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Tue, 13 Oct 2026 13:55:32 -0700 (PDT) From: Pavel Begunkov To: linux-block@vger.kernel.org Cc: asml.silence@gmail.com, linux-kernel@vger.kernel.org, linux-media@vger.kernel.org, dri-devel@lists.freedesktop.org, linaro-mm-sig@lists.linaro.org, linux-nvme@lists.infradead.org, linux-fsdevel@vger.kernel.org, io-uring@vger.kernel.org, Christoph Hellwig , Sumit Semwal , =?UTF-8?q?Christian=20K=C3=B6nig?= , Keith Busch , Sagi Grimberg , Alexander Viro , Christian Brauner , Jan Kara , Andrew Morton , Jens Axboe , Nitesh Shetty , Kanchan Joshi , Anuj Gupta , Tushar Gohad , William Power , Matthew Brost , Alasdair Kergon , Mike Snitzer , Mikulas Patocka , Benjamin Marzinski , dm-devel@lists.linux.dev Subject: [PATCH v10 08/13] nvme-pci: add SGL support for the dmabuf path Date: Tue, 13 Oct 2026 21:54:52 +0100 Message-ID: <892e9887dabf195633d376de113b775b29ae7dd3.1791924581.git.asml.silence@gmail.com> X-Mailer: git-send-email 2.54.0 In-Reply-To: References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Anuj Gupta Add SGL support in addition to PRP for dmabuf-backed requests, building the descriptor list from the mapping's sg_table. Reviewed-by: Christoph Hellwig Signed-off-by: Anuj Gupta Signed-off-by: Pavel Begunkov --- drivers/nvme/host/pci.c | 150 ++++++++++++++++++++++++++++++++++++++-- 1 file changed, 146 insertions(+), 4 deletions(-) diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c index a0506c93fa16..79b3c1092e4d 100644 --- a/drivers/nvme/host/pci.c +++ b/drivers/nvme/host/pci.c @@ -1223,12 +1223,18 @@ static blk_status_t nvme_pci_setup_data_prp(struct request *req, return BLK_STS_IOERR; } +static void nvme_pci_sgl_set_data(struct nvme_sgl_desc *sge, + dma_addr_t addr, u32 len) +{ + sge->addr = cpu_to_le64(addr); + sge->length = cpu_to_le32(len); + sge->type = NVME_SGL_FMT_DATA_DESC << 4; +} + static void nvme_pci_dma_iter_set_sgl(struct nvme_sgl_desc *sge, struct blk_dma_iter *iter) { - sge->addr = cpu_to_le64(iter->addr); - sge->length = cpu_to_le32(iter->len); - sge->type = NVME_SGL_FMT_DATA_DESC << 4; + nvme_pci_sgl_set_data(sge, iter->addr, iter->len); } static void nvme_pci_sgl_set_seg(struct nvme_sgl_desc *sge, @@ -1239,6 +1245,142 @@ static void nvme_pci_sgl_set_seg(struct nvme_sgl_desc *sge, sge->type = NVME_SGL_FMT_LAST_SEG_DESC << 4; } +static unsigned int nvme_pci_dmabuf_sgl_nents(struct request *req) +{ + struct bio *bio = req->bio; + struct nvme_dmabuf_map *map = to_nvme_dmabuf_map(bio->bi_dmabuf_map); + struct scatterlist *sg; + unsigned long tmp; + size_t offset = bio->bi_iter.bi_offset; + size_t remaining = blk_rq_payload_bytes(req); + unsigned int nents = 0; + + for_each_sgtable_dma_sg(map->sgt, sg, tmp) { + size_t sg_len = sg_dma_len(sg); + + if (!remaining) + break; + if (offset >= sg_len) { + offset -= sg_len; + continue; + } + + sg_len -= offset; + offset = 0; + + do { + size_t chunk = min(remaining, sg_len); + + nents++; + sg_len -= chunk; + remaining -= chunk; + } while (sg_len && remaining); + } + + if (unlikely(remaining)) + return 0; + + return nents; +} + +static blk_status_t nvme_rq_setup_dmabuf_sgl(struct request *req, + struct nvme_queue *nvmeq, unsigned int entries) +{ + struct nvme_iod *iod = blk_mq_rq_to_pdu(req); + struct nvme_dmabuf_map *map = nvme_req_to_map(req); + size_t length = blk_rq_payload_bytes(req); + struct nvme_sgl_desc *sg_list = &iod->cmd.common.dptr.sgl; + size_t offset = req->bio->bi_iter.bi_offset; + bool pooled = entries > 1; + dma_addr_t sgl_dma = 0; + unsigned int mapped = 0; + unsigned long tmp; + struct scatterlist *sg; + size_t remaining = length; + + if (!entries) + return BLK_STS_IOERR; + + iod->cmd.common.flags = NVME_CMD_SGL_METABUF; + iod->total_len = length; + + /* entries == 1 fits in the inline descriptor; more needs a pool. */ + if (pooled) { + if (entries <= NVME_SMALL_POOL_SIZE / sizeof(*sg_list)) + iod->flags |= IOD_SMALL_DESCRIPTOR; + + sg_list = dma_pool_alloc(nvme_dma_pool(nvmeq, iod), GFP_ATOMIC, + &sgl_dma); + if (!sg_list) + return BLK_STS_RESOURCE; + iod->descriptors[iod->nr_descriptors++] = sg_list; + } + + for_each_sgtable_dma_sg(map->sgt, sg, tmp) { + size_t sg_len = sg_dma_len(sg); + dma_addr_t addr = sg_dma_address(sg); + + if (!remaining) + break; + if (offset >= sg_len) { + offset -= sg_len; + continue; + } + + addr += offset; + sg_len -= offset; + offset = 0; + + do { + u32 chunk = min_t(size_t, remaining, sg_len); + + if (WARN_ON_ONCE(mapped == entries)) + goto err_free; + nvme_pci_sgl_set_data(&sg_list[mapped++], addr, chunk); + + addr += chunk; + sg_len -= chunk; + remaining -= chunk; + } while (sg_len && remaining); + } + + if (unlikely(remaining)) + goto err_free; + + if (pooled) + nvme_pci_sgl_set_seg(&iod->cmd.common.dptr.sgl, sgl_dma, + mapped); + return BLK_STS_OK; +err_free: + if (pooled) { + iod->nr_descriptors--; + dma_pool_free(nvme_dma_pool(nvmeq, iod), sg_list, sgl_dma); + } + return BLK_STS_IOERR; +} + +static blk_status_t nvme_rq_setup_dmabuf(struct request *req, + struct nvme_queue *nvmeq, enum nvme_use_sgl use_sgl) +{ + unsigned int entries; + size_t avg_seg; + + if (use_sgl == SGL_UNSUPPORTED) + return nvme_rq_setup_dmabuf_map(req, nvmeq); + + entries = nvme_pci_dmabuf_sgl_nents(req); + + if (use_sgl == SGL_FORCED) + return nvme_rq_setup_dmabuf_sgl(req, nvmeq, entries); + + avg_seg = entries ? + DIV_ROUND_UP(blk_rq_payload_bytes(req), entries) : 0; + if (sgl_threshold && avg_seg >= sgl_threshold) + return nvme_rq_setup_dmabuf_sgl(req, nvmeq, entries); + + return nvme_rq_setup_dmabuf_map(req, nvmeq); +} + static blk_status_t nvme_pci_setup_data_sgl(struct request *req, struct blk_dma_iter *iter) { @@ -1334,7 +1476,7 @@ static blk_status_t nvme_map_data(struct request *req) blk_status_t ret; if (blk_mq_rq_is_dmabuf(req)) - return nvme_rq_setup_dmabuf_map(req, nvmeq); + return nvme_rq_setup_dmabuf(req, nvmeq, use_sgl); /* * Try to skip the DMA iterator for single segment requests, as that -- 2.54.0