[PATCH] lib: sbi: Add support to mask/unmask SSE events
Anup Patel
anup at brainfault.org
Thu Sep 19 22:27:23 PDT 2024
On Thu, Sep 19, 2024 at 4:30 PM Himanshu Chauhan
<hchauhan at ventanamicro.com> wrote:
>
> Hi Samuel,
>
> On Thu, Sep 12, 2024 at 08:42:58PM -0500, Samuel Holland wrote:
> > Hi Himanshu,
> >
> > On 2024-09-10 8:24 AM, Himanshu Chauhan wrote:
> > > A hart in non-retentive suspend state can't handle software events
> > > until the hart has come out of the non-retentive suspend and restored
> > > the hart state.
> > >
> > > To support this, define separate hart mask/unmask functions for the
> > > SSE extension which allow supervisor software to globally mask/unmask
> > > software event delivery on the calling hart.
> > >
> > > Signed-off-by: Himanshu Chauhan <hchauhan at ventanamicro.com>
> > > ---
> > > include/sbi/sbi_ecall_interface.h | 2 ++
> > > include/sbi/sbi_sse.h | 2 ++
> > > lib/sbi/sbi_ecall_sse.c | 6 ++++++
> > > lib/sbi/sbi_sse.c | 31 +++++++++++++++++++++++++++++++
> > > 4 files changed, 41 insertions(+)
> > >
> > > diff --git a/include/sbi/sbi_ecall_interface.h b/include/sbi/sbi_ecall_interface.h
> > > index 085b33e7..3bf8f1da 100644
> > > --- a/include/sbi/sbi_ecall_interface.h
> > > +++ b/include/sbi/sbi_ecall_interface.h
> > > @@ -342,6 +342,8 @@ enum sbi_cppc_reg_id {
> > > #define SBI_EXT_SSE_DISABLE 0x00000005
> > > #define SBI_EXT_SSE_COMPLETE 0x00000006
> > > #define SBI_EXT_SSE_INJECT 0x00000007
> > > +#define SBI_EXT_SSE_HART_MASK 0x00000008
> > > +#define SBI_EXT_SSE_HART_UNMASK 0x00000009
> >
> > These function IDs are swapped compared to the proposed spec.
> >
> > >
> > > /* SBI SSE Event Attributes. */
> > > enum sbi_sse_attr_id {
> > > diff --git a/include/sbi/sbi_sse.h b/include/sbi/sbi_sse.h
> > > index e5b0ad69..7419698a 100644
> > > --- a/include/sbi/sbi_sse.h
> > > +++ b/include/sbi/sbi_sse.h
> > > @@ -78,6 +78,8 @@ void sbi_sse_exit(struct sbi_scratch *scratch);
> > > int sbi_sse_register(uint32_t event_id, unsigned long handler_entry_pc,
> > > unsigned long handler_entry_arg);
> > > int sbi_sse_unregister(uint32_t event_id);
> > > +int sbi_sse_hart_mask(void);
> > > +int sbi_sse_hart_unmask(void);
> > > int sbi_sse_enable(uint32_t event_id);
> > > int sbi_sse_disable(uint32_t event_id);
> > > int sbi_sse_complete(struct sbi_trap_regs *regs, struct sbi_ecall_return *out);
> > > diff --git a/lib/sbi/sbi_ecall_sse.c b/lib/sbi/sbi_ecall_sse.c
> > > index a28a033e..beddc2cd 100644
> > > --- a/lib/sbi/sbi_ecall_sse.c
> > > +++ b/lib/sbi/sbi_ecall_sse.c
> > > @@ -36,6 +36,12 @@ static int sbi_ecall_sse_handler(unsigned long extid, unsigned long funcid,
> > > case SBI_EXT_SSE_INJECT:
> > > ret = sbi_sse_inject_from_ecall(regs->a0, regs->a1, out);
> > > break;
> > > + case SBI_EXT_SSE_HART_MASK:
> > > + ret = sbi_sse_hart_mask();
> > > + break;
> > > + case SBI_EXT_SSE_HART_UNMASK:
> > > + ret = sbi_sse_hart_unmask();
> > > + break;
> > > default:
> > > ret = SBI_ENOTSUPP;
> > > }
> > > diff --git a/lib/sbi/sbi_sse.c b/lib/sbi/sbi_sse.c
> > > index 52172fcd..e9085324 100644
> > > --- a/lib/sbi/sbi_sse.c
> > > +++ b/lib/sbi/sbi_sse.c
> > > @@ -141,6 +141,12 @@ struct sse_hart_state {
> > > * List of local events allocated at boot time.
> > > */
> > > struct sbi_sse_event *local_events;
> > > +
> > > + /**
> > > + * State to track if the hart is ready to take sse events.
> > > + * One hart cannot modify this state of another hart.
> > > + */
> > > + bool sse_masked;
> >
> > "sse_" is a bit redundant here, since this whole structure is SSE state.
> >
> > > };
> > >
> > > /**
> > > @@ -608,6 +614,11 @@ void sbi_sse_process_pending_events(struct sbi_trap_regs *regs)
> > > struct sbi_sse_event *e;
> > > struct sse_hart_state *state = sse_thishart_state_ptr();
> > >
> > > + /* if sse is masked on this hart, do nothing */
> > > + if (state->sse_masked) {
> > > + return;
> > > + }
> >
> > This will block global events if the preferred hart has events masked.
> > sse_event_is_ready() needs to ignore the preferred hartid in that case, so the
> > event can be injected on another hart.
> >
>
> This function `sbi_sse_process_pending_events` is called from trap exit. If the
> event was global and its pending on this hart, it means that was already routed.
> Its not pretty late in the game. If the event is not ready, then it is not re-routed.
>
> There is definitely some scope of improvement. Probably, I can sent another patch set for that?
Lets update this patch and get it merged first. The global event rerouting
stuff can be done as a separate patch.
Regards,
Anup
>
> Regards
> Himanshu
>
> > Regards,
> > Samuel
> >
> > > +
> > > spin_lock(&state->enabled_event_lock);
> > >
> > > sbi_list_for_each_entry(e, &state->enabled_event_list, node) {
> > > @@ -805,6 +816,24 @@ int sbi_sse_disable(uint32_t event_id)
> > > return ret;
> > > }
> > >
> > > +int sbi_sse_hart_mask(void)
> > > +{
> > > + struct sse_hart_state *state = sse_thishart_state_ptr();
> > > +
> > > + state->sse_masked = true;
> > > +
> > > + return SBI_SUCCESS;
> > > +}
> > > +
> > > +int sbi_sse_hart_unmask(void)
> > > +{
> > > + struct sse_hart_state *state = sse_thishart_state_ptr();
> > > +
> > > + state->sse_masked = false;
> > > +
> > > + return SBI_SUCCESS;
> > > +}
> > > +
> > > int sbi_sse_inject_from_ecall(uint32_t event_id, unsigned long hartid,
> > > struct sbi_ecall_return *out)
> > > {
> > > @@ -1123,6 +1152,8 @@ int sbi_sse_init(struct sbi_scratch *scratch, bool cold_boot)
> > >
> > > shs->local_events = (struct sbi_sse_event *)(shs + 1);
> > >
> > > + /* SSE events are masked until hart unmasks them */
> > > + shs->sse_masked = true;
> > > sse_set_hart_state_ptr(scratch, shs);
> > > }
> > >
> >
>
> --
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