Re: [PATCH 07/16] PCI/P2PDMA: Make pci_p2pdma_map_type() non-static

Logan Gunthorpe
2021-05-03T16:40:09Z

On 2021-05-02 4:44 p.m., John Hubbard wrote:
> On 4/8/21 10:01 AM, Logan Gunthorpe wrote:
>> pci_p2pdma_map_type() will be needed by the dma-iommu map_sg
>> implementation because it will need to determine the mapping type
>> ahead of actually doing the mapping to create the actual iommu mapping.
>>
>> Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
>> ---
>> drivers/pci/p2pdma.c | 34 +++++++++++++++++++++++-----------
>> include/linux/pci-p2pdma.h | 15 +++++++++++++++
>> 2 files changed, 38 insertions(+), 11 deletions(-)
>>
>> diff --git a/drivers/pci/p2pdma.c b/drivers/pci/p2pdma.c
>> index bcb1a6d6119d..38c93f57a941 100644
>> --- a/drivers/pci/p2pdma.c
>> +++ b/drivers/pci/p2pdma.c
>> @@ -20,13 +20,6 @@
>> #include <linux/seq_buf.h>
>> #include <linux/xarray.h>
>>
>> -enum pci_p2pdma_map_type {
>> - PCI_P2PDMA_MAP_UNKNOWN = 0,
>> - PCI_P2PDMA_MAP_NOT_SUPPORTED,
>> - PCI_P2PDMA_MAP_BUS_ADDR,
>> - PCI_P2PDMA_MAP_THRU_HOST_BRIDGE,
>> -};
>> -
>> struct pci_p2pdma {
>> struct gen_pool *pool;
>> bool p2pmem_published;
>> @@ -822,13 +815,30 @@ void pci_p2pmem_publish(struct pci_dev *pdev, bool publish)
>> }
>> EXPORT_SYMBOL_GPL(pci_p2pmem_publish);
>>
>> -static enum pci_p2pdma_map_type pci_p2pdma_map_type(struct dev_pagemap *pgmap,
>> - struct device *dev)
>> +/**
>> + * pci_p2pdma_map_type - return the type of mapping that should be used for
>> + * a given device and pgmap
>> + * @pgmap: the pagemap of a page to determine the mapping type for
>> + * @dev: device that is mapping the page
>> + * @dma_attrs: the attributes passed to the dma_map operation --
>> + * this is so they can be checked to ensure P2PDMA pages were not
>> + * introduced into an incorrect interface (like dma_map_sg). *
>> + *
>> + * Returns one of:
>> + * PCI_P2PDMA_MAP_NOT_SUPPORTED - The mapping should not be done
>> + * PCI_P2PDMA_MAP_BUS_ADDR - The mapping should use the PCI bus address
>> + * PCI_P2PDMA_MAP_THRU_HOST_BRIDGE - The mapping should be done directly
>> + */
>> +enum pci_p2pdma_map_type pci_p2pdma_map_type(struct dev_pagemap *pgmap,
>> + struct device *dev, unsigned long dma_attrs)
>> {
>> struct pci_dev *provider = to_p2p_pgmap(pgmap)->provider;
>> enum pci_p2pdma_map_type ret;
>> struct pci_dev *client;
>>
>> + WARN_ONCE(!(dma_attrs & __DMA_ATTR_PCI_P2PDMA),
>> + "PCI P2PDMA pages were mapped with dma_map_sg!");
>
> This really ought to also return -EINVAL, assuming that my review suggestions
> about return types, in earlier patches, are acceptable.

That can't happen because, by convention, dma_map_sg() cannot return
-EINVAL. I think the best we can do is proceed normally and just warn
loudly.

Logan