2022-06-15 16:16:21

by Logan Gunthorpe

Subject: [PATCH v7 11/21] RDMA/core: introduce ib_dma_pci_p2p_dma_supported()

Introduce the helper function ib_dma_pci_p2p_dma_supported() to check
if a given ib_device can be used in P2PDMA transfers. This ensures
the ib_device is not using virt_dma and also that the underlying
dma_device supports P2PDMA.

Use the new helper in nvme-rdma to replace the existing check for
ib_uses_virt_dma(). Adding the dma_pci_p2pdma_supported() check allows
switching away from pci_p2pdma_[un]map_sg().

Signed-off-by: Logan Gunthorpe <[email protected]>
Reviewed-by: Jason Gunthorpe <[email protected]>
Reviewed-by: Max Gurtovoy <[email protected]>
---
drivers/nvme/target/rdma.c | 2 +-
include/rdma/ib_verbs.h | 11 +++++++++++
2 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/drivers/nvme/target/rdma.c b/drivers/nvme/target/rdma.c
index 09fdcac87d17..4597bca43a6d 100644
--- a/drivers/nvme/target/rdma.c
+++ b/drivers/nvme/target/rdma.c
@@ -415,7 +415,7 @@ static int nvmet_rdma_alloc_rsp(struct nvmet_rdma_device *ndev,
if (ib_dma_mapping_error(ndev->device, r->send_sge.addr))
goto out_free_rsp;

- if (!ib_uses_virt_dma(ndev->device))
+ if (ib_dma_pci_p2p_dma_supported(ndev->device))
r->req.p2p_client = &ndev->device->dev;
r->send_sge.length = sizeof(*r->req.cqe);
r->send_sge.lkey = ndev->pd->local_dma_lkey;
diff --git a/include/rdma/ib_verbs.h b/include/rdma/ib_verbs.h
index 9c6317cf80d5..523843d9ed6c 100644
--- a/include/rdma/ib_verbs.h
+++ b/include/rdma/ib_verbs.h
@@ -4013,6 +4013,17 @@ static inline bool ib_uses_virt_dma(struct ib_device *dev)
return IS_ENABLED(CONFIG_INFINIBAND_VIRT_DMA) && !dev->dma_device;
}

+/*
+ * Check if a IB device's underlying DMA mapping supports P2PDMA transfers.
+ */
+static inline bool ib_dma_pci_p2p_dma_supported(struct ib_device *dev)
+{
+ if (ib_uses_virt_dma(dev))
+ return false;
+
+ return dma_pci_p2pdma_supported(dev->dma_device);
+}
+
/**
* ib_dma_mapping_error - check a DMA addr for error
* @dev: The device for which the dma_addr was created
--
2.30.2

2022-06-29 07:00:51

by Christoph Hellwig

Subject: Re: [PATCH v7 11/21] RDMA/core: introduce ib_dma_pci_p2p_dma_supported()

On Wed, Jun 15, 2022 at 10:12:23AM -0600, Logan Gunthorpe wrote:
> Introduce the helper function ib_dma_pci_p2p_dma_supported() to check
> if a given ib_device can be used in P2PDMA transfers. This ensures
> the ib_device is not using virt_dma and also that the underlying
> dma_device supports P2PDMA.
>
> Use the new helper in nvme-rdma to replace the existing check for
> ib_uses_virt_dma(). Adding the dma_pci_p2pdma_supported() check allows
> switching away from pci_p2pdma_[un]map_sg().
>
> Signed-off-by: Logan Gunthorpe <[email protected]>
> Reviewed-by: Jason Gunthorpe <[email protected]>
> Reviewed-by: Max Gurtovoy <[email protected]>

Looks good:

Reviewed-by: Christoph Hellwig <[email protected]>