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    SubjectRe: [PATCH] kdump: force page alignment for per-CPU crash notes.
    On Thu, Mar 01, 2012 at 09:04:32AM -0800, Eugene Surovegin wrote:
    > On Thu, Mar 1, 2012 at 7:09 AM, Vivek Goyal <vgoyal@redhat.com> wrote:
    > > On Wed, Feb 29, 2012 at 09:21:23AM -0800, Eugene Surovegin wrote:
    > >> Per-CPU allocations are not guaranteed to be physically contiguous.
    > >> However, kdump kernel and user-space code assumes that per-CPU
    > >> memory, used for saving CPU registers on crash, is.
    > >> This can cause corrupted /proc/vmcore in some cases - the main
    > >> symptom being huge ELF note section.
    > >>
    > >> Force page alignment for note_buf_t to ensure that this assumption holds.
    > >>
    > >
    > > Hi Eugene,
    > >
    > > Where do we make assumption that crash_notes address is page aligned?
    >
    > I never said that. I said that assumption was that note chunks were
    > physically contiguous.
    >
    > [snip]
    >
    > > Are you referring to the fact that note could be stored on two different
    > > physical pages and then kexec-tools does not know about the physical
    > > address of second page, hence second kernel does not know about it
    > > and we never read that data. That sounds like a problem.
    >
    > Yes. This is exactly what happens in some cases.

    Ok. Thanks for clarifying. Patch looks good to me.

    Acked-by: Vivek Goyal <vgoyal@redhat.com>

    Vivek


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