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    SubjectRe: [Fastboot] [PATCH] Reserving backup region for kexec based crashdumps.
    From
    Hi Eric,

    > > Hi Vivek and Eric,
    > >
    > > IMHO, why don't we swap not only the contents of the top 640K
    > > but also kernel working memory for kdump kernel?
    > >
    > > I guess this approach has some good points.
    > >
    > > 1.Preallocating reserved area is not mandatory at boot time.
    > > And the reserved area can be distributed in small pieces
    > > like original kexec does.
    > >
    > > 2.Special linking is not required for kdump kernel.
    > > Each kdump kernel can be linked in the same way,
    > > where the original kernel exists.
    > >
    > > Am I missing something?
    >
    > Preallocating the reserved area is largely to keep it from
    > being the target of DMA accesses. Since we are not able
    > to shutdown any of the drivers in the primary kernel running
    > in a normal swath of memory sounds like a good way to get
    > yourself stomped at the worst possible time.

    So what do you think my another idea?

    I think we can always make a kdump kernel mapped to the same virtual
    address. So we will be free from caring about the physical address
    where the kdump kernel is loaded.

    I believe the memsection functionality which LHMS project is working
    on would help this.

    +
    |
    |
    (user space)
    |
    |
    physical | virtual
    memory | space
    + ------------ +
    | |
    | |
    | |
    + ------------.+
    original | . | map kdump kernel here
    kernel | . |
    | . |
    | . .+
    + . . |
    | . . |
    + . |
    kdump | . |
    kernel | . |
    | . |
    + |
    | |
    | |
    | |



    Thanks,
    Hirokazu Takahashi.
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