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From: Andy Chiu <andy.chiu@sifive.com>
Date: Fri, 10 May 2024 00:26:57 +0800
Subject: [PATCH v5 7/8] riscv: vector: adjust minimum Vector requirement to
 ZVE32X
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Message-Id: <20240510-zve-detection-v5-7-0711bdd26c12@sifive.com>
References: <20240510-zve-detection-v5-0-0711bdd26c12@sifive.com>
In-Reply-To: <20240510-zve-detection-v5-0-0711bdd26c12@sifive.com>
To: Paul Walmsley <paul.walmsley@sifive.com>, 
 Palmer Dabbelt <palmer@dabbelt.com>, Albert Ou <aou@eecs.berkeley.edu>, 
 Conor Dooley <conor.dooley@microchip.com>, Heiko Stuebner <heiko@sntech.de>, 
 Andy Chiu <andy.chiu@sifive.com>, Guo Ren <guoren@kernel.org>, 
 Conor Dooley <conor@kernel.org>, Rob Herring <robh@kernel.org>, 
 Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>, 
 Jonathan Corbet <corbet@lwn.net>, Evan Green <evan@rivosinc.com>, 
 =?utf-8?q?Cl=C3=A9ment_L=C3=A9ger?= <cleger@rivosinc.com>, 
 Shuah Khan <shuah@kernel.org>
Cc: linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org, 
 Palmer Dabbelt <palmer@rivosinc.com>, 
 Vincent Chen <vincent.chen@sifive.com>, 
 Greentime Hu <greentime.hu@sifive.com>, devicetree@vger.kernel.org, 
 linux-doc@vger.kernel.org, linux-kselftest@vger.kernel.org, 
 Joel Granados <j.granados@samsung.com>

Make has_vector() to check for ZVE32X. Every in-kernel usage of V that
requires a more complicate version of V must then call out explicitly.

Also, change riscv_v_first_use_handler(), and boot code that calls
riscv_v_setup_vsize() to accept ZVE32X.

Most kernel/user interfaces requires minimum of ZVE32X. Thus, programs
compiled and run with ZVE32X should be supported by the kernel on most
aspects. This includes context-switch, signal, ptrace, prctl, and
hwprobe.

One exception is that ELF_HWCAP returns 'V' only if full V is supported
on the platform. This means that the system without a full V must not
rely on ELF_HWCAP to tell whether it is allowable to execute Vector
without first invoking a prctl() check.

Signed-off-by: Andy Chiu <andy.chiu@sifive.com>
Acked-by: Joel Granados <j.granados@samsung.com>
---
Changelog v5:
 - Remove the paramerter from has_vector()'s prototype. Instead, make it
   check for ZVE32X only. Everything else should make additional
   alternative checks. (Conor)
Changelog v4:
 - check static_assert for !CONFIG_RISCV_ISA_V case in has_vector.
Changelog v2:
 - update the comment in hwprobe.
---
 arch/riscv/include/asm/vector.h | 10 +++++-----
 arch/riscv/kernel/cpufeature.c  |  5 ++++-
 arch/riscv/kernel/sys_hwprobe.c |  6 +++++-
 arch/riscv/kernel/vector.c      |  5 ++++-
 arch/riscv/lib/uaccess.S        |  2 +-
 5 files changed, 19 insertions(+), 9 deletions(-)

diff --git a/arch/riscv/include/asm/vector.h b/arch/riscv/include/asm/vector.h
index 731dcd0ed4de..be7d309cca8a 100644
--- a/arch/riscv/include/asm/vector.h
+++ b/arch/riscv/include/asm/vector.h
@@ -37,7 +37,7 @@ static inline u32 riscv_v_flags(void)
 
 static __always_inline bool has_vector(void)
 {
-	return riscv_has_extension_unlikely(RISCV_ISA_EXT_v);
+	return riscv_has_extension_unlikely(RISCV_ISA_EXT_ZVE32X);
 }
 
 static inline void __riscv_v_vstate_clean(struct pt_regs *regs)
@@ -91,7 +91,7 @@ static __always_inline void __vstate_csr_restore(struct __riscv_v_ext_state *src
 {
 	asm volatile (
 		".option push\n\t"
-		".option arch, +v\n\t"
+		".option arch, +zve32x\n\t"
 		"vsetvl	 x0, %2, %1\n\t"
 		".option pop\n\t"
 		"csrw	" __stringify(CSR_VSTART) ", %0\n\t"
@@ -109,7 +109,7 @@ static inline void __riscv_v_vstate_save(struct __riscv_v_ext_state *save_to,
 	__vstate_csr_save(save_to);
 	asm volatile (
 		".option push\n\t"
-		".option arch, +v\n\t"
+		".option arch, +zve32x\n\t"
 		"vsetvli	%0, x0, e8, m8, ta, ma\n\t"
 		"vse8.v		v0, (%1)\n\t"
 		"add		%1, %1, %0\n\t"
@@ -131,7 +131,7 @@ static inline void __riscv_v_vstate_restore(struct __riscv_v_ext_state *restore_
 	riscv_v_enable();
 	asm volatile (
 		".option push\n\t"
-		".option arch, +v\n\t"
+		".option arch, +zve32x\n\t"
 		"vsetvli	%0, x0, e8, m8, ta, ma\n\t"
 		"vle8.v		v0, (%1)\n\t"
 		"add		%1, %1, %0\n\t"
@@ -153,7 +153,7 @@ static inline void __riscv_v_vstate_discard(void)
 	riscv_v_enable();
 	asm volatile (
 		".option push\n\t"
-		".option arch, +v\n\t"
+		".option arch, +zve32x\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"
diff --git a/arch/riscv/kernel/cpufeature.c b/arch/riscv/kernel/cpufeature.c
index ad3e613ee30f..53be3365e302 100644
--- a/arch/riscv/kernel/cpufeature.c
+++ b/arch/riscv/kernel/cpufeature.c
@@ -720,11 +720,14 @@ void __init riscv_fill_hwcap(void)
 		elf_hwcap &= ~COMPAT_HWCAP_ISA_F;
 	}
 
-	if (elf_hwcap & COMPAT_HWCAP_ISA_V) {
+	if (__riscv_isa_extension_available(NULL, RISCV_ISA_EXT_ZVE32X)) {
 		/*
 		 * This cannot fail when called on the boot hart
 		 */
 		riscv_v_setup_vsize();
+	}
+
+	if (elf_hwcap & COMPAT_HWCAP_ISA_V) {
 		/*
 		 * ISA string in device tree might have 'v' flag, but
 		 * CONFIG_RISCV_ISA_V is disabled in kernel.
diff --git a/arch/riscv/kernel/sys_hwprobe.c b/arch/riscv/kernel/sys_hwprobe.c
index 35390b4a5a17..83fcc939df67 100644
--- a/arch/riscv/kernel/sys_hwprobe.c
+++ b/arch/riscv/kernel/sys_hwprobe.c
@@ -69,7 +69,7 @@ static void hwprobe_isa_ext0(struct riscv_hwprobe *pair,
 	if (riscv_isa_extension_available(NULL, c))
 		pair->value |= RISCV_HWPROBE_IMA_C;
 
-	if (has_vector())
+	if (has_vector() && riscv_isa_extension_available(NULL, v))
 		pair->value |= RISCV_HWPROBE_IMA_V;
 
 	/*
@@ -113,6 +113,10 @@ static void hwprobe_isa_ext0(struct riscv_hwprobe *pair,
 		EXT_KEY(ZICOND);
 		EXT_KEY(ZIHINTPAUSE);
 
+		/*
+		 * All the following extensions must depend on the kernel
+		 * support of V.
+		 */
 		if (has_vector()) {
 			EXT_KEY(ZVE32X);
 			EXT_KEY(ZVE32F);
diff --git a/arch/riscv/kernel/vector.c b/arch/riscv/kernel/vector.c
index 6727d1d3b8f2..682b3feee451 100644
--- a/arch/riscv/kernel/vector.c
+++ b/arch/riscv/kernel/vector.c
@@ -173,8 +173,11 @@ bool riscv_v_first_use_handler(struct pt_regs *regs)
 	u32 __user *epc = (u32 __user *)regs->epc;
 	u32 insn = (u32)regs->badaddr;
 
+	if (!has_vector())
+		return false;
+
 	/* Do not handle if V is not supported, or disabled */
-	if (!(ELF_HWCAP & COMPAT_HWCAP_ISA_V))
+	if (!riscv_v_vstate_ctrl_user_allowed())
 		return false;
 
 	/* If V has been enabled then it is not the first-use trap */
diff --git a/arch/riscv/lib/uaccess.S b/arch/riscv/lib/uaccess.S
index bc22c078aba8..bbe143bb32a0 100644
--- a/arch/riscv/lib/uaccess.S
+++ b/arch/riscv/lib/uaccess.S
@@ -14,7 +14,7 @@
 
 SYM_FUNC_START(__asm_copy_to_user)
 #ifdef CONFIG_RISCV_ISA_V
-	ALTERNATIVE("j fallback_scalar_usercopy", "nop", 0, RISCV_ISA_EXT_v, CONFIG_RISCV_ISA_V)
+	ALTERNATIVE("j fallback_scalar_usercopy", "nop", 0, RISCV_ISA_EXT_ZVE32X, CONFIG_RISCV_ISA_V)
 	REG_L	t0, riscv_v_usercopy_threshold
 	bltu	a2, t0, fallback_scalar_usercopy
 	tail enter_vector_usercopy

-- 
2.44.0.rc2