) && (((pfn)-pfn_base) < max_mapnr))
-
-#define ARCH_PFN_OFFSET		(pfn_base)
+	(((pfn) >= ARCH_PFN_OFFSET) && (((pfn) - ARCH_PFN_OFFSET) < max_mapnr))
 
 #endif /* __ASSEMBLY__ */
 
@@ -115,8 +119,10 @@ extern unsigned long min_low_pfn;
 #include <asm-generic/memory_model.h>
 #include <asm-generic/getorder.h>
 
+#ifdef CONFIG_MMU
 /* vDSO support */
 /* We do define AT_SYSINFO_EHDR but don't use the gate mechanism */
 #define __HAVE_ARCH_GATE_AREA
+#endif /* CONFIG_MMU */
 
 #endif /* _ASM_RISCV_PAGE_H */
diff --git a/arch/riscv/include/asm/pgalloc.h b/arch/riscv/include/asm/pgalloc.h
index eb8b0195f27f..8d60c862d2f9 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
 static inline void pmd_populate_kernel(struct mm_struct *mm,
 	pmd_t *pmd, pte_t *pte)
 {
@@ -106,6 +107,7 @@ 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 f7c3f7de15f2..dd6a63648e4a 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)
@@ -81,13 +81,6 @@ extern pgd_t swapper_pg_dir[];
 #define __S110	PAGE_SHARED_EXEC
 #define __S111	PAGE_SHARED_EXEC
 
-/*
- * 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));
@@ -392,6 +385,18 @@ 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 })
 
+#define VMALLOC_SIZE		(KERN_VIRT_SIZE >> 1)
+#define VMALLOC_END		(PAGE_OFFSET - 1)
+#define VMALLOC_START		(PAGE_OFFSET - VMALLOC_SIZE)
+
+#else /* CONFIG_MMU */
+
+#define PAGE_KERNEL		__pgprot(0)
+#define swapper_pg_dir		NULL
+#define VMALLOC_START		0
+
+#endif /* CONFIG_MMU */
+
 #ifdef CONFIG_FLATMEM
 #define kern_addr_valid(addr)   (1) /* FIXME */
 #endif
@@ -404,10 +409,7 @@ 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)
-
+#ifdef CONFIG_MMU
 /*
  * Task size is 0x40000000000 for RV64 or 0xb800000 for RV32.
  * Note that PGDIR_SIZE must evenly divide TASK_SIZE.
@@ -417,6 +419,18 @@ static inline void pgtable_cache_init(void)
 #else
 #define TASK_SIZE VMALLOC_START
 #endif
+#else /* CONFIG_MMU */
+#define TASK_SIZE 0xffffffffUL
+#endif /* !CONFIG_MMU */
+
+#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>
 
diff --git a/arch/riscv/include/asm/tlbflush.h b/arch/riscv/include/asm/tlbflush.h
index 687dd19735a7..f127b3d17ec2 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.
@@ -24,8 +25,12 @@ 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 */
 
-#ifndef CONFIG_SMP
+#if !defined(CONFIG_SMP) || !defined(CONFIG_MMU)
 
 #define flush_tlb_all() local_flush_tlb_all()
 #define flush_tlb_page(vma, addr) local_flush_tlb_page(addr)
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 f933c04f89db..d720666283d6 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-$(CONFIG_M_MODE)		+= clint.o
 obj-$(CONFIG_FPU)		+= fpu.o
diff --git a/arch/riscv/kernel/entry.S b/arch/riscv/kernel/entry.S
index b722ce20dc20..0e040573d6a8 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 74feb17737b4..405bd6ccf44a 100644
--- a/arch/riscv/kernel/head.S
+++ b/arch/riscv/kernel/head.S
@@ -68,10 +68,12 @@ clear_bss_done:
 	la a2, boot_cpu_hartid
 	REG_S a0, (a2)
 
+#ifdef CONFIG_MMU
 	/* Initialize page tables and relocate to virtual addresses */
 	la sp, init_thread_union + THREAD_SIZE
 	call setup_vm
 	call relocate
+#endif /* CONFIG_MMU */
 
 	/* Restore C environment */
 	la tp, init_task
@@ -83,6 +85,7 @@ clear_bss_done:
 	call parse_dtb
 	tail start_kernel
 
+#ifdef CONFIG_MMU
 relocate:
 	/* Relocate return address */
 	li a1, PAGE_OFFSET
@@ -134,6 +137,7 @@ relocate:
 	sfence.vma
 
 	ret
+#endif /* CONFIG_MMU */
 
 .Lsecondary_start:
 #ifdef CONFIG_SMP
@@ -162,8 +166,10 @@ relocate:
 	beqz tp, .Lwait_for_cpu_up
 	fence
 
+#ifdef CONFIG_MMU
 	/* Enable virtual memory and relocate to virtual address */
 	call relocate
+#endif
 
 	tail smp_callin
 #endif
diff --git a/arch/riscv/kernel/signal.c b/arch/riscv/kernel/signal.c
index dfb26b64e17a..7de7e539b25b 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 8e364ebf37de..5382e42d0cba 100644
--- a/arch/riscv/lib/Makefile
+++ b/arch/riscv/lib/Makefile
@@ -2,8 +2,6 @@
 lib-y	+= delay.o
 lib-y	+= memcpy.o
 lib-y	+= memset.o
-lib-y	+= uaccess.o
-
-lib-$(CONFIG_64BIT) += tishift.o
-
-lib-$(CONFIG_32BIT) += udivdi3.o
+lib-$(CONFIG_MMU)	+= uaccess.o
+lib-$(CONFIG_64BIT)	+= tishift.o
+lib-$(CONFIG_32BIT)	+= udivdi3.o
diff --git a/arch/riscv/mm/Makefile b/arch/riscv/mm/Makefile
index fc51d3b7876e..8fc2fd148b06 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 10875ea1065e..0fc69eedc921 100644
--- a/arch/riscv/mm/cacheflush.c
+++ b/arch/riscv/mm/cacheflush.c
@@ -90,6 +90,7 @@ 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);
@@ -97,3 +98,4 @@ 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 84747d7a1e85..782be273e714 100644
--- a/arch/riscv/mm/init.c
+++ b/arch/riscv/mm/init.c
@@ -142,6 +142,7 @@ void __init setup_bootmem(void)
 	}
 }
 
+#ifdef CONFIG_MMU
 unsigned long va_pa_offset;
 EXPORT_SYMBOL(va_pa_offset);
 unsigned long pfn_base;
@@ -247,3 +248,4 @@ asmlinkage void __init setup_vm(void)
 				__pgprot(_PAGE_TABLE));
 #endif
 }
+#endif /* CONFIG_MMU */
-- 
2.20.1

Re: RISC-V nommu support v2

[Vladimir Murzin]

Hi,

On 6/24/19 6:42 AM, Christoph Hellwig wrote:
> 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.
> 
> To be useful this series also require the RISC-V binfmt_flat support,
> which I've sent out separately.
> 
> A branch that includes this series and the binfmt_flat support is
> available here:
> 
>     git://git.infradead.org/users/hch/riscv.git riscv-nommu.2
> 
> Gitweb:
> 
>     http://git.infradead.org/users/hch/riscv.git/shortlog/refs/heads/riscv-nommu.2
> 
> 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 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
> 
> 

Since you are using binfmt_flat which is kind of 32-bit only I was expecting to see
CONFIG_COMPAT (or something similar to that, like ILP32) enabled, yet I could not
find it.

I do not know much about RISC-V architecture, so it is why I'm wondering how you deal
with that?

Cheers
Vladimir

Re: RISC-V nommu support v2

[Christoph Hellwig]

On Mon, Jun 24, 2019 at 12:47:07PM +0100, Vladimir Murzin wrote:
> Since you are using binfmt_flat which is kind of 32-bit only I was expecting to see
> CONFIG_COMPAT (or something similar to that, like ILP32) enabled, yet I could not
> find it.

There is no such thing in RISC-V.  I don't know of any 64-bit RISC-V
cpu that can actually run 32-bit RISC-V code, although in theory that
is possible.  There also is nothing like the x86 x32 or mips n32 mode
available either for now.

But it turns out that with a few fixes to binfmt_flat it can run 64-bit
binaries just fine.  I sent that series out a while ago, and IIRC you
actually commented on it.

Re: RISC-V nommu support v2

[Vladimir Murzin]

On 6/24/19 12:54 PM, Christoph Hellwig wrote:
> On Mon, Jun 24, 2019 at 12:47:07PM +0100, Vladimir Murzin wrote:
>> Since you are using binfmt_flat which is kind of 32-bit only I was expecting to see
>> CONFIG_COMPAT (or something similar to that, like ILP32) enabled, yet I could not
>> find it.
> 
> There is no such thing in RISC-V.  I don't know of any 64-bit RISC-V
> cpu that can actually run 32-bit RISC-V code, although in theory that
> is possible.  There also is nothing like the x86 x32 or mips n32 mode
> available either for now.
> 
> But it turns out that with a few fixes to binfmt_flat it can run 64-bit
> binaries just fine.  I sent that series out a while ago, and IIRC you
> actually commented on it.
> 

True, yet my observation was that elf2flt utility assumes that address
space cannot exceed 32-bit (for header and absolute relocations). So,
from my limited point of view straightforward way to guarantee that would
be to build incoming elf in 32-bit mode (it is why I mentioned COMPAT/ILP32).

Also one of your patches expressed somewhat related idea

"binfmt_flat isn't the right binary format for huge executables to
start with"

Since you said there is no support for compat/ilp32, probably I'm missing some
toolchain magic?

Cheers
Vladimir

Re: RISC-V nommu support v2

[Christoph Hellwig]

On Mon, Jun 24, 2019 at 02:08:50PM +0100, Vladimir Murzin wrote:
> True, yet my observation was that elf2flt utility assumes that address
> space cannot exceed 32-bit (for header and absolute relocations). So,
> from my limited point of view straightforward way to guarantee that would
> be to build incoming elf in 32-bit mode (it is why I mentioned COMPAT/ILP32).
> 
> Also one of your patches expressed somewhat related idea
> 
> "binfmt_flat isn't the right binary format for huge executables to
> start with"
> 
> Since you said there is no support for compat/ilp32, probably I'm missing some
> toolchain magic?

There is no magic except for the tiny elf2flt patch, which for
now is just in the buildroot repo pointed to in the cover letter
(and which I plan to upstream once the kernel support has landed
in Linus' tree).  We only support 32-bit code and data address spaces,
but we otherwise use the normal RISC-V ABI, that is 64-bit longs and
pointers.

Re: RISC-V nommu support v2

[Palmer Dabbelt]

On Mon, 24 Jun 2019 06:08:50 PDT (-0700), vladimir.murzin@arm.com wrote:
> On 6/24/19 12:54 PM, Christoph Hellwig wrote:
>> On Mon, Jun 24, 2019 at 12:47:07PM +0100, Vladimir Murzin wrote:
>>> Since you are using binfmt_flat which is kind of 32-bit only I was expecting to see
>>> CONFIG_COMPAT (or something similar to that, like ILP32) enabled, yet I could not
>>> find it.
>>
>> There is no such thing in RISC-V.  I don't know of any 64-bit RISC-V
>> cpu that can actually run 32-bit RISC-V code, although in theory that
>> is possible.  There also is nothing like the x86 x32 or mips n32 mode
>> available either for now.
>>
>> But it turns out that with a few fixes to binfmt_flat it can run 64-bit
>> binaries just fine.  I sent that series out a while ago, and IIRC you
>> actually commented on it.
>>
>
> True, yet my observation was that elf2flt utility assumes that address
> space cannot exceed 32-bit (for header and absolute relocations). So,
> from my limited point of view straightforward way to guarantee that would
> be to build incoming elf in 32-bit mode (it is why I mentioned COMPAT/ILP32).
>
> Also one of your patches expressed somewhat related idea
>
> "binfmt_flat isn't the right binary format for huge executables to
> start with"
>
> Since you said there is no support for compat/ilp32, probably I'm missing some
> toolchain magic?
>
> Cheers
> Vladimir
To:          Christoph Hellwig <hch@lst.de>
CC:          vladimir.murzin@arm.com
CC:          Christoph Hellwig <hch@lst.de>
CC:          Paul Walmsley <paul.walmsley@sifive.com>
CC:          Damien Le Moal <Damien.LeMoal@wdc.com>
CC:          linux-riscv@lists.infradead.org
CC:          linux-mm@kvack.org
CC:          linux-kernel@vger.kernel.org
Subject:     Re: RISC-V nommu support v2
In-Reply-To: <20190624131633.GB10746@lst.de>

On Mon, 24 Jun 2019 06:16:33 PDT (-0700), Christoph Hellwig wrote:
> On Mon, Jun 24, 2019 at 02:08:50PM +0100, Vladimir Murzin wrote:
>> True, yet my observation was that elf2flt utility assumes that address
>> space cannot exceed 32-bit (for header and absolute relocations). So,
>> from my limited point of view straightforward way to guarantee that would
>> be to build incoming elf in 32-bit mode (it is why I mentioned COMPAT/ILP32).
>>
>> Also one of your patches expressed somewhat related idea
>>
>> "binfmt_flat isn't the right binary format for huge executables to
>> start with"
>>
>> Since you said there is no support for compat/ilp32, probably I'm missing some
>> toolchain magic?
>
> There is no magic except for the tiny elf2flt patch, which for
> now is just in the buildroot repo pointed to in the cover letter
> (and which I plan to upstream once the kernel support has landed
> in Linus' tree).  We only support 32-bit code and data address spaces,
> but we otherwise use the normal RISC-V ABI, that is 64-bit longs and
> pointers.

The medlow code model on RISC-V essentially enforces this -- technically it
enforces a 32-bit region centered around address 0, but it's not that hard to
stay away from negative addresses.  That said, as long as elf2flt gives you an
error it should be fine because all medlow is going to do is give you a
different looking error message.

Re: RISC-V nommu support v2

[Vladimir Murzin]

On 6/25/19 8:31 AM, Palmer Dabbelt wrote:
> On Mon, 24 Jun 2019 06:08:50 PDT (-0700), vladimir.murzin@arm.com wrote:
>> On 6/24/19 12:54 PM, Christoph Hellwig wrote:
>>> On Mon, Jun 24, 2019 at 12:47:07PM +0100, Vladimir Murzin wrote:
>>>> Since you are using binfmt_flat which is kind of 32-bit only I was expecting to see
>>>> CONFIG_COMPAT (or something similar to that, like ILP32) enabled, yet I could not
>>>> find it.
>>>
>>> There is no such thing in RISC-V.  I don't know of any 64-bit RISC-V
>>> cpu that can actually run 32-bit RISC-V code, although in theory that
>>> is possible.  There also is nothing like the x86 x32 or mips n32 mode
>>> available either for now.
>>>
>>> But it turns out that with a few fixes to binfmt_flat it can run 64-bit
>>> binaries just fine.  I sent that series out a while ago, and IIRC you
>>> actually commented on it.
>>>
>>
>> True, yet my observation was that elf2flt utility assumes that address
>> space cannot exceed 32-bit (for header and absolute relocations). So,
>> from my limited point of view straightforward way to guarantee that would
>> be to build incoming elf in 32-bit mode (it is why I mentioned COMPAT/ILP32).
>>
>> Also one of your patches expressed somewhat related idea
>>
>> "binfmt_flat isn't the right binary format for huge executables to
>> start with"
>>
>> Since you said there is no support for compat/ilp32, probably I'm missing some
>> toolchain magic?
>>
>> Cheers
>> Vladimir
> To:          Christoph Hellwig <hch@lst.de>
> CC:          vladimir.murzin@arm.com
> CC:          Christoph Hellwig <hch@lst.de>
> CC:          Paul Walmsley <paul.walmsley@sifive.com>
> CC:          Damien Le Moal <Damien.LeMoal@wdc.com>
> CC:          linux-riscv@lists.infradead.org
> CC:          linux-mm@kvack.org
> CC:          linux-kernel@vger.kernel.org
> Subject:     Re: RISC-V nommu support v2
> In-Reply-To: <20190624131633.GB10746@lst.de>
> 
> On Mon, 24 Jun 2019 06:16:33 PDT (-0700), Christoph Hellwig wrote:
>> On Mon, Jun 24, 2019 at 02:08:50PM +0100, Vladimir Murzin wrote:
>>> True, yet my observation was that elf2flt utility assumes that address
>>> space cannot exceed 32-bit (for header and absolute relocations). So,
>>> from my limited point of view straightforward way to guarantee that would
>>> be to build incoming elf in 32-bit mode (it is why I mentioned COMPAT/ILP32).
>>>
>>> Also one of your patches expressed somewhat related idea
>>>
>>> "binfmt_flat isn't the right binary format for huge executables to
>>> start with"
>>>
>>> Since you said there is no support for compat/ilp32, probably I'm missing some
>>> toolchain magic?
>>
>> There is no magic except for the tiny elf2flt patch, which for
>> now is just in the buildroot repo pointed to in the cover letter
>> (and which I plan to upstream once the kernel support has landed
>> in Linus' tree).  We only support 32-bit code and data address spaces,
>> but we otherwise use the normal RISC-V ABI, that is 64-bit longs and
>> pointers.
> 
> The medlow code model on RISC-V essentially enforces this -- technically it
> enforces a 32-bit region centered around address 0, but it's not that hard to
> stay away from negative addresses.  That said, as long as elf2flt gives you an
> error it should be fine because all medlow is going to do is give you a
> different looking error message.
> 

Thanks for explanation!

Vladimir

Re: RISC-V nommu support v2

[Christoph Hellwig]

Palmer, Paul,

any comments?  Let me know if you think it is too late for 5.3
for the full series, then I can at least feed the mm bits to
Andrew.

On Mon, Jun 24, 2019 at 07:42:54AM +0200, Christoph Hellwig wrote:
> 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.
> 
> To be useful this series also require the RISC-V binfmt_flat support,
> which I've sent out separately.
> 
> A branch that includes this series and the binfmt_flat support is
> available here:
> 
>     git://git.infradead.org/users/hch/riscv.git riscv-nommu.2
> 
> Gitweb:
> 
>     http://git.infradead.org/users/hch/riscv.git/shortlog/refs/heads/riscv-nommu.2
> 
> 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 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
> 
> _______________________________________________
> linux-riscv mailing list
> linux-riscv@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-riscv
---end quoted text---

Re: RISC-V nommu support v2

[Paul Walmsley]

Hi Christoph,

Probably best to feed the mm patches to Andrew.  For the RISC-V patches, 
am running a bit behind this merge window.  Combined with the end of the 
week holidays in the US, I doubt I'll make it to to the nommu series for 
v5.3.


- Paul

On Mon, 1 Jul 2019, Christoph Hellwig wrote:

> Palmer, Paul,
> 
> any comments?  Let me know if you think it is too late for 5.3
> for the full series, then I can at least feed the mm bits to
> Andrew.
> 
> On Mon, Jun 24, 2019 at 07:42:54AM +0200, Christoph Hellwig wrote:
> > 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.
> > 
> > To be useful this series also require the RISC-V binfmt_flat support,
> > which I've sent out separately.
> > 
> > A branch that includes this series and the binfmt_flat support is
> > available here:
> > 
> >     git://git.infradead.org/users/hch/riscv.git riscv-nommu.2
> > 
> > Gitweb:
> > 
> >     http://git.infradead.org/users/hch/riscv.git/shortlog/refs/heads/riscv-nommu.2
> > 
> > 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 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
> > 
> > _______________________________________________
> > linux-riscv mailing list
> > linux-riscv@lists.infradead.org
> > http://lists.infradead.org/mailman/listinfo/linux-riscv
> ---end quoted text---
> 

Re: [PATCH 07/17] riscv: abstract out CSR names for supervisor vs machine mode

[Atish Patra]

On Mon, 2019-06-24 at 07:43 +0200, 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>
> ---
>  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 |  8 ++--
>  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, 177 insertions(+), 109 deletions(-)
> 
> diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
> index 2c19baa8d6c3..2185481d1589 100644
> --- a/arch/riscv/Kconfig
> +++ b/arch/riscv/Kconfig
> @@ -52,6 +52,10 @@ config RISCV
>  	select ARCH_HAS_MMIOWB
>  	select HAVE_EBPF_JIT if 64BIT
>  
> +# set if we run in machine mode, cleared if we run in supervisor
> mode
> +config M_MODE
> +	bool
> +

Some nits:

I think RISCV_M_MODE in stead of M_MODE makes it more explicit.
But I am not entire sure about the standard practice in this case.


>  config MMU
>  	def_bool y
>  
> diff --git a/arch/riscv/include/asm/asm.h
> b/arch/riscv/include/asm/asm.h
> index 5a02b7d50940..14604f01e9f8 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_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..026a761835b7 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 */
> +/* MIE / MIP flags: */

Keep the abbreviation definitions for IE & IP ?
They are particulary
help for new RISC-V developers.
> +#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 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_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_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_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 853b65ef656d..4cbe33bb5dd7 100644
> --- a/arch/riscv/include/asm/switch_to.h
> +++ b/arch/riscv/include/asm/switch_to.h
> @@ -16,13 +16,13 @@ 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_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);
>  	}
> @@ -31,7 +31,7 @@ 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);
>  	}
> @@ -43,7 +43,7 @@ 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 bc7a56e1ca6f..b722ce20dc20 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 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 sstatus, SR_SIE
> +	REG_L s0, PT_XSTATUS(sp)
> +	csrc CSR_XSTATUS, SR_XIE
> +#ifdef CONFIG_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 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 1defb0618aff..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 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 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 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 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 4e46f31072da..e5fa5481aa99 100644
> --- a/arch/riscv/kernel/head.S
> +++ b/arch/riscv/kernel/head.S
> @@ -15,8 +15,8 @@
>  __INIT
>  ENTRY(_start)
>  	/* 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
> @@ -29,7 +29,7 @@ ENTRY(_start)
>  	 * floating point in kernel space
>  	 */
>  	li t0, SR_FS
> -	csrc sstatus, t0
> +	csrc CSR_XSTATUS, t0
>  
>  	/* Pick one hart to run the main boot sequence */
>  	la a3, hart_lottery
> @@ -78,7 +78,7 @@ relocate:
>  	/* Point stvec to virtual address of intruction after satp
> write */
>  	la a0, 1f
>  	add a0, a0, a1
> -	csrw CSR_STVEC, a0
> +	csrw CSR_XTVEC, a0
>  
>  	/* Compute satp for kernel page tables, but don't load it yet
> */
>  	la a2, swapper_pg_dir
> @@ -101,7 +101,7 @@ 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
> @@ -127,7 +127,7 @@ 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 f23794bd1e90..1f03920d07d3 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",
> @@ -56,17 +56,17 @@ 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_XPIE;
>  	if (has_fpu)
> -		regs->sstatus |= SR_FS_INITIAL;
> -	regs->sepc = pc;
> +		regs->xstatus |= SR_FS_INITIAL;
> +	regs->xepc = pc;
>  	regs->sp = sp;
>  	set_fs(USER_DS);
>  }
> @@ -101,7 +101,8 @@ 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 1fe1b02e44d0..dfb26b64e17a 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, task);
>  	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 6b32190ba73c..e028276928f8 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);
> @@ -84,7 +84,7 @@ 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,
> @@ -127,12 +127,12 @@ 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");
> @@ -140,7 +140,7 @@ asmlinkage void do_trap_break(struct pt_regs
> *regs)
>  	}
>  #endif /* CONFIG_GENERIC_BUG */
>  
> -	force_sig_fault(SIGTRAP, TRAP_BRKPT, (void __user *)(regs-
> >sepc), current);
> +	force_sig_fault(SIGTRAP, TRAP_BRKPT, (void __user *)(regs-
> >xepc), current);
>  }
>  
>  #ifdef CONFIG_GENERIC_BUG
> @@ -165,9 +165,9 @@ 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 399e6f0c2d98..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 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 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 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 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 sstatus, t6
> +	csrs CSR_XSTATUS, t6
>  	mv a0, a2
>  	ret
>  11:
> -	csrs 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 3e2708c626a8..377248e45bba 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 5e6038fbf115..2e2d363faabf 100644
> --- a/drivers/clocksource/timer-riscv.c
> +++ b/drivers/clocksource/timer-riscv.c
> @@ -28,7 +28,7 @@
>  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;
>  }
> @@ -70,13 +70,13 @@ 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;
>  }
>  
> @@ -85,7 +85,7 @@ 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);
>  }
>  

Apart from the nits,

Reviewed-by: Atish Patra <atish.patra@wdc.com>


>  /*
-- 
Regards,
Atish

Re: [PATCH 05/17] riscv: use CSR_SATP instead of the legacy sptbr name in switch_mm

[Atish Patra]

On Mon, 2019-06-24 at 07:42 +0200, Christoph Hellwig wrote:
> Switch to our own constant for the satp register instead of using
> the old name from a legacy version of the privileged spec.
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> ---
>  arch/riscv/mm/context.c | 7 +------
>  1 file changed, 1 insertion(+), 6 deletions(-)
> 
> diff --git a/arch/riscv/mm/context.c b/arch/riscv/mm/context.c
> index 89ceb3cbe218..beeb5d7f92ea 100644
> --- a/arch/riscv/mm/context.c
> +++ b/arch/riscv/mm/context.c
> @@ -57,12 +57,7 @@ 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));
>  
> -	/*
> -	 * Use the old spbtr name instead of using the current satp
> -	 * name to support binutils 2.29 which doesn't know about the
> -	 * privileged ISA 1.10 yet.
> -	 */
> -	csr_write(sptbr, virt_to_pfn(next->pgd) | SATP_MODE);
> +	csr_write(CSR_SATP, virt_to_pfn(next->pgd) | SATP_MODE);
>  	local_flush_tlb_all();
>  
>  	flush_icache_deferred(next);

Reviewed-by: Atish Patra <atish.patra@wdc.com>

-- 
Regards,
Atish

Re: [PATCH 08/17] riscv: improve the default power off implementation

[Atish Patra]

On Mon, 2019-06-24 at 07:43 +0200, Christoph Hellwig wrote:
> Only call the SBI code if we are not running in M mode, and if we
> didn't
> do the SBI call, or it didn't succeed call wfi in a loop to at least
> save some power.
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> ---
>  arch/riscv/kernel/reset.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/riscv/kernel/reset.c b/arch/riscv/kernel/reset.c
> index d0fe623bfb8f..2f5ca379747e 100644
> --- a/arch/riscv/kernel/reset.c
> +++ b/arch/riscv/kernel/reset.c
> @@ -8,8 +8,11 @@
>  
>  static void default_power_off(void)
>  {
> +#ifndef CONFIG_M_MODE
>  	sbi_shutdown();
> -	while (1);
> +#endif
> +	while (1)
> +		wait_for_interrupt();
>  }
>  
>  void (*pm_power_off)(void) = default_power_off;

Reviewed-by: Atish Patra <atish.patra@wdc.com>

Regards,
Atish

Re: [PATCH 10/17] riscv: read the hart ID from mhartid on boot

[Atish Patra]

On Mon, 2019-06-24 at 07:43 +0200, Christoph Hellwig wrote:
> 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>
> ---
>  arch/riscv/kernel/head.S | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/arch/riscv/kernel/head.S b/arch/riscv/kernel/head.S
> index e5fa5481aa99..a4c170e41a34 100644
> --- a/arch/riscv/kernel/head.S
> +++ b/arch/riscv/kernel/head.S
> @@ -18,6 +18,14 @@ ENTRY(_start)
>  	csrw CSR_XIE, zero
>  	csrw CSR_XIP, zero
>  
> +#ifdef CONFIG_M_MODE
> +	/*
> +	 * The hartid in a0 is expected later on, and we have no
> firmware
> +	 * to hand it to us.
> +	 */
> +	csrr a0, mhartid

I think you should add SR_MHARTID and use that instead of direct csr
name.
The following patch replaced all occurrence of csr name usage from
kernel with CSR numbers.

https://patchwork.kernel.org/patch/10916293/

With that change, 

Reviewed-by: Atish Patra <atish.patra@wdc.com>

> +#endif
> +
>  	/* Load the global pointer */
>  .option push
>  .option norelax

-- 
Regards,
Atish

Re: [PATCH 16/17] riscv: clear the instruction cache and all registers when booting

[Atish Patra]

On Mon, 2019-06-24 at 07:43 +0200, Christoph Hellwig wrote:
> 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.

That means it should be done for S-mode as well. Right ?
I see the reset code is enabled only for M-mode only.

>   Vaguely based on the concepts from opensbi.
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> ---
>  arch/riscv/kernel/head.S | 85
> ++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 85 insertions(+)
> 
> diff --git a/arch/riscv/kernel/head.S b/arch/riscv/kernel/head.S
> index a4c170e41a34..74feb17737b4 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>
>  
>  __INIT
>  ENTRY(_start)
> @@ -19,6 +20,12 @@ ENTRY(_start)
>  	csrw CSR_XIP, zero
>  
>  #ifdef CONFIG_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.
> @@ -168,6 +175,84 @@ relocate:
>  	j .Lsecondary_park
>  END(_start)
>  
> +#ifdef CONFIG_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, misa
> +	andi	t0, t0, (COMPAT_HWCAP_ISA_F | COMPAT_HWCAP_ISA_D)
> +	bnez	t0, .Lreset_regs_done
> +
> +	li	t1, SR_FS
> +	csrs	sstatus, 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
> +#endif /* CONFIG_FPU */
> +.Lreset_regs_done:
> +	ret
> +END(reset_regs)
> +#endif /* CONFIG_M_MODE */
> +
>  __PAGE_ALIGNED_BSS
>  	/* Empty zero page */
>  	.balign PAGE_SIZE

-- 
Regards,
Atish

Re: [PATCH 16/17] riscv: clear the instruction cache and all registers when booting

[Palmer Dabbelt]

On Mon, 01 Jul 2019 14:26:18 PDT (-0700), Atish Patra wrote:
> On Mon, 2019-06-24 at 07:43 +0200, Christoph Hellwig wrote:
>> 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.
> 
> That means it should be done for S-mode as well. Right ?
> I see the reset code is enabled only for M-mode only.
> 
>>   Vaguely based on the concepts from opensbi.
>> 
>> Signed-off-by: Christoph Hellwig <hch@lst.de>
>> ---
>>  arch/riscv/kernel/head.S | 85
>> ++++++++++++++++++++++++++++++++++++++++
>>  1 file changed, 85 insertions(+)
>> 
>> diff --git a/arch/riscv/kernel/head.S b/arch/riscv/kernel/head.S
>> index a4c170e41a34..74feb17737b4 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>
>>  
>>  __INIT
>>  ENTRY(_start)
>> @@ -19,6 +20,12 @@ ENTRY(_start)
>>  	csrw CSR_XIP, zero
>>  
>>  #ifdef CONFIG_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.
>> @@ -168,6 +175,84 @@ relocate:
>>  	j .Lsecondary_park
>>  END(_start)
>>  
>> +#ifdef CONFIG_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, misa
>> +	andi	t0, t0, (COMPAT_HWCAP_ISA_F | COMPAT_HWCAP_ISA_D)
>> +	bnez	t0, .Lreset_regs_done
>> +
>> +	li	t1, SR_FS
>> +	csrs	sstatus, t1

You need to check that the write stuck and branch around the FP instructions.
Specifically, CONFIG_FPU means there may be an FPU, not there's definately an
FPU.  You should also turn the FPU back off after zeroing the state.

>> +	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
>> +#endif /* CONFIG_FPU */
>> +.Lreset_regs_done:
>> +	ret
>> +END(reset_regs)
>> +#endif /* CONFIG_M_MODE */
>> +
>>  __PAGE_ALIGNED_BSS
>>  	/* Empty zero page */
>>  	.balign PAGE_SIZE
> 
> -- 
> Regards,
> Atish

Re: [PATCH 17/17] riscv: add nommu support

[Vladimir Murzin]

Hi Christoph,

On 6/24/19 6:43 AM, Christoph Hellwig wrote:
> 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/elf.h            |  4 +-
>  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           | 12 +++-
>  arch/riscv/include/asm/pgalloc.h        |  2 +
>  arch/riscv/include/asm/pgtable.h        | 38 ++++++++----
>  arch/riscv/include/asm/tlbflush.h       |  7 ++-
>  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                 |  8 +--
>  arch/riscv/mm/Makefile                  |  3 +-
>  arch/riscv/mm/cacheflush.c              |  2 +
>  arch/riscv/mm/context.c                 |  2 +
>  arch/riscv/mm/init.c                    |  2 +
>  20 files changed, 200 insertions(+), 36 deletions(-)
>  create mode 100644 arch/riscv/configs/nommu_virt_defconfig
> 

snip...

>  
> 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

IIUC, RISC-V requires stack pointer to be 16 byte aligned, but flat loader would
align stack pointer to max(sizeof(void *), ARCH_SLAB_MINALIGN). So, I think you
might want to define ARCH_SLAB_MINALIGN.

Cheers
Vladimir

Re: [PATCH 16/17] riscv: clear the instruction cache and all registers when booting

[hch]

On Mon, Jul 01, 2019 at 09:26:18PM +0000, Atish Patra wrote:
> That means it should be done for S-mode as well. Right ?

For S-mode the bootloader/sbi should take care of it.

Re: [PATCH 16/17] riscv: clear the instruction cache and all registers when booting

[Christoph Hellwig]

On Mon, Jul 08, 2019 at 01:26:33AM -0700, Palmer Dabbelt wrote:
>>> +	csrs	sstatus, t1
>
> You need to check that the write stuck and branch around the FP instructions.
> Specifically, CONFIG_FPU means there may be an FPU, not there's definately an
> FPU.  You should also turn the FPU back off after zeroing the state.

Well, that is why we check the hwcaps from misa just above and skip
this fp reg clearing if it doesn't contain the 'F' or 'D' extension.

The caller disables the FPU a few instructions later:

	/*
         * Disable FPU to detect illegal usage of
	 * floating point in kernel space
	 */
	li t0, SR_FS
	csrc CSR_XSTATUS, t0