[RFC PATCH v0] RISCV: Report vector unaligned accesses hwprobe

[Jesse Taube <jesse@rivosinc.com>]

Detected if a system traps into the kernel on an vector unaligned access.
Add the result to a new key in hwprobe.

Signed-off-by: Jesse Taube <jesse@rivosinc.com>
---
 arch/riscv/include/asm/cpufeature.h        |  3 ++
 arch/riscv/include/asm/hwprobe.h           |  2 +-
 arch/riscv/include/uapi/asm/hwprobe.h      |  6 +++
 arch/riscv/kernel/sys_hwprobe.c            | 34 ++++++++++++
 arch/riscv/kernel/traps_misaligned.c       | 60 ++++++++++++++++++++++
 arch/riscv/kernel/unaligned_access_speed.c |  4 ++
 6 files changed, 108 insertions(+), 1 deletion(-)

diff --git a/arch/riscv/include/asm/cpufeature.h b/arch/riscv/include/asm/cpufeature.h
index 347805446151..5ad69cf25b25 100644
--- a/arch/riscv/include/asm/cpufeature.h
+++ b/arch/riscv/include/asm/cpufeature.h
@@ -35,9 +35,12 @@ void riscv_user_isa_enable(void);
 
 #if defined(CONFIG_RISCV_MISALIGNED)
 bool check_unaligned_access_emulated_all_cpus(void);
+bool check_vector_unaligned_access_all_cpus(void);
+
 void unaligned_emulation_finish(void);
 bool unaligned_ctl_available(void);
 DECLARE_PER_CPU(long, misaligned_access_speed);
+DECLARE_PER_CPU(long, vector_misaligned_access);
 #else
 static inline bool unaligned_ctl_available(void)
 {
diff --git a/arch/riscv/include/asm/hwprobe.h b/arch/riscv/include/asm/hwprobe.h
index 630507dff5ea..150a9877b0af 100644
--- a/arch/riscv/include/asm/hwprobe.h
+++ b/arch/riscv/include/asm/hwprobe.h
@@ -8,7 +8,7 @@
 
 #include <uapi/asm/hwprobe.h>
 
-#define RISCV_HWPROBE_MAX_KEY 6
+#define RISCV_HWPROBE_MAX_KEY 7
 
 static inline bool riscv_hwprobe_key_is_valid(__s64 key)
 {
diff --git a/arch/riscv/include/uapi/asm/hwprobe.h b/arch/riscv/include/uapi/asm/hwprobe.h
index 060212331a03..4474e98d17bd 100644
--- a/arch/riscv/include/uapi/asm/hwprobe.h
+++ b/arch/riscv/include/uapi/asm/hwprobe.h
@@ -68,6 +68,12 @@ struct riscv_hwprobe {
 #define		RISCV_HWPROBE_MISALIGNED_UNSUPPORTED	(4 << 0)
 #define		RISCV_HWPROBE_MISALIGNED_MASK		(7 << 0)
 #define RISCV_HWPROBE_KEY_ZICBOZ_BLOCK_SIZE	6
+#define RISCV_HWPROBE_VEC_KEY_MISALIGNED_PERF	7
+#define		RISCV_HWPROBE_VEC_MISALIGNED_UNKNOWN		0
+#define		RISCV_HWPROBE_VEC_MISALIGNED_EMULATED		1
+#define		RISCV_HWPROBE_VEC_MISALIGNED_SLOW		2
+#define		RISCV_HWPROBE_VEC_MISALIGNED_FAST		3
+#define		RISCV_HWPROBE_VEC_MISALIGNED_UNSUPPORTED	4
 /* Increase RISCV_HWPROBE_MAX_KEY when adding items. */
 
 /* Flags */
diff --git a/arch/riscv/kernel/sys_hwprobe.c b/arch/riscv/kernel/sys_hwprobe.c
index b286b73e763e..ce641cc6e47a 100644
--- a/arch/riscv/kernel/sys_hwprobe.c
+++ b/arch/riscv/kernel/sys_hwprobe.c
@@ -184,6 +184,36 @@ static u64 hwprobe_misaligned(const struct cpumask *cpus)
 }
 #endif
 
+#if defined(CONFIG_RISCV_PROBE_UNALIGNED_ACCESS)
+static u64 hwprobe_vec_misaligned(const struct cpumask *cpus)
+{
+	int cpu;
+	u64 perf = -1ULL;
+
+	for_each_cpu(cpu, cpus) {
+		int this_perf = per_cpu(vector_misaligned_access, cpu);
+
+		if (perf == -1ULL)
+			perf = this_perf;
+
+		if (perf != this_perf) {
+			perf = RISCV_HWPROBE_VEC_MISALIGNED_UNKNOWN;
+			break;
+		}
+	}
+
+	if (perf == -1ULL)
+		return RISCV_HWPROBE_VEC_MISALIGNED_UNKNOWN;
+
+	return perf;
+}
+#else
+static u64 hwprobe_vec_misaligned(const struct cpumask *cpus)
+{
+	return RISCV_HWPROBE_VEC_MISALIGNED_UNKNOWN;
+}
+#endif
+
 static void hwprobe_one_pair(struct riscv_hwprobe *pair,
 			     const struct cpumask *cpus)
 {
@@ -211,6 +241,10 @@ static void hwprobe_one_pair(struct riscv_hwprobe *pair,
 		pair->value = hwprobe_misaligned(cpus);
 		break;
 
+	case RISCV_HWPROBE_VEC_KEY_MISALIGNED_PERF:
+		pair->value = hwprobe_vec_misaligned(cpus);
+		break;
+
 	case RISCV_HWPROBE_KEY_ZICBOZ_BLOCK_SIZE:
 		pair->value = 0;
 		if (hwprobe_ext0_has(cpus, RISCV_HWPROBE_EXT_ZICBOZ))
diff --git a/arch/riscv/kernel/traps_misaligned.c b/arch/riscv/kernel/traps_misaligned.c
index 2adb7c3e4dd5..0c07e990e9c5 100644
--- a/arch/riscv/kernel/traps_misaligned.c
+++ b/arch/riscv/kernel/traps_misaligned.c
@@ -16,6 +16,7 @@
 #include <asm/entry-common.h>
 #include <asm/hwprobe.h>
 #include <asm/cpufeature.h>
+#include <asm/vector.h>
 
 #define INSN_MATCH_LB			0x3
 #define INSN_MASK_LB			0x707f
@@ -426,6 +427,14 @@ int handle_misaligned_load(struct pt_regs *regs)
 	if (get_insn(regs, epc, &insn))
 		return -1;
 
+#ifdef CONFIG_RISCV_PROBE_UNALIGNED_ACCESS
+	if (*this_cpu_ptr(&vector_misaligned_access) == RISCV_HWPROBE_VEC_MISALIGNED_UNKNOWN) {
+		*this_cpu_ptr(&vector_misaligned_access) = RISCV_HWPROBE_VEC_MISALIGNED_UNSUPPORTED;
+		regs->epc = epc + INSN_LEN(insn);
+		return 0;
+	}
+#endif
+
 	regs->epc = 0;
 
 	if ((insn & INSN_MASK_LW) == INSN_MATCH_LW) {
@@ -625,6 +634,57 @@ static bool check_unaligned_access_emulated(int cpu)
 	return misaligned_emu_detected;
 }
 
+#ifdef CONFIG_RISCV_ISA_V
+static bool check_vector_unaligned_access(int cpu)
+{
+	long *mas_ptr = per_cpu_ptr(&vector_misaligned_access, cpu);
+	struct riscv_isainfo *isainfo = &hart_isa[cpu];
+	unsigned long tmp_var;
+	bool misaligned_vec_suported;
+
+	if (!riscv_isa_extension_available(isainfo->isa, v))
+		return false;
+
+	/* This case will only happen if a unaligned vector load
+	 * was called by the kernel before this check
+	 */
+	if (*mas_ptr != RISCV_HWPROBE_VEC_MISALIGNED_UNKNOWN)
+		return false;
+
+	kernel_vector_begin();
+	__asm__ __volatile__ (
+		".option push\n\t"
+		".option arch, +v\n\t"
+		"	li t1, 0x1\n"				//size
+		"       vsetvli t0, t1, e16, m2, ta, ma\n\t"	// Vectors of 16b
+		"       addi t0, %[ptr], 1\n\t"			// Misalign address
+		"	vle16.v v0, (t0)\n\t"			// Load bytes
+		".option pop\n\t"
+		: : [ptr] "r" (&tmp_var) : "v0", "t0", "t1", "memory");
+	kernel_vector_end();
+
+	misaligned_vec_suported = (*mas_ptr == RISCV_HWPROBE_VEC_MISALIGNED_UNKNOWN);
+
+	return misaligned_vec_suported;
+}
+#else
+static bool check_vector_unaligned_access(int cpu)
+{
+	return false;
+}
+#endif
+
+bool check_vector_unaligned_access_all_cpus(void)
+{
+	int cpu;
+
+	for_each_online_cpu(cpu)
+		if (!check_vector_unaligned_access(cpu))
+			return false;
+
+	return true;
+}
+
 bool check_unaligned_access_emulated_all_cpus(void)
 {
 	int cpu;
diff --git a/arch/riscv/kernel/unaligned_access_speed.c b/arch/riscv/kernel/unaligned_access_speed.c
index a9a6bcb02acf..92a84239beaa 100644
--- a/arch/riscv/kernel/unaligned_access_speed.c
+++ b/arch/riscv/kernel/unaligned_access_speed.c
@@ -20,6 +20,7 @@
 #define MISALIGNED_COPY_SIZE ((MISALIGNED_BUFFER_SIZE / 2) - 0x80)
 
 DEFINE_PER_CPU(long, misaligned_access_speed);
+DEFINE_PER_CPU(long, vector_misaligned_access) = RISCV_HWPROBE_VEC_MISALIGNED_UNKNOWN;
 
 #ifdef CONFIG_RISCV_PROBE_UNALIGNED_ACCESS
 static cpumask_t fast_misaligned_access;
@@ -264,6 +265,8 @@ static int check_unaligned_access_all_cpus(void)
 {
 	bool all_cpus_emulated = check_unaligned_access_emulated_all_cpus();
 
+	check_vector_unaligned_access_all_cpus();
+
 	if (!all_cpus_emulated)
 		return check_unaligned_access_speed_all_cpus();
 
@@ -273,6 +276,7 @@ static int check_unaligned_access_all_cpus(void)
 static int check_unaligned_access_all_cpus(void)
 {
 	check_unaligned_access_emulated_all_cpus();
+	check_vector_unaligned_access_all_cpus();
 
 	return 0;
 }
-- 
2.43.0