Date:	Thu, 11 Jan 2007 17:13:04 +0900
From:	Horms <horms@...ge.net.au>
To:	Vivek Goyal <vgoyal@...ibm.com>
Cc:	Mohan Kumar M <mohan@...ibm.com>,
	linux kernel mailing list <linux-kernel@...r.kernel.org>,
	Fastboot mailing list <fastboot@...ts.osdl.org>,
	Morton Andrew Morton <akpm@...l.org>
Subject: Re: [PATCH] Kdump documentation update for 2.6.20

On Wed, Jan 10, 2007 at 02:45:15PM +0530, Vivek Goyal wrote:
> On Wed, Jan 10, 2007 at 11:07:05AM +0530, Mohan Kumar M wrote:
> > On Tue, Jan 09, 2007 at 08:17:08PM +0530, Vivek Goyal wrote:
> > >
> > > Mohan, Can you please check the correctness of ppc64 specific details.
> > >
> > 
> > Vivek,
> > 
> > My inputs.
> > 
> 
> Thanks Mohan. I have updated the document as per your feedback.
> 
> Please find attached the latest patch.
> 
> Thanks
> Vivek
> 
> 
> o Kdump documentation update.
> 	- Update details for using relocatable kernel.
> 	- Start using kexec-tools-testing release as it is latest and old
> 	  kexec-tools can't load relocatable bzImage file.
> 	- Also add kdump on ia64 specific details.
> 
> Signed-off-by: Vivek Goyal <vgoyal@...ibm.com>

This seems like a great improvement on the existing document.
Lets get this in the tree and make any further changes from there.
I'll send a patch to add the ia64 details shortly.

Signed-off-by: Simon Horman <horms@...ge.net.au>

> ---
> 
>  Documentation/kdump/kdump.txt |  224 ++++++++++++++++++++++++++++--------------
>  1 file changed, 152 insertions(+), 72 deletions(-)
> 
> diff -puN Documentation/kdump/kdump.txt~kdump-documentation-update Documentation/kdump/kdump.txt
> --- linux-2.6.20-rc2-mm1-reloc/Documentation/kdump/kdump.txt~kdump-documentation-update	2007-01-08 12:32:55.000000000 +0530
> +++ linux-2.6.20-rc2-mm1-reloc-root/Documentation/kdump/kdump.txt	2007-01-10 14:38:58.000000000 +0530
> @@ -17,7 +17,7 @@ You can use common Linux commands, such 
>  memory image to a dump file on the local disk, or across the network to
>  a remote system.
>  
> -Kdump and kexec are currently supported on the x86, x86_64, and ppc64
> +Kdump and kexec are currently supported on the x86, x86_64, ppc64 and IA64
>  architectures.
>  
>  When the system kernel boots, it reserves a small section of memory for
> @@ -54,59 +54,64 @@ memory," in two ways:
>  Setup and Installation
>  ======================
>  
> -Install kexec-tools and the Kdump patch
> ----------------------------------------
> +Install kexec-tools
> +-------------------
>  
>  1) Login as the root user.
>  
>  2) Download the kexec-tools user-space package from the following URL:
>  
> -   http://www.xmission.com/~ebiederm/files/kexec/kexec-tools-1.101.tar.gz
> +http://www.kernel.org/pub/linux/kernel/people/horms/kexec-tools/kexec-tools-testing-20061214.tar.gz
>  
> -3) Unpack the tarball with the tar command, as follows:
> -
> -   tar xvpzf kexec-tools-1.101.tar.gz
> -
> -4) Download the latest consolidated Kdump patch from the following URL:
> -
> -   http://lse.sourceforge.net/kdump/
> +Note: Latest kexec-tools-testing git tree is available at
>  
> -   (This location is being used until all the user-space Kdump patches
> -   are integrated with the kexec-tools package.)
> +git://git.kernel.org/pub/scm/linux/kernel/git/horms/kexec-tools-testing.git
> +or
> +http://www.kernel.org/git/?p=linux/kernel/git/horms/kexec-tools-testing.git;a=summary
>  
> -5) Change to the kexec-tools-1.101 directory, as follows:
> +3) Unpack the tarball with the tar command, as follows:
>  
> -   cd kexec-tools-1.101
> +   tar xvpzf kexec-tools-testing-20061214.tar.gz
>  
> -6) Apply the consolidated patch to the kexec-tools-1.101 source tree
> -   with the patch command, as follows. (Modify the path to the downloaded
> -   patch as necessary.)
> +4) Change to the kexec-tools-1.101 directory, as follows:
>  
> -   patch -p1 < /path-to-kdump-patch/kexec-tools-1.101-kdump.patch
> +   cd kexec-tools-testing-20061214
>  
> -7) Configure the package, as follows:
> +5) Configure the package, as follows:
>  
>     ./configure
>  
> -8) Compile the package, as follows:
> +6) Compile the package, as follows:
>  
>     make
>  
> -9) Install the package, as follows:
> +7) Install the package, as follows:
>  
>     make install
>  
>  
> -Download and build the system and dump-capture kernels
> -------------------------------------------------------
> +Build the system and dump-capture kernels
> +-----------------------------------------
> +There are two possible methods of using Kdump.
> +
> +1) Build a separate custom dump-capture kernel for capturing the
> +   kernel core dump.
> +
> +2) Or use the system kernel binary itself as dump-capture kernel and there is
> +   no need to build a separate dump-capture kernel. This is possible
> +   only with the architecutres which support a relocatable kernel. As
> +   of today i386 and ia64 architectures support relocatable kernel.
> +
> +Building a relocatable kernel is advantageous from the point of view that
> +one does not have to build a second kernel for capturing the dump. But
> +at the same time one might want to build a custom dump capture kernel
> +suitable to his needs.
>  
> -Download the mainline (vanilla) kernel source code (2.6.13-rc1 or newer)
> -from http://www.kernel.org. Two kernels must be built: a system kernel
> -and a dump-capture kernel. Use the following steps to configure these
> -kernels with the necessary kexec and Kdump features:
> +Following are the configuration setting required for system and
> +dump-capture kernels for enabling kdump support.
>  
> -System kernel
> --------------
> +System kernel config options
> +----------------------------
>  
>  1) Enable "kexec system call" in "Processor type and features."
>  
> @@ -132,88 +137,160 @@ System kernel
>     analysis tools require a vmlinux with debug symbols in order to read
>     and analyze a dump file.
>  
> -4) Make and install the kernel and its modules. Update the boot loader
> -   (such as grub, yaboot, or lilo) configuration files as necessary.
> +Dump-capture kernel config options (Arch Independent)
> +-----------------------------------------------------
>  
> -5) Boot the system kernel with the boot parameter "crashkernel=Y@X",
> -   where Y specifies how much memory to reserve for the dump-capture kernel
> -   and X specifies the beginning of this reserved memory. For example,
> -   "crashkernel=64M@16M" tells the system kernel to reserve 64 MB of memory
> -   starting at physical address 0x01000000 for the dump-capture kernel.
> -
> -   On x86 and x86_64, use "crashkernel=64M@16M".
> -
> -   On ppc64, use "crashkernel=128M@32M".
> +1) Enable "kernel crash dumps" support under "Processor type and
> +   features":
>  
> +   CONFIG_CRASH_DUMP=y
>  
> -The dump-capture kernel
> ------------------------
> +2) Enable "/proc/vmcore support" under "Filesystems" -> "Pseudo filesystems".
>  
> -1) Under "General setup," append "-kdump" to the current string in
> -   "Local version."
> +   CONFIG_PROC_VMCORE=y
> +   (CONFIG_PROC_VMCORE is set by default when CONFIG_CRASH_DUMP is selected.)
>  
> -2) On x86, enable high memory support under "Processor type and
> +Dump-capture kernel config options (Arch Dependent, i386)
> +--------------------------------------------------------
> +1) On x86, enable high memory support under "Processor type and
>     features":
>  
>     CONFIG_HIGHMEM64G=y
>     or
>     CONFIG_HIGHMEM4G
>  
> -3) On x86 and x86_64, disable symmetric multi-processing support
> +2) On x86 and x86_64, disable symmetric multi-processing support
>     under "Processor type and features":
>  
>     CONFIG_SMP=n
> +
>     (If CONFIG_SMP=y, then specify maxcpus=1 on the kernel command line
>     when loading the dump-capture kernel, see section "Load the Dump-capture
>     Kernel".)
>  
> -4) On ppc64, disable NUMA support and enable EMBEDDED support:
> +3) If one wants to build and use a relocatable kernel,
> +   Enable "Build a relocatable kernel" support under "Processor type and
> +   features"
>  
> -   CONFIG_NUMA=n
> -   CONFIG_EMBEDDED=y
> -   CONFIG_EEH=N for the dump-capture kernel
> +   CONFIG_RELOCATABLE=y
>  
> -5) Enable "kernel crash dumps" support under "Processor type and
> -   features":
> +4) Use a suitable value for "Physical address where the kernel is
> +   loaded" (under "Processor type and features"). This only appears when
> +   "kernel crash dumps" is enabled. A suitable value depends upon
> +   whether kernel is relocatable or not.
>  
> -   CONFIG_CRASH_DUMP=y
> +   If you are using a relocatable kernel use CONFIG_PHYSICAL_START=0x100000
> +   This will compile the kernel for physical address 1MB, but given the fact
> +   kernel is relocatable, it can be run from any physical address hence
> +   kexec boot loader will load it in memory region reserved for dump-capture
> +   kernel.
> +
> +   Otherwise it should be the start of memory region reserved for
> +   second kernel using boot parameter "crashkernel=Y@X". Here X is
> +   start of memory region reserved for dump-capture kernel.
> +   Generally X is 16MB (0x1000000). So you can set
> +   CONFIG_PHYSICAL_START=0x1000000
> +
> +5) Make and install the kernel and its modules. DO NOT add this kernel
> +   to the boot loader configuration files.
> +  
> +Dump-capture kernel config options (Arch Dependent, x86_64)
> +----------------------------------------------------------
> +1) On x86 and x86_64, disable symmetric multi-processing support
> +   under "Processor type and features":
> +
> +   CONFIG_SMP=n
>  
> -6) Use a suitable value for "Physical address where the kernel is
> +   (If CONFIG_SMP=y, then specify maxcpus=1 on the kernel command line
> +   when loading the dump-capture kernel, see section "Load the Dump-capture
> +   Kernel".)
> +
> +2) Use a suitable value for "Physical address where the kernel is
>     loaded" (under "Processor type and features"). This only appears when
>     "kernel crash dumps" is enabled. By default this value is 0x1000000
>     (16MB). It should be the same as X in the "crashkernel=Y@X" boot
> -   parameter discussed above.
> +   parameter.
>  
> -   On x86 and x86_64, use "CONFIG_PHYSICAL_START=0x1000000".
> +   For x86_64, normally "CONFIG_PHYSICAL_START=0x1000000".
>  
> -   On ppc64 the value is automatically set at 32MB when
> -   CONFIG_CRASH_DUMP is set.
> +3) Make and install the kernel and its modules. DO NOT add this kernel
> +   to the boot loader configuration files.
>  
> -6) Optionally enable "/proc/vmcore support" under "Filesystems" ->
> -   "Pseudo filesystems".
> +Dump-capture kernel config options (Arch Dependent, ppc64)
> +----------------------------------------------------------
>  
> -   CONFIG_PROC_VMCORE=y
> -   (CONFIG_PROC_VMCORE is set by default when CONFIG_CRASH_DUMP is selected.)
> -
> -7) Make and install the kernel and its modules. DO NOT add this kernel
> +-  Make and install the kernel and its modules. DO NOT add this kernel
>     to the boot loader configuration files.
>  
> +Dump-capture kernel config options (Arch Dependent, ia64)
> +----------------------------------------------------------
> +(To be filled)
> +
> +
> +Boot into System Kernel
> +=======================
> +
> +1) Make and install the kernel and its modules. Update the boot loader
> +   (such as grub, yaboot, or lilo) configuration files as necessary.
> +
> +2) Boot the system kernel with the boot parameter "crashkernel=Y@X",
> +   where Y specifies how much memory to reserve for the dump-capture kernel
> +   and X specifies the beginning of this reserved memory. For example,
> +   "crashkernel=64M@16M" tells the system kernel to reserve 64 MB of memory
> +   starting at physical address 0x01000000 (16MB) for the dump-capture kernel.
> +
> +   On x86 and x86_64, use "crashkernel=64M@16M".
> +
> +   On ppc64, use "crashkernel=128M@32M".
>  
>  Load the Dump-capture Kernel
>  ============================
>  
> -After booting to the system kernel, load the dump-capture kernel using
> -the following command:
> +After booting to the system kernel, dump-capture kernel needs to be
> +loaded.
> +
> +Based on the architecture and type of image (relocatable or not), one
> +can choose to load the uncompressed vmlinux or compressed bzImage/vmlinuz
> +of dump-capture kernel. Following is the summary.
> +
> +For i386:
> +	- Use vmlinux if kernel is not relocatable.
> +	- Use bzImage/vmlinuz if kernel is relocatable.
> +For x86_64:
> +	- Use vmlinux
> +For ppc64:
> +	- Use vmlinux
> +For ia64:
> +	(To be filled)
> +
> +If you are using a uncompressed vmlinux image then use following command
> +to load dump-capture kernel.
>  
> -   kexec -p <dump-capture-kernel> \
> +   kexec -p <dump-capture-kernel-vmlinux-image> \
>     --initrd=<initrd-for-dump-capture-kernel> --args-linux \
> -   --append="root=<root-dev> init 1 irqpoll"
> +   --append="root=<root-dev> <arch-specific-options>"
>  
> +If you are using a compressed bzImage/vmlinuz, then use following command
> +to load dump-capture kernel.
>  
> -Notes on loading the dump-capture kernel:
> +   kexec -p <dump-capture-kernel-bzImage> \
> +   --initrd=<initrd-for-dump-capture-kernel> \
> +   --append="root=<root-dev> <arch-specific-options>"
> +
> +Following are the arch specific command line options to be used while
> +loading dump-capture kernel.
> +
> +For i386 and x86_64:
> +	"init 1 irqpoll maxcpus=1"
> +
> +For ppc64:
> +	"init 1 maxcpus=1 noirqdistrib"
>  
> -* <dump-capture-kernel> must be a vmlinux image (that is, an
> -  uncompressed ELF image). bzImage does not work at this time.
> +For IA64
> +	(To be filled)
> +
> +
> +Notes on loading the dump-capture kernel:
>  
>  * By default, the ELF headers are stored in ELF64 format to support
>    systems with more than 4GB memory. The --elf32-core-headers option can
> @@ -231,6 +308,9 @@ Notes on loading the dump-capture kernel
>  * "init 1" boots the dump-capture kernel into single-user mode without
>    networking. If you want networking, use "init 3."
>  
> +* We generally don' have to bring up a SMP kernel just to capture the
> +  dump. Hence generally it is useful either to build a UP dump-capture
> +  kernel or specify maxcpus=1 option while loading dump-capture kernel.
>  
>  Kernel Panic
>  ============
> _

-- 
Horms
  H: http://www.vergenet.net/~horms/
  W: http://www.valinux.co.jp/en/

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