linux-kernel - Re: [PATCH v3 02/29] riscv: define default value for envcfg for task

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Message-ID: <ZkJdDnfjm+DMzgEa@debug.ba.rivosinc.com>
Date: Mon, 13 May 2024 11:33:50 -0700
From: Deepak Gupta <debug@...osinc.com>
To: Charlie Jenkins <charlie@...osinc.com>
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Subject: Re: [PATCH v3 02/29] riscv: define default value for envcfg for task

On Fri, May 10, 2024 at 03:33:36PM -0700, Charlie Jenkins wrote:
>On Wed, Apr 03, 2024 at 04:34:50PM -0700, Deepak Gupta wrote:
>> Defines a base default value for envcfg per task. By default all tasks
>> should have cache zeroing capability. Any future base capabilities that
>> apply to all tasks can be turned on same way.
>>
>> Signed-off-by: Deepak Gupta <debug@...osinc.com>
>> ---
>>  arch/riscv/include/asm/csr.h | 2 ++
>>  arch/riscv/kernel/process.c  | 6 ++++++
>>  2 files changed, 8 insertions(+)
>>
>> diff --git a/arch/riscv/include/asm/csr.h b/arch/riscv/include/asm/csr.h
>> index 2468c55933cd..bbd2207adb39 100644
>> --- a/arch/riscv/include/asm/csr.h
>> +++ b/arch/riscv/include/asm/csr.h
>> @@ -202,6 +202,8 @@
>>  #define ENVCFG_CBIE_FLUSH		_AC(0x1, UL)
>>  #define ENVCFG_CBIE_INV			_AC(0x3, UL)
>>  #define ENVCFG_FIOM			_AC(0x1, UL)
>> +/* by default all threads should be able to zero cache */
>> +#define ENVCFG_BASE			ENVCFG_CBZE
>>
>>  /* Smstateen bits */
>>  #define SMSTATEEN0_AIA_IMSIC_SHIFT	58
>> diff --git a/arch/riscv/kernel/process.c b/arch/riscv/kernel/process.c
>> index 92922dbd5b5c..d3109557f951 100644
>> --- a/arch/riscv/kernel/process.c
>> +++ b/arch/riscv/kernel/process.c
>> @@ -152,6 +152,12 @@ void start_thread(struct pt_regs *regs, unsigned long pc,
>>  	else
>>  		regs->status |= SR_UXL_64;
>>  #endif
>> +	/*
>> +	 * read current envcfg settings, AND it with base settings applicable
>> +	 * for all the tasks. Base settings should've been set up during CPU
>> +	 * bring up.
>> +	 */
>> +	current->thread_info.envcfg = csr_read(CSR_ENVCFG) & ENVCFG_BASE;
>
>This needs to be gated on xlinuxenvcfg.

You're right. This csr read should be gated on xlinuxenvcfg. Will fix it.

>
>- Charlie
>
>>  }
>>
>>  void flush_thread(void)
>> --
>> 2.43.2
>>