[PATCH v9 1/6] RISC-V: Check scalar unaligned access on all CPUs

Jesse Taube
2024-08-20T15:27:40Z

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@rivosinc.com>
Reviewed-by: Charlie Jenkins <charlie@rivosinc.com>
Reviewed-by: Evan Green <evan@rivosinc.com>
Cc: stable@vger.kernel.org
---
V1 -> V2:
- New patch
V2 -> V3:
- Split patch
V3 -> V4:
- Re-add check for a system where a heterogeneous
CPU is hotplugged into a previously homogenous
system.
V4 -> V5:
- Change work_struct *unused to work_struct *work __always_unused
V5 -> V6:
- Change check_unaligned_access_emulated to extern
V6 -> V7:
- No changes
V7 -> V8:
- Rebase onto fixes
V8 -> V9:
- No changes
---
arch/riscv/include/asm/cpufeature.h | 2 ++
arch/riscv/kernel/traps_misaligned.c | 14 +++++++-------
2 files changed, 9 insertions(+), 7 deletions(-)

diff --git a/arch/riscv/include/asm/cpufeature.h b/arch/riscv/include/asm/cpufeature.h
index 45f9c1171a48..dfa5cdddd367 100644
--- 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);
diff --git a/arch/riscv/kernel/traps_misaligned.c b/arch/riscv/kernel/traps_misaligned.c
index 192cd5603e95..1ad981b2c7a3 100644
--- a/arch/riscv/kernel/traps_misaligned.c
+++ b/arch/riscv/kernel/traps_misaligned.c
@@ -526,11 +526,11 @@ int handle_misaligned_store(struct pt_regs *regs)
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;

@@ -538,19 +538,16 @@ static bool check_unaligned_access_emulated(int cpu)
" "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)
@@ -562,8 +559,11 @@ bool check_unaligned_access_emulated_all_cpus(void)
* 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;