On 7/10/24 11:55, Evan Green wrote:

On Mon, Jun 24, 2024 at 5:51 PM Jesse Taube jesse@rivosinc.com wrote:

...

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 Cc: stable@vger.kernel.org

---

V1 -> V2:

• New patch

V2 -> V3:

• Split patch

---

arch/riscv/kernel/traps_misaligned.c | 23 ++++++----------------- 1 file changed, 6 insertions(+), 17 deletions(-)

diff --git a/arch/riscv/kernel/traps_misaligned.c b/arch/riscv/kernel/traps_misaligned.c index b62d5a2f4541..8fadbe00dd62 100644 --- a/arch/riscv/kernel/traps_misaligned.c +++ b/arch/riscv/kernel/traps_misaligned.c @@ -526,31 +526,17 @@ int handle_misaligned_store(struct pt_regs *regs) return 0; }

-static bool check_unaligned_access_emulated(int cpu) +static void check_unaligned_access_emulated(struct work_struct *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_UNKNOWN;
  
     __asm__ __volatile__ (
             "       "REG_L" %[tmp], 1(%[ptr])\n"
             : [tmp] "=r" (tmp_val) : [ptr] "r" (&tmp_var) : "memory");
  

•   misaligned_emu_detected = (*mas_ptr == RISCV_HWPROBE_MISALIGNED_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)) {
  

•           pr_crit("CPU misaligned accesses non homogeneous (expected all emulated)\n");
  

•           while (true)
  

•                   cpu_relax();
  

•   }
  

This chunk was meant to detect and refuse to run on a system where a heterogeneous CPU is hotplugged into a previously homogenous system. The commit message doesn't mention this change, how come you deleted it?

Sorry for the long wait. I do not remember why I removed this. Your right it shouldn't be removed, I added it back.

Thanks, Jesse Taube

...

•   return misaligned_emu_detected;
  

  }

  bool check_unaligned_access_emulated_all_cpus(void)

@@ -562,8 +548,11 @@ 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_EMULATED)
                     return false;
  
     unaligned_ctl = true;
  

-- 2.45.2