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SubjectRe: [v2 4/5] arm64: add kdump support
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
> >
> >
> > _______________________________________________
> > kexec mailing list
> > kexec@lists.infradead.org
> > http://lists.infradead.org/mailman/listinfo/kexec
> >
> >
>
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> kexec@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/kexec
>
>


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