Re: [PATCH v7 08/10] RISC-V: Add SBI HSM extension

[Anup Patel]

On Tue, Jan 28, 2020 at 7:58 AM Atish Patra <atish.patra@xxxxxxx> wrote:
>
> SBI specification defines HSM extension that allows to start/stop a hart
> by a supervisor anytime. The specification is available at
>
> https://github.com/riscv/riscv-sbi-doc/blob/master/riscv-sbi.adoc
>
> Implement SBI HSM extension.
>
> Signed-off-by: Atish Patra <atish.patra@xxxxxxx>
> ---
>  arch/riscv/include/asm/sbi.h | 22 ++++++++++++++++
>  arch/riscv/kernel/sbi.c      | 51 ++++++++++++++++++++++++++++++++++++
>  2 files changed, 73 insertions(+)
>
> diff --git a/arch/riscv/include/asm/sbi.h b/arch/riscv/include/asm/sbi.h
> index d55d8090ab5c..bed6fa26ec84 100644
> --- a/arch/riscv/include/asm/sbi.h
> +++ b/arch/riscv/include/asm/sbi.h
> @@ -26,6 +26,7 @@ enum sbi_ext_id {
>         SBI_EXT_TIME = 0x54494D45,
>         SBI_EXT_IPI = 0x735049,
>         SBI_EXT_RFENCE = 0x52464E43,
> +       SBI_EXT_HSM = 0x48534D,
>  };
>
>  enum sbi_ext_base_fid {
> @@ -56,6 +57,12 @@ enum sbi_ext_rfence_fid {
>         SBI_EXT_RFENCE_REMOTE_HFENCE_VVMA_ASID,
>  };
>
> +enum sbi_ext_hsm_fid {
> +       SBI_EXT_HSM_HART_START = 0,
> +       SBI_EXT_HSM_HART_STOP,
> +       SBI_EXT_HSM_HART_STATUS,
> +};
> +

I think we should also define the possible return values of
SBI_EXT_HSM_HART_STATUS function.

>  #define SBI_SPEC_VERSION_DEFAULT       0x1
>  #define SBI_SPEC_VERSION_MAJOR_SHIFT   24
>  #define SBI_SPEC_VERSION_MAJOR_MASK    0x7f
> @@ -70,6 +77,7 @@ enum sbi_ext_rfence_fid {
>  #define SBI_ERR_INVALID_ADDRESS -5
>
>  extern unsigned long sbi_spec_version;
> +extern bool sbi_hsm_avail;
>  struct sbiret {
>         long error;
>         long value;
> @@ -110,8 +118,18 @@ int sbi_remote_hfence_vvma_asid(const unsigned long *hart_mask,
>                                 unsigned long start,
>                                 unsigned long size,
>                                 unsigned long asid);
> +int sbi_hsm_hart_start(unsigned long hartid, unsigned long saddr,
> +                      unsigned long priv);
> +int sbi_hsm_hart_stop(void);
> +int sbi_hsm_hart_get_status(unsigned long hartid);
> +
>  int sbi_probe_extension(int ext);
>
> +static inline bool sbi_hsm_is_available(void)
> +{
> +       return sbi_hsm_avail;
> +}
> +
>  /* Check if current SBI specification version is 0.1 or not */
>  static inline int sbi_spec_is_0_1(void)
>  {
> @@ -137,5 +155,9 @@ void sbi_clear_ipi(void);
>  void sbi_send_ipi(const unsigned long *hart_mask);
>  void sbi_remote_fence_i(const unsigned long *hart_mask);
>  void sbi_init(void);
> +static inline bool sbi_hsm_is_available(void)
> +{
> +       return false;
> +}
>  #endif /* CONFIG_RISCV_SBI */
>  #endif /* _ASM_RISCV_SBI_H */
> diff --git a/arch/riscv/kernel/sbi.c b/arch/riscv/kernel/sbi.c
> index 3c34aba30f6f..9bdc9801784d 100644
> --- a/arch/riscv/kernel/sbi.c
> +++ b/arch/riscv/kernel/sbi.c
> @@ -12,6 +12,8 @@
>
>  /* default SBI version is 0.1 */
>  unsigned long sbi_spec_version = SBI_SPEC_VERSION_DEFAULT;
> +bool sbi_hsm_avail;
> +
>  EXPORT_SYMBOL(sbi_spec_version);
>
>  static void (*__sbi_set_timer)(uint64_t stime);
> @@ -496,6 +498,54 @@ static void sbi_power_off(void)
>         sbi_shutdown();
>  }
>
> +int sbi_hsm_hart_stop(void)
> +{
> +       struct sbiret ret;
> +
> +       ret = sbi_ecall(SBI_EXT_HSM, SBI_EXT_HSM_HART_STOP, 0, 0, 0, 0, 0, 0);
> +
> +       if (!ret.error)
> +               return ret.value;
> +       else
> +               return sbi_err_map_linux_errno(ret.error);
> +}
> +EXPORT_SYMBOL(sbi_hsm_hart_stop);
> +
> +int sbi_hsm_hart_start(unsigned long hartid, unsigned long saddr,
> +                      unsigned long priv)
> +{
> +       struct sbiret ret;
> +
> +       ret = sbi_ecall(SBI_EXT_HSM, SBI_EXT_HSM_HART_START,
> +                             hartid, saddr, priv, 0, 0, 0);
> +       if (!ret.error)
> +               return ret.value;
> +       else
> +               return sbi_err_map_linux_errno(ret.error);
> +}
> +EXPORT_SYMBOL(sbi_hsm_hart_start);
> +
> +int sbi_hsm_hart_get_status(unsigned long hartid)
> +{
> +       struct sbiret ret;
> +
> +       ret = sbi_ecall(SBI_EXT_HSM, SBI_EXT_HSM_HART_STATUS,
> +                             hartid, 0, 0, 0, 0, 0);
> +       if (!ret.error)
> +               return ret.value;
> +       else
> +               return sbi_err_map_linux_errno(ret.error);
> +}
> +EXPORT_SYMBOL(sbi_hsm_hart_get_status);
> +
> +void __init sbi_hsm_ext_init(void)
> +{
> +       if (sbi_probe_extension(SBI_EXT_HSM) > 0) {
> +               pr_info("SBI v0.2 HSM extension detected\n");
> +               sbi_hsm_avail = true;
> +       }
> +}
> +

If we start adding all present and future extensions in
arch/riscv/kernel/sbi.c then it will blow-up.

IMHO, we should only keep legacy and replacement
extension in arch/riscv/kernel/sbi.c. All other extensions
will be separate based on how they are integrated.

For SBI HSM, all sbi_hsm_xyz() functions should be in
arch/riscv/kernel/cpu_ops_sbi.c which will be only compiled
when CONFIG_RISCV_SBI is enabled.

Maybe merge PATCH8 and PATCH9 ?

Regards,
Anup

>  int __init sbi_init(void)
>  {
>         int ret;
> @@ -532,5 +582,6 @@ int __init sbi_init(void)
>                 __sbi_rfence    = __sbi_rfence_v01;
>         }
>
> +       sbi_hsm_ext_init();

We don't need sbi_hsm_ext_init() because we can check
and set CPU ops at boot-time in cpu_set_ops()

>         return 0;
>  }
> --
> 2.24.0
>

Regards,
Anup