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[PW_SID:1102480] riscv: Some misaligned cleanups #2031

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[PW_SID:1102480] riscv: Some misaligned cleanups #2031

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29166d0
riscv: misaligned: Fix fast_unaligned_access_speed_key init
covanam May 28, 2026
3f33145
riscv: traps_misaligned: Avoid redundant unaligned access speed probe
covanam May 28, 2026
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4 changes: 2 additions & 2 deletions arch/riscv/kernel/traps_misaligned.c
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Original file line number Diff line number Diff line change
Expand Up @@ -522,10 +522,10 @@ static bool unaligned_ctl __read_mostly;
static void check_unaligned_access_emulated(void *arg __always_unused)
{
int cpu = smp_processor_id();
long *mas_ptr = per_cpu_ptr(&misaligned_access_speed, cpu);
unsigned long tmp_var, tmp_val;

*mas_ptr = RISCV_HWPROBE_MISALIGNED_SCALAR_UNKNOWN;
if (per_cpu(misaligned_access_speed, cpu) != RISCV_HWPROBE_MISALIGNED_SCALAR_UNKNOWN)
return;

__asm__ __volatile__ (
" "REG_L" %[tmp], 1(%[ptr])\n"
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69 changes: 22 additions & 47 deletions arch/riscv/kernel/unaligned_access_speed.c
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Original file line number Diff line number Diff line change
Expand Up @@ -27,8 +27,6 @@ DEFINE_PER_CPU(long, vector_misaligned_access) = RISCV_HWPROBE_MISALIGNED_VECTOR
static long unaligned_scalar_speed_param = RISCV_HWPROBE_MISALIGNED_SCALAR_UNKNOWN;
static long unaligned_vector_speed_param = RISCV_HWPROBE_MISALIGNED_VECTOR_UNKNOWN;

static cpumask_t fast_misaligned_access;

static u64 __maybe_unused
measure_cycles(void (*func)(void *dst, const void *src, size_t len),
void *dst, void *src, size_t len)
Expand Down Expand Up @@ -131,13 +129,10 @@ static int check_unaligned_access(struct page *page)
* Set the value of fast_misaligned_access of a CPU. These operations
* are atomic to avoid race conditions.
*/
if (ret) {
if (ret)
per_cpu(misaligned_access_speed, cpu) = RISCV_HWPROBE_MISALIGNED_SCALAR_FAST;
cpumask_set_cpu(cpu, &fast_misaligned_access);
} else {
else
per_cpu(misaligned_access_speed, cpu) = RISCV_HWPROBE_MISALIGNED_SCALAR_SLOW;
cpumask_clear_cpu(cpu, &fast_misaligned_access);
}

return 0;
}
Expand Down Expand Up @@ -192,49 +187,24 @@ static void __init check_unaligned_access_speed_all_cpus(void)

DEFINE_STATIC_KEY_FALSE(fast_unaligned_access_speed_key);

static void modify_unaligned_access_branches(cpumask_t *mask, int weight)
static void modify_unaligned_access_branches(const cpumask_t *mask)
{
if (cpumask_weight(mask) == weight)
bool fast = true;
int cpu;

for_each_cpu(cpu, mask) {
if (per_cpu(misaligned_access_speed, cpu) != RISCV_HWPROBE_MISALIGNED_SCALAR_FAST) {
fast = false;
break;
}
}

if (fast)
static_branch_enable_cpuslocked(&fast_unaligned_access_speed_key);
else
static_branch_disable_cpuslocked(&fast_unaligned_access_speed_key);
}

static void set_unaligned_access_static_branches_except_cpu(int cpu)
{
/*
* Same as set_unaligned_access_static_branches, except excludes the
* given CPU from the result. When a CPU is hotplugged into an offline
* state, this function is called before the CPU is set to offline in
* the cpumask, and thus the CPU needs to be explicitly excluded.
*/

cpumask_t fast_except_me;

cpumask_and(&fast_except_me, &fast_misaligned_access, cpu_online_mask);
cpumask_clear_cpu(cpu, &fast_except_me);

modify_unaligned_access_branches(&fast_except_me, num_online_cpus() - 1);
}

static void set_unaligned_access_static_branches(void)
{
/*
* This will be called after check_unaligned_access_all_cpus so the
* result of unaligned access speed for all CPUs will be available.
*
* To avoid the number of online cpus changing between reading
* cpu_online_mask and calling num_online_cpus, cpus_read_lock must be
* held before calling this function.
*/

cpumask_t fast_and_online;

cpumask_and(&fast_and_online, &fast_misaligned_access, cpu_online_mask);

modify_unaligned_access_branches(&fast_and_online, num_online_cpus());
}

static int riscv_online_cpu(unsigned int cpu)
{
int ret = cpu_online_unaligned_access_init(cpu);
Expand Down Expand Up @@ -266,14 +236,19 @@ static int riscv_online_cpu(unsigned int cpu)
#endif

exit:
set_unaligned_access_static_branches();
modify_unaligned_access_branches(cpu_online_mask);

return 0;
}

static int riscv_offline_cpu(unsigned int cpu)
{
set_unaligned_access_static_branches_except_cpu(cpu);
cpumask_t mask;

cpumask_copy(&mask, cpu_online_mask);
cpumask_clear_cpu(cpu, &mask);

modify_unaligned_access_branches(&mask);

return 0;
}
Expand Down Expand Up @@ -430,7 +405,7 @@ static int __init check_unaligned_access_all_cpus(void)
riscv_online_cpu_vec, NULL);

cpus_read_lock();
set_unaligned_access_static_branches();
modify_unaligned_access_branches(cpu_online_mask);
cpus_read_unlock();

return 0;
Expand Down