riscv: smp: fail booting up smp if inconsistent vlen is detected

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@spud/
Signed-off-by: Andy Chiu <andy.chiu@sifive.com>
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
Reviewed-by: Yunhui Cui <cuiyunhui@bytedance.com>
Link: https://lore.kernel.org/r/20240510-zve-detection-v5-2-0711bdd26c12@sifive.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>

diff --git a/arch/riscv/kernel/head.S b/arch/riscv/kernel/head.S
index 4236a69c35cb33524cdb7190d8ecb294768d8e56..a00f7523cb91f20516df57a2a05cf70343773e32 100644 (file)
--- 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 1319b29ce3b59bd4daa203acad44919b9d05db24..19baf0d574d359bdbdfaeaef91c8dd7a6398e685 100644 (file)
--- 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, true);
 
-       if (has_vector()) {
-               if (riscv_v_setup_vsize())
-                       elf_hwcap &= ~COMPAT_HWCAP_ISA_V;
-       }
-
        riscv_user_isa_enable();
 
        /*