[v3] riscv: cbo.zero fixes

[PATCH -fixes v3 1/2] riscv: Fix enabling cbo.zero when running in M-mode

Posted by Samuel Holland 1 year, 12 months ago

When the kernel is running in M-mode, the CBZE bit must be set in the
menvcfg CSR, not in senvcfg.

Cc: <stable@vger.kernel.org>
Fixes: 43c16d51a19b ("RISC-V: Enable cbo.zero in usermode")
Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
Signed-off-by: Samuel Holland <samuel.holland@sifive.com>
---

(no changes since v1)

 arch/riscv/include/asm/csr.h   | 2 ++
 arch/riscv/kernel/cpufeature.c | 2 +-
 2 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/arch/riscv/include/asm/csr.h b/arch/riscv/include/asm/csr.h
index 510014051f5d..2468c55933cd 100644
--- a/arch/riscv/include/asm/csr.h
+++ b/arch/riscv/include/asm/csr.h
@@ -424,6 +424,7 @@
 # define CSR_STATUS	CSR_MSTATUS
 # define CSR_IE		CSR_MIE
 # define CSR_TVEC	CSR_MTVEC
+# define CSR_ENVCFG	CSR_MENVCFG
 # define CSR_SCRATCH	CSR_MSCRATCH
 # define CSR_EPC	CSR_MEPC
 # define CSR_CAUSE	CSR_MCAUSE
@@ -448,6 +449,7 @@
 # define CSR_STATUS	CSR_SSTATUS
 # define CSR_IE		CSR_SIE
 # define CSR_TVEC	CSR_STVEC
+# define CSR_ENVCFG	CSR_SENVCFG
 # define CSR_SCRATCH	CSR_SSCRATCH
 # define CSR_EPC	CSR_SEPC
 # define CSR_CAUSE	CSR_SCAUSE
diff --git a/arch/riscv/kernel/cpufeature.c b/arch/riscv/kernel/cpufeature.c
index 89920f84d0a3..c5b13f7dd482 100644
--- a/arch/riscv/kernel/cpufeature.c
+++ b/arch/riscv/kernel/cpufeature.c
@@ -950,7 +950,7 @@ arch_initcall(check_unaligned_access_all_cpus);
 void riscv_user_isa_enable(void)
 {
 	if (riscv_cpu_has_extension_unlikely(smp_processor_id(), RISCV_ISA_EXT_ZICBOZ))
-		csr_set(CSR_SENVCFG, ENVCFG_CBZE);
+		csr_set(CSR_ENVCFG, ENVCFG_CBZE);
 }
 
 #ifdef CONFIG_RISCV_ALTERNATIVE
-- 
2.43.0

Re: [PATCH -fixes v3 1/2] riscv: Fix enabling cbo.zero when running in M-mode

Posted by Andrew Jones 1 year, 12 months ago

On Wed, Feb 14, 2024 at 01:01:56AM -0800, Samuel Holland wrote:
> When the kernel is running in M-mode, the CBZE bit must be set in the
> menvcfg CSR, not in senvcfg.
> 
> Cc: <stable@vger.kernel.org>
> Fixes: 43c16d51a19b ("RISC-V: Enable cbo.zero in usermode")
> Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
> Signed-off-by: Samuel Holland <samuel.holland@sifive.com>
> ---
> 
> (no changes since v1)
> 
>  arch/riscv/include/asm/csr.h   | 2 ++
>  arch/riscv/kernel/cpufeature.c | 2 +-
>  2 files changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/riscv/include/asm/csr.h b/arch/riscv/include/asm/csr.h
> index 510014051f5d..2468c55933cd 100644
> --- a/arch/riscv/include/asm/csr.h
> +++ b/arch/riscv/include/asm/csr.h
> @@ -424,6 +424,7 @@
>  # define CSR_STATUS	CSR_MSTATUS
>  # define CSR_IE		CSR_MIE
>  # define CSR_TVEC	CSR_MTVEC
> +# define CSR_ENVCFG	CSR_MENVCFG
>  # define CSR_SCRATCH	CSR_MSCRATCH
>  # define CSR_EPC	CSR_MEPC
>  # define CSR_CAUSE	CSR_MCAUSE
> @@ -448,6 +449,7 @@
>  # define CSR_STATUS	CSR_SSTATUS
>  # define CSR_IE		CSR_SIE
>  # define CSR_TVEC	CSR_STVEC
> +# define CSR_ENVCFG	CSR_SENVCFG
>  # define CSR_SCRATCH	CSR_SSCRATCH
>  # define CSR_EPC	CSR_SEPC
>  # define CSR_CAUSE	CSR_SCAUSE
> diff --git a/arch/riscv/kernel/cpufeature.c b/arch/riscv/kernel/cpufeature.c
> index 89920f84d0a3..c5b13f7dd482 100644
> --- a/arch/riscv/kernel/cpufeature.c
> +++ b/arch/riscv/kernel/cpufeature.c
> @@ -950,7 +950,7 @@ arch_initcall(check_unaligned_access_all_cpus);
>  void riscv_user_isa_enable(void)
>  {
>  	if (riscv_cpu_has_extension_unlikely(smp_processor_id(), RISCV_ISA_EXT_ZICBOZ))
> -		csr_set(CSR_SENVCFG, ENVCFG_CBZE);
> +		csr_set(CSR_ENVCFG, ENVCFG_CBZE);
>  }
>  
>  #ifdef CONFIG_RISCV_ALTERNATIVE
> -- 
> 2.43.0
>

After our back and forth on how we determine the existence of the *envcfg
CSRs, I wonder if we shouldn't put a comment above this
riscv_user_isa_enable() function capturing the [current] decision.

Something like

 /*
  * While the [ms]envcfg CSRs weren't defined until priv spec 1.12,
  * they're assumed to be present when an extension is present which
  * specifies [ms]envcfg bit(s). Hence, we don't do any additional
  * priv spec version checks or CSR probes here.
  */

Thanks,
drew

Re: [PATCH -fixes v3 1/2] riscv: Fix enabling cbo.zero when running in M-mode

Posted by Alexandre Ghiti 1 year, 11 months ago

Hi Samuel,

On 14/02/2024 10:28, Andrew Jones wrote:
> On Wed, Feb 14, 2024 at 01:01:56AM -0800, Samuel Holland wrote:
>> When the kernel is running in M-mode, the CBZE bit must be set in the
>> menvcfg CSR, not in senvcfg.
>>
>> Cc: <stable@vger.kernel.org>
>> Fixes: 43c16d51a19b ("RISC-V: Enable cbo.zero in usermode")
>> Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
>> Signed-off-by: Samuel Holland <samuel.holland@sifive.com>
>> ---
>>
>> (no changes since v1)
>>
>>   arch/riscv/include/asm/csr.h   | 2 ++
>>   arch/riscv/kernel/cpufeature.c | 2 +-
>>   2 files changed, 3 insertions(+), 1 deletion(-)
>>
>> diff --git a/arch/riscv/include/asm/csr.h b/arch/riscv/include/asm/csr.h
>> index 510014051f5d..2468c55933cd 100644
>> --- a/arch/riscv/include/asm/csr.h
>> +++ b/arch/riscv/include/asm/csr.h
>> @@ -424,6 +424,7 @@
>>   # define CSR_STATUS	CSR_MSTATUS
>>   # define CSR_IE		CSR_MIE
>>   # define CSR_TVEC	CSR_MTVEC
>> +# define CSR_ENVCFG	CSR_MENVCFG
>>   # define CSR_SCRATCH	CSR_MSCRATCH
>>   # define CSR_EPC	CSR_MEPC
>>   # define CSR_CAUSE	CSR_MCAUSE
>> @@ -448,6 +449,7 @@
>>   # define CSR_STATUS	CSR_SSTATUS
>>   # define CSR_IE		CSR_SIE
>>   # define CSR_TVEC	CSR_STVEC
>> +# define CSR_ENVCFG	CSR_SENVCFG
>>   # define CSR_SCRATCH	CSR_SSCRATCH
>>   # define CSR_EPC	CSR_SEPC
>>   # define CSR_CAUSE	CSR_SCAUSE
>> diff --git a/arch/riscv/kernel/cpufeature.c b/arch/riscv/kernel/cpufeature.c
>> index 89920f84d0a3..c5b13f7dd482 100644
>> --- a/arch/riscv/kernel/cpufeature.c
>> +++ b/arch/riscv/kernel/cpufeature.c
>> @@ -950,7 +950,7 @@ arch_initcall(check_unaligned_access_all_cpus);
>>   void riscv_user_isa_enable(void)
>>   {
>>   	if (riscv_cpu_has_extension_unlikely(smp_processor_id(), RISCV_ISA_EXT_ZICBOZ))
>> -		csr_set(CSR_SENVCFG, ENVCFG_CBZE);
>> +		csr_set(CSR_ENVCFG, ENVCFG_CBZE);
>>   }
>>   
>>   #ifdef CONFIG_RISCV_ALTERNATIVE
>> -- 
>> 2.43.0
>>
> After our back and forth on how we determine the existence of the *envcfg
> CSRs, I wonder if we shouldn't put a comment above this
> riscv_user_isa_enable() function capturing the [current] decision.
>
> Something like
>
>   /*
>    * While the [ms]envcfg CSRs weren't defined until priv spec 1.12,
>    * they're assumed to be present when an extension is present which
>    * specifies [ms]envcfg bit(s). Hence, we don't do any additional
>    * priv spec version checks or CSR probes here.
>    */


I was about to read the whole discussion in v2 to understand the 
v3...thank you Drew :) I think it really makes sense to add this 
comment, do you intend to do so Samuel?

Thanks,

Alex


>
> Thanks,
> drew
>
> _______________________________________________
> linux-riscv mailing list
> linux-riscv@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-riscv

Re: [PATCH -fixes v3 1/2] riscv: Fix enabling cbo.zero when running in M-mode

Posted by Samuel Holland 1 year, 11 months ago

Hi Alex,

On 2024-02-27 1:48 PM, Alexandre Ghiti wrote:
> Hi Samuel,
> 
> On 14/02/2024 10:28, Andrew Jones wrote:
>> On Wed, Feb 14, 2024 at 01:01:56AM -0800, Samuel Holland wrote:
>>> When the kernel is running in M-mode, the CBZE bit must be set in the
>>> menvcfg CSR, not in senvcfg.
>>>
>>> Cc: <stable@vger.kernel.org>
>>> Fixes: 43c16d51a19b ("RISC-V: Enable cbo.zero in usermode")
>>> Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
>>> Signed-off-by: Samuel Holland <samuel.holland@sifive.com>
>>> ---
>>>
>>> (no changes since v1)
>>>
>>>   arch/riscv/include/asm/csr.h   | 2 ++
>>>   arch/riscv/kernel/cpufeature.c | 2 +-
>>>   2 files changed, 3 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/arch/riscv/include/asm/csr.h b/arch/riscv/include/asm/csr.h
>>> index 510014051f5d..2468c55933cd 100644
>>> --- a/arch/riscv/include/asm/csr.h
>>> +++ b/arch/riscv/include/asm/csr.h
>>> @@ -424,6 +424,7 @@
>>>   # define CSR_STATUS    CSR_MSTATUS
>>>   # define CSR_IE        CSR_MIE
>>>   # define CSR_TVEC    CSR_MTVEC
>>> +# define CSR_ENVCFG    CSR_MENVCFG
>>>   # define CSR_SCRATCH    CSR_MSCRATCH
>>>   # define CSR_EPC    CSR_MEPC
>>>   # define CSR_CAUSE    CSR_MCAUSE
>>> @@ -448,6 +449,7 @@
>>>   # define CSR_STATUS    CSR_SSTATUS
>>>   # define CSR_IE        CSR_SIE
>>>   # define CSR_TVEC    CSR_STVEC
>>> +# define CSR_ENVCFG    CSR_SENVCFG
>>>   # define CSR_SCRATCH    CSR_SSCRATCH
>>>   # define CSR_EPC    CSR_SEPC
>>>   # define CSR_CAUSE    CSR_SCAUSE
>>> diff --git a/arch/riscv/kernel/cpufeature.c b/arch/riscv/kernel/cpufeature.c
>>> index 89920f84d0a3..c5b13f7dd482 100644
>>> --- a/arch/riscv/kernel/cpufeature.c
>>> +++ b/arch/riscv/kernel/cpufeature.c
>>> @@ -950,7 +950,7 @@ arch_initcall(check_unaligned_access_all_cpus);
>>>   void riscv_user_isa_enable(void)
>>>   {
>>>       if (riscv_cpu_has_extension_unlikely(smp_processor_id(),
>>> RISCV_ISA_EXT_ZICBOZ))
>>> -        csr_set(CSR_SENVCFG, ENVCFG_CBZE);
>>> +        csr_set(CSR_ENVCFG, ENVCFG_CBZE);
>>>   }
>>>     #ifdef CONFIG_RISCV_ALTERNATIVE
>>> -- 
>>> 2.43.0
>>>
>> After our back and forth on how we determine the existence of the *envcfg
>> CSRs, I wonder if we shouldn't put a comment above this
>> riscv_user_isa_enable() function capturing the [current] decision.
>>
>> Something like
>>
>>   /*
>>    * While the [ms]envcfg CSRs weren't defined until priv spec 1.12,
>>    * they're assumed to be present when an extension is present which
>>    * specifies [ms]envcfg bit(s). Hence, we don't do any additional
>>    * priv spec version checks or CSR probes here.
>>    */
> 
> 
> I was about to read the whole discussion in v2 to understand the v3...thank you
> Drew :) I think it really makes sense to add this comment, do you intend to do
> so Samuel?

Yes, I am about to send a v4 with the changes from the previous discussion,
including a RISCV_ISA_EXT_XLINUXENVCFG bit specifically for the presence of the
[ms]envcfg CSR and a comment like the above.

Regards,
Samuel