Messages in this thread | | | Subject | Re: [PATCH 10/16] dma-mapping: Add flags to dma_map_ops to indicate PCI P2PDMA support | From | Don Dutile <> | Date | Tue, 11 May 2021 12:06:16 -0400 |
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On 4/8/21 1:01 PM, Logan Gunthorpe wrote: > Add a flags member to the dma_map_ops structure with one flag to > indicate support for PCI P2PDMA. > > Also, add a helper to check if a device supports PCI P2PDMA. > > Signed-off-by: Logan Gunthorpe <logang@deltatee.com> > --- > include/linux/dma-map-ops.h | 3 +++ > include/linux/dma-mapping.h | 5 +++++ > kernel/dma/mapping.c | 18 ++++++++++++++++++ > 3 files changed, 26 insertions(+) > > diff --git a/include/linux/dma-map-ops.h b/include/linux/dma-map-ops.h > index 51872e736e7b..481892822104 100644 > --- a/include/linux/dma-map-ops.h > +++ b/include/linux/dma-map-ops.h > @@ -12,6 +12,9 @@ > struct cma; > > struct dma_map_ops { > + unsigned int flags; > +#define DMA_F_PCI_P2PDMA_SUPPORTED (1 << 0) > + I'm not a fan of in-line define's; if we're going to add a flags field to the dma-ops -- and logically it'd be good to have p2pdma go through the dma-ops struct -- then let's move this up in front of the dma-ops description.
And now that the dma-ops struct is being 'opened' for p2pdma, should p2pdma ops be added to this struct, so all this work can be mimic'd/reflected/leveraged/refactored for CXL, GenZ, etc. p2pdma in (the near?) future?
> void *(*alloc)(struct device *dev, size_t size, > dma_addr_t *dma_handle, gfp_t gfp, > unsigned long attrs); > diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h > index 50b8f586cf59..c31980ecca62 100644 > --- a/include/linux/dma-mapping.h > +++ b/include/linux/dma-mapping.h > @@ -146,6 +146,7 @@ int dma_mmap_attrs(struct device *dev, struct vm_area_struct *vma, > unsigned long attrs); > bool dma_can_mmap(struct device *dev); > int dma_supported(struct device *dev, u64 mask); > +bool dma_pci_p2pdma_supported(struct device *dev); > int dma_set_mask(struct device *dev, u64 mask); > int dma_set_coherent_mask(struct device *dev, u64 mask); > u64 dma_get_required_mask(struct device *dev); > @@ -247,6 +248,10 @@ static inline int dma_supported(struct device *dev, u64 mask) > { > return 0; > } > +static inline bool dma_pci_p2pdma_supported(struct device *dev) > +{ > + return 0; > +} > static inline int dma_set_mask(struct device *dev, u64 mask) > { > return -EIO; > diff --git a/kernel/dma/mapping.c b/kernel/dma/mapping.c > index 923089c4267b..ce44a0fcc4e5 100644 > --- a/kernel/dma/mapping.c > +++ b/kernel/dma/mapping.c > @@ -573,6 +573,24 @@ int dma_supported(struct device *dev, u64 mask) > } > EXPORT_SYMBOL(dma_supported); > > +bool dma_pci_p2pdma_supported(struct device *dev) > +{ > + const struct dma_map_ops *ops = get_dma_ops(dev); > + > + /* if ops is not set, dma direct will be used which supports P2PDMA */ > + if (!ops) > + return true; So, this means one cannot have p2pdma with IOMMU's? ... -- or is this 'for now' and this may change? if it may change, add a note here.
> + > + /* > + * Note: dma_ops_bypass is not checked here because P2PDMA should > + * not be used with dma mapping ops that do not have support even > + * if the specific device is bypassing them. > + */ > + > + return ops->flags & DMA_F_PCI_P2PDMA_SUPPORTED; that's a bool?
> +} > +EXPORT_SYMBOL_GPL(dma_pci_p2pdma_supported); > + > #ifdef CONFIG_ARCH_HAS_DMA_SET_MASK > void arch_dma_set_mask(struct device *dev, u64 mask); > #else
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