linux-kernel - [PATCH v2 3/3] block: sed-opal: Cache-line-align the cmd/resp buffers

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Date:   Fri, 30 Sep 2022 01:46:48 +0300
From:   Serge Semin <Sergey.Semin@...kalelectronics.ru>
To:     Jens Axboe <axboe@...nel.dk>, Keith Busch <kbusch@...nel.org>,
        Jens Axboe <axboe@...com>, Christoph Hellwig <hch@....de>,
        Sagi Grimberg <sagi@...mberg.me>,
        Jonathan Derrick <jonathan.derrick@...el.com>,
        Revanth Rajashekar <revanth.rajashekar@...el.com>,
        Rafael Antognolli <Rafael.Antognolli@...el.com>,
        Scott Bauer <scott.bauer@...el.com>
CC:     Serge Semin <Sergey.Semin@...kalelectronics.ru>,
        Serge Semin <fancer.lancer@...il.com>,
        Alexey Malahov <Alexey.Malahov@...kalelectronics.ru>,
        Pavel Parkhomenko <Pavel.Parkhomenko@...kalelectronics.ru>,
        Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        <linux-nvme@...ts.infradead.org>, <linux-block@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
Subject: [PATCH v2 3/3] block: sed-opal: Cache-line-align the cmd/resp buffers

In accordance with [1] the DMA-able memory buffers must be
cacheline-aligned otherwise the cache writing-back and invalidation
performed during the mapping may cause the adjacent data being lost. It's
specifically required for the DMA-noncoherent platforms. Seeing the
opal_dev.{cmd,resp} buffers are used for DMAs in the NVME and SCSI/SD
drivers in framework of the nvme_sec_submit() and sd_sec_submit() methods
respectively we must make sure the passed buffers are cacheline-aligned to
prevent the denoted problem.

[1] Documentation/core-api/dma-api.rst

Fixes: 455a7b238cd6 ("block: Add Sed-opal library")
Signed-off-by: Serge Semin <Sergey.Semin@...kalelectronics.ru>
---
 block/sed-opal.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/block/sed-opal.c b/block/sed-opal.c
index 9700197000f2..222acbd1f03a 100644
--- a/block/sed-opal.c
+++ b/block/sed-opal.c
@@ -73,6 +73,7 @@ struct parsed_resp {
 	struct opal_resp_tok toks[MAX_TOKS];
 };
 
+/* Presumably DMA-able buffers must be cache-aligned */
 struct opal_dev {
 	bool supported;
 	bool mbr_enabled;
@@ -88,8 +89,8 @@ struct opal_dev {
 	u64 lowest_lba;
 
 	size_t pos;
-	u8 cmd[IO_BUFFER_LENGTH];
-	u8 resp[IO_BUFFER_LENGTH];
+	u8 cmd[IO_BUFFER_LENGTH] ____cacheline_aligned;
+	u8 resp[IO_BUFFER_LENGTH] ____cacheline_aligned;
 
 	struct parsed_resp parsed;
 	size_t prev_d_len;
-- 
2.37.3