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From: Charlie Jenkins <charlie@rivosinc.com>
Date: Mon, 15 Apr 2024 21:12:10 -0700
Subject: [PATCH v2 13/17] riscv: vector: Support xtheadvector save/restore
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Message-Id: <20240415-dev-charlie-support_thead_vector_6_9-v2-13-c7d68c603268@rivosinc.com>
References: <20240415-dev-charlie-support_thead_vector_6_9-v2-0-c7d68c603268@rivosinc.com>
In-Reply-To: <20240415-dev-charlie-support_thead_vector_6_9-v2-0-c7d68c603268@rivosinc.com>
To: Conor Dooley <conor@kernel.org>, Rob Herring <robh@kernel.org>, 
 Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>, 
 Paul Walmsley <paul.walmsley@sifive.com>, 
 Palmer Dabbelt <palmer@dabbelt.com>, Albert Ou <aou@eecs.berkeley.edu>, 
 Guo Ren <guoren@kernel.org>, Conor Dooley <conor+dt@kernel.org>, 
 Chen-Yu Tsai <wens@csie.org>, Jernej Skrabec <jernej.skrabec@gmail.com>, 
 Samuel Holland <samuel@sholland.org>, 
 Conor Dooley <conor.dooley@microchip.com>, Evan Green <evan@rivosinc.com>, 
 =?utf-8?q?Cl=C3=A9ment_L=C3=A9ger?= <cleger@rivosinc.com>, 
 Jonathan Corbet <corbet@lwn.net>, Shuah Khan <shuah@kernel.org>
Cc: linux-riscv@lists.infradead.org, devicetree@vger.kernel.org, 
 linux-kernel@vger.kernel.org, Palmer Dabbelt <palmer@rivosinc.com>, 
 linux-arm-kernel@lists.infradead.org, linux-sunxi@lists.linux.dev, 
 linux-doc@vger.kernel.org, linux-kselftest@vger.kernel.org, 
 Charlie Jenkins <charlie@rivosinc.com>

Use alternatives to add support for xtheadvector vector save/restore
routines.

Signed-off-by: Charlie Jenkins <charlie@rivosinc.com>
---
 arch/riscv/Kconfig                     |   2 +
 arch/riscv/Kconfig.vendor              |  11 ++
 arch/riscv/include/asm/csr.h           |   6 +
 arch/riscv/include/asm/switch_to.h     |   2 +-
 arch/riscv/include/asm/vector.h        | 246 ++++++++++++++++++++++++++-------
 arch/riscv/kernel/cpufeature.c         |   2 +-
 arch/riscv/kernel/kernel_mode_vector.c |   8 +-
 arch/riscv/kernel/process.c            |   4 +-
 arch/riscv/kernel/signal.c             |   6 +-
 arch/riscv/kernel/vector.c             |  35 +++--
 10 files changed, 250 insertions(+), 72 deletions(-)

diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index be09c8836d56..fec86fba3acd 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -759,6 +759,8 @@ config RISCV_EFFICIENT_UNALIGNED_ACCESS
 
 endchoice
 
+source "arch/riscv/Kconfig.vendor"
+
 endmenu # "Platform type"
 
 menu "Kernel features"
diff --git a/arch/riscv/Kconfig.vendor b/arch/riscv/Kconfig.vendor
new file mode 100644
index 000000000000..be7bd3b4d936
--- /dev/null
+++ b/arch/riscv/Kconfig.vendor
@@ -0,0 +1,11 @@
+config RISCV_ISA_XTHEADVECTOR
+	bool "xtheadvector extension support"
+	depends on RISCV_ISA_V
+	depends on FPU
+	default y
+	help
+	  Say N here if you want to disable all xtheadvector related procedure
+	  in the kernel. This will disable vector for any T-Head board that
+	  contains xtheadvector rather than the standard vector.
+
+	  If you don't know what to do here, say Y.
diff --git a/arch/riscv/include/asm/csr.h b/arch/riscv/include/asm/csr.h
index e5a35efd56e0..13657d096e7d 100644
--- a/arch/riscv/include/asm/csr.h
+++ b/arch/riscv/include/asm/csr.h
@@ -30,6 +30,12 @@
 #define SR_VS_CLEAN	_AC(0x00000400, UL)
 #define SR_VS_DIRTY	_AC(0x00000600, UL)
 
+#define SR_VS_THEAD		_AC(0x01800000, UL) /* xtheadvector Status */
+#define SR_VS_OFF_THEAD		_AC(0x00000000, UL)
+#define SR_VS_INITIAL_THEAD	_AC(0x00800000, UL)
+#define SR_VS_CLEAN_THEAD	_AC(0x01000000, UL)
+#define SR_VS_DIRTY_THEAD	_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)
diff --git a/arch/riscv/include/asm/switch_to.h b/arch/riscv/include/asm/switch_to.h
index 7efdb0584d47..ada6b5cf2d94 100644
--- a/arch/riscv/include/asm/switch_to.h
+++ b/arch/riscv/include/asm/switch_to.h
@@ -78,7 +78,7 @@ do {							\
 	struct task_struct *__next = (next);		\
 	if (has_fpu())					\
 		__switch_to_fpu(__prev, __next);	\
-	if (has_vector())					\
+	if (has_vector() || has_xtheadvector())		\
 		__switch_to_vector(__prev, __next);	\
 	((last) = __switch_to(__prev, __next));		\
 } while (0)
diff --git a/arch/riscv/include/asm/vector.h b/arch/riscv/include/asm/vector.h
index 731dcd0ed4de..9871f59c7cfc 100644
--- a/arch/riscv/include/asm/vector.h
+++ b/arch/riscv/include/asm/vector.h
@@ -18,6 +18,26 @@
 #include <asm/cpufeature.h>
 #include <asm/csr.h>
 #include <asm/asm.h>
+#include <asm/vendorid_list.h>
+#include <asm/xtheadvector.h>
+
+#define __riscv_v_vstate_or(_val, TYPE) ({				\
+	typeof(_val) _res = _val;					\
+	if (has_xtheadvector()) \
+		_res = (_res & ~SR_VS_THEAD) | SR_VS_##TYPE##_THEAD;	\
+	else								\
+		_res = (_res & ~SR_VS) | SR_VS_##TYPE;			\
+	_res;								\
+})
+
+#define __riscv_v_vstate_check(_val, TYPE) ({				\
+	bool _res;							\
+	if (has_xtheadvector()) \
+		_res = ((_val) & SR_VS_THEAD) == SR_VS_##TYPE##_THEAD;	\
+	else								\
+		_res = ((_val) & SR_VS) == SR_VS_##TYPE;		\
+	_res;								\
+})
 
 extern unsigned long riscv_v_vsize;
 int riscv_v_setup_vsize(void);
@@ -40,39 +60,62 @@ static __always_inline bool has_vector(void)
 	return riscv_has_extension_unlikely(RISCV_ISA_EXT_v);
 }
 
+static __always_inline bool has_xtheadvector_no_alternatives(void)
+{
+	if (IS_ENABLED(CONFIG_RISCV_ISA_XTHEADVECTOR) && hart_isa_vendorid == THEAD_VENDOR_ID)
+		return riscv_isa_vendor_extension_available(NULL, XTHEADVECTOR);
+	else
+		return false;
+}
+
+static __always_inline bool has_xtheadvector(void)
+{
+	if (IS_ENABLED(CONFIG_RISCV_ISA_XTHEADVECTOR))
+		return riscv_has_vendor_extension_unlikely(THEAD_VENDOR_ID,
+							   RISCV_ISA_VENDOR_EXT_XTHEADVECTOR);
+	else
+		return false;
+}
+
 static inline void __riscv_v_vstate_clean(struct pt_regs *regs)
 {
-	regs->status = (regs->status & ~SR_VS) | SR_VS_CLEAN;
+	regs->status = __riscv_v_vstate_or(regs->status, CLEAN);
 }
 
 static inline void __riscv_v_vstate_dirty(struct pt_regs *regs)
 {
-	regs->status = (regs->status & ~SR_VS) | SR_VS_DIRTY;
+	regs->status = __riscv_v_vstate_or(regs->status, DIRTY);
 }
 
 static inline void riscv_v_vstate_off(struct pt_regs *regs)
 {
-	regs->status = (regs->status & ~SR_VS) | SR_VS_OFF;
+	regs->status = __riscv_v_vstate_or(regs->status, OFF);
 }
 
 static inline void riscv_v_vstate_on(struct pt_regs *regs)
 {
-	regs->status = (regs->status & ~SR_VS) | SR_VS_INITIAL;
+	regs->status = __riscv_v_vstate_or(regs->status, INITIAL);
 }
 
 static inline bool riscv_v_vstate_query(struct pt_regs *regs)
 {
-	return (regs->status & SR_VS) != 0;
+	return !__riscv_v_vstate_check(regs->status, OFF);
 }
 
 static __always_inline void riscv_v_enable(void)
 {
-	csr_set(CSR_SSTATUS, SR_VS);
+	if (has_xtheadvector())
+		csr_set(CSR_SSTATUS, SR_VS_THEAD);
+	else
+		csr_set(CSR_SSTATUS, SR_VS);
 }
 
 static __always_inline void riscv_v_disable(void)
 {
-	csr_clear(CSR_SSTATUS, SR_VS);
+	if (has_xtheadvector())
+		csr_clear(CSR_SSTATUS, SR_VS_THEAD);
+	else
+		csr_clear(CSR_SSTATUS, SR_VS);
 }
 
 static __always_inline void __vstate_csr_save(struct __riscv_v_ext_state *dest)
@@ -81,10 +124,47 @@ static __always_inline void __vstate_csr_save(struct __riscv_v_ext_state *dest)
 		"csrr	%0, " __stringify(CSR_VSTART) "\n\t"
 		"csrr	%1, " __stringify(CSR_VTYPE) "\n\t"
 		"csrr	%2, " __stringify(CSR_VL) "\n\t"
-		"csrr	%3, " __stringify(CSR_VCSR) "\n\t"
-		"csrr	%4, " __stringify(CSR_VLENB) "\n\t"
 		: "=r" (dest->vstart), "=r" (dest->vtype), "=r" (dest->vl),
-		  "=r" (dest->vcsr), "=r" (dest->vlenb) : :);
+		"=r" (dest->vcsr) : :);
+
+	if (has_xtheadvector()) {
+		u32 tmp_vcsr;
+		bool restore_fpu = false;
+		unsigned long status = csr_read(CSR_SSTATUS);
+
+		/*
+		 * CSR_VCSR is defined as
+		 * [2:1] - vxrm[1:0]
+		 * [0] - vxsat
+		 * The earlier vector spec implemented by T-Head uses separate
+		 * registers for the same bit-elements, so just combine those
+		 * into the existing output field.
+		 *
+		 * Additionally T-Head cores need FS to be enabled when accessing
+		 * the VXRM and VXSAT CSRs, otherwise ending in illegal instructions.
+		 * Though the cores do not implement the VXRM and VXSAT fields in the
+		 * FCSR CSR that vector-0.7.1 specifies.
+		 */
+		if ((status & SR_FS) == SR_FS_OFF) {
+			csr_set(CSR_SSTATUS, (status & ~SR_FS) | SR_FS_CLEAN);
+			restore_fpu = true;
+		}
+
+		asm volatile (
+			"csrr	%[tmp_vcsr], " __stringify(VCSR_VXRM) "\n\t"
+			"slliw	%[vcsr], %[tmp_vcsr], " __stringify(VCSR_VXRM_SHIFT) "\n\t"
+			"csrr	%[tmp_vcsr], " __stringify(VCSR_VXSAT) "\n\t"
+			"or	%[vcsr], %[vcsr], %[tmp_vcsr]\n\t"
+			: [vcsr] "=r" (dest->vcsr), [tmp_vcsr] "=&r" (tmp_vcsr));
+
+		if (restore_fpu)
+			csr_set(CSR_SSTATUS, status);
+	} else {
+		asm volatile (
+			"csrr	%[vcsr], " __stringify(CSR_VCSR) "\n\t"
+			"csrr	%[vlenb], " __stringify(CSR_VLENB) "\n\t"
+			: [vcsr] "=r" (dest->vcsr), [vlenb] "=r" (dest->vlenb));
+	}
 }
 
 static __always_inline void __vstate_csr_restore(struct __riscv_v_ext_state *src)
@@ -95,9 +175,37 @@ static __always_inline void __vstate_csr_restore(struct __riscv_v_ext_state *src
 		"vsetvl	 x0, %2, %1\n\t"
 		".option pop\n\t"
 		"csrw	" __stringify(CSR_VSTART) ", %0\n\t"
-		"csrw	" __stringify(CSR_VCSR) ", %3\n\t"
-		: : "r" (src->vstart), "r" (src->vtype), "r" (src->vl),
-		    "r" (src->vcsr) :);
+		: : "r" (src->vstart), "r" (src->vtype), "r" (src->vl));
+
+	if (has_xtheadvector()) {
+		u32 tmp_vcsr;
+		bool restore_fpu = false;
+		unsigned long status = csr_read(CSR_SSTATUS);
+
+		/*
+		 * Similar to __vstate_csr_save above, restore values for the
+		 * separate VXRM and VXSAT CSRs from the vcsr variable.
+		 */
+		if ((status & SR_FS) == SR_FS_OFF) {
+			csr_set(CSR_SSTATUS, (status & ~SR_FS) | SR_FS_CLEAN);
+			restore_fpu = true;
+		}
+
+		asm volatile (
+			"srliw	%[tmp_vcsr], %[vcsr], " __stringify(VCSR_VXRM_SHIFT) "\n\t"
+			"andi	%[tmp_vcsr], %[tmp_vcsr], " __stringify(VCSR_VXRM_MASK) "\n\t"
+			"csrw	" __stringify(VCSR_VXRM) ", %[tmp_vcsr]\n\t"
+			"andi	%[tmp_vcsr], %[vcsr], " __stringify(VCSR_VXSAT_MASK) "\n\t"
+			"csrw	" __stringify(VCSR_VXSAT) ", %[tmp_vcsr]\n\t"
+			: [tmp_vcsr] "=&r" (tmp_vcsr) : [vcsr] "r" (src->vcsr));
+
+		if (restore_fpu)
+			csr_set(CSR_SSTATUS, status);
+	} else {
+		asm volatile (
+			"csrw	" __stringify(CSR_VCSR) ", %[vcsr]\n\t"
+			: : [vcsr] "r" (src->vcsr));
+	}
 }
 
 static inline void __riscv_v_vstate_save(struct __riscv_v_ext_state *save_to,
@@ -107,19 +215,33 @@ static inline void __riscv_v_vstate_save(struct __riscv_v_ext_state *save_to,
 
 	riscv_v_enable();
 	__vstate_csr_save(save_to);
-	asm volatile (
-		".option push\n\t"
-		".option arch, +v\n\t"
-		"vsetvli	%0, x0, e8, m8, ta, ma\n\t"
-		"vse8.v		v0, (%1)\n\t"
-		"add		%1, %1, %0\n\t"
-		"vse8.v		v8, (%1)\n\t"
-		"add		%1, %1, %0\n\t"
-		"vse8.v		v16, (%1)\n\t"
-		"add		%1, %1, %0\n\t"
-		"vse8.v		v24, (%1)\n\t"
-		".option pop\n\t"
-		: "=&r" (vl) : "r" (datap) : "memory");
+	if (has_xtheadvector()) {
+		asm volatile (
+			"mv t0, %0\n\t"
+			THEAD_VSETVLI_T4X0E8M8D1
+			THEAD_VSB_V_V0T0
+			"add		t0, t0, t4\n\t"
+			THEAD_VSB_V_V0T0
+			"add		t0, t0, t4\n\t"
+			THEAD_VSB_V_V0T0
+			"add		t0, t0, t4\n\t"
+			THEAD_VSB_V_V0T0
+			: : "r" (datap) : "memory", "t0", "t4");
+	} else {
+		asm volatile (
+			".option push\n\t"
+			".option arch, +v\n\t"
+			"vsetvli	%0, x0, e8, m8, ta, ma\n\t"
+			"vse8.v		v0, (%1)\n\t"
+			"add		%1, %1, %0\n\t"
+			"vse8.v		v8, (%1)\n\t"
+			"add		%1, %1, %0\n\t"
+			"vse8.v		v16, (%1)\n\t"
+			"add		%1, %1, %0\n\t"
+			"vse8.v		v24, (%1)\n\t"
+			".option pop\n\t"
+			: "=&r" (vl) : "r" (datap) : "memory");
+	}
 	riscv_v_disable();
 }
 
@@ -129,55 +251,77 @@ static inline void __riscv_v_vstate_restore(struct __riscv_v_ext_state *restore_
 	unsigned long vl;
 
 	riscv_v_enable();
-	asm volatile (
-		".option push\n\t"
-		".option arch, +v\n\t"
-		"vsetvli	%0, x0, e8, m8, ta, ma\n\t"
-		"vle8.v		v0, (%1)\n\t"
-		"add		%1, %1, %0\n\t"
-		"vle8.v		v8, (%1)\n\t"
-		"add		%1, %1, %0\n\t"
-		"vle8.v		v16, (%1)\n\t"
-		"add		%1, %1, %0\n\t"
-		"vle8.v		v24, (%1)\n\t"
-		".option pop\n\t"
-		: "=&r" (vl) : "r" (datap) : "memory");
+	if (has_xtheadvector()) {
+		asm volatile (
+			"mv t0, %0\n\t"
+			THEAD_VSETVLI_T4X0E8M8D1
+			THEAD_VLB_V_V0T0
+			"add		t0, t0, t4\n\t"
+			THEAD_VLB_V_V0T0
+			"add		t0, t0, t4\n\t"
+			THEAD_VLB_V_V0T0
+			"add		t0, t0, t4\n\t"
+			THEAD_VLB_V_V0T0
+			: : "r" (datap) : "memory", "t0", "t4");
+	} else {
+		asm volatile (
+			".option push\n\t"
+			".option arch, +v\n\t"
+			"vsetvli	%0, x0, e8, m8, ta, ma\n\t"
+			"vle8.v		v0, (%1)\n\t"
+			"add		%1, %1, %0\n\t"
+			"vle8.v		v8, (%1)\n\t"
+			"add		%1, %1, %0\n\t"
+			"vle8.v		v16, (%1)\n\t"
+			"add		%1, %1, %0\n\t"
+			"vle8.v		v24, (%1)\n\t"
+			".option pop\n\t"
+			: "=&r" (vl) : "r" (datap) : "memory");
+	}
 	__vstate_csr_restore(restore_from);
 	riscv_v_disable();
 }
 
 static inline void __riscv_v_vstate_discard(void)
 {
-	unsigned long vl, vtype_inval = 1UL << (BITS_PER_LONG - 1);
+	unsigned long vtype_inval = 1UL << (BITS_PER_LONG - 1);
 
 	riscv_v_enable();
+	if (has_xtheadvector())
+		asm volatile (THEAD_VSETVLI_X0X0E8M8D1);
+	else
+		asm volatile (
+			".option push\n\t"
+			".option arch, +v\n\t"
+			"vsetvli	x0, x0, e8, m8, ta, ma\n\t"
+			".option pop\n\t");
+
 	asm volatile (
 		".option push\n\t"
 		".option arch, +v\n\t"
-		"vsetvli	%0, x0, e8, m8, ta, ma\n\t"
 		"vmv.v.i	v0, -1\n\t"
 		"vmv.v.i	v8, -1\n\t"
 		"vmv.v.i	v16, -1\n\t"
 		"vmv.v.i	v24, -1\n\t"
-		"vsetvl		%0, x0, %1\n\t"
+		"vsetvl		x0, x0, %0\n\t"
 		".option pop\n\t"
-		: "=&r" (vl) : "r" (vtype_inval) : "memory");
+		: : "r" (vtype_inval));
+
 	riscv_v_disable();
 }
 
 static inline void riscv_v_vstate_discard(struct pt_regs *regs)
 {
-	if ((regs->status & SR_VS) == SR_VS_OFF)
-		return;
-
-	__riscv_v_vstate_discard();
-	__riscv_v_vstate_dirty(regs);
+	if (riscv_v_vstate_query(regs)) {
+		__riscv_v_vstate_discard();
+		__riscv_v_vstate_dirty(regs);
+	}
 }
 
 static inline void riscv_v_vstate_save(struct __riscv_v_ext_state *vstate,
 				       struct pt_regs *regs)
 {
-	if ((regs->status & SR_VS) == SR_VS_DIRTY) {
+	if (__riscv_v_vstate_check(regs->status, DIRTY)) {
 		__riscv_v_vstate_save(vstate, vstate->datap);
 		__riscv_v_vstate_clean(regs);
 	}
@@ -186,7 +330,7 @@ static inline void riscv_v_vstate_save(struct __riscv_v_ext_state *vstate,
 static inline void riscv_v_vstate_restore(struct __riscv_v_ext_state *vstate,
 					  struct pt_regs *regs)
 {
-	if ((regs->status & SR_VS) != SR_VS_OFF) {
+	if (riscv_v_vstate_query(regs)) {
 		__riscv_v_vstate_restore(vstate, vstate->datap);
 		__riscv_v_vstate_clean(regs);
 	}
@@ -195,7 +339,7 @@ static inline void riscv_v_vstate_restore(struct __riscv_v_ext_state *vstate,
 static inline void riscv_v_vstate_set_restore(struct task_struct *task,
 					      struct pt_regs *regs)
 {
-	if ((regs->status & SR_VS) != SR_VS_OFF) {
+	if (riscv_v_vstate_query(regs)) {
 		set_tsk_thread_flag(task, TIF_RISCV_V_DEFER_RESTORE);
 		riscv_v_vstate_on(regs);
 	}
diff --git a/arch/riscv/kernel/cpufeature.c b/arch/riscv/kernel/cpufeature.c
index 949c06970c4f..c62f4bf8b607 100644
--- a/arch/riscv/kernel/cpufeature.c
+++ b/arch/riscv/kernel/cpufeature.c
@@ -774,7 +774,7 @@ void __init riscv_fill_hwcap(void)
 		elf_hwcap &= ~COMPAT_HWCAP_ISA_F;
 	}
 
-	if (elf_hwcap & COMPAT_HWCAP_ISA_V) {
+	if (elf_hwcap & COMPAT_HWCAP_ISA_V || has_xtheadvector_no_alternatives()) {
 		riscv_v_setup_vsize();
 		/*
 		 * ISA string in device tree might have 'v' flag, but
diff --git a/arch/riscv/kernel/kernel_mode_vector.c b/arch/riscv/kernel/kernel_mode_vector.c
index 6afe80c7f03a..99972a48e86b 100644
--- a/arch/riscv/kernel/kernel_mode_vector.c
+++ b/arch/riscv/kernel/kernel_mode_vector.c
@@ -143,7 +143,7 @@ static int riscv_v_start_kernel_context(bool *is_nested)
 
 	/* Transfer the ownership of V from user to kernel, then save */
 	riscv_v_start(RISCV_PREEMPT_V | RISCV_PREEMPT_V_DIRTY);
-	if ((task_pt_regs(current)->status & SR_VS) == SR_VS_DIRTY) {
+	if (__riscv_v_vstate_check(task_pt_regs(current)->status, DIRTY)) {
 		uvstate = &current->thread.vstate;
 		__riscv_v_vstate_save(uvstate, uvstate->datap);
 	}
@@ -160,7 +160,7 @@ asmlinkage void riscv_v_context_nesting_start(struct pt_regs *regs)
 		return;
 
 	depth = riscv_v_ctx_get_depth();
-	if (depth == 0 && (regs->status & SR_VS) == SR_VS_DIRTY)
+	if (depth == 0 && __riscv_v_vstate_check(regs->status, DIRTY))
 		riscv_preempt_v_set_dirty();
 
 	riscv_v_ctx_depth_inc();
@@ -208,7 +208,7 @@ void kernel_vector_begin(void)
 {
 	bool nested = false;
 
-	if (WARN_ON(!has_vector()))
+	if (WARN_ON(!(has_vector() || has_xtheadvector())))
 		return;
 
 	BUG_ON(!may_use_simd());
@@ -236,7 +236,7 @@ EXPORT_SYMBOL_GPL(kernel_vector_begin);
  */
 void kernel_vector_end(void)
 {
-	if (WARN_ON(!has_vector()))
+	if (WARN_ON(!(has_vector() || has_xtheadvector())))
 		return;
 
 	riscv_v_disable();
diff --git a/arch/riscv/kernel/process.c b/arch/riscv/kernel/process.c
index 92922dbd5b5c..eabca86fc3c0 100644
--- a/arch/riscv/kernel/process.c
+++ b/arch/riscv/kernel/process.c
@@ -178,7 +178,7 @@ void flush_thread(void)
 void arch_release_task_struct(struct task_struct *tsk)
 {
 	/* Free the vector context of datap. */
-	if (has_vector())
+	if (has_vector() || has_xtheadvector())
 		riscv_v_thread_free(tsk);
 }
 
@@ -225,7 +225,7 @@ int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
 		p->thread.s[0] = 0;
 	}
 	p->thread.riscv_v_flags = 0;
-	if (has_vector())
+	if (has_vector() || has_xtheadvector())
 		riscv_v_thread_alloc(p);
 	p->thread.ra = (unsigned long)ret_from_fork;
 	p->thread.sp = (unsigned long)childregs; /* kernel sp */
diff --git a/arch/riscv/kernel/signal.c b/arch/riscv/kernel/signal.c
index 501e66debf69..5d3ba8e46807 100644
--- a/arch/riscv/kernel/signal.c
+++ b/arch/riscv/kernel/signal.c
@@ -188,7 +188,7 @@ static long restore_sigcontext(struct pt_regs *regs,
 
 			return 0;
 		case RISCV_V_MAGIC:
-			if (!has_vector() || !riscv_v_vstate_query(regs) ||
+			if (!(has_vector() || has_xtheadvector()) || !riscv_v_vstate_query(regs) ||
 			    size != riscv_v_sc_size)
 				return -EINVAL;
 
@@ -210,7 +210,7 @@ static size_t get_rt_frame_size(bool cal_all)
 
 	frame_size = sizeof(*frame);
 
-	if (has_vector()) {
+	if (has_vector() || has_xtheadvector()) {
 		if (cal_all || riscv_v_vstate_query(task_pt_regs(current)))
 			total_context_size += riscv_v_sc_size;
 	}
@@ -283,7 +283,7 @@ static long setup_sigcontext(struct rt_sigframe __user *frame,
 	if (has_fpu())
 		err |= save_fp_state(regs, &sc->sc_fpregs);
 	/* Save the vector state. */
-	if (has_vector() && riscv_v_vstate_query(regs))
+	if ((has_vector() || has_xtheadvector()) && riscv_v_vstate_query(regs))
 		err |= save_v_state(regs, (void __user **)&sc_ext_ptr);
 	/* Write zero to fp-reserved space and check it on restore_sigcontext */
 	err |= __put_user(0, &sc->sc_extdesc.reserved);
diff --git a/arch/riscv/kernel/vector.c b/arch/riscv/kernel/vector.c
index 6727d1d3b8f2..f42eaa8178e9 100644
--- a/arch/riscv/kernel/vector.c
+++ b/arch/riscv/kernel/vector.c
@@ -33,10 +33,24 @@ int riscv_v_setup_vsize(void)
 {
 	unsigned long this_vsize;
 
-	/* There are 32 vector registers with vlenb length. */
-	riscv_v_enable();
-	this_vsize = csr_read(CSR_VLENB) * 32;
-	riscv_v_disable();
+	/*
+	 * This is called before alternatives have been patched so can't use
+	 * riscv_has_vendor_extension_unlikely
+	 */
+	if (has_xtheadvector_no_alternatives()) {
+		/*
+		 * Although xtheadvector states that th.vlenb exists and
+		 * overlaps with the vector 1.0 vlenb, an illegal instruction is
+		 * raised if read. These systems all currently have a fixed
+		 * vector length of 128, so hardcode that value.
+		 */
+		this_vsize = 128;
+	} else {
+		/* There are 32 vector registers with vlenb length. */
+		riscv_v_enable();
+		this_vsize = csr_read(CSR_VLENB) * 32;
+		riscv_v_disable();
+	}
 
 	if (!riscv_v_vsize) {
 		riscv_v_vsize = this_vsize;
@@ -53,7 +67,7 @@ int riscv_v_setup_vsize(void)
 
 void __init riscv_v_setup_ctx_cache(void)
 {
-	if (!has_vector())
+	if (!(has_vector() || has_xtheadvector()))
 		return;
 
 	riscv_v_user_cachep = kmem_cache_create_usercopy("riscv_vector_ctx",
@@ -174,7 +188,8 @@ bool riscv_v_first_use_handler(struct pt_regs *regs)
 	u32 insn = (u32)regs->badaddr;
 
 	/* Do not handle if V is not supported, or disabled */
-	if (!(ELF_HWCAP & COMPAT_HWCAP_ISA_V))
+	if (!(ELF_HWCAP & COMPAT_HWCAP_ISA_V) &&
+	    !(has_xtheadvector() && riscv_v_vstate_ctrl_user_allowed()))
 		return false;
 
 	/* If V has been enabled then it is not the first-use trap */
@@ -213,7 +228,7 @@ void riscv_v_vstate_ctrl_init(struct task_struct *tsk)
 	bool inherit;
 	int cur, next;
 
-	if (!has_vector())
+	if (!(has_vector() || has_xtheadvector()))
 		return;
 
 	next = riscv_v_ctrl_get_next(tsk);
@@ -235,7 +250,7 @@ void riscv_v_vstate_ctrl_init(struct task_struct *tsk)
 
 long riscv_v_vstate_ctrl_get_current(void)
 {
-	if (!has_vector())
+	if (!(has_vector() || has_xtheadvector()))
 		return -EINVAL;
 
 	return current->thread.vstate_ctrl & PR_RISCV_V_VSTATE_CTRL_MASK;
@@ -246,7 +261,7 @@ long riscv_v_vstate_ctrl_set_current(unsigned long arg)
 	bool inherit;
 	int cur, next;
 
-	if (!has_vector())
+	if (!(has_vector() || has_xtheadvector()))
 		return -EINVAL;
 
 	if (arg & ~PR_RISCV_V_VSTATE_CTRL_MASK)
@@ -296,7 +311,7 @@ static struct ctl_table riscv_v_default_vstate_table[] = {
 
 static int __init riscv_v_sysctl_init(void)
 {
-	if (has_vector())
+	if (has_vector() || has_xtheadvector())
 		if (!register_sysctl("abi", riscv_v_default_vstate_table))
 			return -EINVAL;
 	return 0;

-- 
2.44.0