x86, gdt, hibernate: Store/load GDT for hibernate path.

The git commite7a5cd063c7b4c58417f674821d63f5eb6747e37
("x86-64, gdt: Store/load GDT for ACPI S3 or hibernate/resume path
is not needed.") assumes that for the hibernate path the booting
kernel and the resuming kernel MUST be the same. That is certainly
the case for a 32-bit kernel (see check_image_kernel and
CONFIG_ARCH_HIBERNATION_HEADER config option).

However for 64-bit kernels it is OK to have a different kernel
version (and size of the image) of the booting and resuming kernels.
Hence the above mentioned git commit introduces an regression.

This patch fixes it by introducing a 'struct desc_ptr gdt_desc'
back in the 'struct saved_context'. However instead of having in the
'save_processor_state' and 'restore_processor_state' the
store/load_gdt calls, we are only saving the GDT in the
save_processor_state.

For the restore path the lgdt operation is done in
hibernate_asm_[32|64].S in the 'restore_registers' path.

The apt reader of this description will recognize that only 64-bit
kernels need this treatment, not 32-bit. This patch adds the logic
in the 32-bit path to be more similar to 64-bit so that in the future
the unification process can take advantage of this.

[ hpa: this also reverts an inadvertent on-disk format change ]

Suggested-by: "H. Peter Anvin" <hpa@zytor.com>
Acked-by: "Rafael J. Wysocki" <rjw@sisk.pl>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Link: http://lkml.kernel.org/r/1367459610-9656-2-git-send-email-konrad.wilk@oracle.com
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>

2 files changed, 3 insertions, 0 deletions

diff --git a/arch/x86/include/asm/suspend_32.h b/arch/x86/include/asm/suspend_32.h
index f6064b7385b0..552d6c90a6d4 100644
--- a/arch/x86/include/asm/suspend_32.h
+++ b/arch/x86/include/asm/suspend_32.h
@@ -15,6 +15,7 @@ struct saved_context {
         unsigned long cr0, cr2, cr3, cr4;
         u64 misc_enable;
         bool misc_enable_saved;
+        struct desc_ptr gdt_desc;
         struct desc_ptr idt;
         u16 ldt;
         u16 tss;
diff --git a/arch/x86/include/asm/suspend_64.h b/arch/x86/include/asm/suspend_64.h
index 97b84e08a211..bc6232834bab 100644
--- a/arch/x86/include/asm/suspend_64.h
+++ b/arch/x86/include/asm/suspend_64.h
@@ -25,6 +25,8 @@ struct saved_context {
         u64 misc_enable;
         bool misc_enable_saved;
         unsigned long efer;
+        u16 gdt_pad; /* Unused */
+        struct desc_ptr gdt_desc;
         u16 idt_pad;
         u16 idt_limit;
         unsigned long idt_base;