riscv: mm: Unconditionally sfence.vma for spurious fault

riscv: mm: Unconditionally sfence.vma for spurious fault

Svvptc does not guarantee that it's safe to just return here. Since we
have already cleared our bit, if, theoretically, the bounded timeframe
for the accessed page to become valid still hasn't happened after sret,
we could fault again and actually crash.

Hopefully, these spurious faults should be rare enough that this is an
acceptable slowdown.

Cc: stable@vger.kernel.org
Fixes: 503638e0babf ("riscv: Stop emitting preventive sfence.vma for new vmalloc mappings")
Signed-off-by: Vivian Wang <wangruikang@iscas.ac.cn>
Link: https://patch.msgid.link/20260303-handle-kfence-protect-spurious-fault-v2-5-f80d8354d79d@iscas.ac.cn
Signed-off-by: Paul Walmsley <pjw@kernel.org>