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* [PATCH] RISC-V: Issue a local tlb flush if possible.
@ 2019-08-10  1:43 Atish Patra
  2019-08-10  3:30 ` Anup Patel
                   ` (5 more replies)
  0 siblings, 6 replies; 18+ messages in thread
From: Atish Patra @ 2019-08-10  1:43 UTC (permalink / raw)
  To: linux-kernel
  Cc: Albert Ou, Alexios Zavras, Greg Kroah-Hartman, Palmer Dabbelt,
	Atish Patra, Anup Patel, Paul Walmsley, linux-riscv,
	Allison Randal

In RISC-V, tlb flush happens via SBI which is expensive.
If the target cpumask contains a local hartid, some cost
can be saved by issuing a local tlb flush as we do that
in OpenSBI anyways.

Signed-off-by: Atish Patra <atish.patra@wdc.com>
---
 arch/riscv/include/asm/tlbflush.h | 33 +++++++++++++++++++++++++++----
 1 file changed, 29 insertions(+), 4 deletions(-)

diff --git a/arch/riscv/include/asm/tlbflush.h b/arch/riscv/include/asm/tlbflush.h
index 687dd19735a7..b32ba4fa5888 100644
--- a/arch/riscv/include/asm/tlbflush.h
+++ b/arch/riscv/include/asm/tlbflush.h
@@ -8,6 +8,7 @@
 #define _ASM_RISCV_TLBFLUSH_H
 
 #include <linux/mm_types.h>
+#include <linux/sched.h>
 #include <asm/smp.h>
 
 /*
@@ -46,14 +47,38 @@ static inline void remote_sfence_vma(struct cpumask *cmask, unsigned long start,
 				     unsigned long size)
 {
 	struct cpumask hmask;
+	struct cpumask tmask;
+	int cpuid = smp_processor_id();
 
 	cpumask_clear(&hmask);
-	riscv_cpuid_to_hartid_mask(cmask, &hmask);
-	sbi_remote_sfence_vma(hmask.bits, start, size);
+	cpumask_clear(&tmask);
+
+	if (cmask)
+		cpumask_copy(&tmask, cmask);
+	else
+		cpumask_copy(&tmask, cpu_online_mask);
+
+	if (cpumask_test_cpu(cpuid, &tmask)) {
+		/* Save trap cost by issuing a local tlb flush here */
+		if ((start == 0 && size == -1) || (size > PAGE_SIZE))
+			local_flush_tlb_all();
+		else if (size == PAGE_SIZE)
+			local_flush_tlb_page(start);
+		cpumask_clear_cpu(cpuid, &tmask);
+	} else if (cpumask_empty(&tmask)) {
+		/* cpumask is empty. So just do a local flush */
+		local_flush_tlb_all();
+		return;
+	}
+
+	if (!cpumask_empty(&tmask)) {
+		riscv_cpuid_to_hartid_mask(&tmask, &hmask);
+		sbi_remote_sfence_vma(hmask.bits, start, size);
+	}
 }
 
-#define flush_tlb_all() sbi_remote_sfence_vma(NULL, 0, -1)
-#define flush_tlb_page(vma, addr) flush_tlb_range(vma, addr, 0)
+#define flush_tlb_all() remote_sfence_vma(NULL, 0, -1)
+#define flush_tlb_page(vma, addr) flush_tlb_range(vma, addr, (addr) + PAGE_SIZE)
 #define flush_tlb_range(vma, start, end) \
 	remote_sfence_vma(mm_cpumask((vma)->vm_mm), start, (end) - (start))
 #define flush_tlb_mm(mm) \
-- 
2.21.0


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^ permalink raw reply related	[flat|nested] 18+ messages in thread

end of thread, other threads:[~2019-08-20  0:03 UTC | newest]

Thread overview: 18+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2019-08-10  1:43 [PATCH] RISC-V: Issue a local tlb flush if possible Atish Patra
2019-08-10  3:30 ` Anup Patel
2019-08-10  5:28   ` Atish Patra
2019-08-10  6:37 ` Andreas Schwab
2019-08-10  9:21 ` Atish Patra
2019-08-12 14:56 ` Christoph Hellwig
2019-08-13  0:15   ` Atish Patra
2019-08-13 14:30     ` hch
2019-08-15 20:37       ` Atish Patra
2019-08-19 14:46         ` hch
2019-08-19 15:09           ` Anup Patel
2019-08-19 15:10             ` hch
2019-08-20  0:02               ` Atish Patra
2019-08-12 15:36 ` Troy Benjegerdes
2019-08-12 17:13   ` Atish Patra
2019-08-12 17:55   ` Christoph Hellwig
2019-08-13 18:25 ` Paul Walmsley
2019-08-14  1:49   ` Atish Patra

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