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

[Hari Bathini]

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@xxxxxxxxxx> writes:
> >
> > > On 03/20/17 at 10:33pm, Eric W. Biederman wrote:
> > > > Xunlei Pang <xlpang@xxxxxxxxxx> 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