linux-kernel - [PATCH v2] scsi: libsas: Allocation SMP request is aligned to ARCH_DMA

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Date: Tue, 26 Mar 2024 20:43:58 +0800
From: Yihang Li <liyihang9@...wei.com>
To: <john.g.garry@...cle.com>, <yanaijie@...wei.com>, <jejb@...ux.ibm.com>,
	<martin.petersen@...cle.com>, <dlemoal@...nel.org>,
	<chenxiang66@...ilicon.com>
CC: <linux-scsi@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<linuxarm@...wei.com>, <prime.zeng@...wei.com>, <yangxingui@...wei.com>,
	<liyihang9@...wei.com>
Subject: [PATCH v2] scsi: libsas: Allocation SMP request is aligned to ARCH_DMA_MINALIGN

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@...wei.com>
---
Changes since v1:
- Directly modify alloc_smp_req() instead of using handler callback.
---
 drivers/scsi/libsas/sas_expander.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/scsi/libsas/sas_expander.c b/drivers/scsi/libsas/sas_expander.c
index a2204674b680..941abc7298df 100644
--- a/drivers/scsi/libsas/sas_expander.c
+++ b/drivers/scsi/libsas/sas_expander.c
@@ -135,7 +135,10 @@ 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;
+
+	size = ALIGN(size, ARCH_DMA_MINALIGN);
+	p = kzalloc(size, GFP_KERNEL);
 	if (p)
 		p[0] = SMP_REQUEST;
 	return p;
-- 
2.33.0