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

Charlie Jenkins
2024-05-10T22:33:41Z

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@rivosinc.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.

- Charlie

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