RISC-V: Do not invoke SBI call if cpumask is empty

SBI calls are expensive. If cpumask is empty, there is no need to
trap via SBI as no remote tlb flushing is required.

Signed-off-by: Atish Patra <atish.patra@wdc.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Paul Walmsley <paul.walmsley@sifive.com>

diff --git a/arch/riscv/mm/tlbflush.c b/arch/riscv/mm/tlbflush.c
index 24cd33d2c48f3cee41bd219f33ca1d857bbbd9d7..9ecaf73cd0515170fb5c61bca6b089202194d628 100644 (file)
--- a/arch/riscv/mm/tlbflush.c
+++ b/arch/riscv/mm/tlbflush.c
@@ -14,6 +14,9 @@ static void __sbi_tlb_flush_range(struct cpumask *cmask, unsigned long start,
 {
        struct cpumask hmask;
 
+       if (cpumask_empty(cmask))
+               return;
+
        riscv_cpuid_to_hartid_mask(cmask, &hmask);
        sbi_remote_sfence_vma(hmask.bits, start, size);
 }