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[PATCH v3 3/8] RISC-V: Check scalar unaligned access on all CPUs

Jesse Taube posted 8 patches 1 year, 7 months ago
There is a newer version of this series
[PATCH v3 3/8] RISC-V: Check scalar unaligned access on all CPUs
Posted by Jesse Taube 1 year, 7 months ago 
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();
-	}
-
-	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
Re: [PATCH v3 3/8] RISC-V: Check scalar unaligned access on all CPUs
Posted by Evan Green 1 year, 7 months ago 
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?


> -
> -       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
>
Re: [PATCH v3 3/8] RISC-V: Check scalar unaligned access on all CPUs
Posted by Jesse Taube 1 year, 7 months ago 

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
>>

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