[PATCH V8 5/5] libata: Align DMA buffer to dma_get_cache_alignment()

[Huacai Chen <chenhc@lemote.com>]

In non-coherent DMA mode, kernel uses cache flushing operations to
maintain I/O coherency, so in ata_do_dev_read_id() the DMA buffer
should be aligned to ARCH_DMA_MINALIGN. Otherwise, If a DMA buffer
and a kernel structure share a same cache line, and if the kernel
structure has dirty data, cache_invalidate (no writeback) will cause
data corruption.

Cc: stable@vger.kernel.org
Signed-off-by: Huacai Chen <chenhc@lemote.com>
---
 drivers/ata/libata-core.c | 15 +++++++++++++--
 1 file changed, 13 insertions(+), 2 deletions(-)

diff --git a/drivers/ata/libata-core.c b/drivers/ata/libata-core.c
index ee4c1ec..e134955 100644
--- a/drivers/ata/libata-core.c
+++ b/drivers/ata/libata-core.c
@@ -1833,8 +1833,19 @@ static u32 ata_pio_mask_no_iordy(const struct ata_device *adev)
 unsigned int ata_do_dev_read_id(struct ata_device *dev,
 					struct ata_taskfile *tf, u16 *id)
 {
-	return ata_exec_internal(dev, tf, NULL, DMA_FROM_DEVICE,
-				     id, sizeof(id[0]) * ATA_ID_WORDS, 0);
+	u16 *devid;
+	int res, size = sizeof(u16) * ATA_ID_WORDS;
+
+	if (IS_ALIGNED((unsigned long)id, dma_get_cache_alignment(&dev->tdev)))
+		res = ata_exec_internal(dev, tf, NULL, DMA_FROM_DEVICE, id, size, 0);
+	else {
+		devid = kmalloc(size, GFP_KERNEL);
+		res = ata_exec_internal(dev, tf, NULL, DMA_FROM_DEVICE, devid, size, 0);
+		memcpy(id, devid, size);
+		kfree(devid);
+	}
+
+	return res;
 }
 
 /**
-- 
2.7.0