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Diffstat (limited to 'Documentation/admin-guide')
| -rw-r--r-- | Documentation/admin-guide/mm/kho.rst | 53 |
1 files changed, 11 insertions, 42 deletions
diff --git a/Documentation/admin-guide/mm/kho.rst b/Documentation/admin-guide/mm/kho.rst index 6dc18ed4b886..cb9a20f64920 100644 --- a/Documentation/admin-guide/mm/kho.rst +++ b/Documentation/admin-guide/mm/kho.rst @@ -28,20 +28,10 @@ per NUMA node scratch regions on boot. Perform a KHO kexec =================== -First, before you perform a KHO kexec, you need to move the system into -the :ref:`KHO finalization phase <kho-finalization-phase>` :: - - $ echo 1 > /sys/kernel/debug/kho/out/finalize - -After this command, the KHO FDT is available in -``/sys/kernel/debug/kho/out/fdt``. Other subsystems may also register -their own preserved sub FDTs under -``/sys/kernel/debug/kho/out/sub_fdts/``. - -Next, load the target payload and kexec into it. It is important that you -use the ``-s`` parameter to use the in-kernel kexec file loader, as user -space kexec tooling currently has no support for KHO with the user space -based file loader :: +To perform a KHO kexec, load the target payload and kexec into it. It +is important that you use the ``-s`` parameter to use the in-kernel +kexec file loader, as user space kexec tooling currently has no +support for KHO with the user space based file loader :: # kexec -l /path/to/bzImage --initrd /path/to/initrd -s # kexec -e @@ -52,40 +42,19 @@ For example, if you used ``reserve_mem`` command line parameter to create an early memory reservation, the new kernel will have that memory at the same physical address as the old kernel. -Abort a KHO exec -================ - -You can move the system out of KHO finalization phase again by calling :: - - $ echo 0 > /sys/kernel/debug/kho/out/active - -After this command, the KHO FDT is no longer available in -``/sys/kernel/debug/kho/out/fdt``. - debugfs Interfaces ================== +These debugfs interfaces are available when the kernel is compiled with +``CONFIG_KEXEC_HANDOVER_DEBUGFS`` enabled. + Currently KHO creates the following debugfs interfaces. Notice that these interfaces may change in the future. They will be moved to sysfs once KHO is stabilized. -``/sys/kernel/debug/kho/out/finalize`` - Kexec HandOver (KHO) allows Linux to transition the state of - compatible drivers into the next kexec'ed kernel. To do so, - device drivers will instruct KHO to preserve memory regions, - which could contain serialized kernel state. - While the state is serialized, they are unable to perform - any modifications to state that was serialized, such as - handed over memory allocations. - - When this file contains "1", the system is in the transition - state. When contains "0", it is not. To switch between the - two states, echo the respective number into this file. - ``/sys/kernel/debug/kho/out/fdt`` - When KHO state tree is finalized, the kernel exposes the - flattened device tree blob that carries its current KHO - state in this file. Kexec user space tooling can use this + The kernel exposes the flattened device tree blob that carries its + current KHO state in this file. Kexec user space tooling can use this as input file for the KHO payload image. ``/sys/kernel/debug/kho/out/scratch_len`` @@ -100,8 +69,8 @@ stabilized. it should place its payload images. ``/sys/kernel/debug/kho/out/sub_fdts/`` - In the KHO finalization phase, KHO producers register their own - FDT blob under this directory. + KHO producers can register their own FDT or another binary blob under + this directory. ``/sys/kernel/debug/kho/in/fdt`` When the kernel was booted with Kexec HandOver (KHO), |