[RFC PATCH 02/14] RISC-V: Add SBI STA extension definitions

[Guo Ren <guoren@kernel.org>]

On Mon, Apr 17, 2023 at 12:33:50PM +0200, Andrew Jones wrote:
> The SBI STA extension enables steal-time accounting. Add the
> definitions it specifies.
> 
> Signed-off-by: Andrew Jones <ajones@ventanamicro.com>
> ---
>  arch/riscv/include/asm/sbi.h | 15 +++++++++++++++
>  1 file changed, 15 insertions(+)
> 
> diff --git a/arch/riscv/include/asm/sbi.h b/arch/riscv/include/asm/sbi.h
> index 945b7be249c1..485b9ec20399 100644
> --- a/arch/riscv/include/asm/sbi.h
> +++ b/arch/riscv/include/asm/sbi.h
> @@ -30,6 +30,7 @@ enum sbi_ext_id {
>  	SBI_EXT_HSM = 0x48534D,
>  	SBI_EXT_SRST = 0x53525354,
>  	SBI_EXT_PMU = 0x504D55,
> +	SBI_EXT_STA = 0x535441,
>  
>  	/* Experimentals extensions must lie within this range */
>  	SBI_EXT_EXPERIMENTAL_START = 0x08000000,
> @@ -236,6 +237,20 @@ enum sbi_pmu_ctr_type {
>  /* Flags defined for counter stop function */
>  #define SBI_PMU_STOP_FLAG_RESET (1 << 0)
>  
> +/* SBI STA (steal-time accounting) extension */
> +enum sbi_ext_sta_fid {
> +	SBI_EXT_STA_SET_STEAL_TIME_SHMEM = 0,
> +};
> +
> +struct sbi_sta_struct {
> +	__le32 sequence;
> +	__le32 flags;
> +	__le64 steal;
Could we wrap the "sequence & steal" into one 64-bit variable? Then only
rv32 needs double READs, and only one ld instruction for rv64 ISA.

> +	u8 preempted;
> +	u8 pad[47];
> +} __packed;
> +
> +/* SBI spec version fields */
>  #define SBI_SPEC_VERSION_DEFAULT	0x1
>  #define SBI_SPEC_VERSION_MAJOR_SHIFT	24
>  #define SBI_SPEC_VERSION_MAJOR_MASK	0x7f
> -- 
> 2.39.2
> 
> 
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