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    SubjectRe: [PATCH] x86-64: disable the GART before allocate aperture
    Date
    On Saturday 23 June 2007 00:19:51 Alan Cox wrote:
    > > YH do you think you can look at simply reserving a portion of the iommu?
    > > And having the kexec on panic kernel use the reserved portion?
    >
    > How about simply reserving all of it for the base kernel and using soft
    > iommu for the panic kernel, its hardly high performance criticial at this
    > point.

    The kdump kernel should be normally all <4GB anyways. You won't
    need any IOMMU for its IO unless you O_DIRECT/sendfile out of /proc/kcore.
    Just don't do that (but I suspect it won't work anyways)

    If it's not then swiotlb will also not work because it won't get
    any memory <4GB.

    But I doubt this was YH's problem - the panic kernel memory
    is always reserved and there shouldn't be any ongoing DMAs in this
    area anyways. And what happens outside the kdump kernel shouldn't matter.

    I suspect he rather saw problems with non kdump kexec where we
    can just shut down the GART properly beforehand.

    -Andi
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