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SubjectRe: [PATCH] Hibernation: Document __save_processor_state() on x86-64
Hi!

> From: Rafael J. Wysocki <rjw@sisk.pl>
>
> Document the fact that __save_processor_state() has to save all CPU
> registers referred to by the kernel in case a different kernel is
> used to load and restore a hibernation image containing it.


> Sigend-off-by: Rafael J. Wysocki <rjw@sisk.pl>
> ---
> arch/x86/kernel/suspend_64.c | 20 ++++++++++++++++++++
> 1 file changed, 20 insertions(+)
>
> Index: linux-2.6/arch/x86/kernel/suspend_64.c
> ===================================================================
> --- linux-2.6.orig/arch/x86/kernel/suspend_64.c
> +++ linux-2.6/arch/x86/kernel/suspend_64.c
> @@ -19,6 +19,21 @@ extern const void __nosave_begin, __nosa
>
> struct saved_context saved_context;
>
> +/**
> + * __save_processor_state - save CPU registers before creating a
> + * hibernation image and before restoring the memory state from it
> + * @ctxt - structure to store the registers contents in
> + *
> + * NOTE: If there is a CPU register the modification of which by the
> + * boot kernel (ie. the kernel used for loading the hibernation image)
> + * might affect the operations of the restored target kernel (ie. the one
> + * saved in the hibernation image), then its contents must be saved by this
> + * function. In other words, if kernel A is hibernated and different
> + * kernel B is used for loading the hibernation image into memory, the
> + * kernel A's __save_processor_state() function must save all registers
> + * needed by kernel A, so that it can operate correctly after the resume
> + * regardless of what kernel B does in the meantime.
> + */

Maybe this warning should be appended to struct saved_context
definition? Reordering its fields (etc) would be bad news, too, and
documentation near data structures is easier to find...

Thanks,
Pavel

--
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html


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