diff mbox series

[4/5] lib: sbi: Ensure coldboot HART supports next privilege mode

Message ID 20200909145028.446794-5-anup.patel@wdc.com
State Accepted
Headers show
Series Hold E-core in HSM STOPPED State | expand

Commit Message

Anup Patel Sept. 9, 2020, 2:50 p.m. UTC 
The coldboot HART jumps to the next booting stage at the end of
init_coldboot() so it is absolutely necessary for coldboot HART
to support the privilege mode expected by the next booting stage.

We extend the coldboot HART selection in sbi_init() to ensure that
the selected coldboot HART always supports privilege mode specified
in scratch space (i.e. scratch->next_mode). This will further help
us allow E-core (without MMU) on SiFive Unleashed and PolarFire
ICICLE boards to proceed further and wait in HSM STOPPED state.

Signed-off-by: Anup Patel <anup.patel@wdc.com>
---
 lib/sbi/sbi_init.c | 29 ++++++++++++++++++++++++++++-
 1 file changed, 28 insertions(+), 1 deletion(-)

Comments

Atish Patra Sept. 11, 2020, 1:09 a.m. UTC | #1 
On Wed, Sep 9, 2020 at 7:51 AM Anup Patel <anup.patel@wdc.com> wrote:
>
> The coldboot HART jumps to the next booting stage at the end of
> init_coldboot() so it is absolutely necessary for coldboot HART
> to support the privilege mode expected by the next booting stage.
>
> We extend the coldboot HART selection in sbi_init() to ensure that
> the selected coldboot HART always supports privilege mode specified
> in scratch space (i.e. scratch->next_mode). This will further help
> us allow E-core (without MMU) on SiFive Unleashed and PolarFire
> ICICLE boards to proceed further and wait in HSM STOPPED state.
>
> Signed-off-by: Anup Patel <anup.patel@wdc.com>
> ---
>  lib/sbi/sbi_init.c | 29 ++++++++++++++++++++++++++++-
>  1 file changed, 28 insertions(+), 1 deletion(-)
>
> diff --git a/lib/sbi/sbi_init.c b/lib/sbi/sbi_init.c
> index e1a1d96..65d81ba 100644
> --- a/lib/sbi/sbi_init.c
> +++ b/lib/sbi/sbi_init.c
> @@ -295,6 +295,7 @@ static atomic_t coldboot_lottery = ATOMIC_INITIALIZER(0);
>   */
>  void __noreturn sbi_init(struct sbi_scratch *scratch)
>  {
> +       bool next_mode_supported        = FALSE;
>         bool coldboot                   = FALSE;
>         u32 hartid                      = current_hartid();
>         const struct sbi_platform *plat = sbi_platform_ptr(scratch);
> @@ -303,7 +304,33 @@ void __noreturn sbi_init(struct sbi_scratch *scratch)
>             sbi_platform_hart_invalid(plat, hartid))
>                 sbi_hart_hang();
>
> -       if (atomic_xchg(&coldboot_lottery, 1) == 0)
> +       switch (scratch->next_mode) {
> +       case PRV_M:
> +               next_mode_supported = TRUE;
> +               break;
> +       case PRV_S:
> +               if (misa_extension('S'))
> +                       next_mode_supported = TRUE;
> +               break;
> +       case PRV_U:
> +               if (misa_extension('U'))
> +                       next_mode_supported = TRUE;
> +               break;
> +       default:
> +               sbi_hart_hang();
> +       }
> +
> +       /*
> +        * Only the HART supporting privilege mode specified in the
> +        * scratch->next_mode should be allowed to become the coldboot
> +        * HART because the coldboot HART will be directly jumping to
> +        * the next booting stage.
> +        *
> +        * We use a lottery mechanism to select coldboot HART among
> +        * HARTs which satisfy above condition.
> +        */
> +
> +       if (next_mode_supported && atomic_xchg(&coldboot_lottery, 1) == 0)
>                 coldboot = TRUE;
>
>         if (coldboot)
> --
> 2.25.1
>
>
> --
> opensbi mailing list
> opensbi@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/opensbi


Reviewed-by: Atish Patra <atish.patra@wdc.com>
Anup Patel Sept. 16, 2020, 5:31 a.m. UTC | #2 
> -----Original Message-----
> From: Atish Patra <atishp@atishpatra.org>
> Sent: 11 September 2020 06:40
> To: Anup Patel <Anup.Patel@wdc.com>
> Cc: Atish Patra <Atish.Patra@wdc.com>; Alistair Francis
> <Alistair.Francis@wdc.com>; Anup Patel <anup@brainfault.org>; OpenSBI
> <opensbi@lists.infradead.org>
> Subject: Re: [PATCH 4/5] lib: sbi: Ensure coldboot HART supports next
> privilege mode
> 
> On Wed, Sep 9, 2020 at 7:51 AM Anup Patel <anup.patel@wdc.com> wrote:
> >
> > The coldboot HART jumps to the next booting stage at the end of
> > init_coldboot() so it is absolutely necessary for coldboot HART to
> > support the privilege mode expected by the next booting stage.
> >
> > We extend the coldboot HART selection in sbi_init() to ensure that the
> > selected coldboot HART always supports privilege mode specified in
> > scratch space (i.e. scratch->next_mode). This will further help us
> > allow E-core (without MMU) on SiFive Unleashed and PolarFire ICICLE
> > boards to proceed further and wait in HSM STOPPED state.
> >
> > Signed-off-by: Anup Patel <anup.patel@wdc.com>
> > ---
> >  lib/sbi/sbi_init.c | 29 ++++++++++++++++++++++++++++-
> >  1 file changed, 28 insertions(+), 1 deletion(-)
> >
> > diff --git a/lib/sbi/sbi_init.c b/lib/sbi/sbi_init.c index
> > e1a1d96..65d81ba 100644
> > --- a/lib/sbi/sbi_init.c
> > +++ b/lib/sbi/sbi_init.c
> > @@ -295,6 +295,7 @@ static atomic_t coldboot_lottery =
> ATOMIC_INITIALIZER(0);
> >   */
> >  void __noreturn sbi_init(struct sbi_scratch *scratch)  {
> > +       bool next_mode_supported        = FALSE;
> >         bool coldboot                   = FALSE;
> >         u32 hartid                      = current_hartid();
> >         const struct sbi_platform *plat = sbi_platform_ptr(scratch);
> > @@ -303,7 +304,33 @@ void __noreturn sbi_init(struct sbi_scratch
> *scratch)
> >             sbi_platform_hart_invalid(plat, hartid))
> >                 sbi_hart_hang();
> >
> > -       if (atomic_xchg(&coldboot_lottery, 1) == 0)
> > +       switch (scratch->next_mode) {
> > +       case PRV_M:
> > +               next_mode_supported = TRUE;
> > +               break;
> > +       case PRV_S:
> > +               if (misa_extension('S'))
> > +                       next_mode_supported = TRUE;
> > +               break;
> > +       case PRV_U:
> > +               if (misa_extension('U'))
> > +                       next_mode_supported = TRUE;
> > +               break;
> > +       default:
> > +               sbi_hart_hang();
> > +       }
> > +
> > +       /*
> > +        * Only the HART supporting privilege mode specified in the
> > +        * scratch->next_mode should be allowed to become the coldboot
> > +        * HART because the coldboot HART will be directly jumping to
> > +        * the next booting stage.
> > +        *
> > +        * We use a lottery mechanism to select coldboot HART among
> > +        * HARTs which satisfy above condition.
> > +        */
> > +
> > +       if (next_mode_supported && atomic_xchg(&coldboot_lottery, 1)
> > + == 0)
> >                 coldboot = TRUE;
> >
> >         if (coldboot)
> > --
> > 2.25.1
> >
> >
> > --
> > opensbi mailing list
> > opensbi@lists.infradead.org
> > http://lists.infradead.org/mailman/listinfo/opensbi
> 
> 
> Reviewed-by: Atish Patra <atish.patra@wdc.com>

Applied this patch to the riscv/opensbi repo

Regards,
Anup
diff mbox series

Patch

diff --git a/lib/sbi/sbi_init.c b/lib/sbi/sbi_init.c
index e1a1d96..65d81ba 100644
--- a/lib/sbi/sbi_init.c
+++ b/lib/sbi/sbi_init.c
@@ -295,6 +295,7 @@  static atomic_t coldboot_lottery = ATOMIC_INITIALIZER(0);
  */
 void __noreturn sbi_init(struct sbi_scratch *scratch)
 {
+	bool next_mode_supported	= FALSE;
 	bool coldboot			= FALSE;
 	u32 hartid			= current_hartid();
 	const struct sbi_platform *plat = sbi_platform_ptr(scratch);
@@ -303,7 +304,33 @@  void __noreturn sbi_init(struct sbi_scratch *scratch)
 	    sbi_platform_hart_invalid(plat, hartid))
 		sbi_hart_hang();
 
-	if (atomic_xchg(&coldboot_lottery, 1) == 0)
+	switch (scratch->next_mode) {
+	case PRV_M:
+		next_mode_supported = TRUE;
+		break;
+	case PRV_S:
+		if (misa_extension('S'))
+			next_mode_supported = TRUE;
+		break;
+	case PRV_U:
+		if (misa_extension('U'))
+			next_mode_supported = TRUE;
+		break;
+	default:
+		sbi_hart_hang();
+	}
+
+	/*
+	 * Only the HART supporting privilege mode specified in the
+	 * scratch->next_mode should be allowed to become the coldboot
+	 * HART because the coldboot HART will be directly jumping to
+	 * the next booting stage.
+	 *
+	 * We use a lottery mechanism to select coldboot HART among
+	 * HARTs which satisfy above condition.
+	 */
+
+	if (next_mode_supported && atomic_xchg(&coldboot_lottery, 1) == 0)
 		coldboot = TRUE;
 
 	if (coldboot)