[PATCH v4 1/3] RISC-V: Do not invoke SBI call if cpumask is empty

From: Atish Patra <atish.patra@wdc.com>
To: linux-kernel@vger.kernel.org
Cc: Atish Patra <atish.patra@wdc.com>,
	Albert Ou <aou@eecs.berkeley.edu>,
	linux-riscv@lists.infradead.org,
	Palmer Dabbelt <palmer@sifive.com>,
	Paul Walmsley <paul.walmsley@sifive.com>,
	Christoph Hellwig <hch@lst.de>, Anup Patel <Anup.Patel@wdc.com>
Subject: [PATCH v4 1/3] RISC-V: Do not invoke SBI call if cpumask is empty
Date: Thu, 22 Aug 2019 00:51:49 -0700	[thread overview]
Message-ID: <20190822075151.24838-2-atish.patra@wdc.com> (raw)
In-Reply-To: <20190822075151.24838-1-atish.patra@wdc.com>

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>
---
 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 df93b26f1b9d..1293b8017ee0 100644
--- 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);
 }
-- 
2.21.0

