diff --git a/arch/x86/kernel/include/ihk/context.h b/arch/x86/kernel/include/ihk/context.h
index 22448e66..2aebc038 100644
--- a/arch/x86/kernel/include/ihk/context.h
+++ b/arch/x86/kernel/include/ihk/context.h
@@ -25,7 +25,19 @@ typedef struct x86_kregs ihk_mc_kernel_context_t;
 
 /* XXX: User context should contain floating point registers */
 struct x86_user_context {
-	struct x86_basic_regs gpr;
+	struct x86_sregs sr;
+
+	/* 16-byte boundary here */
+	uint8_t is_gpr_valid;
+	uint8_t is_sr_valid;
+	uint8_t spare_flags6;
+	uint8_t spare_flags5;
+	uint8_t spare_flags4;
+	uint8_t spare_flags3;
+	uint8_t spare_flags2;
+	uint8_t spare_flags1;
+	struct x86_basic_regs gpr;	/* must be last */
+	/* 16-byte boundary here */
 };
 typedef struct x86_user_context ihk_mc_user_context_t;
 
diff --git a/arch/x86/kernel/include/registers.h b/arch/x86/kernel/include/registers.h
index a016865b..a70a8489 100644
--- a/arch/x86/kernel/include/registers.h
+++ b/arch/x86/kernel/include/registers.h
@@ -184,6 +184,15 @@ struct x86_basic_regs {
 	unsigned long rip, cs, rflags, rsp, ss;
 };
 
+struct x86_sregs {
+	unsigned long fs_base;
+	unsigned long gs_base;
+	unsigned long ds;
+	unsigned long es;
+	unsigned long fs;
+	unsigned long gs;
+};
+
 #define	REGS_GET_STACK_POINTER(regs)	(((struct x86_regs *)regs)->rsp)
 
 /*
diff --git a/arch/x86/kernel/interrupt.S b/arch/x86/kernel/interrupt.S
index d8f9abbf..4cdf496b 100644
--- a/arch/x86/kernel/interrupt.S
+++ b/arch/x86/kernel/interrupt.S
@@ -25,9 +25,16 @@
 #define USER_DS                     (56 + 3)
 
 /* struct x86_user_context */
-#define RAX_OFFSET       80
-#define ERROR_OFFSET    120
-#define RSP_OFFSET      152
+#define X86_SREGS_BASE  (0)
+#define X86_SREGS_SIZE  48
+
+#define X86_FLAGS_BASE  (X86_SREGS_BASE + X86_SREGS_SIZE)
+#define X86_FLAGS_SIZE  8
+
+#define X86_REGS_BASE   (X86_FLAGS_BASE + X86_FLAGS_SIZE)
+#define RAX_OFFSET      (X86_REGS_BASE + 80)
+#define ERROR_OFFSET    (X86_REGS_BASE + 120)
+#define RSP_OFFSET      (X86_REGS_BASE + 152)
 
 #define PUSH_ALL_REGS   \
         pushq %rdi;     \
@@ -44,9 +51,13 @@
         pushq %r12;     \
         pushq %r13;     \
         pushq %r14;     \
-        pushq %r15
+        pushq %r15;     \
+        pushq $1;               /* is_gpr_valid is set, and others are cleared */ \
+        subq  $X86_FLAGS_BASE,%rsp      /* for x86_sregs, etc. */
 
 #define POP_ALL_REGS    \
+        movq  $0,X86_FLAGS_BASE(%rsp);  /* clear all flags */ \
+        addq  $X86_REGS_BASE,%rsp;      /* discard x86_sregs, flags, etc. */ \
         popq  %r15;     \
         popq  %r14;     \
         popq  %r13;     \