linux-kernel - [PATCH 3.18 05/85] MIPS: io: Add barrier after register read in readX()

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Date:   Sun,  1 Jul 2018 18:01:23 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Sinan Kaya <okaya@...eaurora.org>,
        Arnd Bergmann <arnd@...db.de>,
        Ralf Baechle <ralf@...ux-mips.org>,
        Paul Burton <paul.burton@...s.com>, linux-mips@...ux-mips.org,
        James Hogan <jhogan@...nel.org>,
        Sasha Levin <alexander.levin@...rosoft.com>
Subject: [PATCH 3.18 05/85] MIPS: io: Add barrier after register read in readX()

3.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Sinan Kaya <okaya@...eaurora.org>

[ Upstream commit a1cc7034e33d12dc17d13fbcd7d597d552889097 ]

While a barrier is present in the writeX() functions before the register
write, a similar barrier is missing in the readX() functions after the
register read. This could allow memory accesses following readX() to
observe stale data.

Signed-off-by: Sinan Kaya <okaya@...eaurora.org>
Reported-by: Arnd Bergmann <arnd@...db.de>
Cc: Ralf Baechle <ralf@...ux-mips.org>
Cc: Paul Burton <paul.burton@...s.com>
Cc: linux-mips@...ux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/19069/
[jhogan@...nel.org: Tidy commit message]
Signed-off-by: James Hogan <jhogan@...nel.org>
Signed-off-by: Sasha Levin <alexander.levin@...rosoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 arch/mips/include/asm/io.h |    2 ++
 1 file changed, 2 insertions(+)

--- a/arch/mips/include/asm/io.h
+++ b/arch/mips/include/asm/io.h
@@ -375,6 +375,8 @@ static inline type pfx##read##bwlq(const
 		BUG();							\
 	}								\
 									\
+	/* prevent prefetching of coherent DMA data prematurely */	\
+	rmb();								\
 	return pfx##ioswab##bwlq(__mem, __val);				\
 }