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

[Atish Patra <atishp@atishpatra.org>]

On Mon, Jan 27, 2020 at 8:54 PM Anup Patel <anup@brainfault.org> wrote:
>
> On Tue, Jan 28, 2020 at 7:58 AM Atish Patra <atish.patra@wdc.com> 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@wdc.com>
> > ---
> >  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.
>

Done.

> >  #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 ?
>

Sure. I am fine with that. However, I think we don't need to move
spinwait ops to its
own file as it won't grow in the future. I have refactored the series
in the following way.

1. Move cpu_sbi_ops and sbi_hsm_xyz to its own file which can be
compiled out with CONFIG_RISCV_SBI.
2. Keep spinwait and other cpu_ops related functions in cpu_ops.c

Let me know if you think that's not a good idea.

> 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
>


-- 
Regards,
Atish