On 28/03/2024 09:06, Yihang Li wrote:
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.
I'd say that we must align to at least ARCH_DMA_MINALIGN for memory
which we want to map for DMA. ARCH_DMA_MINALIGN would never be less than
the 16B requirement for hisi_sas, so just align to ARCH_DMA_MINALIGN.
Link: https://urldefense.com/v3/__https://lkml.kernel.org/r/20230612153201.554742-1-catalin.marinas@arm.com__;!!ACWV5N9M2RV99hQ!LbkCJSfklWds8mk0UGjtg0qRNpWuAc-ibudDMl7sI_Qip4Hd6WNqHZmRbuJfObd4fcZXj0sC8nGTs1UbA5PlCA$ [1]
Signed-off-by: Yihang Li <liyihang9@xxxxxxxxxx>
Reviewed-by: Damien Le Moal <dlemoal@xxxxxxxxxx>
Reviewed-by: John Garry <john.g.garry@xxxxxxxxxx>
---
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;
