On Thu, Mar 21, 2019 at 04:10:36PM -0700, Christoph Hellwig wrote: > If the controller supports SGLs we can take another short cut for single > segment request, given that we can always map those without another > indirection structure, and thus don't need to create a scatterlist > structure. > > Signed-off-by: Christoph Hellwig <[email protected]> > --- > drivers/nvme/host/pci.c | 22 ++++++++++++++++++++++ > 1 file changed, 22 insertions(+) > > diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c > index 47fc4d653961..38869f59c296 100644 > --- a/drivers/nvme/host/pci.c > +++ b/drivers/nvme/host/pci.c > @@ -819,6 +819,23 @@ static blk_status_t nvme_setup_prp_simple(struct > nvme_dev *dev, > return 0; > } > > +static blk_status_t nvme_setup_sgl_simple(struct nvme_dev *dev, > + struct request *req, struct nvme_rw_command *cmnd, > + struct bio_vec *bv) > +{ > + struct nvme_iod *iod = blk_mq_rq_to_pdu(req); > + > + iod->first_dma = dma_map_bvec(dev->dev, bv, rq_dma_dir(req), 0); > + if (dma_mapping_error(dev->dev, iod->first_dma)) > + return BLK_STS_RESOURCE; > + iod->dma_len = bv->bv_len; > + > + cmnd->dptr.sgl.addr = cpu_to_le64(iod->first_dma); > + cmnd->dptr.sgl.length = cpu_to_le32(iod->dma_len); > + cmnd->dptr.sgl.type = NVME_SGL_FMT_DATA_DESC << 4; > + return 0; > +} > + > static blk_status_t nvme_map_data(struct nvme_dev *dev, struct request *req, > struct nvme_command *cmnd) > { > @@ -836,6 +853,11 @@ static blk_status_t nvme_map_data(struct nvme_dev *dev, > struct request *req, > if (bv.bv_offset + bv.bv_len <= dev->ctrl.page_size * 2) > return nvme_setup_prp_simple(dev, req, > &cmnd->rw, &bv); > + > + if (iod->nvmeq->qid && > + dev->ctrl.sgls & ((1 << 0) | (1 << 1))) > + return nvme_setup_sgl_simple(dev, req, > + &cmnd->rw, &bv); > } > } > > -- > 2.20.1 >
Hi Christoph, nvme_setup_sgl_simple does not set the PSDT field, so bypassing nvme_pci_setup_sgls causing controllers to assume PRP. Adding `cmnd->flags = NVME_CMD_SGL_METABUF` in nvme_setup_sgl_simple fixes the issue. -- Klaus
