[RESEND PATCH 23/32] hostmem: Add the reset interface for EPC backend reset

[Yang Zhong]

Add the sgx_memory_backend_reset() interface to handle EPC backend
reset when VM is reset. This reset function will destroy previous
backend memory region and re-mmap the EPC section for guest.

Signed-off-by: Yang Zhong <yang.zh...@intel.com>
---
 backends/hostmem-epc.c | 16 ++++++++++++++++
 include/hw/i386/pc.h   |  2 ++
 2 files changed, 18 insertions(+)

diff --git a/backends/hostmem-epc.c b/backends/hostmem-epc.c
index f267cf9f91..f12f26d39f 100644
--- a/backends/hostmem-epc.c
+++ b/backends/hostmem-epc.c
@@ -16,6 +16,7 @@
 #include "qom/object_interfaces.h"
 #include "qapi/error.h"
 #include "sysemu/hostmem.h"
+#include "hw/i386/pc.h"
 
 #define TYPE_MEMORY_BACKEND_EPC "memory-backend-epc"
 
@@ -53,6 +54,21 @@ sgx_epc_backend_memory_alloc(HostMemoryBackend *backend, 
Error **errp)
     g_free(name);
 }
 
+void sgx_memory_backend_reset(HostMemoryBackend *backend, int fd,
+                              Error **errp)
+{
+    MemoryRegion *mr = &backend->mr;
+
+    mr->enabled = false;
+
+    /* destroy the old memory region if it exist */
+    if (fd > 0 && mr->destructor) {
+        mr->destructor(mr);
+    }
+
+    sgx_epc_backend_memory_alloc(backend, errp);
+}
+
 static void sgx_epc_backend_instance_init(Object *obj)
 {
     HostMemoryBackend *m = MEMORY_BACKEND(obj);
diff --git a/include/hw/i386/pc.h b/include/hw/i386/pc.h
index 71e2fc6f26..44b8c5d271 100644
--- a/include/hw/i386/pc.h
+++ b/include/hw/i386/pc.h
@@ -202,6 +202,8 @@ void pc_madt_cpu_entry(AcpiDeviceIf *adev, int uid,
 
 /* sgx-epc.c */
 void pc_machine_init_sgx_epc(PCMachineState *pcms);
+void sgx_memory_backend_reset(HostMemoryBackend *backend, int fd,
+                              Error **errp);
 
 extern GlobalProperty pc_compat_5_2[];
 extern const size_t pc_compat_5_2_len;
-- 
2.29.2.334.gfaefdd61ec