linux-kernel - [RFC PATCH 02/15] PCI/P2PDMA: Attempt to set map

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Message-Id: <20201106170036.18713-3-logang@deltatee.com>
Date:   Fri,  6 Nov 2020 10:00:23 -0700
From:   Logan Gunthorpe <logang@...tatee.com>
To:     linux-kernel@...r.kernel.org, linux-nvme@...ts.infradead.org,
        linux-block@...r.kernel.org, linux-pci@...r.kernel.org,
        linux-mm@...ck.org, iommu@...ts.linux-foundation.org
Cc:     Stephen Bates <sbates@...thlin.com>,
        Christoph Hellwig <hch@....de>,
        Dan Williams <dan.j.williams@...el.com>,
        Jason Gunthorpe <jgg@...pe.ca>,
        Christian König <christian.koenig@....com>,
        Ira Weiny <iweiny@...el.com>,
        John Hubbard <jhubbard@...dia.com>,
        Don Dutile <ddutile@...hat.com>,
        Matthew Wilcox <willy@...radead.org>,
        Daniel Vetter <daniel.vetter@...ll.ch>,
        Logan Gunthorpe <logang@...tatee.com>
Subject: [RFC PATCH 02/15] PCI/P2PDMA: Attempt to set map_type if it has not been set

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@...tatee.com>
---
 drivers/pci/p2pdma.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/drivers/pci/p2pdma.c b/drivers/pci/p2pdma.c
index 94583779c36e..ea8472278b11 100644
--- a/drivers/pci/p2pdma.c
+++ b/drivers/pci/p2pdma.c
@@ -824,11 +824,17 @@ 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);
 }
 
 static int __pci_p2pdma_map_sg(struct pci_p2pdma_pagemap *p2p_pgmap,
@@ -890,7 +896,6 @@ 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);
 		return 0;
 	}
 }
-- 
2.20.1