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    SubjectRe: [PATCH v3 1/3] kexec: Move vmcoreinfo out of the kernel's .bss section
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    Hi Dave,


    On Wednesday 22 March 2017 10:00 AM, Dave Young wrote:
    > On 03/21/17 at 10:18pm, Eric W. Biederman wrote:
    >> Dave Young <dyoung@redhat.com> writes:
    >>
    >>> On 03/20/17 at 10:33pm, Eric W. Biederman wrote:
    >>>> Xunlei Pang <xlpang@redhat.com> writes:
    >>>>
    >>>>> As Eric said,
    >>>>> "what we need to do is move the variable vmcoreinfo_note out
    >>>>> of the kernel's .bss section. And modify the code to regenerate
    >>>>> and keep this information in something like the control page.
    >>>>>
    >>>>> Definitely something like this needs a page all to itself, and ideally
    >>>>> far away from any other kernel data structures. I clearly was not
    >>>>> watching closely the data someone decided to keep this silly thing
    >>>>> in the kernel's .bss section."
    >>>>>
    >>>>> This patch allocates extra pages for these vmcoreinfo_XXX variables,
    >>>>> one advantage is that it enhances some safety of vmcoreinfo, because
    >>>>> vmcoreinfo now is kept far away from other kernel data structures.
    >>>> Can you preceed this patch with a patch that removes CRASHTIME from
    >>>> vmcoreinfo? If someone actually cares we can add a separate note that holds
    >>>> a 64bit crashtime in the per cpu notes.
    >>> I think makedumpfile is using it, but I also vote to remove the
    >>> CRASHTIME. It is better not to do this while crashing and a makedumpfile
    >>> userspace patch is needed to drop the use of it.
    >>>
    >>>> As we are looking at reliability concerns removing CRASHTIME should make
    >>>> everything in vmcoreinfo a boot time constant. Which should simplify
    >>>> everything considerably.
    >>> It is a nice improvement..
    >> We also need to take a close look at what s390 is doing with vmcoreinfo.
    >> As apparently it is reading it in a different kind of crashdump process.
    > Yes, need careful review from s390 and maybe ppc64 especially about
    > patch 2/3, better to have comments from IBM about s390 dump tool and ppc
    > fadump. Added more cc.

    w.r.t powerpc/fadump, this patch-set works fine..

    Thanks
    Hari

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