On Mon, 16 Jul 2007, Al Boldi wrote:
david@xxxxxxx wrote:
On Mon, 16 Jul 2007, Al Boldi wrote:
david@xxxxxxx wrote:
suspend-to-RAM should not involve kexec, the only reason for doing the
kexec to to get a seperate userspace to use for suspend-to-disk
operations instead of trying to partially freeze the sustem and keep
useing it.
Or you could do suspend-to-disk-and-RAM. But in the above case, it was
meant to test kexec compatibility with device suspend/resume calls.
the point I am trying to make here is that there is no reason that the
kexec approach needs to do _any_ suspend/resume calls.
When you go through ACPI, then that implies calling suspend/resume calls.
then don't go through ACPI
all that is needed is the ability of the new kernel to initialize the
devices it needs.
We have to go through ACPI, for wakeup functions to succeed. A simple
power-off won't do.
the kexec switch being posted requires ACPI be disabled, so it's clearly
possible to switch kernels and initialize devices without ACPI
suspend-to-disk-and-ram could be implemented as three
seperate steps
1. suspend-to-disk
2. resume-from-disk
3. suspend-to-ram
followed by either
4. resume-from-ram
or
4. battery dies and loptop powers off completely
5. power-on boot.
6. resume-from-disk
all that you need to do is to make sure that the system doesn't run
anything that would affect permanent media or the outside world between
steps #2 and #3
Exactly, which is why your scheme would break down on #3, and that's why you
need to call S3 from within the kexec'd hibernation kernel after saving the
hibernation image.
when a kexec is called, how does the kernel know what to execute?
something needs to tell it what to do, and I think that something is
either something in the kexec image, or it's something passed as a
parameter to that image.
all that would be needed to do #3 safely is to have the kernel that you
restarted on #2 do a suspend-to-ram before it does anything else.
David Lang
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