From: Michael Holzheu <holzheu@linux.vnet.ibm.com>
To: Vivek Goyal <vgoyal@redhat.com>
Cc: HATAYAMA Daisuke <d.hatayama@jp.fujitsu.com>,
Jan Willeke <willeke@de.ibm.com>,
Martin Schwidefsky <schwidefsky@de.ibm.com>,
Heiko Carstens <heiko.carstens@de.ibm.com>,
linux-kernel@vger.kernel.org, kexec@lists.infradead.org
Subject: Re: [PATCH v5 1/5] vmcore: Introduce ELF header in new memory feature
Date: Mon, 1 Jul 2013 20:29:59 +0200 [thread overview]
Message-ID: <20130701202959.178a1697@holzheu> (raw)
In-Reply-To: <20130701173727.GD9840@redhat.com>
On Mon, 1 Jul 2013 13:37:27 -0400
Vivek Goyal <vgoyal@redhat.com> wrote:
> On Fri, Jun 28, 2013 at 10:15:52AM +0200, Michael Holzheu wrote:
> > On Thu, 27 Jun 2013 16:23:34 -0400
> > Vivek Goyal <vgoyal@redhat.com> wrote:
> >
> > > On Thu, Jun 27, 2013 at 03:32:02PM -0400, Vivek Goyal wrote:
> > > > On Fri, Jun 21, 2013 at 04:17:03PM +0200, Michael Holzheu wrote:
> > > > > On Fri, 14 Jun 2013 14:54:02 -0400
> > > > > Vivek Goyal <vgoyal@redhat.com> wrote:
> >
> > [snip]
> >
> > > Thinking more about it, I think let us cleanup with this little ugly
> > > bit too so that future changes become easy.
> > >
> > > Current convention is that elfcorehdr_addr and elfcorehdr_size are
> > > already set by arch code by the time vmcore.c starts reading it. Can't
> > > s390 allocate elf headers in early boot code and elfcorehdr_addr? Then
> > > we don't have to call elfcorehdr_alloc().
> > >
> > > And once we are done with reading headers, we can call elfcorehdr_free()
> > > and s390 could free memory and set elfcorehdr_addr to ELFCORE_ADDR_ERR
> > > and elfcorehdr_size=0. That would signify that one can not try to read
> > > elf headers now and it must have been freed.
> > >
> > > is_kdump_kernel() will continue to work as elfcorehdr_addr is
> > > ELFCORE_ADDR_ERR. And that will mean that either elfcorehdr were not
> > > readable/usable to begin with or they have been freed now.
> >
> > Hello Vivek,
> >
> > We would like to keep the alloc/free symmetry as you have suggested in a
> > previous mail. This also has the advantage that we do not have to rely
> > on the ordering of init calls.
> >
> > Wouldn't it be sufficient to just set elfcorehdr_addr to ELFCORE_ADDR_ERR
> > after elfcorehdr_free() and remove the comment?
> >
>
> Hi Michael,
>
> This has only one problem and that is what's the initialization semantics
> of elfcorehdr_addr.
>
> So far we expected it to be initialized very early in boot process and
> once this is set, any component in the system could figure out if it
> is kdump kernel (is_kdump_kernel()) and do kdump specific things.
>
> But if we move initialization of this variable little late, then it
> might be a problem for early users of is_kdump_kernel(). Though right
> now I don't see drivers making use of it and only arch specific early
> boot up code seems to have it.
>
> So either we can stick to existing semantics of initializing headers
> early or we could create a separate variable for is_kdump_kernel() which
> is set in early boot and then one can delay initialization of
> elfcorehdr_addr() in vmcore_init().
The later makes much sense to me. This would also make the s390 code
easier to read since we then could exchange some early kdump checks
with the official is_kdump() function.
Perhaps we can do that as an additional patch after we are ready with
this patch series.
>
> Given the fact that I don't see any users of is_kdump_kernel() in arch
> independent directory, and I am assuming that you will tackle all early
> users of is_kdump_kernel() in s390, I will be fine even with your patch
> below.
Ok great, so I will send you the current patch set version 6 with all the
discussed changes.
Thanks!
Michael
next prev parent reply other threads:[~2013-07-01 18:30 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-06-07 16:55 [PATCH v5 0/5] kdump: Allow ELF header creation in new kernel Michael Holzheu
2013-06-07 16:55 ` [PATCH v5 1/5] vmcore: Introduce ELF header in new memory feature Michael Holzheu
2013-06-10 13:35 ` HATAYAMA Daisuke
2013-06-10 13:53 ` Michael Holzheu
2013-06-14 18:54 ` Vivek Goyal
2013-06-21 14:17 ` Michael Holzheu
2013-06-27 19:32 ` Vivek Goyal
2013-06-27 20:10 ` Cliff Wickman
2013-06-27 20:23 ` Vivek Goyal
2013-06-28 8:15 ` Michael Holzheu
2013-07-01 17:37 ` Vivek Goyal
2013-07-01 18:29 ` Michael Holzheu [this message]
2013-06-07 16:55 ` [PATCH v5 2/5] s390/vmcore: Use " Michael Holzheu
2013-06-10 13:36 ` HATAYAMA Daisuke
2013-06-10 13:48 ` Michael Holzheu
2013-06-14 19:16 ` Vivek Goyal
2013-06-07 16:55 ` [PATCH v5 3/5] vmcore: Introduce remap_oldmem_pfn_range() Michael Holzheu
[not found] ` <CAJGZr0+_W0dp2f9VtVAiUT2fqiwe91gHXd9zYzfMMzBZSZogww@mail.gmail.com>
2013-06-10 8:00 ` Michael Holzheu
2013-06-10 13:40 ` HATAYAMA Daisuke
2013-06-10 14:03 ` Michael Holzheu
2013-06-10 15:37 ` Michael Holzheu
2013-06-11 12:42 ` HATAYAMA Daisuke
2013-06-12 9:13 ` Michael Holzheu
2013-06-13 1:32 ` HATAYAMA Daisuke
2013-06-13 8:54 ` Michael Holzheu
2013-06-13 4:00 ` HATAYAMA Daisuke
2013-06-11 13:20 ` HATAYAMA Daisuke
2013-06-07 16:56 ` [PATCH v5 4/5] s390/vmcore: Implement remap_oldmem_pfn_range for s390 Michael Holzheu
2013-06-14 20:08 ` Vivek Goyal
2013-06-07 16:56 ` [PATCH v5 5/5] s390/vmcore: Use vmcore for zfcpdump Michael Holzheu
2013-06-11 23:47 ` HATAYAMA Daisuke
2013-06-12 9:14 ` Michael Holzheu
2013-06-14 18:54 ` [PATCH v5 0/5] kdump: Allow ELF header creation in new kernel Vivek Goyal
2013-06-21 13:39 ` Michael Holzheu
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