On 9/28/26 13:19, Leon Romanovsky wrote:
From: Leon Romanovsky leonro@nvidia.com
Exporters keep the &struct p2pdma_provider backing a buffer in their own private data. An importer cannot reach it, so it has no way to learn how its own peer-to-peer traffic would be routed before it programs its hardware.
Add an optional @p2pdma_provider callback for an exporter to hand that provider out, and dma_buf_p2pdma_map_type() for an importer to ask by TLP class. Exporters keep the provider where it already lives, so this adds an operation rather than changing any existing signature or structure.
Tested-by: Tushar Dave tdave@nvidia.com Signed-off-by: Leon Romanovsky leonro@nvidia.com
drivers/dma-buf/dma-buf-mapping.c | 39 +++++++++++++++++++++++++++++++++++++++ include/linux/dma-buf-mapping.h | 3 +++ include/linux/dma-buf.h | 19 +++++++++++++++++++ 3 files changed, 61 insertions(+)
diff --git a/drivers/dma-buf/dma-buf-mapping.c b/drivers/dma-buf/dma-buf-mapping.c index 794acff2546a..41702045f803 100644 --- a/drivers/dma-buf/dma-buf-mapping.c +++ b/drivers/dma-buf/dma-buf-mapping.c @@ -6,6 +6,45 @@ #include <linux/dma-buf-mapping.h> #include <linux/dma-resv.h> +/**
- dma_buf_p2pdma_map_type - How peer-to-peer traffic to a buffer is routed
- @attach: attachment of the importer that will issue the traffic
- @tlp_flags: &enum pci_p2pdma_tlp_flags describing the TLPs it will issue
- Reports how the PCIe fabric routes @tlp_flags traffic between the buffer
- behind @attach and the importer attached to it, so that an importer can
- choose the TLP attributes that earn it a direct route before it programs
- its hardware.
- The caller must hold the reservation lock. The provider is owned by the
- exporter's driver binding, and exporters revoke under that lock before
- letting an unbind proceed, so dropping it any earlier would leave this
- racing a teardown that frees the provider.
- Return: the mapping type for @tlp_flags traffic, or PCI_P2PDMA_MAP_NONE
- when the exporter names no &struct p2pdma_provider and nothing is known
- about the route.
- */
+enum pci_p2pdma_map_type +dma_buf_p2pdma_map_type(struct dma_buf_attachment *attach,
unsigned int tlp_flags)+{
- struct dma_buf *dmabuf = attach->dmabuf;
- struct p2pdma_provider *provider;
- dma_resv_assert_held(dmabuf->resv);
- if (!dmabuf->ops->p2pdma_provider)
return PCI_P2PDMA_MAP_NONE;- provider = dmabuf->ops->p2pdma_provider(dmabuf);
- if (!provider)
return PCI_P2PDMA_MAP_NONE;
- return pci_p2pdma_map_type_tlp(provider, attach->dev, tlp_flags);
This function call here *must* be in the exporter and not the DMA-buf framework.
So clear NAK to putting that here.
Regards, Christian.
+} +EXPORT_SYMBOL_NS_GPL(dma_buf_p2pdma_map_type, "DMA_BUF");
static struct scatterlist *fill_sg_entry(struct scatterlist *sgl, size_t length, dma_addr_t addr) { diff --git a/include/linux/dma-buf-mapping.h b/include/linux/dma-buf-mapping.h index 09bde3f748e4..37b3da10b17a 100644 --- a/include/linux/dma-buf-mapping.h +++ b/include/linux/dma-buf-mapping.h @@ -7,6 +7,9 @@ #define __DMA_BUF_MAPPING_H__ #include <linux/dma-buf.h> +enum pci_p2pdma_map_type +dma_buf_p2pdma_map_type(struct dma_buf_attachment *attach,
unsigned int tlp_flags);struct sg_table *dma_buf_phys_vec_to_sgt(struct dma_buf_attachment *attach, struct p2pdma_provider *provider, struct phys_vec *phys_vec, diff --git a/include/linux/dma-buf.h b/include/linux/dma-buf.h index d1203da56fc5..d56a48d41215 100644 --- a/include/linux/dma-buf.h +++ b/include/linux/dma-buf.h @@ -186,6 +186,25 @@ struct dma_buf_ops { * if the call would block. */
- /**
* @p2pdma_provider:** Returns the &struct p2pdma_provider backing this buffer, so that an* importer can ask how its peer-to-peer traffic would be routed before* it programs its hardware. Importers reach this through* dma_buf_p2pdma_map_type() rather than calling it directly.** Exporters of MMIO memory that is reachable peer-to-peer should* implement this. Called with the &dma_buf.resv reservation lock held,* which is what lets an exporter refuse once it has revoked the buffer* and started tearing the provider down. This callback is optional.** Returns:** The provider backing the buffer.*/- struct p2pdma_provider *(*p2pdma_provider)(struct dma_buf *dmabuf);
- /**
- @release: