linux-kernel - [PATCH v2] powerpc/32s: Don't flush all TLBs when flushing one page

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Message-Id: <b30b2eae6960502eaf0d9e36c60820b839693c33.1580542939.git.christophe.leroy@c-s.fr>
Date:   Sat,  1 Feb 2020 08:04:31 +0000 (UTC)
From:   Christophe Leroy <christophe.leroy@....fr>
To:     Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>
Cc:     linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org
Subject: [PATCH v2] powerpc/32s: Don't flush all TLBs when flushing one page

When flushing any memory range, the flushing function
flushes all TLBs.

When (start) and (end - 1) are in the same memory page,
flush that page instead.

Signed-off-by: Christophe Leroy <christophe.leroy@....fr>
---
v2: Reworked the test as the previous one was always false (end - start was PAGE_SIZE - 1 for a single page)
---
 arch/powerpc/mm/book3s32/tlb.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/arch/powerpc/mm/book3s32/tlb.c b/arch/powerpc/mm/book3s32/tlb.c
index 2fcd321040ff..724c0490fb17 100644
--- a/arch/powerpc/mm/book3s32/tlb.c
+++ b/arch/powerpc/mm/book3s32/tlb.c
@@ -79,11 +79,14 @@ static void flush_range(struct mm_struct *mm, unsigned long start,
 	int count;
 	unsigned int ctx = mm->context.id;
 
+	start &= PAGE_MASK;
 	if (!Hash) {
-		_tlbia();
+		if (end - start <= PAGE_SIZE)
+			_tlbie(start);
+		else
+			_tlbia();
 		return;
 	}
-	start &= PAGE_MASK;
 	if (start >= end)
 		return;
 	end = (end - 1) | ~PAGE_MASK;
-- 
2.25.0