[c-host] windows: update ivshmem driver header and usage

VERSION

@@ -1 +1 @@
-B1-12-g9377fdfc37+1
+B1-13-ge1bfb1234b+1

c-host/platform/Windows/src/platform.c

@@ -368,11 +368,16 @@ bool os_shmemMmap(void **ptr)
     return true;
   }
 
+  IVSHMEM_MMAP_CONFIG config =
+  {
+    .cacheMode = IVSHMEM_CACHE_WRITECOMBINED
+  };
+
   memset(&app.shmemMap, 0, sizeof(IVSHMEM_MMAP));
   if (!DeviceIoControl(
     app.shmemHandle,
     IOCTL_IVSHMEM_REQUEST_MMAP,
-    NULL, 0,
+    &config, sizeof(IVSHMEM_MMAP_CONFIG),
     &app.shmemMap, sizeof(IVSHMEM_MMAP),
     NULL, NULL))
   {

vendor/ivshmem/ivshmem.h

@@ -7,6 +7,19 @@ DEFINE_GUID (GUID_DEVINTERFACE_IVSHMEM,
 typedef UINT16 IVSHMEM_PEERID;
 typedef UINT64 IVSHMEM_SIZE;
 
+#define IVSHMEM_CACHE_NONCACHED     0
+#define IVSHMEM_CACHE_CACHED        1
+#define IVSHMEM_CACHE_WRITECOMBINED 2
+
+/*
+    This structure is for use with the IOCTL_IVSHMEM_REQUEST_MMAP IOCTL
+*/
+typedef struct IVSHMEM_MMAP_CONFIG
+{
+    UINT8 cacheMode; // the caching mode of the mapping, see IVSHMEM_CACHE_* for options
+}
+IVSHMEM_MMAP_CONFIG, *PIVSHMEM_MMAP_CONFIG;
+
 /*
     This structure is for use with the IOCTL_IVSHMEM_REQUEST_MMAP IOCTL
 */