Re: [External] [PATCH v4 2/9] riscv: smp: fail booting up smp if inconsistent vlen is detected

Hi Andy,

On Fri, Apr 12, 2024 at 2:50 PM Andy Chiu andy.chiu@sifive.com 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@microchip.com Closes: https://lore.kernel.org/linux-riscv/20240228-vicinity-cornstalk-4b8eb5fe5730... Signed-off-by: Andy Chiu andy.chiu@sifive.com

---

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@bytedance.com

Thanks, Yunhui