Mailing List Archive

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>
---
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