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>

7 files changed, 24 insertions, 5 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;
diff --git a/arch/x86/kernel/asm-offsets_32.c b/arch/x86/kernel/asm-offsets_32.c
index 85d98ab15cdc..0ef4bba2acb7 100644
--- a/arch/x86/kernel/asm-offsets_32.c
+++ b/arch/x86/kernel/asm-offsets_32.c
@@ -60,6 +60,9 @@ void foo(void)
         OFFSET(IA32_RT_SIGFRAME_sigcontext, rt_sigframe, uc.uc_mcontext);
         BLANK();
 
+        OFFSET(saved_context_gdt_desc, saved_context, gdt_desc);
+        BLANK();
+
         /* Offset from the sysenter stack to tss.sp0 */
         DEFINE(TSS_sysenter_sp0, offsetof(struct tss_struct, x86_tss.sp0) -
                  sizeof(struct tss_struct));
diff --git a/arch/x86/kernel/asm-offsets_64.c b/arch/x86/kernel/asm-offsets_64.c
index 1b4754f82ba7..e7c798b354fa 100644
--- a/arch/x86/kernel/asm-offsets_64.c
+++ b/arch/x86/kernel/asm-offsets_64.c
@@ -73,6 +73,7 @@ int main(void)
         ENTRY(cr3);
         ENTRY(cr4);
         ENTRY(cr8);
+        ENTRY(gdt_desc);
         BLANK();
 #undef ENTRY
 
diff --git a/arch/x86/power/cpu.c b/arch/x86/power/cpu.c
index 6d6e907cee46..1cf5b300305e 100644
--- a/arch/x86/power/cpu.c
+++ b/arch/x86/power/cpu.c
@@ -25,16 +25,12 @@
 #include <asm/cpu.h>
 
 #ifdef CONFIG_X86_32
-static struct saved_context saved_context;
-
 unsigned long saved_context_ebx;
 unsigned long saved_context_esp, saved_context_ebp;
 unsigned long saved_context_esi, saved_context_edi;
 unsigned long saved_context_eflags;
-#else
-/* CONFIG_X86_64 */
-struct saved_context saved_context;
 #endif
+struct saved_context saved_context;
 
 /**
  *      __save_processor_state - save CPU registers before creating a
@@ -67,6 +63,15 @@ static void __save_processor_state(struct saved_context *ctxt)
 /* CONFIG_X86_64 */
         store_idt((struct desc_ptr *)&ctxt->idt_limit);
 #endif
+        /*
+         * We save it here, but restore it only in the hibernate case.
+         * For ACPI S3 resume, this is loaded via 'early_gdt_desc' in 64-bit
+         * mode in "secondary_startup_64". In 32-bit mode it is done via
+         * 'pmode_gdt' in wakeup_start.
+         */
+        ctxt->gdt_desc.size = GDT_SIZE - 1;
+        ctxt->gdt_desc.address = (unsigned long)get_cpu_gdt_table(smp_processor_id());
+
         store_tr(ctxt->tr);
 
         /* XMM0..XMM15 should be handled by kernel_fpu_begin(). */
diff --git a/arch/x86/power/hibernate_asm_32.S b/arch/x86/power/hibernate_asm_32.S
index ad47daeafa4e..1d0fa0e24070 100644
--- a/arch/x86/power/hibernate_asm_32.S
+++ b/arch/x86/power/hibernate_asm_32.S
@@ -75,6 +75,10 @@ done:
         pushl saved_context_eflags
         popfl
 
+        /* Saved in save_processor_state. */
+        movl $saved_context, %eax
+        lgdt saved_context_gdt_desc(%eax)
+
         xorl    %eax, %eax
 
         ret
diff --git a/arch/x86/power/hibernate_asm_64.S b/arch/x86/power/hibernate_asm_64.S
index 9356547d8c01..3c4469a7a929 100644
--- a/arch/x86/power/hibernate_asm_64.S
+++ b/arch/x86/power/hibernate_asm_64.S
@@ -139,6 +139,9 @@ ENTRY(restore_registers)
         pushq   pt_regs_flags(%rax)
         popfq
 
+        /* Saved in save_processor_state. */
+        lgdt    saved_context_gdt_desc(%rax)
+
         xorq    %rax, %rax
 
         /* tell the hibernation core that we've just restored the memory */