[PATCH V2 4/4] riscv: Add vector ISA support

[guoren@kernel.org]

From: Guo Ren <ren_guo@c-sky.com>

The implementation follow the RISC-V "V" Vector Extension draft v0.8 with
128bit-vlen and it's based on linux-5.5-rc4.

The patch implement basic context switch, signal and ptrace interface
with a new regset NT_RISCV_VECTOR. Only fixed 128bit-vlen is implemented.
We need to discuss about the abi for libc sigcontext. (The maximum size of
vlen for libc signal context structure 128/256/512 ?)

Signed-off-by: Guo Ren <ren_guo@c-sky.com>
Cc: Paul Walmsley <paul.walmsley@sifive.com>
Cc: Palmer Dabbelt <palmer@dabbelt.com>
Cc: Albert Ou <aou@eecs.berkeley.edu>
Cc: Alan Kao <alankao@andestech.com>
Cc: Anup Patel <Anup.Patel@wdc.com>
CC: Andreas Schwab <schwab@linux-m68k.org>

---
Changelog V2:
 - Fixup typo "vecotr, fstate_save->vstate_save".
 - Fixup wrong saved registers' length in vector.S.
 - Seperate unrelated patches from this one.
---
 arch/riscv/Kconfig                       |   9 ++
 arch/riscv/Makefile                      |   1 +
 arch/riscv/include/asm/csr.h             |  17 +-
 arch/riscv/include/asm/processor.h       |   1 +
 arch/riscv/include/asm/switch_to.h       |  48 ++++++
 arch/riscv/include/uapi/asm/elf.h        |   1 +
 arch/riscv/include/uapi/asm/ptrace.h     |   9 ++
 arch/riscv/include/uapi/asm/sigcontext.h |   1 +
 arch/riscv/kernel/Makefile               |   1 +
 arch/riscv/kernel/asm-offsets.c          | 188 +++++++++++++++++++++++
 arch/riscv/kernel/cpufeature.c           |   8 +
 arch/riscv/kernel/entry.S                |   2 +-
 arch/riscv/kernel/head.S                 |  49 +++++-
 arch/riscv/kernel/process.c              |  10 ++
 arch/riscv/kernel/ptrace.c               |  41 +++++
 arch/riscv/kernel/signal.c               |  40 +++++
 arch/riscv/kernel/vector.S               |  84 ++++++++++
 include/uapi/linux/elf.h                 |   1 +
 18 files changed, 506 insertions(+), 5 deletions(-)
 create mode 100644 arch/riscv/kernel/vector.S

diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index b16954229c96..c5b2e5df1349 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -292,6 +292,15 @@ config FPU
 
 	  If you don't know what to do here, say Y.
 
+config VECTOR
+	bool "VECTOR support"
+	default n
+	help
+	  Say N here if you want to disable all vector related procedure
+	  in the kernel.
+
+	  If you don't know what to do here, say Y.
+
 endmenu
 
 menu "Kernel features"
diff --git a/arch/riscv/Makefile b/arch/riscv/Makefile
index 6d09b53cf106..071eb1148e01 100644
--- a/arch/riscv/Makefile
+++ b/arch/riscv/Makefile
@@ -44,6 +44,7 @@ riscv-march-aflags-$(CONFIG_ARCH_RV32I)		:= rv32ima
 riscv-march-aflags-$(CONFIG_ARCH_RV64I)		:= rv64ima
 riscv-march-aflags-$(CONFIG_FPU)		:= $(riscv-march-aflags-y)fd
 riscv-march-aflags-$(CONFIG_RISCV_ISA_C)	:= $(riscv-march-aflags-y)c
+riscv-march-aflags-$(CONFIG_VECTOR)		:= $(riscv-march-aflags-y)v
 
 KBUILD_CFLAGS += -march=$(riscv-march-cflags-y)
 KBUILD_AFLAGS += -march=$(riscv-march-aflags-y)
diff --git a/arch/riscv/include/asm/csr.h b/arch/riscv/include/asm/csr.h
index 6a06277a84d6..ce3aa826bb16 100644
--- a/arch/riscv/include/asm/csr.h
+++ b/arch/riscv/include/asm/csr.h
@@ -24,6 +24,12 @@
 #define SR_FS_CLEAN	_AC(0x00004000, UL)
 #define SR_FS_DIRTY	_AC(0x00006000, UL)
 
+#define SR_VS           _AC(0x01800000, UL) /* Vector Status */
+#define SR_VS_OFF       _AC(0x00000000, UL)
+#define SR_VS_INITIAL   _AC(0x00800000, UL)
+#define SR_VS_CLEAN     _AC(0x01000000, UL)
+#define SR_VS_DIRTY     _AC(0x01800000, UL)
+
 #define SR_XS		_AC(0x00018000, UL) /* Extension Status */
 #define SR_XS_OFF	_AC(0x00000000, UL)
 #define SR_XS_INITIAL	_AC(0x00008000, UL)
@@ -31,9 +37,9 @@
 #define SR_XS_DIRTY	_AC(0x00018000, UL)
 
 #ifndef CONFIG_64BIT
-#define SR_SD		_AC(0x80000000, UL) /* FS/XS dirty */
+#define SR_SD		_AC(0x80000000, UL) /* FS/VS/XS dirty */
 #else
-#define SR_SD		_AC(0x8000000000000000, UL) /* FS/XS dirty */
+#define SR_SD		_AC(0x8000000000000000, UL) /* FS/VS/XS dirty */
 #endif
 
 /* SATP flags */
@@ -108,6 +114,13 @@
 #define CSR_MIP			0x344
 #define CSR_MHARTID		0xf14
 
+#define CSR_VSTART		0x8
+#define CSR_VXSAT		0x9
+#define CSR_VXRM		0xa
+#define CSR_VL			0xc20
+#define CSR_VTYPE		0xc21
+#define CSR_VLENB		0xc22
+
 #ifdef CONFIG_RISCV_M_MODE
 # define CSR_STATUS	CSR_MSTATUS
 # define CSR_IE		CSR_MIE
diff --git a/arch/riscv/include/asm/processor.h b/arch/riscv/include/asm/processor.h
index 3ddb798264f1..217273375cfb 100644
--- a/arch/riscv/include/asm/processor.h
+++ b/arch/riscv/include/asm/processor.h
@@ -32,6 +32,7 @@ struct thread_struct {
 	unsigned long sp;	/* Kernel mode stack */
 	unsigned long s[12];	/* s[0]: frame pointer */
 	struct __riscv_d_ext_state fstate;
+	struct __riscv_v_state vstate;
 };
 
 #define INIT_THREAD {					\
diff --git a/arch/riscv/include/asm/switch_to.h b/arch/riscv/include/asm/switch_to.h
index b9234e7178d0..6e1c7fa599be 100644
--- a/arch/riscv/include/asm/switch_to.h
+++ b/arch/riscv/include/asm/switch_to.h
@@ -63,6 +63,52 @@ extern bool has_fpu;
 #define __switch_to_fpu(__prev, __next) do { } while (0)
 #endif
 
+#ifdef CONFIG_VECTOR
+extern void __vstate_save(struct task_struct *save_to);
+extern void __vstate_restore(struct task_struct *restore_from);
+
+static inline void __vstate_clean(struct pt_regs *regs)
+{
+	regs->status |= (regs->status & ~(SR_VS)) | SR_VS_CLEAN;
+}
+
+static inline void vstate_save(struct task_struct *task,
+			       struct pt_regs *regs)
+{
+	if ((regs->status & SR_VS) == SR_VS_DIRTY) {
+		__vstate_save(task);
+		__vstate_clean(regs);
+	}
+}
+
+static inline void vstate_restore(struct task_struct *task,
+				  struct pt_regs *regs)
+{
+	if ((regs->status & SR_VS) != SR_VS_OFF) {
+		__vstate_restore(task);
+		__vstate_clean(regs);
+	}
+}
+
+static inline void __switch_to_vector(struct task_struct *prev,
+				   struct task_struct *next)
+{
+	struct pt_regs *regs;
+
+	regs = task_pt_regs(prev);
+	if (unlikely(regs->status & SR_SD))
+		vstate_save(prev, regs);
+	vstate_restore(next, task_pt_regs(next));
+}
+
+extern bool has_vector;
+#else
+#define has_vector false
+#define vstate_save(task, regs) do { } while (0)
+#define vstate_restore(task, regs) do { } while (0)
+#define __switch_to_vector(__prev, __next) do { } while (0)
+#endif
+
 extern struct task_struct *__switch_to(struct task_struct *,
 				       struct task_struct *);
 
@@ -72,6 +118,8 @@ do {							\
 	struct task_struct *__next = (next);		\
 	if (has_fpu)					\
 		__switch_to_fpu(__prev, __next);	\
+	if (has_vector)					\
+		__switch_to_vector(__prev, __next);	\
 	((last) = __switch_to(__prev, __next));		\
 } while (0)
 
diff --git a/arch/riscv/include/uapi/asm/elf.h b/arch/riscv/include/uapi/asm/elf.h
index d696d6610231..099434d075a7 100644
--- a/arch/riscv/include/uapi/asm/elf.h
+++ b/arch/riscv/include/uapi/asm/elf.h
@@ -23,6 +23,7 @@ typedef struct user_regs_struct elf_gregset_t;
 typedef __u64 elf_fpreg_t;
 typedef union __riscv_fp_state elf_fpregset_t;
 #define ELF_NFPREG (sizeof(struct __riscv_d_ext_state) / sizeof(elf_fpreg_t))
+#define ELF_NVREG  (sizeof(struct __riscv_v_state) / sizeof(elf_greg_t))
 
 #if __riscv_xlen == 64
 #define ELF_RISCV_R_SYM(r_info)		ELF64_R_SYM(r_info)
diff --git a/arch/riscv/include/uapi/asm/ptrace.h b/arch/riscv/include/uapi/asm/ptrace.h
index 882547f6bd5c..d913e8949b87 100644
--- a/arch/riscv/include/uapi/asm/ptrace.h
+++ b/arch/riscv/include/uapi/asm/ptrace.h
@@ -71,6 +71,15 @@ struct __riscv_q_ext_state {
 	__u32 reserved[3];
 };
 
+struct __riscv_v_state {
+	__uint128_t v[32];
+	unsigned long vstart;
+	unsigned long vxsat;
+	unsigned long vxrm;
+	unsigned long vl;
+	unsigned long vtype;
+};
+
 union __riscv_fp_state {
 	struct __riscv_f_ext_state f;
 	struct __riscv_d_ext_state d;
diff --git a/arch/riscv/include/uapi/asm/sigcontext.h b/arch/riscv/include/uapi/asm/sigcontext.h
index 84f2dfcfdbce..f74b3c814423 100644
--- a/arch/riscv/include/uapi/asm/sigcontext.h
+++ b/arch/riscv/include/uapi/asm/sigcontext.h
@@ -17,6 +17,7 @@
 struct sigcontext {
 	struct user_regs_struct sc_regs;
 	union __riscv_fp_state sc_fpregs;
+	struct __riscv_v_state sc_vregs;
 };
 
 #endif /* _UAPI_ASM_RISCV_SIGCONTEXT_H */
diff --git a/arch/riscv/kernel/Makefile b/arch/riscv/kernel/Makefile
index f40205cb9a22..e5276c3bdffc 100644
--- a/arch/riscv/kernel/Makefile
+++ b/arch/riscv/kernel/Makefile
@@ -30,6 +30,7 @@ obj-$(CONFIG_MMU) += vdso.o vdso/
 
 obj-$(CONFIG_RISCV_M_MODE)	+= clint.o
 obj-$(CONFIG_FPU)		+= fpu.o
+obj-$(CONFIG_VECTOR)		+= vector.o
 obj-$(CONFIG_SMP)		+= smpboot.o
 obj-$(CONFIG_SMP)		+= smp.o
 obj-$(CONFIG_MODULES)		+= module.o
diff --git a/arch/riscv/kernel/asm-offsets.c b/arch/riscv/kernel/asm-offsets.c
index 07cb9c10de4e..b662db7c71c0 100644
--- a/arch/riscv/kernel/asm-offsets.c
+++ b/arch/riscv/kernel/asm-offsets.c
@@ -70,6 +70,45 @@ void asm_offsets(void)
 	OFFSET(TASK_THREAD_F31, task_struct, thread.fstate.f[31]);
 	OFFSET(TASK_THREAD_FCSR, task_struct, thread.fstate.fcsr);
 
+	OFFSET(TASK_THREAD_V0,  task_struct, thread.vstate.v[0]);
+	OFFSET(TASK_THREAD_V1,  task_struct, thread.vstate.v[1]);
+	OFFSET(TASK_THREAD_V2,  task_struct, thread.vstate.v[2]);
+	OFFSET(TASK_THREAD_V3,  task_struct, thread.vstate.v[3]);
+	OFFSET(TASK_THREAD_V4,  task_struct, thread.vstate.v[4]);
+	OFFSET(TASK_THREAD_V5,  task_struct, thread.vstate.v[5]);
+	OFFSET(TASK_THREAD_V6,  task_struct, thread.vstate.v[6]);
+	OFFSET(TASK_THREAD_V7,  task_struct, thread.vstate.v[7]);
+	OFFSET(TASK_THREAD_V8,  task_struct, thread.vstate.v[8]);
+	OFFSET(TASK_THREAD_V9,  task_struct, thread.vstate.v[9]);
+	OFFSET(TASK_THREAD_V10, task_struct, thread.vstate.v[10]);
+	OFFSET(TASK_THREAD_V11, task_struct, thread.vstate.v[11]);
+	OFFSET(TASK_THREAD_V12, task_struct, thread.vstate.v[12]);
+	OFFSET(TASK_THREAD_V13, task_struct, thread.vstate.v[13]);
+	OFFSET(TASK_THREAD_V14, task_struct, thread.vstate.v[14]);
+	OFFSET(TASK_THREAD_V15, task_struct, thread.vstate.v[15]);
+	OFFSET(TASK_THREAD_V16, task_struct, thread.vstate.v[16]);
+	OFFSET(TASK_THREAD_V17, task_struct, thread.vstate.v[17]);
+	OFFSET(TASK_THREAD_V18, task_struct, thread.vstate.v[18]);
+	OFFSET(TASK_THREAD_V19, task_struct, thread.vstate.v[19]);
+	OFFSET(TASK_THREAD_V20, task_struct, thread.vstate.v[20]);
+	OFFSET(TASK_THREAD_V21, task_struct, thread.vstate.v[21]);
+	OFFSET(TASK_THREAD_V22, task_struct, thread.vstate.v[22]);
+	OFFSET(TASK_THREAD_V23, task_struct, thread.vstate.v[23]);
+	OFFSET(TASK_THREAD_V24, task_struct, thread.vstate.v[24]);
+	OFFSET(TASK_THREAD_V25, task_struct, thread.vstate.v[25]);
+	OFFSET(TASK_THREAD_V26, task_struct, thread.vstate.v[26]);
+	OFFSET(TASK_THREAD_V27, task_struct, thread.vstate.v[27]);
+	OFFSET(TASK_THREAD_V28, task_struct, thread.vstate.v[28]);
+	OFFSET(TASK_THREAD_V29, task_struct, thread.vstate.v[29]);
+	OFFSET(TASK_THREAD_V30, task_struct, thread.vstate.v[30]);
+	OFFSET(TASK_THREAD_V31, task_struct, thread.vstate.v[31]);
+	OFFSET(TASK_THREAD_VSTART, task_struct, thread.vstate.vstart);
+	OFFSET(TASK_THREAD_VXSAT, task_struct, thread.vstate.vxsat);
+	OFFSET(TASK_THREAD_VXRM, task_struct, thread.vstate.vxrm);
+	OFFSET(TASK_THREAD_VL, task_struct, thread.vstate.vl);
+	OFFSET(TASK_THREAD_VTYPE, task_struct, thread.vstate.vtype);
+	DEFINE(RISCV_VECTOR_VLENB, sizeof(__uint128_t));
+
 	DEFINE(PT_SIZE, sizeof(struct pt_regs));
 	OFFSET(PT_EPC, pt_regs, epc);
 	OFFSET(PT_RA, pt_regs, ra);
@@ -304,6 +343,155 @@ void asm_offsets(void)
 		- offsetof(struct task_struct, thread.fstate.f[0])
 	);
 
+	DEFINE(TASK_THREAD_V0_V0,
+		  offsetof(struct task_struct, thread.vstate.v[0])
+		- offsetof(struct task_struct, thread.vstate.v[0])
+	);
+	DEFINE(TASK_THREAD_V1_V0,
+		  offsetof(struct task_struct, thread.vstate.v[1])
+		- offsetof(struct task_struct, thread.vstate.v[0])
+	);
+	DEFINE(TASK_THREAD_V2_V0,
+		  offsetof(struct task_struct, thread.vstate.v[2])
+		- offsetof(struct task_struct, thread.vstate.v[0])
+	);
+	DEFINE(TASK_THREAD_V3_V0,
+		  offsetof(struct task_struct, thread.vstate.v[3])
+		- offsetof(struct task_struct, thread.vstate.v[0])
+	);
+	DEFINE(TASK_THREAD_V4_V0,
+		  offsetof(struct task_struct, thread.vstate.v[4])
+		- offsetof(struct task_struct, thread.vstate.v[0])
+	);
+	DEFINE(TASK_THREAD_V5_V0,
+		  offsetof(struct task_struct, thread.vstate.v[5])
+		- offsetof(struct task_struct, thread.vstate.v[0])
+	);
+	DEFINE(TASK_THREAD_V6_V0,
+		  offsetof(struct task_struct, thread.vstate.v[6])
+		- offsetof(struct task_struct, thread.vstate.v[0])
+	);
+	DEFINE(TASK_THREAD_V7_V0,
+		  offsetof(struct task_struct, thread.vstate.v[7])
+		- offsetof(struct task_struct, thread.vstate.v[0])
+	);
+	DEFINE(TASK_THREAD_V8_V0,
+		  offsetof(struct task_struct, thread.vstate.v[8])
+		- offsetof(struct task_struct, thread.vstate.v[0])
+	);
+	DEFINE(TASK_THREAD_V9_V0,
+		  offsetof(struct task_struct, thread.vstate.v[9])
+		- offsetof(struct task_struct, thread.vstate.v[0])
+	);
+	DEFINE(TASK_THREAD_V10_V0,
+		  offsetof(struct task_struct, thread.vstate.v[10])
+		- offsetof(struct task_struct, thread.vstate.v[0])
+	);
+	DEFINE(TASK_THREAD_V11_V0,
+		  offsetof(struct task_struct, thread.vstate.v[11])
+		- offsetof(struct task_struct, thread.vstate.v[0])
+	);
+	DEFINE(TASK_THREAD_V12_V0,
+		  offsetof(struct task_struct, thread.vstate.v[12])
+		- offsetof(struct task_struct, thread.vstate.v[0])
+	);
+	DEFINE(TASK_THREAD_V13_V0,
+		  offsetof(struct task_struct, thread.vstate.v[13])
+		- offsetof(struct task_struct, thread.vstate.v[0])
+	);
+	DEFINE(TASK_THREAD_V14_V0,
+		  offsetof(struct task_struct, thread.vstate.v[14])
+		- offsetof(struct task_struct, thread.vstate.v[0])
+	);
+	DEFINE(TASK_THREAD_V15_V0,
+		  offsetof(struct task_struct, thread.vstate.v[15])
+		- offsetof(struct task_struct, thread.vstate.v[0])
+	);
+	DEFINE(TASK_THREAD_V16_V0,
+		  offsetof(struct task_struct, thread.vstate.v[16])
+		- offsetof(struct task_struct, thread.vstate.v[0])
+	);
+	DEFINE(TASK_THREAD_V17_V0,
+		  offsetof(struct task_struct, thread.vstate.v[17])
+		- offsetof(struct task_struct, thread.vstate.v[0])
+	);
+	DEFINE(TASK_THREAD_V18_V0,
+		  offsetof(struct task_struct, thread.vstate.v[18])
+		- offsetof(struct task_struct, thread.vstate.v[0])
+	);
+	DEFINE(TASK_THREAD_V19_V0,
+		  offsetof(struct task_struct, thread.vstate.v[19])
+		- offsetof(struct task_struct, thread.vstate.v[0])
+	);
+	DEFINE(TASK_THREAD_V20_V0,
+		  offsetof(struct task_struct, thread.vstate.v[20])
+		- offsetof(struct task_struct, thread.vstate.v[0])
+	);
+	DEFINE(TASK_THREAD_V21_V0,
+		  offsetof(struct task_struct, thread.vstate.v[21])
+		- offsetof(struct task_struct, thread.vstate.v[0])
+	);
+	DEFINE(TASK_THREAD_V22_V0,
+		  offsetof(struct task_struct, thread.vstate.v[22])
+		- offsetof(struct task_struct, thread.vstate.v[0])
+	);
+	DEFINE(TASK_THREAD_V23_V0,
+		  offsetof(struct task_struct, thread.vstate.v[23])
+		- offsetof(struct task_struct, thread.vstate.v[0])
+	);
+	DEFINE(TASK_THREAD_V24_V0,
+		  offsetof(struct task_struct, thread.vstate.v[24])
+		- offsetof(struct task_struct, thread.vstate.v[0])
+	);
+	DEFINE(TASK_THREAD_V25_V0,
+		  offsetof(struct task_struct, thread.vstate.v[25])
+		- offsetof(struct task_struct, thread.vstate.v[0])
+	);
+	DEFINE(TASK_THREAD_V26_V0,
+		  offsetof(struct task_struct, thread.vstate.v[26])
+		- offsetof(struct task_struct, thread.vstate.v[0])
+	);
+	DEFINE(TASK_THREAD_V27_V0,
+		  offsetof(struct task_struct, thread.vstate.v[27])
+		- offsetof(struct task_struct, thread.vstate.v[0])
+	);
+	DEFINE(TASK_THREAD_V28_V0,
+		  offsetof(struct task_struct, thread.vstate.v[28])
+		- offsetof(struct task_struct, thread.vstate.v[0])
+	);
+	DEFINE(TASK_THREAD_V29_V0,
+		  offsetof(struct task_struct, thread.vstate.v[29])
+		- offsetof(struct task_struct, thread.vstate.v[0])
+	);
+	DEFINE(TASK_THREAD_V30_V0,
+		  offsetof(struct task_struct, thread.vstate.v[30])
+		- offsetof(struct task_struct, thread.vstate.v[0])
+	);
+	DEFINE(TASK_THREAD_V31_V0,
+		  offsetof(struct task_struct, thread.vstate.v[31])
+		- offsetof(struct task_struct, thread.vstate.v[0])
+	);
+	DEFINE(TASK_THREAD_VSTART_V0,
+		  offsetof(struct task_struct, thread.vstate.vstart)
+		- offsetof(struct task_struct, thread.vstate.v[0])
+	);
+	DEFINE(TASK_THREAD_VXSAT_V0,
+		  offsetof(struct task_struct, thread.vstate.vxsat)
+		- offsetof(struct task_struct, thread.vstate.v[0])
+	);
+	DEFINE(TASK_THREAD_VXRM_V0,
+		  offsetof(struct task_struct, thread.vstate.vxrm)
+		- offsetof(struct task_struct, thread.vstate.v[0])
+	);
+	DEFINE(TASK_THREAD_VL_V0,
+		  offsetof(struct task_struct, thread.vstate.vl)
+		- offsetof(struct task_struct, thread.vstate.v[0])
+	);
+	DEFINE(TASK_THREAD_VTYPE_V0,
+		  offsetof(struct task_struct, thread.vstate.vtype)
+		- offsetof(struct task_struct, thread.vstate.v[0])
+	);
+
 	/*
 	 * We allocate a pt_regs on the stack when entering the kernel.  This
 	 * ensures the alignment is sane.
diff --git a/arch/riscv/kernel/cpufeature.c b/arch/riscv/kernel/cpufeature.c
index c8527d770c98..c9ab24e3c79e 100644
--- a/arch/riscv/kernel/cpufeature.c
+++ b/arch/riscv/kernel/cpufeature.c
@@ -16,6 +16,9 @@ unsigned long elf_hwcap __read_mostly;
 #ifdef CONFIG_FPU
 bool has_fpu __read_mostly;
 #endif
+#ifdef CONFIG_VECTOR
+bool has_vector __read_mostly;
+#endif
 
 void riscv_fill_hwcap(void)
 {
@@ -73,4 +76,9 @@ void riscv_fill_hwcap(void)
 	if (elf_hwcap & (COMPAT_HWCAP_ISA_F | COMPAT_HWCAP_ISA_D))
 		has_fpu = true;
 #endif
+
+#ifdef CONFIG_VECTOR
+	if (elf_hwcap & COMPAT_HWCAP_ISA_V)
+		has_vector = true;
+#endif
 }
diff --git a/arch/riscv/kernel/entry.S b/arch/riscv/kernel/entry.S
index e163b7b64c86..828f0ebce4b5 100644
--- a/arch/riscv/kernel/entry.S
+++ b/arch/riscv/kernel/entry.S
@@ -76,7 +76,7 @@ _save_context:
 	 * Disable the FPU to detect illegal usage of floating point in kernel
 	 * space.
 	 */
-	li t0, SR_SUM | SR_FS
+	li t0, SR_SUM | SR_FS | SR_VS
 
 	REG_L s0, TASK_TI_USER_SP(tp)
 	csrrc s1, CSR_STATUS, t0
diff --git a/arch/riscv/kernel/head.S b/arch/riscv/kernel/head.S
index 2227db63f895..fab03292284e 100644
--- a/arch/riscv/kernel/head.S
+++ b/arch/riscv/kernel/head.S
@@ -72,10 +72,10 @@ _start_kernel:
 .option pop
 
 	/*
-	 * Disable FPU to detect illegal usage of
+	 * Disable FPU & VECTOR to detect illegal usage of
 	 * floating point in kernel space
 	 */
-	li t0, SR_FS
+	li t0, SR_FS | SR_VS
 	csrc CSR_STATUS, t0
 
 #ifdef CONFIG_SMP
@@ -290,6 +290,51 @@ ENTRY(reset_regs)
 	csrw	fcsr, 0
 	/* note that the caller must clear SR_FS */
 #endif /* CONFIG_FPU */
+
+#ifdef CONFIG_VECTOR
+	csrr	t0, CSR_MISA
+	li	t1, (COMPAT_HWCAP_ISA_V >> 16)
+	slli	t1, t1, 16
+	and	t0, t0, t1
+	beqz	t0, .Lreset_regs_done
+
+	li	t1, SR_VS
+	csrs	CSR_STATUS, t1
+	vmv.v.i v0, 0
+	vmv.v.i v1, 0
+	vmv.v.i v2, 0
+	vmv.v.i v3, 0
+	vmv.v.i v4, 0
+	vmv.v.i v5, 0
+	vmv.v.i v6, 0
+	vmv.v.i v7, 0
+	vmv.v.i v8, 0
+	vmv.v.i v9, 0
+	vmv.v.i v10, 0
+	vmv.v.i v11, 0
+	vmv.v.i v12, 0
+	vmv.v.i v13, 0
+	vmv.v.i v14, 0
+	vmv.v.i v15, 0
+	vmv.v.i v16, 0
+	vmv.v.i v17, 0
+	vmv.v.i v18, 0
+	vmv.v.i v19, 0
+	vmv.v.i v20, 0
+	vmv.v.i v21, 0
+	vmv.v.i v22, 0
+	vmv.v.i v23, 0
+	vmv.v.i v24, 0
+	vmv.v.i v25, 0
+	vmv.v.i v26, 0
+	vmv.v.i v27, 0
+	vmv.v.i v28, 0
+	vmv.v.i v29, 0
+	vmv.v.i v30, 0
+	vmv.v.i v31, 0
+	/* note that the caller must clear SR_VS */
+#endif /* CONFIG_VECTOR */
+
 .Lreset_regs_done:
 	ret
 END(reset_regs)
diff --git a/arch/riscv/kernel/process.c b/arch/riscv/kernel/process.c
index 95a3031e5c7c..3665f8c1a2c1 100644
--- a/arch/riscv/kernel/process.c
+++ b/arch/riscv/kernel/process.c
@@ -74,6 +74,16 @@ void start_thread(struct pt_regs *regs, unsigned long pc,
 		 */
 		fstate_restore(current, regs);
 	}
+
+	if (has_vector) {
+		regs->status |= SR_VS_INITIAL;
+		/*
+		 * Restore the initial value to the vector register
+		 * before starting the user program.
+		 */
+		vstate_restore(current, regs);
+	}
+
 	regs->epc = pc;
 	regs->sp = sp;
 	set_fs(USER_DS);
diff --git a/arch/riscv/kernel/ptrace.c b/arch/riscv/kernel/ptrace.c
index 407464201b91..0e3c3543476c 100644
--- a/arch/riscv/kernel/ptrace.c
+++ b/arch/riscv/kernel/ptrace.c
@@ -26,6 +26,9 @@ enum riscv_regset {
 #ifdef CONFIG_FPU
 	REGSET_F,
 #endif
+#ifdef CONFIG_VECTOR
+	REGSET_V,
+#endif
 };
 
 static int riscv_gpr_get(struct task_struct *target,
@@ -92,6 +95,34 @@ static int riscv_fpr_set(struct task_struct *target,
 }
 #endif
 
+#ifdef CONFIG_VECTOR
+static int riscv_vr_get(struct task_struct *target,
+			 const struct user_regset *regset,
+			 unsigned int pos, unsigned int count,
+			 void *kbuf, void __user *ubuf)
+{
+	int ret;
+	struct __riscv_v_state *vstate = &target->thread.vstate;
+
+	ret = user_regset_copyout(&pos, &count, &kbuf, &ubuf, vstate, 0,
+				  offsetof(struct __riscv_v_state, vtype));
+	return ret;
+}
+
+static int riscv_vr_set(struct task_struct *target,
+			 const struct user_regset *regset,
+			 unsigned int pos, unsigned int count,
+			 const void *kbuf, const void __user *ubuf)
+{
+	int ret;
+	struct __riscv_v_state *vstate = &target->thread.vstate;
+
+	ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf, vstate, 0,
+				 offsetof(struct __riscv_v_state, vtype));
+	return ret;
+}
+#endif
+
 static const struct user_regset riscv_user_regset[] = {
 	[REGSET_X] = {
 		.core_note_type = NT_PRSTATUS,
@@ -111,6 +142,16 @@ static const struct user_regset riscv_user_regset[] = {
 		.set = &riscv_fpr_set,
 	},
 #endif
+#ifdef CONFIG_VECTOR
+	[REGSET_V] = {
+		.core_note_type = NT_RISCV_VECTOR,
+		.n = ELF_NVREG,
+		.size = sizeof(elf_greg_t),
+		.align = sizeof(elf_greg_t),
+		.get = &riscv_vr_get,
+		.set = &riscv_vr_set,
+	},
+#endif
 };
 
 static const struct user_regset_view riscv_user_native_view = {
diff --git a/arch/riscv/kernel/signal.c b/arch/riscv/kernel/signal.c
index 17ba190e84a5..4295c00e8934 100644
--- a/arch/riscv/kernel/signal.c
+++ b/arch/riscv/kernel/signal.c
@@ -83,6 +83,40 @@ static long save_fp_state(struct pt_regs *regs,
 #define restore_fp_state(task, regs) (0)
 #endif
 
+#ifdef CONFIG_VECTOR
+static long restore_v_state(struct pt_regs *regs,
+			    struct __riscv_v_state *sc_vregs)
+{
+	long err;
+	struct __riscv_v_state __user *state = sc_vregs;
+
+	err = __copy_from_user(&current->thread.vstate, state, sizeof(*state));
+	if (unlikely(err))
+		return err;
+
+	vstate_restore(current, regs);
+
+	return err;
+}
+
+static long save_v_state(struct pt_regs *regs,
+			 struct __riscv_v_state *sc_vregs)
+{
+	long err;
+	struct __riscv_v_state __user *state = sc_vregs;
+
+	vstate_save(current, regs);
+	err = __copy_to_user(state, &current->thread.vstate, sizeof(*state));
+	if (unlikely(err))
+		return err;
+
+	return err;
+}
+#else
+#define save_v_state(task, regs) (0)
+#define restore_v_state(task, regs) (0)
+#endif
+
 static long restore_sigcontext(struct pt_regs *regs,
 	struct sigcontext __user *sc)
 {
@@ -92,6 +126,9 @@ static long restore_sigcontext(struct pt_regs *regs,
 	/* Restore the floating-point state. */
 	if (has_fpu)
 		err |= restore_fp_state(regs, &sc->sc_fpregs);
+	/* Restore the vector state. */
+	if (has_vector)
+		err |= restore_v_state(regs, &sc->sc_vregs);
 	return err;
 }
 
@@ -145,6 +182,9 @@ static long setup_sigcontext(struct rt_sigframe __user *frame,
 	/* Save the floating-point state. */
 	if (has_fpu)
 		err |= save_fp_state(regs, &sc->sc_fpregs);
+	/* Save the vector state. */
+	if (has_vector)
+		err |= save_v_state(regs, &sc->sc_vregs);
 	return err;
 }
 
diff --git a/arch/riscv/kernel/vector.S b/arch/riscv/kernel/vector.S
new file mode 100644
index 000000000000..0afc308a6e02
--- /dev/null
+++ b/arch/riscv/kernel/vector.S
@@ -0,0 +1,84 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2012 Regents of the University of California
+ * Copyright (C) 2017 SiFive
+ * Copyright (C) 2019 T-HEAD
+ *
+ *   This program is free software; you can redistribute it and/or
+ *   modify it under the terms of the GNU General Public License
+ *   as published by the Free Software Foundation, version 2.
+ *
+ *   This program is distributed in the hope that it will be useful,
+ *   but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *   GNU General Public License for more details.
+ */
+
+#include <linux/linkage.h>
+
+#include <asm/asm.h>
+#include <asm/csr.h>
+#include <asm/asm-offsets.h>
+
+ENTRY(__vstate_save)
+	li	a2,  TASK_THREAD_V0
+	add	a0,  a0, a2
+
+	li	t1, (SR_VS | SR_FS)
+	csrs	sstatus, t1
+
+	csrr	t0,  CSR_VSTART
+	sd	t0,  TASK_THREAD_VSTART_V0(a0)
+	csrr	t0,  CSR_VXSAT
+	sd	t0,  TASK_THREAD_VXSAT_V0(a0)
+	csrr	t0,  CSR_VXRM
+	sd	t0,  TASK_THREAD_VXRM_V0(a0)
+	csrr	t0,  CSR_VL
+	sd	t0,  TASK_THREAD_VL_V0(a0)
+	csrr	t0,  CSR_VTYPE
+	sd	t0,  TASK_THREAD_VTYPE_V0(a0)
+
+	vsetvli	t0, x0, e8,m8
+	vsb.v	v0,  (a0)
+	addi	a0, a0, RISCV_VECTOR_VLENB*8
+	vsb.v	v8,  (a0)
+	addi	a0, a0, RISCV_VECTOR_VLENB*8
+	vsb.v	v16, (a0)
+	addi	a0, a0, RISCV_VECTOR_VLENB*8
+	vsb.v	v24, (a0)
+
+	csrc	sstatus, t1
+	ret
+ENDPROC(__vstate_save)
+
+ENTRY(__vstate_restore)
+	li	a2,  TASK_THREAD_V0
+	add	a0,  a0, a2
+	mv	t2,  a0
+
+	li	t1, (SR_VS | SR_FS)
+	csrs	sstatus, t1
+
+	vsetvli	t0, x0, e8,m8
+	vlb.v	v0,  (a0)
+	addi	a0, a0, RISCV_VECTOR_VLENB*8
+	vlb.v	v8,  (a0)
+	addi	a0, a0, RISCV_VECTOR_VLENB*8
+	vlb.v	v16, (a0)
+	addi	a0, a0, RISCV_VECTOR_VLENB*8
+	vlb.v	v24, (a0)
+
+	mv	a0,  t2
+	ld	t0,  TASK_THREAD_VSTART_V0(a0)
+	csrw	CSR_VSTART, t0
+	ld	t0,  TASK_THREAD_VXSAT_V0(a0)
+	csrw	CSR_VXSAT, t0
+	ld	t0,  TASK_THREAD_VXRM_V0(a0)
+	csrw	CSR_VXRM, t0
+	ld	t0,  TASK_THREAD_VL_V0(a0)
+	ld	t2,  TASK_THREAD_VTYPE_V0(a0)
+	vsetvl	t0, t0, t2
+
+	csrc	sstatus, t1
+	ret
+ENDPROC(__vstate_restore)
diff --git a/include/uapi/linux/elf.h b/include/uapi/linux/elf.h
index 34c02e4290fe..e428f9e8710a 100644
--- a/include/uapi/linux/elf.h
+++ b/include/uapi/linux/elf.h
@@ -428,6 +428,7 @@ typedef struct elf64_shdr {
 #define NT_MIPS_DSP	0x800		/* MIPS DSP ASE registers */
 #define NT_MIPS_FP_MODE	0x801		/* MIPS floating-point mode */
 #define NT_MIPS_MSA	0x802		/* MIPS SIMD registers */
+#define NT_RISCV_VECTOR	0x900		/* RISC-V vector registers */
 
 /* Note header in a PT_NOTE section */
 typedef struct elf32_note {
-- 
2.17.0