[PATCH V2 3/3] Adding device_dma_parameters->offset_preserve_mask to NVMe driver.

[Jianxiong Gao]

NVMe driver relies on the address offset to function properly.
This patch adds the offset preserve mask to NVMe driver when mapping
via dma_map_sg_attrs and unmapping via nvme_unmap_sg. The mask
depends on the page size defined by CC.MPS register of NVMe
controller.

Signed-off-by: Jianxiong Gao <jx...@google.com>
---
 drivers/nvme/host/pci.c | 19 +++++++++++++++++--
 1 file changed, 17 insertions(+), 2 deletions(-)

diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c
index 81e6389b2042..30e45f7e0f75 100644
--- a/drivers/nvme/host/pci.c
+++ b/drivers/nvme/host/pci.c
@@ -580,12 +580,15 @@ static void nvme_free_sgls(struct nvme_dev *dev, struct 
request *req)
 static void nvme_unmap_sg(struct nvme_dev *dev, struct request *req)
 {
        struct nvme_iod *iod = blk_mq_rq_to_pdu(req);
-
+       if (dma_set_min_align_mask(dev->dev, NVME_CTRL_PAGE_SIZE - 1))
+               dev_warn(dev->dev, "dma_set_min_align_mask failed to set 
offset\n");
        if (is_pci_p2pdma_page(sg_page(iod->sg)))
                pci_p2pdma_unmap_sg(dev->dev, iod->sg, iod->nents,
                                    rq_dma_dir(req));
        else
                dma_unmap_sg(dev->dev, iod->sg, iod->nents, rq_dma_dir(req));
+       if (dma_set_min_align_mask(dev->dev, 0))
+               dev_warn(dev->dev, "dma_set_min_align_mask failed to reset 
offset\n");
 }
 
 static void nvme_unmap_data(struct nvme_dev *dev, struct request *req)
@@ -842,7 +845,7 @@ static blk_status_t nvme_map_data(struct nvme_dev *dev, 
struct request *req,
 {
        struct nvme_iod *iod = blk_mq_rq_to_pdu(req);
        blk_status_t ret = BLK_STS_RESOURCE;
-       int nr_mapped;
+       int nr_mapped, offset_ret;
 
        if (blk_rq_nr_phys_segments(req) == 1) {
                struct bio_vec bv = req_bvec(req);
@@ -868,12 +871,24 @@ static blk_status_t nvme_map_data(struct nvme_dev *dev, 
struct request *req,
        if (!iod->nents)
                goto out_free_sg;
 
+       offset_ret = dma_set_min_align_mask(dev->dev, NVME_CTRL_PAGE_SIZE - 1);
+       if (offset_ret) {
+               dev_warn(dev->dev, "dma_set_min_align_mask failed to set 
offset\n");
+               goto out_free_sg;
+       }
+
        if (is_pci_p2pdma_page(sg_page(iod->sg)))
                nr_mapped = pci_p2pdma_map_sg_attrs(dev->dev, iod->sg,
                                iod->nents, rq_dma_dir(req), DMA_ATTR_NO_WARN);
        else
                nr_mapped = dma_map_sg_attrs(dev->dev, iod->sg, iod->nents,
                                             rq_dma_dir(req), DMA_ATTR_NO_WARN);
+
+       offset_ret = dma_set_min_align_mask(dev->dev, 0);
+       if (offset_ret) {
+               dev_warn(dev->dev, "dma_set_min_align_mask failed to reset 
offset\n");
+               goto out_free_sg;
+       }
        if (!nr_mapped)
                goto out_free_sg;
 
-- 
2.27.0