linux-kernel - [PATCH 3.16.y-ckt 084/142] libata: Align ata

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Message-Id: <1458643271-4227-85-git-send-email-luis.henriques@canonical.com>
Date:	Tue, 22 Mar 2016 10:40:13 +0000
From:	Luis Henriques <luis.henriques@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	Harvey Hunt <harvey.hunt@...tec.com>, Tejun Heo <tj@...nel.org>,
	Luis Henriques <luis.henriques@...onical.com>
Subject: [PATCH 3.16.y-ckt 084/142] libata: Align ata_device's id on a cacheline

3.16.7-ckt26 -stable review patch.  If anyone has any objections, please let me know.

---8<------------------------------------------------------------

From: Harvey Hunt <harvey.hunt@...tec.com>

commit 4ee34ea3a12396f35b26d90a094c75db95080baa upstream.

The id buffer in ata_device is a DMA target, but it isn't explicitly
cacheline aligned. Due to this, adjacent fields can be overwritten with
stale data from memory on non coherent architectures. As a result, the
kernel is sometimes unable to communicate with an ATA device.

Fix this by ensuring that the id buffer is cacheline aligned.

This issue is similar to that fixed by Commit 84bda12af31f
("libata: align ap->sector_buf").

Signed-off-by: Harvey Hunt <harvey.hunt@...tec.com>
Cc: linux-kernel@...r.kernel.org
Signed-off-by: Tejun Heo <tj@...nel.org>
Signed-off-by: Luis Henriques <luis.henriques@...onical.com>
---
 include/linux/libata.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/libata.h b/include/linux/libata.h
index 714274450c07..bd83b8e83cfe 100644
--- a/include/linux/libata.h
+++ b/include/linux/libata.h
@@ -714,7 +714,7 @@ struct ata_device {
 	union {
 		u16		id[ATA_ID_WORDS]; /* IDENTIFY xxx DEVICE data */
 		u32		gscr[SATA_PMP_GSCR_DWORDS]; /* PMP GSCR block */
-	};
+	} ____cacheline_aligned;
 
 	/* DEVSLP Timing Variables from Identify Device Data Log */
 	u8			devslp_timing[ATA_LOG_DEVSLP_SIZE];