Re: [PATCH v7 1/4] powerpc/fadump: reduce memory consumption for capture kernel
From: Hari Bathini
Date: Fri Aug 18 2017 - 10:02:10 EST
On Friday 18 August 2017 05:27 PM, Michal SuchÃnek wrote:
On Fri, 18 Aug 2017 16:20:53 +0530
Hari Bathini <hbathini@xxxxxxxxxxxxxxxxxx> wrote:
Hi Michal,
Thanks for the patches. I tried testing with the patches:
[ 0.000000] fadump: Firmware-assisted dump is active.
[ 0.000000] fadump: Modifying command line to enforce the
additional parameters passed through 'fadump_extra_args='
[ 0.000000] fadump: Original command line:
BOOT_IMAGE=/vmlinux-4.13.0-rc1-bz155783+ root=/dev/mapper/rhel-root
ro crashkernel=2048M fadump=on fadump_reserve_mem=1024M
"fadump_extra_args=nr_cpus=1 numa=off udev.childern-max=2"
rd.lvm.lv=rhel/root rd.lvm.lv=rhel/swap
[ 0.000000] fadump: Modified command line:
BOOT_IMAGE=/vmlinux-4.13.0-rc1-bz155783+ root=/dev/mapper/rhel-root
ro crashkernel=2048M fadump=on fadump_reserve_mem=1024M
"fadump_extra_args nr_cpus=1 numa=off udev.childern-max=2"
rd.lvm.lv=rhel/root rd.lvm.lv=rhel/swap
Looks like the quotes are retained not enforcing the parameters...
Hello,
You are passing an argument >>"fadump_extra_args<< - that is an
argument containing a quote in the name. I did not test this scenario
Actually, this was not intentional..
I passed fadump_extra_args="nr_cpus=1 numa=off udev.childern-max=2"
through grub loader
but chosen/bootargs ended up having "fadump_extra_args=nr_cpus=1
numa=off udev.childern-max=2".
Need to check why that is..
Thanks
Hari
assuming the argument name would not match in this case. It would
probably not match if the quote was in the middle of the argument
name but at the start it is skipped. Note that due to the requirement
to remove quotes symmetrically which is added in the third patch this
case does not break the commandline - it merely makes the arguments
ineffective.
The format suggested in the documentation is
fadump_extra_args="nr_cpus=1 numa=off udev.childern-max=2"<< - that
is quotes around the value. This format worked in my testing.
Unfortunately, the format with quote before argument name would
probably require another extra parameter to the callback to detect
properly.
Thanks
Michal
I am yet to test the patches in other scenarios though..
Thanks
Hari
On Friday 18 August 2017 01:44 AM, Michal Suchanek wrote:
From: Hari Bathini <hbathini@xxxxxxxxxxxxxxxxxx>
With fadump (dump capture) kernel booting like a regular kernel, it
needs almost the same amount of memory to boot as the production
kernel, which is unwarranted for a dump capture kernel. But with no
option to disable some of the unnecessary subsystems in fadump
kernel, that much memory is wasted on fadump, depriving the
production kernel of that memory.
Introduce kernel parameter 'fadump_extra_args=' that would take
regular parameters as a space separated quoted string, to be
enforced when fadump is active. This 'fadump_extra_args=' parameter
can be leveraged to pass parameters like nr_cpus=1,
cgroup_disable=memory and numa=off, to disable unwarranted
resources/subsystems.
Also, ensure the log "Firmware-assisted dump is active" is printed
early in the boot process to put the subsequent fadump messages in
context.
Suggested-by: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Signed-off-by: Hari Bathini <hbathini@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Michal Suchanek <msuchanek@xxxxxxx>
---
Changes from v6:
Correct and simplify quote handling. Ideally I would like to extend
parse_args to give the length of the original quoted value to
callback. However, parse_args removes at most one doubel-quote from
the start and one from the end so that is easy to detect. Otherwise
all other users will have to be updated to trash the new argument.
---
arch/powerpc/include/asm/fadump.h | 2 +
arch/powerpc/kernel/fadump.c | 109
++++++++++++++++++++++++++++++++++++--
arch/powerpc/kernel/prom.c | 7 +++ 3 files changed, 115
insertions(+), 3 deletions(-)
diff --git a/arch/powerpc/include/asm/fadump.h
b/arch/powerpc/include/asm/fadump.h index
ce88bbe1d809..98ae00943fb3 100644 ---
a/arch/powerpc/include/asm/fadump.h +++
b/arch/powerpc/include/asm/fadump.h @@ -208,11 +208,13 @@ extern
int early_init_dt_scan_fw_dump(unsigned long node, const char
*uname, int depth, void *data); extern int fadump_reserve_mem(void);
extern int setup_fadump(void);
+extern void enforce_fadump_extra_args(char *cmdline);
extern int is_fadump_active(void);
extern void crash_fadump(struct pt_regs *, const char *);
extern void fadump_cleanup(void);
#else /* CONFIG_FA_DUMP */
+static inline void enforce_fadump_extra_args(char *cmdline) { }
static inline int is_fadump_active(void) { return 0; }
static inline void crash_fadump(struct pt_regs *regs, const char
*str) { } #endif
diff --git a/arch/powerpc/kernel/fadump.c
b/arch/powerpc/kernel/fadump.c index dc0c49cfd90a..a1614d9b8a21
100644 --- a/arch/powerpc/kernel/fadump.c
+++ b/arch/powerpc/kernel/fadump.c
@@ -78,8 +78,10 @@ int __init early_init_dt_scan_fw_dump(unsigned
long node,
* dump data waiting for us.
*/
fdm_active = of_get_flat_dt_prop(node, "ibm,kernel-dump",
NULL);
- if (fdm_active)
+ if (fdm_active) {
+ pr_info("Firmware-assisted dump is active.\n");
fw_dump.dump_active = 1;
+ }
/* Get the sizes required to store dump data for the
firmware provided
* dump sections.
@@ -332,8 +334,11 @@ int __init fadump_reserve_mem(void)
{
unsigned long base, size, memory_boundary;
- if (!fw_dump.fadump_enabled)
+ if (!fw_dump.fadump_enabled) {
+ if (fw_dump.dump_active)
+ pr_warn("Firmware-assisted dump was active
but kernel booted with fadump disabled!\n"); return 0;
+ }
if (!fw_dump.fadump_supported) {
printk(KERN_INFO "Firmware-assisted dump is not
supported on" @@ -373,7 +378,6 @@ int __init
fadump_reserve_mem(void) memory_boundary = memblock_end_of_DRAM();
if (fw_dump.dump_active) {
- printk(KERN_INFO "Firmware-assisted dump is
active.\n"); /*
* If last boot has crashed then reserve all the
memory
* above boot_memory_size so that we don't touch
it until @@ -460,6 +464,105 @@ static int __init
early_fadump_reserve_mem(char *p) }
early_param("fadump_reserve_mem", early_fadump_reserve_mem);
+#define FADUMP_EXTRA_ARGS_PARAM "fadump_extra_args="
+#define FADUMP_EXTRA_ARGS_LEN
(strlen(FADUMP_EXTRA_ARGS_PARAM) - 1) +
+struct param_info {
+ char *cmdline;
+ char *tmp_cmdline;
+ int shortening;
+};
+
+static void __init fadump_update_params(struct param_info
*param_info,
+ char *param, char *val)
+{
+ ptrdiff_t param_offset = param - param_info->tmp_cmdline;
+ size_t vallen = val ? strlen(val) : 0;
+ char *tgt = param_info->cmdline + param_offset +
+ FADUMP_EXTRA_ARGS_LEN - param_info->shortening;
+ int shortening = 0;
+
+ if (!val)
+ return;
+
+ /* remove '=' */
+ *tgt++ = ' ';
+
+ /* next_arg removes one leading and one trailing '"' */
+ if (*tgt == '"')
+ shortening += 1;
+ if (*(tgt + vallen + shortening) == '"')
+ shortening += 1;
+
+ /* remove one leading and one trailing quote if both are
present */
+ if ((val[0] == '"') && (val[vallen - 1] == '"')) {
+ shortening += 2;
+ vallen -= 2;
+ val++;
+ }
+
+ /* some characters were removed - move the trailing part
of cmdline */
+ if (shortening) {
+ char *src;
+
+ strncpy(tgt, val, vallen);
+ tgt += vallen;
+ src = tgt + shortening;
+ memmove(tgt, src, strlen(src) + 1);
+ }
+
+ param_info->shortening += shortening;
+}
+
+/*
+ * Reworks command line parameters and splits 'fadump_extra_args='
param
+ * to enforce the parameters passed through it
+ */
+static int __init fadump_rework_cmdline_params(char *param, char
*val,
+ const char *unused,
void *arg) +{
+ struct param_info *param_info = (struct param_info *)arg;
+
+ if (strncmp(param, FADUMP_EXTRA_ARGS_PARAM,
+ strlen(FADUMP_EXTRA_ARGS_PARAM) - 1))
+ return 0;
+
+ fadump_update_params(param_info, param, val);
+
+ return 0;
+}
+
+/*
+ * Replace every occurrence of 'fadump_extra_args="param1 param2
param3"'
+ * in cmdline with 'fadump_extra_args param1 param2 param3' by
stripping
+ * off '=' and quotes, if any. This ensures that the additional
parameters
+ * passed with 'fadump_extra_args=' are enforced.
+ */
+void __init enforce_fadump_extra_args(char *cmdline)
+{
+ static char tmp_cmdline[COMMAND_LINE_SIZE] __initdata;
+ static char init_cmdline[COMMAND_LINE_SIZE] __initdata;
+ struct param_info param_info;
+
+ if (strstr(cmdline, FADUMP_EXTRA_ARGS_PARAM) == NULL)
+ return;
+
+ pr_info("Modifying command line to enforce the additional
parameters passed through 'fadump_extra_args='"); +
+ param_info.cmdline = cmdline;
+ param_info.tmp_cmdline = tmp_cmdline;
+ param_info.shortening = 0;
+
+ strlcpy(init_cmdline, cmdline, COMMAND_LINE_SIZE);
+
+ strlcpy(tmp_cmdline, cmdline, COMMAND_LINE_SIZE);
+ parse_args("fadump params", tmp_cmdline, NULL, 0, 0, 0,
+ ¶m_info,
&fadump_rework_cmdline_params); +
+ pr_info("Original command line: %s\n", init_cmdline);
+ pr_info("Modified command line: %s\n", cmdline);
+}
+
static int register_fw_dump(struct fadump_mem_struct *fdm)
{
int rc, err;
diff --git a/arch/powerpc/kernel/prom.c b/arch/powerpc/kernel/prom.c
index f83056297441..2e6f40217266 100644
--- a/arch/powerpc/kernel/prom.c
+++ b/arch/powerpc/kernel/prom.c
@@ -693,6 +693,13 @@ void __init early_init_devtree(void *params)
of_scan_flat_dt(early_init_dt_scan_root, NULL);
of_scan_flat_dt(early_init_dt_scan_memory_ppc, NULL);
+ /*
+ * Look for 'fadump_extra_args=' parameter and enfore the
additional
+ * parameters passed to it if fadump is active.
+ */
+ if (is_fadump_active())
+ enforce_fadump_extra_args(boot_command_line);
+
parse_early_param();
/* make sure we've parsed cmdline for mem= before this
*/