DMA-BUF API allows devices to export buffers for other devices to
access. This can provide a means to implement peer to peer communication
for RDMA. A device with internal memory would expose its memory to the
PCIe BAR, and export that region as a DMA-BUF object. Then, the user or
ULP would register a memory region that is backed by the DMA-BUF object.
Signed-off-by: Haggai Eran <haggaie@xxxxxxxxxxxx>
---
drivers/infiniband/core/verbs.c | 60 +++++++++++++++++++++++++++++++++++++++++
include/rdma/ib_verbs.h | 9 +++++++
2 files changed, 69 insertions(+)
diff --git a/drivers/infiniband/core/verbs.c b/drivers/infiniband/core/verbs.c
index 6298f54b4137..633831e77a62 100644
--- a/drivers/infiniband/core/verbs.c
+++ b/drivers/infiniband/core/verbs.c
@@ -44,6 +44,7 @@
#include <linux/in.h>
#include <linux/in6.h>
#include <net/addrconf.h>
+#include <linux/dma-buf.h>
#include <rdma/ib_verbs.h>
#include <rdma/ib_cache.h>
@@ -1922,3 +1923,62 @@ void ib_drain_qp(struct ib_qp *qp)
ib_drain_rq(qp);
}
EXPORT_SYMBOL(ib_drain_qp);
+
+int ib_mr_attach_dmabuf(struct ib_mr *mr, struct dma_buf *dmabuf, int access)
+{
+ struct device *dev = mr->device->dma_device;
+ struct dma_buf_attachment *attach;
+ struct sg_table *sg;
+ int err;
+ int n;
+
+ get_dma_buf(dmabuf);
+
+ attach = dma_buf_attach(dmabuf, dev);
+ if (IS_ERR(attach)) {
+ dev_err(dev, "unable to attach to DMA-BUF object (from %s): %ld",
+ dmabuf->exp_name, PTR_ERR(attach));
+ err = PTR_ERR(attach);
+ goto put_dma_buf;
+ }
+
+ sg = dma_buf_map_attachment(attach, DMA_BIDIRECTIONAL);
+ if (IS_ERR(sg)) {
+ dev_err(dev, "unable to map a DMA-BUF object (from %s): %ld",
+ dmabuf->exp_name, PTR_ERR(sg));
+ err = PTR_ERR(sg);
+ goto detach;
+ }
+
+ n = ib_map_mr_sg_zbva(mr, sg->sgl, sg->nents, NULL, PAGE_SIZE);
+ if (unlikely(n != sg->nents)) {
+ dev_err(dev, "failed to map sg (%d/%d) of DMA-BUF object (from %s)\n",
+ n, sg->nents, dmabuf->exp_name);
+ err = n < 0 ? n : -EINVAL;
+ goto unmap;
+ }
+
+ mr->attach = attach;
+ mr->sg = sg;
+ return 0;
+
+unmap:
+ dma_buf_unmap_attachment(attach, sg, DMA_BIDIRECTIONAL);
+detach:
+ dma_buf_detach(dmabuf, attach);
+put_dma_buf:
+ dma_buf_put(dmabuf);
+ return err;
+}
+EXPORT_SYMBOL(ib_mr_attach_dmabuf);
+
+void ib_mr_detach_dmabuf(struct dma_buf_attachment *attach,
+ struct sg_table *sg)
+{
+ struct dma_buf *dmabuf = attach->dmabuf;
+
+ dma_buf_unmap_attachment(attach, sg, DMA_BIDIRECTIONAL);
+ dma_buf_detach(dmabuf, attach);
+ dma_buf_put(dmabuf);
+}
+EXPORT_SYMBOL(ib_mr_detach_dmabuf);
diff --git a/include/rdma/ib_verbs.h b/include/rdma/ib_verbs.h
index 7e440d41487a..da23ec0a06d7 100644
--- a/include/rdma/ib_verbs.h
+++ b/include/rdma/ib_verbs.h
@@ -1465,6 +1465,9 @@ struct ib_mr {
struct ib_uobject *uobject; /* user */
struct list_head qp_entry; /* FR */
};
+ /* For MRs that expose a DMA-BUF */
+ struct dma_buf_attachment *attach;
+ struct sg_table *sg;
};
struct ib_mw {
@@ -3189,4 +3192,10 @@ int ib_sg_to_pages(struct ib_mr *mr, struct scatterlist *sgl, int sg_nents,
void ib_drain_rq(struct ib_qp *qp);
void ib_drain_sq(struct ib_qp *qp);
void ib_drain_qp(struct ib_qp *qp);
+
+struct dma_buf;
+int ib_mr_attach_dmabuf(struct ib_mr *mr, struct dma_buf *dmabuf, int access);
+void ib_mr_detach_dmabuf(struct dma_buf_attachment *attach,
+ struct sg_table *sg);
+
#endif /* IB_VERBS_H */
--
1.7.11.2
--
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