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Subject[PATCH v3 1/3] RISC-V: Issue a local tlbflush if possible.
Date
In RISC-V, tlb flush happens via SBI which is expensive. If the local
cpu is the only cpu in cpumask, there is no need to invoke a SBI call.

Just do a local flush and return.

Signed-off-by: Atish Patra <atish.patra@wdc.com>
---
arch/riscv/mm/tlbflush.c | 15 +++++++++++++++
1 file changed, 15 insertions(+)

diff --git a/arch/riscv/mm/tlbflush.c b/arch/riscv/mm/tlbflush.c
index df93b26f1b9d..36430ee3bed9 100644
--- a/arch/riscv/mm/tlbflush.c
+++ b/arch/riscv/mm/tlbflush.c
@@ -2,6 +2,7 @@

#include <linux/mm.h>
#include <linux/smp.h>
+#include <linux/sched.h>
#include <asm/sbi.h>

void flush_tlb_all(void)
@@ -13,9 +14,23 @@ static void __sbi_tlb_flush_range(struct cpumask *cmask, unsigned long start,
unsigned long size)
{
struct cpumask hmask;
+ unsigned int cpuid = get_cpu();

+ if (!cmask) {
+ riscv_cpuid_to_hartid_mask(cpu_online_mask, &hmask);
+ goto issue_sfence;
+ }
+
+ if (cpumask_test_cpu(cpuid, cmask) && cpumask_weight(cmask) == 1) {
+ local_flush_tlb_all();
+ goto done;
+ }
riscv_cpuid_to_hartid_mask(cmask, &hmask);
+
+issue_sfence:
sbi_remote_sfence_vma(hmask.bits, start, size);
+done:
+ put_cpu();
}

void flush_tlb_mm(struct mm_struct *mm)
--
2.21.0
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