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xen-devel
[Xen-devel] Re: [PATCH] infiniband/mthca : Fix userland mapping of mthca
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To: |
Vivien Bernet-Rollande <vbr@xxxxxxxxxxx> |
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Subject: |
[Xen-devel] Re: [PATCH] infiniband/mthca : Fix userland mapping of mthca infiniband cards in Xen dom0 |
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From: |
Roland Dreier <rdreier@xxxxxxxxx> |
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Date: |
Thu, 06 Jan 2011 11:15:34 -0800 |
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sj-iport-6.cisco.com; dkim=neutral (message not signed) header.i=none |
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jackm@xxxxxxxxxxxxxx, Jeremy Fitzhardinge <jeremy@xxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxx, linux-rdma@xxxxxxxxxxxxxxx, rdreir@xxxxxxxxx, sean.hefty@xxxxxxxxx |
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Thu, 06 Jan 2011 11:16:11 -0800 |
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<AANLkTi=zMiVJfTRDeYvbxT46b0iASKG9jPgXqG81bqAK@xxxxxxxxxxxxxx> (Vivien Bernet-Rollande's message of "Thu, 6 Jan 2011 12:08:11 +0100") |
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<1293034260.30522.426.camel@trax> <adamxnfdty8.fsf@xxxxxxxxx> <AANLkTi=zMiVJfTRDeYvbxT46b0iASKG9jPgXqG81bqAK@xxxxxxxxxxxxxx> |
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Gnus/5.13 (Gnus v5.13) Emacs/23.1 (gnu/linux) |
> > Finally as a stylistic thing I would probably prefer to see the
> > vm_page_prot manipulation written as
> >
> > vma->vm_page_prot =
> > pgprot_noncached(vm_get_page_prot(vma->vm_flags));
> >
>
> Makes sense.
> While digging, I've also seen things like :
>
> vma->vm_page_prot = pgprot_noncached(vm_get_page_prot(vma->vm_flags |
> VM_IO));
This isn't the same, since it doesn't set VM_IO in vm_flags.
> > wrapped up in a helper function; presumably every instance of
> >
> > vma->vm_page_prot = pgprot_FOO(vma->vm_page_prot)
> >
> > under drivers/ would need the same fix for Xen.
>
> The issue is actually only related to mappings of bus memory to
> userland. In kernel space, ioremap() is generaly used, which I
> understand sets the _PAGE_IOMAP flag.
Right, but setting vm_page_prot means a driver is doing userspace
mapping of something, and if it's setting pgprot, that would generally
mean it's not mapping RAM.
- R.
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