[PATCH] lib: Fix MSTATUS_FS bit usage in sbi_fp_save()

[Huamao Wu]

The sbi_fp_save() function incorrectly uses MSTATUS_VS (0x600, Vector
extension state) instead of MSTATUS_FS (0x6000, Floating-Point extension
state) when enabling floating-point instructions before saving FP registers.

This causes an illegal instruction exception when executing the first fsd/fsw
instruction, because the FP unit remains disabled (MSTATUS.FS=0) while the
code attempts to access FP registers.

The bug was introduced in commit 718e1d194f5a ("lib: Add FP context save/restore
support", 2026-05-18) and affects OpenSBI v1.9 and later versions.

Symptom observed on a development platform with dual 40-hart RVA23 CPUs and OP-TEE:
- Domain context switch triggers sbi_fp_save()
- First fsd instruction at PC 0x23ce4 raises illegal instruction trap
- System fails to enter OP-TEE trusted domain

The sbi_fp_restore() function in the same file correctly uses MSTATUS_FS
(line 112), confirming this is a copy-paste error.

Fix: Change MSTATUS_VS to MSTATUS_FS in sbi_fp_save().

Signed-off-by: Huamao Wu <huamao.wu at spacemit.com>
---
 lib/sbi/sbi_fp.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/sbi/sbi_fp.c b/lib/sbi/sbi_fp.c
index c8941252..38fb7a01 100644
--- a/lib/sbi/sbi_fp.c
+++ b/lib/sbi/sbi_fp.c
@@ -20,7 +20,7 @@ void sbi_fp_save(struct sbi_fp_context *dst)
        if (!dst)
                return;

-       mstatus_orig = csr_read_set(CSR_MSTATUS, MSTATUS_VS);
+       mstatus_orig = csr_read_set(CSR_MSTATUS, MSTATUS_FS);

        asm volatile(
 #if defined(__riscv_d)
--
2.43.0


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