Hello Michal,
On Wednesday 10 May 2017 09:31 PM, Michal Suchánek wrote:
Hello,
On Wed, 03 May 2017 23:52:52 +0530
Hari Bathini <hbath...@linux.vnet.ibm.com> wrote:
With the introduction of 'fadump_append=' parameter to pass additional
parameters to fadump (capture) kernel, update documentation about it.
Signed-off-by: Hari Bathini <hbath...@linux.vnet.ibm.com>
---
Changes from v4:
* Based on top of patchset that includes
https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/commit/?h=akpm&id=05f383cdfba8793240e73f9a9fbff4e25d66003f
Documentation/powerpc/firmware-assisted-dump.txt | 10 +++++++++-
1 file changed, 9 insertions(+), 1 deletion(-)
diff --git a/Documentation/powerpc/firmware-assisted-dump.txt
b/Documentation/powerpc/firmware-assisted-dump.txt index
8394bc8..6327193 100644 ---
a/Documentation/powerpc/firmware-assisted-dump.txt +++
b/Documentation/powerpc/firmware-assisted-dump.txt @@ -162,7 +162,15
@@ How to enable firmware-assisted dump (fadump):
1. Set config option CONFIG_FA_DUMP=y and build kernel.
2. Boot into linux kernel with 'fadump=on' kernel cmdline option.
-3. Optionally, user can also set 'crashkernel=' kernel cmdline
+3. A user can pass additional command line parameters as a comma
+ separated list through 'fadump_append=' parameter, to be enforced
+ when fadump is active. For example, if parameters like nr_cpus=1,
+ numa=off & udev.children-max=2 are to be enforced when fadump is
+ active, 'fadump_append=nr_cpus=1,numa=off,udev.children-max=2'
+ can be passed in command line, which will be replaced with
+ "nr_cpus=1 numa=off udev.children-max=2" when fadump is active.
+ This helps in reducing memory consumption during dump capture.
+4. Optionally, user can also set 'crashkernel=' kernel cmdline
to specify size of the memory to reserve for boot memory dump
preservation.
Writing your own deficient parser for comma separated arguments when
perfectly fine parser for space separated quoted arguments exists in
the kernel and the bootloader does not seem like a good idea to me.
Couple of things that prompted me for v5 are:
1. Using parse_early_options() limits the kind of parameters
that can be passed to fadump capture kernel. Passing parameters
like systemd.unit= & udev.childern.max= has no effect with v4.
Updating
boot_command_line parameter, when fadump is active, seems a better
alternative.
2. Passing space-separated quoted arguments is not working
as intended with lilo. Updating bootloader with the below
entry in /etc/lilo.conf file results in a missing append
entry in /etc/yaboot.conf file.
append = "quiet sysrq=1 insmod=sym53c8xx insmod=ipr
crashkernel=512M-:256M fadump_append=\"nr_cpus=1 numa=off
udev.children-max=2\""
Because lilo doesn't seem to handle quoted arguments as intended,
comma-separated list syntax was the obvious choice. Quoted arguments
for a comma-separated list sounds plausible though, provided the
bootloader can handle it. Will try and address that..
I also do not see how this addresses
On Wed, 26 Apr 2017 20:32:55 +1000
Michael Ellerman <m...@ellerman.id.au> wrote:
Hari Bathini <hbath...@linux.vnet.ibm.com> writes:
diff --git a/arch/powerpc/kernel/fadump.c
b/arch/powerpc/kernel/fadump.c index 8ff0dd4..87edc7b 100644
--- a/arch/powerpc/kernel/fadump.c
+++ b/arch/powerpc/kernel/fadump.c
@@ -338,6 +343,36 @@ unsigned long __init
arch_reserved_kernel_pages(void) return memblock_reserved_size() /
PAGE_SIZE; }
+static void __init parse_fadump_append_params(const char *p)
+{
+ static char fadump_cmdline[COMMAND_LINE_SIZE] __initdata;
+ char *token;
+
+ strlcpy(fadump_cmdline, p, COMMAND_LINE_SIZE);
+ token = strchr(fadump_cmdline, ',');
+ while (token) {
+ *token = ' ';
+ token = strchr(token, ',');
+ }
+
+ pr_info("enforcing additional parameters (%s) passed
through "
+ "'fadump_append=' parameter\n", fadump_cmdline);
+ parse_early_options(fadump_cmdline);
Using parse_early_options() means it only works for parameters defined
with early_param() or __setup() doesn't it?
That might be OK but at least you need to clearly document it.
which was your gripe with v4 of the patchset. Unfortunately the flags
in Documentation/kernel-parameters.txt do not include a flag that
denotes parameters available with parse_early_options - unless it is
the KNL flag and is quite bitrotten.
The addtional comments Michael was asking for was when fadump_append=
is limited to early parsing only. But with this approach, we don't
have such limitation. Though I do agree that there is always scope
to improve the documentation further..
Thanks
Hari
