Re: IB on s390 broken with commit 99db94940 "IB/core: Remove ib_device.dma_device"

From	Sebastian Ott <sebott@linux.vnet.ibm.com>
Newsgroups	linux.kernel
Subject	Re: IB on s390 broken with commit 99db94940 "IB/core: Remove ib_device.dma_device"
Date	2017-02-28 11:00 +0100
Message-ID	<tfMJz-2En-7@gated-at.bofh.it> (permalink)
References	<tfFI5-6em-1@gated-at.bofh.it> <tfMJz-2En-9@gated-at.bofh.it>
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On Mon, 27 Feb 2017, Bart Van Assche wrote:

> On Mon, 2017-02-27 at 21:17 +0100, Sebastian Ott wrote:
> > commit 99db94940 "IB/core: Remove ib_device.dma_device"
> > breaks infiniband on s390 (and I think also other archs that do something
> > like to_pci_dev(dev) in one of their dma_ops callbacks).
> > 
> > With this commit you use the dma_ops of the device that called
> > ib_register_device but you call e.g. dma_map with ib_device->dev
> > as an argument.
> > 
> > S390's (pci specific) dma_map uses to_pci_dev(dev) to look into the
> > pci device (and its arch specific data) and oopses.
> > 
> > Calling dma_map with ib_device->dev.parent would work but then it
> > wouldn't make sense to copy dma_ops and mask from ib_device->dev.parent
> > to ib_device->dev..
> 
> How about something like the untested patch below?

It works but it doesn't feel right (why should all pci devices have this
duplicated data).

Frankly I don't get the usecase of infiniband (sometimes) using
device->dev.dma_ops instead of parent->dma_ops. Also that these values are
selectively copied from the parent looks weird (opposed to all or nothing).

What about reintroducing dma_device (as an infiniband internal) and set it
to &ib_device->dev if you have to and to parent in all other cases?

Sebastian

Thread

IB on s390 broken with commit 99db94940 "IB/core: Remove  ib_device.dma_device" Sebastian Ott <sebott@linux.vnet.ibm.com> - 2017-02-28 03:30 +0100
  Re: IB on s390 broken with commit 99db94940 "IB/core: Remove  ib_device.dma_device" Sebastian Ott <sebott@linux.vnet.ibm.com> - 2017-02-28 11:00 +0100
    Re: IB on s390 broken with commit 99db94940 "IB/core: Remove  ib_device.dma_device" Sebastian Ott <sebott@linux.vnet.ibm.com> - 2017-02-28 12:00 +0100
    RE: IB on s390 broken with commit 99db94940 "IB/core: Remove  ib_device.dma_device" Parav Pandit <parav@mellanox.com> - 2017-02-28 22:40 +0100

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