linux-kernel - [PATCH v3 3/3] RISC-V: Do not invoke SBI call if cpumask is empty

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Date:   Wed, 21 Aug 2019 17:46:44 -0700
From:   Atish Patra <atish.patra@....com>
To:     linux-kernel@...r.kernel.org
Cc:     Atish Patra <atish.patra@....com>,
        Albert Ou <aou@...s.berkeley.edu>,
        linux-riscv@...ts.infradead.org,
        Palmer Dabbelt <palmer@...ive.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Christoph Hellwig <hch@....de>,
        Anup Patel <Anup.Patel@....com>,
        Andreas Schwab <schwab@...ux-m68k.org>
Subject: [PATCH v3 3/3] 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@....com>
---
 arch/riscv/mm/tlbflush.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/riscv/mm/tlbflush.c b/arch/riscv/mm/tlbflush.c
index 9f58b3790baa..2bd3c418d769 100644
--- a/arch/riscv/mm/tlbflush.c
+++ b/arch/riscv/mm/tlbflush.c
@@ -21,6 +21,9 @@ static void __sbi_tlb_flush_range(struct cpumask *cmask, unsigned long start,
 		goto issue_sfence;
 	}
 
+	if (cpumask_empty(cmask))
+		goto done;
+
 	if (cpumask_test_cpu(cpuid, cmask) && cpumask_weight(cmask) == 1) {
 		if (size <= PAGE_SIZE && size != -1)
 			local_flush_tlb_page(start);
-- 
2.21.0