Since bios do the reset when qemu boot up, and sgx epc will be
reset by the registered reset callback function. Like this, the
sgx epc will do two times initialization. This patch will check
protected mode from cr0 register, and will bypass reset operation
from bios. The reset callback will only accept reset operation
from guest.

Signed-off-by: Yang Zhong <yang.zhong@intel.com>
---
 hw/i386/sgx-epc.c | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/hw/i386/sgx-epc.c b/hw/i386/sgx-epc.c
index 9880d832d5..70075db37c 100644
--- a/hw/i386/sgx-epc.c
+++ b/hw/i386/sgx-epc.c
@@ -19,6 +19,7 @@
 #include "target/i386/cpu.h"
 #include "exec/address-spaces.h"
 #include "sysemu/reset.h"
+#include "sysemu/hw_accel.h"
 
 uint32_t epc_num;
 
@@ -97,6 +98,21 @@ static void sgx_epc_initialization(DeviceState *dev)
     sgx_epc->size += memory_device_get_region_size(md, &errp);
 }
 
+static bool check_reset_from_guest(void)
+{
+    CPUState *cs = first_cpu;
+    X86CPU *cpu = X86_CPU(cs);
+    CPUX86State *env = &cpu->env;
+
+    cpu_synchronize_state(cs);
+
+    if (env->cr[0] & CR0_PE_MASK) {
+        return true;
+    }
+
+    return false;
+}
+
 static void sgx_epc_reset(void *opaque)
 {
     DeviceState *dev = opaque;
@@ -104,6 +120,9 @@ static void sgx_epc_reset(void *opaque)
     Error *errp = NULL;
     int fd;
 
+    if (!check_reset_from_guest())
+        return;
+
     if (!epc->hostmem) {
         error_setg(&errp, "'" SGX_EPC_MEMDEV_PROP "' property is not set");
         return;