On 05/08/15 at 08:19pm, Dave Young wrote:

Hi,

On 04/24/15 at 04:53pm, AKASHI Takahiro wrote:

...

Please read the following commits for arm64-specific constraints: arm64: kdump: reserve memory for crash dump kernel arm64: kdump: do not go into EL2 before starting a crash dump kernel

Signed-off-by: AKASHI Takahiro takahiro.akashi@linaro.org

Documentation/kdump/kdump.txt | 31 ++++++++++++++++++++++++++++++- arch/arm64/Kconfig | 12 ++++++++++++ 2 files changed, 42 insertions(+), 1 deletion(-)

diff --git a/Documentation/kdump/kdump.txt b/Documentation/kdump/kdump.txt index bc4bd5a..f9cf6f5 100644 --- a/Documentation/kdump/kdump.txt +++ b/Documentation/kdump/kdump.txt @@ -18,7 +18,7 @@ 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, ppc64, ia64, -s390x and arm architectures. +s390x, arm and arm64 architectures. When the system kernel boots, it reserves a small section of memory for the dump-capture kernel. This ensures that ongoing Direct Memory Access @@ -249,6 +249,29 @@ Dump-capture kernel config options (Arch Dependent, arm) AUTO_ZRELADDR=y +Dump-capture kernel config options (Arch Dependent, arm64) +----------------------------------------------------------

+1) 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".)

+2) Under uefi, the maximum memory size on the dump-capture kernel must be

• limited by specifying:
• mem=X[MG]
• where X should be less than or equal to the size in "crashkernel="
• boot parameter. Kexec-tools will automatically add this.

I noticed you are passing mem=X in kexec-tools, Pratyush found a problem that vmcore is corrupted because kdump kernel is using the crash notes memory.

How does kdump kernel know the system ram range especially the mem_start? Only with the size from mem=? parammeter?

In X86 because it use E820 so kexec-tools can pass the memory range to kdump kernel even for UEFI booting. But in arm64 may need find other way to communicate with 2nd kernel like memmap=exactmap in X86..

Discussed with Pratyush in irc, he mentioned that start address is get from kernel->entry which was passed by kexec-tools.

So sorry for the noise, it will works fine with the UEFI mem= limitation fix from Mark Salter

...

+3) Currently, kvm will not be initialized on the dump-capture kernel even

• if it is configured.

Extended crashkernel syntax

@@ -312,6 +335,7 @@ Boot into System Kernel any space below the alignment point may be overwritten by the dump-capture kernel, which means it is possible that the vmcore is not that precise as expected.

• On arm64, use "crashkernel=Y@X".

Load the Dump-capture Kernel ============================ @@ -334,6 +358,8 @@ For s390x:

• Use image or bzImage

For arm:

• Use zImage

+For arm64:

• • Use vmlinux

If you are using a uncompressed vmlinux image then use following command to load dump-capture kernel. @@ -377,6 +403,9 @@ For s390x: For arm: "1 maxcpus=1 reset_devices" +For arm64:

• "1 maxcpus=1 mem=X[MG] reset_devices"

Notes on loading the dump-capture kernel:

• By default, the ELF headers are stored in ELF64 format to support

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig index 5716edf..8e2f545 100644 --- a/arch/arm64/Kconfig +++ b/arch/arm64/Kconfig @@ -562,6 +562,18 @@ config KEXEC but it is independent of the system firmware. And like a reboot you can start any kernel with it, not just Linux. +config CRASH_DUMP

• bool "Build kdump crash kernel"
• help

•  Generate crash dump after being started by kexec. This should
  

•  be normally only set in special crash dump kernels which are
  

•  loaded in the main kernel with kexec-tools into a specially
  

•  reserved region and then later executed after a crash by
  

•  kdump/kexec. The crash dump kernel must be compiled to a
  

•  memory address not used by the main kernel.
  

•  For more details see Documentation/kdump/kdump.txt
  

config XEN_DOM0 def_bool y depends on XEN -- 1.7.9.5

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