Hi Andy,
On Fri, Apr 12, 2024 at 2:50 PM Andy Chiu <andy.chiu@xxxxxxxxxx> 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.
>
> Also, move .Lsecondary_park forward and chage `tail smp_callin` into a
> regular call in the early assembly. So a core would be parked right
> after a return from smp_callin. Note that a successful smp_callin
> does not return.
>
> Fixes: 7017858eb2d7 ("riscv: Introduce riscv_v_vsize to record size of Vector context")
> Reported-by: Conor Dooley <conor.dooley@xxxxxxxxxxxxx>
> Closes: https://lore.kernel.org/linux-riscv/20240228-vicinity-cornstalk-4b8eb5fe5730@spud/
> Signed-off-by: Andy Chiu <andy.chiu@xxxxxxxxxx>
> ---
> Changelog v4:
> - update comment also in the assembly code (Yunhui)
> Changelog v2:
> - update commit message to explain asm code change (Conor)
> ---
> arch/riscv/kernel/head.S | 19 ++++++++++++-------
> arch/riscv/kernel/smpboot.c | 14 +++++++++-----
> 2 files changed, 21 insertions(+), 12 deletions(-)
>
> diff --git a/arch/riscv/kernel/head.S b/arch/riscv/kernel/head.S
> index 4236a69c35cb..a00f7523cb91 100644
> --- a/arch/riscv/kernel/head.S
> +++ b/arch/riscv/kernel/head.S
> @@ -165,9 +165,20 @@ secondary_start_sbi:
> #endif
> call .Lsetup_trap_vector
> scs_load_current
> - tail smp_callin
> + call smp_callin
> #endif /* CONFIG_SMP */
>
> +.align 2
> +.Lsecondary_park:
> + /*
> + * Park this hart if we:
> + * - have too many harts on CONFIG_RISCV_BOOT_SPINWAIT
> + * - receive an early trap, before setup_trap_vector finished
> + * - fail in smp_callin(), as a successful one wouldn't return
> + */
> + wfi
> + j .Lsecondary_park
> +
> .align 2
> .Lsetup_trap_vector:
> /* Set trap vector to exception handler */
> @@ -181,12 +192,6 @@ 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)
> diff --git a/arch/riscv/kernel/smpboot.c b/arch/riscv/kernel/smpboot.c
> index d41090fc3203..673437ccc13d 100644
> --- a/arch/riscv/kernel/smpboot.c
> +++ b/arch/riscv/kernel/smpboot.c
> @@ -214,6 +214,15 @@ asmlinkage __visible void smp_callin(void)
> struct mm_struct *mm = &init_mm;
> unsigned int curr_cpuid = smp_processor_id();
>
> + if (has_vector()) {
> + /*
> + * Return as early as possible so the hart with a mismatching
> + * vlen won't boot.
> + */
> + if (riscv_v_setup_vsize())
> + return;
> + }
> +
> /* All kernel threads share the same mm context. */
> mmgrab(mm);
> current->active_mm = mm;
> @@ -226,11 +235,6 @@ asmlinkage __visible void smp_callin(void)
> numa_add_cpu(curr_cpuid);
> set_cpu_online(curr_cpuid, 1);
>
> - if (has_vector()) {
> - if (riscv_v_setup_vsize())
> - elf_hwcap &= ~COMPAT_HWCAP_ISA_V;
> - }
> -
> riscv_user_isa_enable();
>
> /*
>
> --
> 2.44.0.rc2
>
>
Reviewed-by: Yunhui Cui <cuiyunhui@xxxxxxxxxxxxx>
Thanks,
Yunhui
