[PATCH v5 2/4] lib: sbi: add zicfilp/zicfiss and elp cfi state reflect back in status

[Samuel Holland]

On 2024-09-10 11:35 AM, Deepak Gupta wrote:
> This patch adds support to check for zicfilp / zicfiss extension.
> 
> zicfilp record status of hart's ELP state in *status csr. Missing landing pad
> sets MPELP in mstatus. When SBI is redirecting back to S/VS/HS, SPELP is
> set in sstatus/vsstatus.
> 
> Signed-off-by: Deepak Gupta <debug at rivosinc.com>
> ---
>  include/sbi/sbi_hart.h |  3 +++
>  lib/sbi/sbi_hart.c     |  2 ++
>  lib/sbi/sbi_trap.c     | 20 ++++++++++++++++++++
>  3 files changed, 25 insertions(+)
> 
> diff --git a/include/sbi/sbi_hart.h b/include/sbi/sbi_hart.h
> index 81ec061..2aa6867 100644
> --- a/include/sbi/sbi_hart.h
> +++ b/include/sbi/sbi_hart.h
> @@ -67,6 +67,9 @@ enum sbi_hart_extensions {
>  	SBI_HART_EXT_SVADE,
>  	/** Hart has Svadu extension */
>  	SBI_HART_EXT_SVADU,
> +	/** HART has zicfiss & zicfilp extension */
> +	SBI_HART_EXT_ZICFILP,
> +	SBI_HART_EXT_ZICFISS,
>  
>  	/** Maximum index of Hart extension */
>  	SBI_HART_EXT_MAX,
> diff --git a/lib/sbi/sbi_hart.c b/lib/sbi/sbi_hart.c
> index c366701..e1bc346 100644
> --- a/lib/sbi/sbi_hart.c
> +++ b/lib/sbi/sbi_hart.c
> @@ -680,6 +680,8 @@ const struct sbi_hart_ext_data sbi_hart_ext[] = {
>  	__SBI_HART_EXT_DATA(ssccfg, SBI_HART_EXT_SSCCFG),
>  	__SBI_HART_EXT_DATA(svade, SBI_HART_EXT_SVADE),
>  	__SBI_HART_EXT_DATA(svadu, SBI_HART_EXT_SVADU),
> +	__SBI_HART_EXT_DATA(zicfilp, SBI_HART_EXT_ZICFILP),
> +	__SBI_HART_EXT_DATA(zicfiss, SBI_HART_EXT_ZICFISS),
>  };
>  
>  _Static_assert(SBI_HART_EXT_MAX == array_size(sbi_hart_ext),
> diff --git a/lib/sbi/sbi_trap.c b/lib/sbi/sbi_trap.c
> index b4f3a17..e2502f2 100644
> --- a/lib/sbi/sbi_trap.c
> +++ b/lib/sbi/sbi_trap.c
> @@ -103,6 +103,7 @@ int sbi_trap_redirect(struct sbi_trap_regs *regs,
>  		      const struct sbi_trap_info *trap)
>  {
>  	ulong hstatus, vsstatus, prev_mode;
> +	bool elp = false;
>  #if __riscv_xlen == 32
>  	bool prev_virt = (regs->mstatusH & MSTATUSH_MPV) ? true : false;
>  #else
> @@ -116,6 +117,17 @@ int sbi_trap_redirect(struct sbi_trap_regs *regs,
>  	if (prev_mode != PRV_S && prev_mode != PRV_U)
>  		return SBI_ENOTSUPP;
>  
> +	/* If extension has support for CFI, clear MPELP because redirecting to VS or (H)S */

Did you mean "If hart has support for CFI" here?

> +	if (sbi_hart_has_extension(sbi_scratch_thishart_ptr(), SBI_HART_EXT_ZICFILP)) {
> +#if __riscv_xlen == 32
> +		elp = regs->mstatusH & MSTATUSH_MPELP;
> +		regs->mstatusH &= ~MSTATUSH_MPELP;
> +#else
> +		elp = regs->mstatus & MSTATUS_MPELP;
> +		regs->mstatus &= ~MSTATUS_MPELP;
> +#endif
> +	}
> +
>  	/* If exceptions came from VS/VU-mode, redirect to VS-mode if
>  	 * delegated in hedeleg
>  	 */
> @@ -169,6 +181,10 @@ int sbi_trap_redirect(struct sbi_trap_regs *regs,
>  		/* Get VS-mode SSTATUS CSR */
>  		vsstatus = csr_read(CSR_VSSTATUS);
>  
> +		/*if elp was set, set it back in vsstatus */

Missing space before "if". With this fixed:

Reviewed-by: Samuel Holland <samuel.holland at sifive.com>

> +		if (elp)
> +			vsstatus |= MSTATUS_SPELP;
> +
>  		/* Set SPP for VS-mode */
>  		vsstatus &= ~SSTATUS_SPP;
>  		if (prev_mode == PRV_S)
> @@ -209,6 +225,10 @@ int sbi_trap_redirect(struct sbi_trap_regs *regs,
>  
>  		/* Clear SIE for S-mode */
>  		regs->mstatus &= ~MSTATUS_SIE;
> +
> +		/* if elp was set, set it back in mstatus */
> +		if (elp)
> +			regs->mstatus |= MSTATUS_SPELP;
>  	}
>  
>  	return 0;