On 4/8/21 10:01 AM, Logan Gunthorpe wrote:
Attempt to find the mapping type for P2PDMA pages on the first
DMA map attempt if it has not been done ahead of time.
Previously, the mapping type was expected to be calculated ahead of
time, but if pages are to come from userspace then there's no
way to ensure the path was checked ahead of time.
Signed-off-by: Logan Gunthorpe <logang@xxxxxxxxxxxx>
---
drivers/pci/p2pdma.c | 12 +++++++++---
1 file changed, 9 insertions(+), 3 deletions(-)
diff --git a/drivers/pci/p2pdma.c b/drivers/pci/p2pdma.c
index 473a08940fbc..2574a062a255 100644
--- a/drivers/pci/p2pdma.c
+++ b/drivers/pci/p2pdma.c
@@ -825,11 +825,18 @@ EXPORT_SYMBOL_GPL(pci_p2pmem_publish);
static enum pci_p2pdma_map_type pci_p2pdma_map_type(struct pci_dev *provider,
struct pci_dev *client)
{
+ enum pci_p2pdma_map_type ret;
+
if (!provider->p2pdma)
return PCI_P2PDMA_MAP_NOT_SUPPORTED;
- return xa_to_value(xa_load(&provider->p2pdma->map_types,
- map_types_idx(client)));
+ ret = xa_to_value(xa_load(&provider->p2pdma->map_types,
+ map_types_idx(client)));
+ if (ret != PCI_P2PDMA_MAP_UNKNOWN)
+ return ret;
+
+ return upstream_bridge_distance_warn(provider, client, NULL,
+ GFP_ATOMIC);
Returning a "bridge distance" from a "get map type" routine is jarring,
and I think it is because of a pre-existing problem: the above function
is severely misnamed. Let's try renaming it (and the other one) to
approximately:
upstream_bridge_map_type_warn()
upstream_bridge_map_type()
...and that should fix that. Well, that, plus tweaking the kernel doc
comments, which are also confused. I think someone started off thinking
about distances through PCIe, but in the end, the routine boils down to
just a few situations that are not distances at all.
Also, the above will read a little better if it is written like this:
ret = xa_to_value(xa_load(&provider->p2pdma->map_types,
map_types_idx(client)));
if (ret == PCI_P2PDMA_MAP_UNKNOWN)
ret = upstream_bridge_map_type_warn(provider, client, NULL,
GFP_ATOMIC);
return ret;
}
static int __pci_p2pdma_map_sg(struct pci_p2pdma_pagemap *p2p_pgmap,
@@ -877,7 +884,6 @@ int pci_p2pdma_map_sg_attrs(struct device *dev, struct scatterlist *sg,
case PCI_P2PDMA_MAP_BUS_ADDR:
return __pci_p2pdma_map_sg(p2p_pgmap, dev, sg, nents);
default:
- WARN_ON_ONCE(1);
Why? Or at least, why, in this patch? It looks like an accidental
leftover from something, seeing as how it is not directly related to the
patch, and is not mentioned at all.
thanks,
--
John Hubbard
NVIDIA
return 0;
}
}
