[PATCH v4 RFT 1/2] powerpc/fadump: reduce memory consumption for capture kernel

With fadump (dump capture) kernel booting like a regular kernel, it almost
needs 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_append=' that would take regular kernel
parameters to be appended when fadump is active.
This 'fadump_append=' 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@ellerman.id.au>
Signed-off-by: Hari Bathini <redacted>
Signed-off-by: Michal Suchanek <redacted>
---
v4:
 - use space separated arguments instead of comma separated
 - do not append parameters when fadummp is disabled
---
 arch/powerpc/kernel/fadump.c | 27 ++++++++++++++++++++++++---
 1 file changed, 24 insertions(+), 3 deletions(-)

diff --git a/arch/powerpc/kernel/fadump.c b/arch/powerpc/kernel/fadump.c
index ebf2e9c..e0c728a 100644
--- a/arch/powerpc/kernel/fadump.c
+++ b/arch/powerpc/kernel/fadump.c

@@ -79,8 +79,10 @@ 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.

@@ -263,8 +265,12 @@ 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"

@@ -304,7 +310,6 @@ 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

@@ -363,6 +368,22 @@ unsigned long __init arch_reserved_kernel_pages(void)
 	return memblock_reserved_size() / PAGE_SIZE;
 }
 
+/* Look for fadump_append= cmdline option. */
+static int __init early_fadump_append_param(char *p)
+{
+	if (!p)
+		return 1;
+
+	if (fw_dump.fadump_enabled && fw_dump.dump_active) {
+	pr_info("enforcing additional parameters (%s) passed through "
+		"'fadump_append=' parameter\n", p);
+		parse_early_options(p);
+	}
+
+	return 0;
+}
+early_param("fadump_append", early_fadump_append_param);
+
 /* Look for fadump= cmdline option. */
 static int __init early_fadump_param(char *p)
 {

-- 
2.10.2

With the introduction of 'fadump_append=' parameter to pass additional
parameters to fadump (capture) kernel, update documentation about it.

Signed-off-by: Hari Bathini <redacted>
Signed-off-by: Michal Suchanek <redacted>
---
 Documentation/powerpc/firmware-assisted-dump.txt | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/Documentation/powerpc/firmware-assisted-dump.txt b/Documentation/powerpc/firmware-assisted-dump.txt
index 9cabaf8..99ab8f4 100644
--- a/Documentation/powerpc/firmware-assisted-dump.txt
+++ b/Documentation/powerpc/firmware-assisted-dump.txt

@@ -162,7 +162,11 @@ 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 kernel parameters as a comma separated list
+   through 'fadump_append=' parameter, to be be appended when fadump is active.
+   This can be used to pass parameters like nr_cpus=1, numa=off to reduce
+   memory consumption during dump capture.
+4. Optionally, user can also set 'fadump_reserve_mem=' kernel cmdline
    to specify size of the memory to reserve for boot memory dump
    preservation.
 

@@ -172,6 +176,8 @@ NOTE: 1. 'fadump_reserve_mem=' parameter has been deprecated. Instead
       2. If firmware-assisted dump fails to reserve memory then it
          will fallback to existing kdump mechanism if 'crashkernel='
          option is set at kernel cmdline.
+      3. 'fadump_append=' parameter con be quoted to append multiple arguments
+         as in 'fadump_append="nr_cpus=8 numa=off"'
 
 Sysfs/debugfs files:
 ------------

-- 
2.10.2

Hi Michal,


On Tuesday 02 May 2017 09:26 PM, Michal Suchanek wrote:

I don't think this addresses Michael's concern in v3..
IIUC, we should actually be editing boot_command_line early
in the boot process instead of using parse_early_options() to enforce
the additional parameters..

Thanks
Hari

On Tuesday 02 May 2017 09:26 PM, Michal Suchanek wrote:

While testing this on a system with yaboot bootloader, it seems that parsing
a parameter with syntax like fadump_append="nr_cpus numa=off" is not
resulting in the intended way..

Thanks
Hari

On Wednesday 03 May 2017 12:43 PM, Hari Bathini wrote:

On Tuesday 02 May 2017 09:26 PM, Michal Suchanek wrote:

quoted

With fadump (dump capture) kernel booting like a regular kernel, it 
almost
needs 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_append=' that would take regular 
kernel
parameters to be appended when fadump is active.
This 'fadump_append=' 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@ellerman.id.au>
Signed-off-by: Hari Bathini <redacted>
Signed-off-by: Michal Suchanek <redacted>
---
v4:
  - use space separated arguments instead of comma separated
  - do not append parameters when fadummp is disabled
---
  arch/powerpc/kernel/fadump.c | 27 ++++++++++++++++++++++++---
  1 file changed, 24 insertions(+), 3 deletions(-)

diff --git a/arch/powerpc/kernel/fadump.c b/arch/powerpc/kernel/fadump.c
index ebf2e9c..e0c728a 100644
--- a/arch/powerpc/kernel/fadump.c
+++ b/arch/powerpc/kernel/fadump.c

@@ -79,8 +79,10 @@ 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.

@@ -263,8 +265,12 @@ 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"

@@ -304,7 +310,6 @@ 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

@@ -363,6 +368,22 @@ unsigned long __init 

arch_reserved_kernel_pages(void)
      return memblock_reserved_size() / PAGE_SIZE;
  }

+/* Look for fadump_append= cmdline option. */
+static int __init early_fadump_append_param(char *p)
+{
+    if (!p)
+        return 1;
+
+    if (fw_dump.fadump_enabled && fw_dump.dump_active) {
+    pr_info("enforcing additional parameters (%s) passed through "
+        "'fadump_append=' parameter\n", p);
+        parse_early_options(p);

While testing this on a system with yaboot bootloader, it seems that 
parsing
a parameter with syntax like fadump_append="nr_cpus numa=off" is not

fadump_append="nr_cpus numa=off" should have read 
fadump_append="nr_cpus=1 numa=off".
Nonetheless, considering different environments this is supposed to 
work, I was trying to convey
comma-separated append list maybe better over space-separated one..

Thanks
Hari

On Wed, 3 May 2017 12:43:33 +0530
Hari Bathini [off-list ref] wrote:

On Tuesday 02 May 2017 09:26 PM, Michal Suchanek wrote:

quoted

With fadump (dump capture) kernel booting like a regular kernel, it
almost needs 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_append=' that would take regular
kernel parameters to be appended when fadump is active.
This 'fadump_append=' 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@ellerman.id.au>
Signed-off-by: Hari Bathini <redacted>
Signed-off-by: Michal Suchanek <redacted>
---
v4:
  - use space separated arguments instead of comma separated
  - do not append parameters when fadummp is disabled
---
  arch/powerpc/kernel/fadump.c | 27 ++++++++++++++++++++++++---
  1 file changed, 24 insertions(+), 3 deletions(-)

diff --git a/arch/powerpc/kernel/fadump.c

b/arch/powerpc/kernel/fadump.c index ebf2e9c..e0c728a 100644

--- a/arch/powerpc/kernel/fadump.c
+++ b/arch/powerpc/kernel/fadump.c

@@ -79,8 +79,10 @@ 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.

@@ -263,8 +265,12 @@ 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" @@ -304,7 +310,6 @@ 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 @@ -363,6 +368,22 @@ unsigned long __init
arch_reserved_kernel_pages(void) return memblock_reserved_size() /
PAGE_SIZE; }

+/* Look for fadump_append= cmdline option. */
+static int __init early_fadump_append_param(char *p)
+{
+	if (!p)
+		return 1;
+
+	if (fw_dump.fadump_enabled && fw_dump.dump_active) {
+	pr_info("enforcing additional parameters (%s) passed
through "
+		"'fadump_append=' parameter\n", p);
+		parse_early_options(p);  

While testing this on a system with yaboot bootloader, it seems that
parsing a parameter with syntax like fadump_append="nr_cpus=1
numa=off" is not resulting in the intended way..

Since yaboot arguments are quoted you will probably want something like

append = "quiet splash somearg1 somearg2 fadump_append=\"nr_cpus=1
numa=off\""

in yaboot.conf

Looking at the yaboot parser it seems to handle quoting of quotes so
unlike your parser that does not handle quoting of commas it allows
passing arbitrary arguments to both the normal kernel and the fadump
kernel. 

Thanks

Michal

On Wednesday 10 May 2017 08:28 PM, Michal Suchánek wrote:

On Wed, 3 May 2017 12:43:33 +0530
Hari Bathini [off-list ref] wrote:

quoted

On Tuesday 02 May 2017 09:26 PM, Michal Suchanek wrote:

quoted

With fadump (dump capture) kernel booting like a regular kernel, it
almost needs 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_append=' that would take regular
kernel parameters to be appended when fadump is active.
This 'fadump_append=' 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@ellerman.id.au>
Signed-off-by: Hari Bathini <redacted>
Signed-off-by: Michal Suchanek <redacted>
---
v4:
   - use space separated arguments instead of comma separated
   - do not append parameters when fadummp is disabled
---
   arch/powerpc/kernel/fadump.c | 27 ++++++++++++++++++++++++---
   1 file changed, 24 insertions(+), 3 deletions(-)

diff --git a/arch/powerpc/kernel/fadump.c

b/arch/powerpc/kernel/fadump.c index ebf2e9c..e0c728a 100644

--- a/arch/powerpc/kernel/fadump.c
+++ b/arch/powerpc/kernel/fadump.c

@@ -79,8 +79,10 @@ 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.

@@ -263,8 +265,12 @@ 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" @@ -304,7 +310,6 @@ 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 @@ -363,6 +368,22 @@ unsigned long __init
arch_reserved_kernel_pages(void) return memblock_reserved_size() /
PAGE_SIZE; }

+/* Look for fadump_append= cmdline option. */
+static int __init early_fadump_append_param(char *p)
+{
+	if (!p)
+		return 1;
+
+	if (fw_dump.fadump_enabled && fw_dump.dump_active) {
+	pr_info("enforcing additional parameters (%s) passed
through "
+		"'fadump_append=' parameter\n", p);
+		parse_early_options(p);

While testing this on a system with yaboot bootloader, it seems that
parsing a parameter with syntax like fadump_append="nr_cpus=1
numa=off" is not resulting in the intended way..

Since yaboot arguments are quoted you will probably want something like

append = "quiet splash somearg1 somearg2 fadump_append=\"nr_cpus=1
numa=off\""

I did try this out. But it wasn't helping either..

in yaboot.conf

Looking at the yaboot parser it seems to handle quoting of quotes so
unlike your parser that does not handle quoting of commas it allows
passing arbitrary arguments to both the normal kernel and the fadump
kernel.

Will improve on v5 to ensure quotes are taken care of..

Thanks
Hari