| Message ID | 20210916234100.122368-7-logang@deltatee.com (mailing list archive) |
|---|---|
| State | Superseded |
| Delegated to: | Bjorn Helgaas |
| Headers | show |
| Series | Userspace P2PDMA with O_DIRECT NVMe devices | expand |
On Thu, Sep 16, 2021 at 05:40:46PM -0600, Logan Gunthorpe wrote: > Add PCI P2PDMA support for dma_direct_map_sg() so that it can map > PCI P2PDMA pages directly without a hack in the callers. This allows > for heterogeneous SGLs that contain both P2PDMA and regular pages. > > A P2PDMA page may have three possible outcomes when being mapped: > 1) If the data path between the two devices doesn't go through the > root port, then it should be mapped with a PCI bus address > 2) If the data path goes through the host bridge, it should be mapped > normally, as though it were a CPU physical address > 3) It is not possible for the two devices to communicate and thus > the mapping operation should fail (and it will return -EREMOTEIO). > > SGL segments that contain PCI bus addresses are marked with > sg_dma_mark_pci_p2pdma() and are ignored when unmapped. > > Signed-off-by: Logan Gunthorpe <logang@deltatee.com> > kernel/dma/direct.c | 44 ++++++++++++++++++++++++++++++++++++++------ > 1 file changed, 38 insertions(+), 6 deletions(-) > > diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c > index 4c6c5e0635e3..fa8317e8ff44 100644 > +++ b/kernel/dma/direct.c > @@ -13,6 +13,7 @@ > #include <linux/vmalloc.h> > #include <linux/set_memory.h> > #include <linux/slab.h> > +#include <linux/pci-p2pdma.h> > #include "direct.h" > > /* > @@ -421,29 +422,60 @@ void dma_direct_sync_sg_for_cpu(struct device *dev, > arch_sync_dma_for_cpu_all(); > } > > +/* > + * Unmaps segments, except for ones marked as pci_p2pdma which do not > + * require any further action as they contain a bus address. > + */ > void dma_direct_unmap_sg(struct device *dev, struct scatterlist *sgl, > int nents, enum dma_data_direction dir, unsigned long attrs) > { > struct scatterlist *sg; > int i; > > - for_each_sg(sgl, sg, nents, i) > - dma_direct_unmap_page(dev, sg->dma_address, sg_dma_len(sg), dir, > - attrs); > + for_each_sg(sgl, sg, nents, i) { > + if (sg_is_dma_pci_p2pdma(sg)) { > + sg_dma_unmark_pci_p2pdma(sg); > + } else { > + dma_direct_unmap_page(dev, sg->dma_address, > + sg_dma_len(sg), dir, attrs); > + } If the main usage of this SGL bit is to indicate if it has been DMA mapped, or not, I think it should be renamed to something clearer. p2pdma is being used for lots of things now, it feels very counter-intuitive that P2PDMA pages are not flagged with something called sg_is_dma_pci_p2pdma(). How about sg_is_dma_unmapped_address() ? > > for_each_sg(sgl, sg, nents, i) { > + if (is_pci_p2pdma_page(sg_page(sg))) { > + map = pci_p2pdma_map_segment(&p2pdma_state, dev, sg); > + switch (map) { > + case PCI_P2PDMA_MAP_BUS_ADDR: > + continue; > + case PCI_P2PDMA_MAP_THRU_HOST_BRIDGE: > + /* > + * Mapping through host bridge should be > + * mapped normally, thus we do nothing > + * and continue below. > + */ > + break; > + default: > + ret = -EREMOTEIO; > + goto out_unmap; > + } > + } > + > sg->dma_address = dma_direct_map_page(dev, sg_page(sg), > sg->offset, sg->length, dir, attrs); dma_direct_map_page() can trigger swiotlb and I didn't see this series dealing with that? It would probably be fine for now to fail swiotlb_map() for p2p pages? Jason
diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c index 4c6c5e0635e3..fa8317e8ff44 100644 --- a/kernel/dma/direct.c +++ b/kernel/dma/direct.c @@ -13,6 +13,7 @@ #include <linux/vmalloc.h> #include <linux/set_memory.h> #include <linux/slab.h> +#include <linux/pci-p2pdma.h> #include "direct.h" /* @@ -421,29 +422,60 @@ void dma_direct_sync_sg_for_cpu(struct device *dev, arch_sync_dma_for_cpu_all(); } +/* + * Unmaps segments, except for ones marked as pci_p2pdma which do not + * require any further action as they contain a bus address. + */ void dma_direct_unmap_sg(struct device *dev, struct scatterlist *sgl, int nents, enum dma_data_direction dir, unsigned long attrs) { struct scatterlist *sg; int i; - for_each_sg(sgl, sg, nents, i) - dma_direct_unmap_page(dev, sg->dma_address, sg_dma_len(sg), dir, - attrs); + for_each_sg(sgl, sg, nents, i) { + if (sg_is_dma_pci_p2pdma(sg)) { + sg_dma_unmark_pci_p2pdma(sg); + } else { + dma_direct_unmap_page(dev, sg->dma_address, + sg_dma_len(sg), dir, attrs); + } + } } #endif int dma_direct_map_sg(struct device *dev, struct scatterlist *sgl, int nents, enum dma_data_direction dir, unsigned long attrs) { - int i; + struct pci_p2pdma_map_state p2pdma_state = {}; + enum pci_p2pdma_map_type map; struct scatterlist *sg; + int i, ret; for_each_sg(sgl, sg, nents, i) { + if (is_pci_p2pdma_page(sg_page(sg))) { + map = pci_p2pdma_map_segment(&p2pdma_state, dev, sg); + switch (map) { + case PCI_P2PDMA_MAP_BUS_ADDR: + continue; + case PCI_P2PDMA_MAP_THRU_HOST_BRIDGE: + /* + * Mapping through host bridge should be + * mapped normally, thus we do nothing + * and continue below. + */ + break; + default: + ret = -EREMOTEIO; + goto out_unmap; + } + } + sg->dma_address = dma_direct_map_page(dev, sg_page(sg), sg->offset, sg->length, dir, attrs); - if (sg->dma_address == DMA_MAPPING_ERROR) + if (sg->dma_address == DMA_MAPPING_ERROR) { + ret = -EIO; goto out_unmap; + } sg_dma_len(sg) = sg->length; } @@ -451,7 +483,7 @@ int dma_direct_map_sg(struct device *dev, struct scatterlist *sgl, int nents, out_unmap: dma_direct_unmap_sg(dev, sgl, i, dir, attrs | DMA_ATTR_SKIP_CPU_SYNC); - return -EIO; + return ret; } dma_addr_t dma_direct_map_resource(struct device *dev, phys_addr_t paddr,
Add PCI P2PDMA support for dma_direct_map_sg() so that it can map PCI P2PDMA pages directly without a hack in the callers. This allows for heterogeneous SGLs that contain both P2PDMA and regular pages. A P2PDMA page may have three possible outcomes when being mapped: 1) If the data path between the two devices doesn't go through the root port, then it should be mapped with a PCI bus address 2) If the data path goes through the host bridge, it should be mapped normally, as though it were a CPU physical address 3) It is not possible for the two devices to communicate and thus the mapping operation should fail (and it will return -EREMOTEIO). SGL segments that contain PCI bus addresses are marked with sg_dma_mark_pci_p2pdma() and are ignored when unmapped. Signed-off-by: Logan Gunthorpe <logang@deltatee.com> --- kernel/dma/direct.c | 44 ++++++++++++++++++++++++++++++++++++++------ 1 file changed, 38 insertions(+), 6 deletions(-)