[PATCH 0/8] arm64 kexec kernel patches V6

Geoff Levand geoff at infradead.org
Thu Nov 13 17:22:15 PST 2014

Hi All,

This series adds the core support for kexec re-boots on arm64.  I have tested
with the ARM VE fast model, the ARM Base model and the ARM Foundation
model with various kernel config options for both the first and second stage

To load a second stage kernel and execute a kexec re-boot on arm64 my patches to
kexec-tools [2], which have not yet been merged upstream, are needed.

Patches 1-3 rework the arm64 hcall mechanism to give the arm64 soft_restart()
routine the ability to switch exception levels from EL1 to EL2 for kernels that
were entered in EL2.

Patch 4 moves proc-macros.S from arm64/mm to arm64/include/asm so that the
dcache_line_size macro it defines can be uesd by kexec's relocate kernel

Patches 5-8 add the actual kexec support.

Please consider all patches for inclusion.  Any comments or suggestions on how 
to improve are welcome.

[1]  https://git.linaro.org/people/geoff.levand/linux-kexec.git
[2]  https://git.linaro.org/people/geoff.levand/kexec-tools.git

Several things are known to have problems on kexec re-boot:


PROBLEM: The spin-table enable method does not implement all the methods needed
for CPU hot-plug, so the first stage kernel cannot be shutdown properly.

WORK-AROUND: Upgrade to system firmware that provides PSCI enable method
support, OR build the first stage kernel with CONFIG_SMP=n, OR pass 'maxcpus=1'
on the first stage kernel command line.

FIX: Upgrade system firmware to provide PSCI enable method support or add
missing spin-table support to the kernel.


PROBLEM: KVM acquires hypervisor resources on startup, but does not free those
resources on shutdown, so the first stage kernel cannot be shutdown properly.

WORK-AROUND:  Build the first stage kernel with CONFIG_KVM=n.

FIX: Fix KVM to support soft_restart().  KVM needs to restore default exception
vectors, etc.


PROBLEM: UEFI does not manage its runtime services virtual mappings in a way
that is compatible with a kexec re-boot, so the second stage kernel hangs on

WORK-AROUND: Disable UEFI in firmware, OR use EFI uboot emulation if provided
by your firmware.

FIX: Fix kernel to manage UEFI virtual mappings properly.


PROBLEM: The use of device tree /memreserve/ entries is not compatible with
kexec re-boot.  The second stage kernel will use the reserved regions and the
system will become unstable.

WORK-AROUND: Pass a user specified DTB using the kexec --dtb option.

FIX: Convert device tree source files (.dts) and/or bootloaders to use device
tree reserved-memory nodes to specify reserved memory or provide an in kernel
mechanism to export the /memreserve/ entries to user space.


PROBLEM: The kernel for ACPI based systems does not export a device tree to the
standard user space location of 'proc/device-tree'.  Current applications
expect to access device tree information from this standard location.

WORK-AROUND: Disable ACPI in firmware, OR pass 'acpi=off' on the first stage
kernel command line, OR pass a user specified DTB using the kexec --dtb option.

FIX: Fix ACPI kernel support to export device tree information suitable for a
kexec re-boot, and if this information is exported to somewhere other than
'proc/device-tree' update existing kexec user applications to use this new

The following changes since commit 302cd37c417d59549d073a8986fd028998409cb9:

  arm64: kvm: eliminate literal pool entries (2014-11-07 15:04:54 +0000)

are available in the git repository at:

  git://git.linaro.org/people/geoff.levand/linux-kexec.git kexec-v6

for you to fetch changes up to 3fc5a4ba22342ccd8e7e5a09620b00f4b81667a6:

  arm64/kexec: Enable kexec in the arm64 defconfig (2014-11-13 16:52:16 -0800)

Geoff Levand (8):
      arm64: Convert hcalls to use ISS field
      arm64: Add new hcall HVC_CALL_FUNC
      arm64: Add EL2 switch to soft_restart
      arm64: Move proc-macros.S to include/asm
      arm64/kexec: Add core kexec support
      arm64/kexec: Add pr_devel output
      arm64/kexec: Add checks for KVM and EFI
      arm64/kexec: Enable kexec in the arm64 defconfig

 arch/arm64/Kconfig                           |   9 ++
 arch/arm64/configs/defconfig                 |   1 +
 arch/arm64/include/asm/kexec.h               |  47 ++++++
 arch/arm64/include/asm/proc-fns.h            |   4 +-
 arch/arm64/{mm => include/asm}/proc-macros.S |   0
 arch/arm64/include/asm/virt.h                |  33 ++++
 arch/arm64/kernel/Makefile                   |   1 +
 arch/arm64/kernel/hyp-stub.S                 |  45 ++++--
 arch/arm64/kernel/machine_kexec.c            | 232 +++++++++++++++++++++++++++
 arch/arm64/kernel/process.c                  |  10 +-
 arch/arm64/kernel/relocate_kernel.S          | 160 ++++++++++++++++++
 arch/arm64/kvm/hyp.S                         |  18 ++-
 arch/arm64/mm/cache.S                        |   3 +-
 arch/arm64/mm/proc.S                         |  50 ++++--
 include/uapi/linux/kexec.h                   |   1 +
 15 files changed, 576 insertions(+), 38 deletions(-)
 create mode 100644 arch/arm64/include/asm/kexec.h
 rename arch/arm64/{mm => include/asm}/proc-macros.S (100%)
 create mode 100644 arch/arm64/kernel/machine_kexec.c
 create mode 100644 arch/arm64/kernel/relocate_kernel.S


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