[PATCH v5 09/13] riscv: misaligned: add a function to check misalign trap delegability

[Clément Léger]

Checking for the delegability of the misaligned access trap is needed
for the KVM FWFT extension implementation. Add a function to get the
delegability of the misaligned trap exception.

Signed-off-by: Clément Léger <cleger at rivosinc.com>
Reviewed-by: Andrew Jones <ajones at ventanamicro.com>
---
 arch/riscv/include/asm/cpufeature.h  |  5 +++++
 arch/riscv/kernel/traps_misaligned.c | 17 +++++++++++++++--
 2 files changed, 20 insertions(+), 2 deletions(-)

diff --git a/arch/riscv/include/asm/cpufeature.h b/arch/riscv/include/asm/cpufeature.h
index dbe5970d4fe6..3a87f612035c 100644
--- a/arch/riscv/include/asm/cpufeature.h
+++ b/arch/riscv/include/asm/cpufeature.h
@@ -72,12 +72,17 @@ int cpu_online_unaligned_access_init(unsigned int cpu);
 #if defined(CONFIG_RISCV_SCALAR_MISALIGNED)
 void unaligned_emulation_finish(void);
 bool unaligned_ctl_available(void);
+bool misaligned_traps_can_delegate(void);
 DECLARE_PER_CPU(long, misaligned_access_speed);
 #else
 static inline bool unaligned_ctl_available(void)
 {
 	return false;
 }
+static inline bool misaligned_traps_can_delegate(void)
+{
+	return false;
+}
 #endif
 
 bool __init check_vector_unaligned_access_emulated_all_cpus(void);
diff --git a/arch/riscv/kernel/traps_misaligned.c b/arch/riscv/kernel/traps_misaligned.c
index a0007552e7a5..7ff1e21f619e 100644
--- a/arch/riscv/kernel/traps_misaligned.c
+++ b/arch/riscv/kernel/traps_misaligned.c
@@ -709,10 +709,10 @@ static int cpu_online_check_unaligned_access_emulated(unsigned int cpu)
 }
 #endif
 
-#ifdef CONFIG_RISCV_SBI
-
 static bool misaligned_traps_delegated;
 
+#ifdef CONFIG_RISCV_SBI
+
 static int cpu_online_sbi_unaligned_setup(unsigned int cpu)
 {
 	if (sbi_fwft_set(SBI_FWFT_MISALIGNED_EXC_DELEG, 1, 0) &&
@@ -748,6 +748,7 @@ static int cpu_online_sbi_unaligned_setup(unsigned int cpu __always_unused)
 {
 	return 0;
 }
+
 #endif
 
 int cpu_online_unaligned_access_init(unsigned int cpu)
@@ -760,3 +761,15 @@ int cpu_online_unaligned_access_init(unsigned int cpu)
 
 	return cpu_online_check_unaligned_access_emulated(cpu);
 }
+
+bool misaligned_traps_can_delegate(void)
+{
+	/*
+	 * Either we successfully requested misaligned traps delegation for all
+	 * CPUS or the SBI does not implemented FWFT extension but delegated the
+	 * exception by default.
+	 */
+	return misaligned_traps_delegated ||
+	       all_cpus_unaligned_scalar_access_emulated();
+}
+EXPORT_SYMBOL_GPL(misaligned_traps_can_delegate);
-- 
2.49.0