[PATCH v2 3/4] makedumpfile/xen: Fail immediately on every architecture if dump level is invalid

[Atsushi Kumagai]

Hello Daniel,	

>On 2013/12/10 19:41:54, kexec <kexec-bounces at lists.infradead.org> wrote:
>> > > > Did you say that dump level 2 or larger are no longer effective even for x86_64 ?
>> > > > I thought it works by the patch below, but I'm not sure about Xen.
>> > > > So I would like to know why you sent this patch.
>> > > >
>> > > >
>> > > > commit ec5b5835a113cf62a168d4a7354564a38de6b52c
>> > > > Author: ken1_ohmichi <ken1_ohmichi>
>> > > > Date:   Fri Oct 9 03:05:41 2009 +0000
>> > > >
>> > > >     [v1.3.4-10] Add dump filtering on an x86_64 xen domain-0.
>> > > >
>> > > >     This patch adds the dump filtering for excluding unnecessary pages (cache
>> > > >     pages, user process data pages, and free pages) on on x86_64 xen domain-0.
>> > > >
>> > > >     On the existing makedumpfile (v1.3.3 or former), a user could specify 0
>> > > >     or 1 only as a dump_level. By this patch, he/she can specify 2 or larger
>> > > >     also as a dump_level.
>> > > >
>> > > >     Now, this feature is effective on x86_64 machine only.
>> > >
>> > > Hmmm... Thanks for this. I missed this patch. However, it looks that I
>> > > do not understand something. AIUI, from Xen point of view we are not able
>> > > to use dump level higher than 1 because there is no e.g. cache pages (it
>> > > looks that we could also skip free pages but this stuff is not implemented).
>> > > Above mentioned patch suggest that there is a way to extract just only Dom0
>> > > stuff taking into account Linux internals only. If my reasoning is true
>> > > then dump level higher than 1 is possible only if we look at Dom0 from Linux
>> > > point of view.
>> >
>> > I've reviewed the code for Xen, my understanding is the same as yours.
>> > The memory regions corresponding to hypervisor and DomU will remain even if
>> > specifying the dump level higher than 1.
>> >
>> > > However, I can not find any description how to do that.
>> > > So I am CC-ing Ken'ichi as author of this patch but I do not know that
>> > > he works for NEC still.
>> >
>> > I'm sorry but I missed your point. Did you mention a lack of description
>> > in man page about an effect when specifying the dump level higher than 1
>> > for Xen's memory ?
>> > At least, I still think this patch is wrong because any dump level is
>> > effective for x86_64.
>>
>> Docs are not consistent because man and help displayed from makedumpfile
>> are different. Additionally, even man says nothing how to use this feature
>> on Xen vmcore file. If you use makedumpfile e.g.
>>
>> makedumpfile -Ed 2 /proc/vmcore vmcore
>>
>> it will not work because it uses VMCOREINFO_XEN instead of VMCOREINFO.
>> I discovered that if you would like to use feature from above mentioned
>> patch you must run makedumpfile in following way:
>>
>> makedumpfile -Ed 2 -x vmlinux /proc/vmcore vmcore
>>
>> Then makedumpfile will get info about dom0 directly from vmlinux.
>
>Certainly the documents should be fixed as you said, I'll do it.

Sorry for my too late job, how about this fix ?
I'll merge it into v1.5.7 if you have no objection.


Thanks
Atsushi Kumagai

From: Atsushi Kumagai <kumagai-atsushi at mxc.nes.nec.co.jp>
Date: Fri, 29 Aug 2014 15:11:27 +0900
Subject: [PATCH] Fix description about filtering for Xen.

Correct the following points for Xen dump:

  - Add how to filter the pages of domain-0.
  - Fix the difference between man and help.

Reported-by: Daniel Kiper <daniel.kiper at oracle.com>
Signed-off-by: Atsushi Kumagai <kumagai-atsushi at mxc.nes.nec.co.jp>
---
 makedumpfile.8 | 5 +++--
 print_info.c   | 5 ++++-
 2 files changed, 7 insertions(+), 3 deletions(-)

diff --git a/makedumpfile.8 b/makedumpfile.8
index 25fe74e..0f51bf2 100644
--- a/makedumpfile.8
+++ b/makedumpfile.8
@@ -150,8 +150,9 @@ Pages of the specified type are not copied to \fIDUMPFILE\fR. The page type
 marked in the following table is excluded. A user can specify multiple page
 types by setting the sum of each page type for dump_level. The maximum of
 dump_level is 31. Note that a dump_level for Xen dump filtering is 0 or 1 on
-a machine other than x86_64 (On an x86_64 machine, it is possible to specify
-2 or bigger as a dump_level).
+a machine other than x86_64. On a x86_64 machine, even 2 or bigger dump level
+will be effective if you specify domain-0's \fIvmlinux\fR with \-x option.
+Then the pages are excluded only from domain-0.
 .br
 If specifying multiple dump_levels with the delimiter ',', makedumpfile retries
 to create a \fIDUMPFILE\fR by other dump_level when "No space on device" error
diff --git a/print_info.c b/print_info.c
index 7592690..1fca7c3 100644
--- a/print_info.c
+++ b/print_info.c
@@ -89,6 +89,9 @@ print_usage(void)
 	MSG("  Creating DUMPFILE of Xen:\n");
 	MSG("  # makedumpfile -E [--xen-syms XEN-SYMS|--xen-vmcoreinfo VMCOREINFO] VMCORE DUMPFILE\n");
 	MSG("\n");
+	MSG("  Filtering domain-0 of Xen:\n");
+	MSG("  # makedumpfile -E -d DL -x vmlinux VMCORE DUMPFILE\n");
+	MSG("\n");
 	MSG("  Generating VMCOREINFO of Xen:\n");
 	MSG("  # makedumpfile -g VMCOREINFO --xen-syms XEN-SYMS\n");
 	MSG("\n");
@@ -111,7 +114,7 @@ print_usage(void)
 	MSG("      marked in the following table is excluded. A user can specify multiple\n");
 	MSG("      page types by setting the sum of each page type for Dump_Level (DL).\n");
 	MSG("      The maximum of Dump_Level is 31.\n");
-	MSG("      Note that Dump_Level for Xen dump filtering is 0 or 1.\n");
+	MSG("      Note that Dump_Level for Xen dump filtering is 0 or 1 except on x86_64\n");
 	MSG("\n");
 	MSG("            |         cache    cache\n");
 	MSG("      Dump  |  zero   without  with     user    free\n");
-- 
1.9.0