Re: [RFC PATCH 03/15] PCI/P2PDMA: Introduce pci_p2pdma_should_map_bus() and pci_p2pdma_bus_offset()
From: Bjorn Helgaas <helgaas@kernel.org>
Date: 2020-11-10 23:25:19
Also in:
linux-iommu, linux-mm, linux-nvme, linux-pci, lkml
On Fri, Nov 06, 2020 at 10:00:24AM -0700, Logan Gunthorpe wrote:
Introduce pci_p2pdma_should_map_bus() which is meant to be called by dma map functions to determine how to map a given p2pdma page.
s/dma/DMA/ for consistency (also below in function comment)
quoted hunk ↗ jump to hunk
pci_p2pdma_bus_offset() is also added to allow callers to get the bus offset if they need to map the bus address. Signed-off-by: Logan Gunthorpe <logang@deltatee.com> --- drivers/pci/p2pdma.c | 46 ++++++++++++++++++++++++++++++++++++++ include/linux/pci-p2pdma.h | 11 +++++++++ 2 files changed, 57 insertions(+)diff --git a/drivers/pci/p2pdma.c b/drivers/pci/p2pdma.c index ea8472278b11..9961e779f430 100644 --- a/drivers/pci/p2pdma.c +++ b/drivers/pci/p2pdma.c@@ -930,6 +930,52 @@ void pci_p2pdma_unmap_sg_attrs(struct device *dev, struct scatterlist *sg, } EXPORT_SYMBOL_GPL(pci_p2pdma_unmap_sg_attrs); +/** + * pci_p2pdma_bus_offset - returns the bus offset for a given page + * @page: page to get the offset for + * + * Must be passed a pci p2pdma page.
s/pci/PCI/
+ */
+u64 pci_p2pdma_bus_offset(struct page *page)
+{
+ struct pci_p2pdma_pagemap *p2p_pgmap = to_p2p_pgmap(page->pgmap);
+
+ WARN_ON(!is_pci_p2pdma_page(page));
+
+ return p2p_pgmap->bus_offset;
+}
+EXPORT_SYMBOL_GPL(pci_p2pdma_bus_offset);
+
+/**
+ * pci_p2pdma_should_map_bus - determine if a dma mapping should use the
+ * bus address
+ * @dev: device doing the DMA request
+ * @pgmap: dev_pagemap structure for the mapping
+ *
+ * Returns 1 if the page should be mapped with a bus address, 0 otherwise
+ * and -1 the device should not be mapping P2PDMA pages.I think this is missing a word. I'm not really sure how to interpret the "should" in pci_p2pdma_should_map_bus(). If this returns -1, does that mean the patches *cannot* be mapped? They *could* be mapped, but you really *shouldn't*? Something else? 1 means page should be mapped with bus address. 0 means ... what, exactly? It should be mapped with some different address? Sorry these are naive questions because I don't know how all this works.
quoted hunk ↗ jump to hunk
+ */ +int pci_p2pdma_should_map_bus(struct device *dev, struct dev_pagemap *pgmap) +{ + struct pci_p2pdma_pagemap *p2p_pgmap = to_p2p_pgmap(pgmap); + struct pci_dev *client; + + if (!dev_is_pci(dev)) + return -1; + + client = to_pci_dev(dev); + + switch (pci_p2pdma_map_type(p2p_pgmap->provider, client)) { + case PCI_P2PDMA_MAP_THRU_HOST_BRIDGE: + return 0; + case PCI_P2PDMA_MAP_BUS_ADDR: + return 1; + default: + return -1; + } +} +EXPORT_SYMBOL_GPL(pci_p2pdma_should_map_bus); + /** * pci_p2pdma_enable_store - parse a configfs/sysfs attribute store * to enable p2pdmadiff --git a/include/linux/pci-p2pdma.h b/include/linux/pci-p2pdma.h index 8318a97c9c61..fc5de47eeac4 100644 --- a/include/linux/pci-p2pdma.h +++ b/include/linux/pci-p2pdma.h@@ -34,6 +34,8 @@ int pci_p2pdma_map_sg_attrs(struct device *dev, struct scatterlist *sg, int nents, enum dma_data_direction dir, unsigned long attrs); void pci_p2pdma_unmap_sg_attrs(struct device *dev, struct scatterlist *sg, int nents, enum dma_data_direction dir, unsigned long attrs); +u64 pci_p2pdma_bus_offset(struct page *page); +int pci_p2pdma_should_map_bus(struct device *dev, struct dev_pagemap *pgmap); int pci_p2pdma_enable_store(const char *page, struct pci_dev **p2p_dev, bool *use_p2pdma); ssize_t pci_p2pdma_enable_show(char *page, struct pci_dev *p2p_dev,@@ -83,6 +85,15 @@ static inline void pci_p2pmem_free_sgl(struct pci_dev *pdev, static inline void pci_p2pmem_publish(struct pci_dev *pdev, bool publish) { } +static inline u64 pci_p2pdma_bus_offset(struct page *page) +{ + return -1; +} +static inline int pci_p2pdma_should_map_bus(struct device *dev, + struct dev_pagemap *pgmap) +{ + return -1; +} static inline int pci_p2pdma_map_sg_attrs(struct device *dev, struct scatterlist *sg, int nents, enum dma_data_direction dir, unsigned long attrs)-- 2.20.1