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From: Yihang Li <liyihang9@huawei.com>
To: <john.g.garry@oracle.com>, <yanaijie@huawei.com>, <jejb@linux.ibm.com>,
	<martin.petersen@oracle.com>, <dlemoal@kernel.org>,
	<chenxiang66@hisilicon.com>
CC: <linux-scsi@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
	<linuxarm@huawei.com>, <prime.zeng@huawei.com>, <yangxingui@huawei.com>,
	<liyihang9@huawei.com>
Subject: [PATCH v4] scsi: libsas: Allocation SMP request is aligned to ARCH_DMA_MINALIGN
Date: Thu, 28 Mar 2024 17:06:26 +0800
Message-ID: <20240328090626.621147-1-liyihang9@huawei.com>
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This series [1] reducing the kmalloc() minimum alignment on arm64 to 8
(from 128). In libsas, this will cause SMP requests to be 8-byte-aligned
through kmalloc() allocation. However, for the hisi_sas hardware, all
commands address must be 16-byte-aligned. Otherwise, the commands fail to
be executed.

ARCH_DMA_MINALIGN represents the minimum (static) alignment for safe DMA
operations, so use ARCH_DMA_MINALIGN as the alignment for SMP request.

Link: https://lkml.kernel.org/r/20230612153201.554742-1-catalin.marinas@arm.com [1]
Signed-off-by: Yihang Li <liyihang9@huawei.com>
Reviewed-by: Damien Le Moal <dlemoal@kernel.org>
---
Changes since v3:
- Still aligned to ARCH_DMA_MINALIGN for safe DMA operations.

Changes since v2:
- Use 16B as alignment for SMP requests instead of ARCH_DMA_MINALIGN.

Changes since v1:
- Directly modify alloc_smp_req() instead of using handler callback.
---
 drivers/scsi/libsas/sas_expander.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/scsi/libsas/sas_expander.c b/drivers/scsi/libsas/sas_expander.c
index a2204674b680..c989d182fc75 100644
--- a/drivers/scsi/libsas/sas_expander.c
+++ b/drivers/scsi/libsas/sas_expander.c
@@ -135,7 +135,7 @@ static int smp_execute_task(struct domain_device *dev, void *req, int req_size,
 
 static inline void *alloc_smp_req(int size)
 {
-	u8 *p = kzalloc(size, GFP_KERNEL);
+	u8 *p = kzalloc(ALIGN(size, ARCH_DMA_MINALIGN), GFP_KERNEL);
 	if (p)
 		p[0] = SMP_REQUEST;
 	return p;
-- 
2.33.0