[PATCH 6.11 704/817] RISC-V: Check scalar unaligned access on all CPUs

[Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>]

6.11-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Jesse Taube <jesse@xxxxxxxxxxxx>

commit 8d20a739f17a2de9e269db72330f5655d6545dd4 upstream.

Originally, the check_unaligned_access_emulated_all_cpus function
only checked the boot hart. This fixes the function to check all
harts.

Fixes: 71c54b3d169d ("riscv: report misaligned accesses emulation to hwprobe")
Signed-off-by: Jesse Taube <jesse@xxxxxxxxxxxx>
Reviewed-by: Charlie Jenkins <charlie@xxxxxxxxxxxx>
Reviewed-by: Evan Green <evan@xxxxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Link: https://lore.kernel.org/r/20241017-jesse_unaligned_vector-v10-1-5b33500160f8@xxxxxxxxxxxx
Signed-off-by: Palmer Dabbelt <palmer@xxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 arch/riscv/include/asm/cpufeature.h  |    2 ++
 arch/riscv/kernel/traps_misaligned.c |   14 +++++++-------
 2 files changed, 9 insertions(+), 7 deletions(-)

--- a/arch/riscv/include/asm/cpufeature.h
+++ b/arch/riscv/include/asm/cpufeature.h
@@ -8,6 +8,7 @@
 
 #include <linux/bitmap.h>
 #include <linux/jump_label.h>
+#include <linux/workqueue.h>
 #include <asm/hwcap.h>
 #include <asm/alternative-macros.h>
 #include <asm/errno.h>
@@ -60,6 +61,7 @@ void riscv_user_isa_enable(void);
 
 #if defined(CONFIG_RISCV_MISALIGNED)
 bool check_unaligned_access_emulated_all_cpus(void);
+void check_unaligned_access_emulated(struct work_struct *work __always_unused);
 void unaligned_emulation_finish(void);
 bool unaligned_ctl_available(void);
 DECLARE_PER_CPU(long, misaligned_access_speed);
--- a/arch/riscv/kernel/traps_misaligned.c
+++ b/arch/riscv/kernel/traps_misaligned.c
@@ -524,11 +524,11 @@ int handle_misaligned_store(struct pt_re
 	return 0;
 }
 
-static bool check_unaligned_access_emulated(int cpu)
+void check_unaligned_access_emulated(struct work_struct *work __always_unused)
 {
+	int cpu = smp_processor_id();
 	long *mas_ptr = per_cpu_ptr(&misaligned_access_speed, cpu);
 	unsigned long tmp_var, tmp_val;
-	bool misaligned_emu_detected;
 
 	*mas_ptr = RISCV_HWPROBE_MISALIGNED_SCALAR_UNKNOWN;
 
@@ -536,19 +536,16 @@ static bool check_unaligned_access_emula
 		"       "REG_L" %[tmp], 1(%[ptr])\n"
 		: [tmp] "=r" (tmp_val) : [ptr] "r" (&tmp_var) : "memory");
 
-	misaligned_emu_detected = (*mas_ptr == RISCV_HWPROBE_MISALIGNED_SCALAR_EMULATED);
 	/*
 	 * If unaligned_ctl is already set, this means that we detected that all
 	 * CPUS uses emulated misaligned access at boot time. If that changed
 	 * when hotplugging the new cpu, this is something we don't handle.
 	 */
-	if (unlikely(unaligned_ctl && !misaligned_emu_detected)) {
+	if (unlikely(unaligned_ctl && (*mas_ptr != RISCV_HWPROBE_MISALIGNED_SCALAR_EMULATED))) {
 		pr_crit("CPU misaligned accesses non homogeneous (expected all emulated)\n");
 		while (true)
 			cpu_relax();
 	}
-
-	return misaligned_emu_detected;
 }
 
 bool check_unaligned_access_emulated_all_cpus(void)
@@ -560,8 +557,11 @@ bool check_unaligned_access_emulated_all
 	 * accesses emulated since tasks requesting such control can run on any
 	 * CPU.
 	 */
+	schedule_on_each_cpu(check_unaligned_access_emulated);
+
 	for_each_online_cpu(cpu)
-		if (!check_unaligned_access_emulated(cpu))
+		if (per_cpu(misaligned_access_speed, cpu)
+		    != RISCV_HWPROBE_MISALIGNED_SCALAR_EMULATED)
 			return false;
 
 	unaligned_ctl = true;