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Subject[PATCH] Hibernation: Document __save_processor_state() on x86-64
Date
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.
+ */
void __save_processor_state(struct saved_context *ctxt)
{
kernel_fpu_begin();
@@ -69,6 +84,11 @@ static void do_fpu_end(void)
kernel_fpu_end();
}

+/**
+ * __restore_processor_state - restore the contents of CPU registers saved
+ * by __save_processor_state()
+ * @ctxt - structure to load the registers contents from
+ */
void __restore_processor_state(struct saved_context *ctxt)
{
/*

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