[tip:x86/smap] x86, suspend: On wakeup always initialize cr4 and EFER

[tip-bot for H. Peter Anvin]

Commit-ID:  73201dbec64aebf6b0dca855b523f437972dc7bb
Gitweb:     http://git.kernel.org/tip/73201dbec64aebf6b0dca855b523f437972dc7bb
Author:     H. Peter Anvin <hpa@xxxxxxxxxxxxxxx>
AuthorDate: Wed, 26 Sep 2012 15:02:34 -0700
Committer:  H. Peter Anvin <hpa@xxxxxxxxxxxxxxx>
CommitDate: Wed, 26 Sep 2012 15:06:22 -0700

x86, suspend: On wakeup always initialize cr4 and EFER

We already have a flag word to indicate the existence of MISC_ENABLES,
so use the same flag word to indicate existence of cr4 and EFER, and
always restore them if they exist.  That way if something passes a
nonzero value when the value *should* be zero, we will still
initialize it.

Signed-off-by: H. Peter Anvin <hpa@xxxxxxxxxxxxxxx>
Cc: Rafael J. Wysocki <rjw@xxxxxxx>
Link: http://lkml.kernel.org/r/1348529239-17943-1-git-send-email-hpa@xxxxxxxxxxxxxxx
---
 arch/x86/kernel/acpi/sleep.c      |   15 ++++++++++-----
 arch/x86/realmode/rm/wakeup.h     |    2 ++
 arch/x86/realmode/rm/wakeup_asm.S |   29 +++++++++++++++++++----------
 3 files changed, 31 insertions(+), 15 deletions(-)

diff --git a/arch/x86/kernel/acpi/sleep.c b/arch/x86/kernel/acpi/sleep.c
index 1b8e5a0..11676cf 100644
--- a/arch/x86/kernel/acpi/sleep.c
+++ b/arch/x86/kernel/acpi/sleep.c
@@ -43,17 +43,22 @@ int acpi_suspend_lowlevel(void)
 
 	header->video_mode = saved_video_mode;
 
+	header->pmode_behavior = 0;
+
 #ifndef CONFIG_64BIT
 	store_gdt((struct desc_ptr *)&header->pmode_gdt);
 
-	if (rdmsr_safe(MSR_EFER, &header->pmode_efer_low,
-		       &header->pmode_efer_high))
-		header->pmode_efer_low = header->pmode_efer_high = 0;
+	if (!rdmsr_safe(MSR_EFER,
+			&header->pmode_efer_low,
+			&header->pmode_efer_high))
+		header->pmode_behavior |= (1 << WAKEUP_BEHAVIOR_RESTORE_EFER);
 #endif /* !CONFIG_64BIT */
 
 	header->pmode_cr0 = read_cr0();
-	header->pmode_cr4 = read_cr4_safe();
-	header->pmode_behavior = 0;
+	if (__this_cpu_read(cpu_info.cpuid_level) >= 0) {
+		header->pmode_cr4 = read_cr4();
+		header->pmode_behavior |= (1 << WAKEUP_BEHAVIOR_RESTORE_CR4);
+	}
 	if (!rdmsr_safe(MSR_IA32_MISC_ENABLE,
 			&header->pmode_misc_en_low,
 			&header->pmode_misc_en_high))
diff --git a/arch/x86/realmode/rm/wakeup.h b/arch/x86/realmode/rm/wakeup.h
index 9317e00..7dd86a4 100644
--- a/arch/x86/realmode/rm/wakeup.h
+++ b/arch/x86/realmode/rm/wakeup.h
@@ -36,5 +36,7 @@ extern struct wakeup_header wakeup_header;
 
 /* Wakeup behavior bits */
 #define WAKEUP_BEHAVIOR_RESTORE_MISC_ENABLE     0
+#define WAKEUP_BEHAVIOR_RESTORE_CR4		1
+#define WAKEUP_BEHAVIOR_RESTORE_EFER		2
 
 #endif /* ARCH_X86_KERNEL_ACPI_RM_WAKEUP_H */
diff --git a/arch/x86/realmode/rm/wakeup_asm.S b/arch/x86/realmode/rm/wakeup_asm.S
index 8905166..e56479e 100644
--- a/arch/x86/realmode/rm/wakeup_asm.S
+++ b/arch/x86/realmode/rm/wakeup_asm.S
@@ -74,9 +74,18 @@ ENTRY(wakeup_start)
 
 	lidtl	wakeup_idt
 
-	/* Clear the EFLAGS */
-	pushl	$0
+	/* Clear the EFLAGS but remember if we have EFLAGS.ID */
+	movl $X86_EFLAGS_ID, %ecx
+	pushl %ecx
 	popfl
+	pushfl
+	popl %edi
+	pushl $0
+	popfl
+	pushfl
+	popl %edx
+	xorl %edx, %edi
+	andl %ecx, %edi		/* %edi is zero iff CPUID & %cr4 are missing */
 
 	/* Check header signature... */
 	movl	signature, %eax
@@ -93,8 +102,8 @@ ENTRY(wakeup_start)
 
 	/* Restore MISC_ENABLE before entering protected mode, in case
 	   BIOS decided to clear XD_DISABLE during S3. */
-	movl	pmode_behavior, %eax
-	btl	$WAKEUP_BEHAVIOR_RESTORE_MISC_ENABLE, %eax
+	movl	pmode_behavior, %edi
+	btl	$WAKEUP_BEHAVIOR_RESTORE_MISC_ENABLE, %edi
 	jnc	1f
 
 	movl	pmode_misc_en, %eax
@@ -110,15 +119,15 @@ ENTRY(wakeup_start)
 	movl	pmode_cr3, %eax
 	movl	%eax, %cr3
 
-	movl	pmode_cr4, %ecx
-	jecxz	1f
-	movl	%ecx, %cr4
+	btl	$WAKEUP_BEHAVIOR_RESTORE_CR4, %edi
+	jz	1f
+	movl	pmode_cr4, %eax
+	movl	%eax, %cr4
 1:
+	btl	$WAKEUP_BEHAVIOR_RESTORE_EFER, %edi
+	jz	1f
 	movl	pmode_efer, %eax
 	movl	pmode_efer + 4, %edx
-	movl	%eax, %ecx
-	orl	%edx, %ecx
-	jz	1f
 	movl	$MSR_EFER, %ecx
 	wrmsr
 1:
--
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