Re: [PATCH 00/22] DMA-API/PCI map_peer_resource support for peer-to-peer

[Bjorn Helgaas <helgaas@kernel.org>]

Hi Will,

On Tue, Sep 15, 2015 at 12:10:45PM -0500, Will Davis wrote:
> Hi,
> 
> This is the sixth version of a patchset to add the DMA APIs necessary to
> map and unmap a PCI device's BAR to and from another PCI device's IOVA
> domain. This enables PCI peer-to-peer traffic on x86 platforms where an
> IOMMU is enabled (this requires that peer-to-peer traffic be supported by
> the underlying chipset as well, of course).

It's not essential, but it makes my life a little easier if you
include the version in the subject, e.g., "[PATCH v6 0/22]".  

Checkpatch complains about a few things.  You should look at all of
them, but I think you can ignore most of them.  There is at least one
whitespace error (space before tab or similar) that should be fixed.

Many of your changelogs don't make sense unless you include the
subject line.  Can you update them so the body is self-contained?
It's OK if that means you have to repeat the subject line.

This doesn't include any actual users of pci_map_peer_resource(); do
you plan to include one?  Usually we don't merge things with no
in-tree users.

Bjorn

> v6:
> - added stubs for remaining x86 dma_map_ops: calgary, gart, sta2x11,
>   swiotlb, xen-swiotlb
> - factored part of x86 PCI nommu implementation into a generic PCI
>   helper, pci_resource_to_peer()
> - split x86 dma_peer_mapping_error() implementation into a separate
>   patch
> 
> v5: http://www.spinics.net/lists/linux-pci/msg43975.html
> - moved topology and ACS checks into a separate
>   pci_peer_traffic_supported() API, which determines whether PCI peer-
>   to-peer traffic may work based on language in the PCI and PCI Express
>   specifications (excerpts included in comments)
> - added CONFIG_HAS_DMA_P2P guards to x86 PCI no-mmu implementation of
>   map_peer_resource
> - modified a few patch descriptions for style
> 
> v4: http://www.spinics.net/lists/linux-pci/msg43136.html
> - added HAS_DMA_P2P Kconfig option to guard new APIs, which are only
>   supported on x86 with this patch series
> - added a new dma_peer_addr_t type to handle future platform support
>   where the dma_peer_addr_t needs to have the same width as the bus
>   address, which can be wider than the dma_addr_t returned by other
>   DMA APIs
> - added a new dma_peer_mapping_error() and associated PCI wrapper to
>   detect errors returned via dma_map_peer_resource() API and its
>   PCI wrapper
> - modified the interface of the new API to explicitly take the peer
>   device as an argument
> - renamed the (un)map_resource APIs to (un)map_peer_resource, since
>   they directly receive a 'peer' argument now
> - modified the new PCI interface to take the BAR index instead of the
>   actual struct resource
> - modified the pci-nommu implementation to perform topology and ACS
>   checks before allowing
> - modified both the AMD and Intel IOMMU implementations to require
>   that both devices be behind the same host bridge
> - exposed a couple of preexisting PCI utility functions to aid in the
>   topology checks for all of the x86 implementations
> 
> v3: http://www.spinics.net/lists/linux-pci/msg41703.html
> - changed dma_map_resource() to BUG() if the map_resource DMA op is not
>   provided, instead of returning 0
> - updated documentation to remove requirement to check for 0 return value
>   as an error
> - remove const keyword from struct dma_map_ops in new DMA APIs for
>   consistency with other APIs
> 
> v2: http://www.spinics.net/lists/linux-pci/msg41192.html
> - added documentation for the new DMA APIs
> - fixed physical-to-bus address conversion in the nommu implementation
> 
> v1: http://www.spinics.net/lists/linux-pci/msg40747.html
> 
> Will Davis (22):
>   lib/Kconfig: add HAS_DMA_P2P for peer-to-peer support
>   linux/types.h: Add dma_peer_addr_t type
>   dma-debug: add checking for map/unmap_peer_resource
>   DMA-API: Introduce dma_(un)map_peer_resource
>   dma-mapping: pci: add pci_(un)map_peer_resource
>   DMA-API: Add peer resource mapping documentation
>   PCI: Export pci_find_host_bridge()
>   PCI: Add pci_find_common_upstream_dev()
>   PCI: Add pci_peer_traffic_supported()
>   PCI: Add pci_resource_to_peer()
>   swiotlb: Add map_peer_resource stub
>   x86, swiotlb: Add swiotlb_map_peer_resource() to swiotlb_dma_ops
>   x86, platform: Add swiotlb_map_peer_resource() to sta2x11_dma_ops
>   swiotlb-xen: add map_peer_resource stub
>   pci-swiotlb-xen: add xen_swiotlb_map_peer_resource to
>     xen_swiotlb_dma_ops
>   iommu/amd: Implement (un)map_peer_resource
>   iommu/vt-d: implement (un)map_peer_resource
>   x86: add pci-nommu implementation of map_peer_resource
>   x86: Calgary: Add map_peer_resource stub
>   x86: gart: Add map_peer_resource stub
>   x86: add dma_peer_mapping_error()
>   x86: declare support for DMA P2P
> 
>  Documentation/DMA-API-HOWTO.txt          | 69 ++++++++++++++++++++++
>  Documentation/DMA-API.txt                | 38 ++++++++++--
>  arch/x86/Kconfig                         |  1 +
>  arch/x86/include/asm/dma-mapping.h       | 18 +++++-
>  arch/x86/kernel/amd_gart_64.c            | 16 ++++++
>  arch/x86/kernel/pci-calgary_64.c         | 16 ++++++
>  arch/x86/kernel/pci-nommu.c              | 30 ++++++++++
>  arch/x86/kernel/pci-swiotlb.c            |  3 +
>  arch/x86/pci/sta2x11-fixup.c             |  3 +
>  arch/x86/xen/pci-swiotlb-xen.c           |  3 +
>  drivers/iommu/amd_iommu.c                | 99 +++++++++++++++++++++++++++-----
>  drivers/iommu/intel-iommu.c              | 38 ++++++++++++
>  drivers/pci/host-bridge.c                | 19 +-----
>  drivers/pci/pci.c                        | 99 ++++++++++++++++++++++++++++++++
>  drivers/pci/search.c                     | 25 ++++++++
>  drivers/xen/swiotlb-xen.c                | 20 +++++++
>  include/asm-generic/dma-mapping-common.h | 43 ++++++++++++++
>  include/asm-generic/pci-dma-compat.h     | 23 ++++++++
>  include/linux/dma-debug.h                | 39 ++++++++++++-
>  include/linux/dma-mapping.h              | 12 ++++
>  include/linux/pci.h                      | 28 +++++++++
>  include/linux/swiotlb.h                  |  8 +++
>  include/linux/types.h                    | 13 ++++-
>  include/xen/swiotlb-xen.h                | 11 ++++
>  lib/Kconfig                              |  5 ++
>  lib/dma-debug.c                          | 86 ++++++++++++++++++++++++++-
>  lib/swiotlb.c                            | 17 ++++++
>  27 files changed, 740 insertions(+), 42 deletions(-)
> 
> -- 
> 2.5.1
> 
> --
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