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

[Conor Dooley]

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.

Thanks,
Conor.
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