[v1, 2/6] riscv: smp: fail booting up smp if inconsistent vlen is detected

[Andy Chiu]

On Tue, Mar 12, 2024 at 8:59 PM Conor Dooley <conor at kernel.org> wrote:
>
> On Tue, Mar 12, 2024 at 08:36:23PM +0800, Andy Chiu wrote:
> > Currently we only support Vector for SMP platforms, that is, all SMP
> > cores have the same vlenb. If we happen to detect a mismatching vlen, it
> > is better to just fail bootting it up to prevent further race/scheduling
> > issues.
> >
> > Fixes: 7017858eb2d7 ("riscv: Introduce riscv_v_vsize to record size of Vector context")
> > Signed-off-by: Andy Chiu <andy.chiu at sifive.com>
>
> Reported-by: Conor Dooley <conor.dooley at microchip.com>
> Closes: https://lore.kernel.org/linux-riscv/20240228-vicinity-cornstalk-4b8eb5fe5730@spud/
> cc: stable at vger.kernel.org
>
> I actually thought I had sent a patch for this, but I don't seem to
> have. I did write one, so I guess I just did not send it.
>
> > ---
> >  arch/riscv/kernel/head.S    | 14 +++++++-------
> >  arch/riscv/kernel/smpboot.c | 14 +++++++++-----
> >  2 files changed, 16 insertions(+), 12 deletions(-)
> >
> > diff --git a/arch/riscv/kernel/head.S b/arch/riscv/kernel/head.S
> > index 4236a69c35cb..a158fa9f2656 100644
> > --- a/arch/riscv/kernel/head.S
> > +++ b/arch/riscv/kernel/head.S
> > @@ -165,9 +165,15 @@ secondary_start_sbi:
> >  #endif
> >       call .Lsetup_trap_vector
> >       scs_load_current
> > -     tail smp_callin
> > +     call smp_callin
> >  #endif /* CONFIG_SMP */
> >
> > +.align 2
> > +.Lsecondary_park:
> > +     /* We lack SMP support or have too many harts, so park this hart */
> > +     wfi
> > +     j .Lsecondary_park
> > +
> >  .align 2
> >  .Lsetup_trap_vector:
> >       /* Set trap vector to exception handler */
> > @@ -181,12 +187,6 @@ secondary_start_sbi:
> >       csrw CSR_SCRATCH, zero
> >       ret
> >
> > -.align 2
> > -.Lsecondary_park:
> > -     /* We lack SMP support or have too many harts, so park this hart */
> > -     wfi
> > -     j .Lsecondary_park
> > -
> >  SYM_CODE_END(_start)
> >
> >  SYM_CODE_START(_start_kernel)
>
> Why does this change? There's no mention of why in the commit message.

Ok, I will add some explanation in the commit message.

This directs the core to secondary_park whenever smp_callin() faills
and returns. So we don't have to re-write the infinity loop in the c
function.

>
> Thanks,
> Conor.

Thanks,
Andy