Add backend_adjust_offset to avoid the windows overlap

In mihawk, the windows overlap will cause the cache coherence.
Hostboot writes the SPD data to BMC through a window and read it
back with another window. It causes the data missed and DIMM lost.

Hostboot log
   23.80714|<<DBG-956|SPD::getMemType() - MemType: 0xff, Error: NoHUID: 0x30008.

BMC log: The overlaped windows
  Window @ 0x756e0000 for size 0x00046000 maps flash offset 0x000e7000
  Window @ 0x757e0000 for size 0x00048000 maps flash offset 0x000e5000

Tested: 1. In mihawk, it can fix the SPD cache coherence issue
        2. Add unit test to verify VPNOR offset alignment

Change-Id: I92670ade4e2a91b5c49a0acabfc0456f90d49b93
Signed-off-by: Alvin Wang <alvinwang@msn.com>
[AJ: Remove some MSG_INFO() spam, fix whitespace issues]
Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
diff --git a/vpnor/test/create_aligned_window.cpp b/vpnor/test/create_aligned_window.cpp
new file mode 100644
index 0000000..910e7c5
--- /dev/null
+++ b/vpnor/test/create_aligned_window.cpp
@@ -0,0 +1,84 @@
+// SPDX-License-Identifier: Apache-2.0
+// Copyright (C) 2018 IBM Corp.
+
+#include "config.h"
+
+extern "C" {
+#include "test/mbox.h"
+#include "test/system.h"
+}
+
+#include "vpnor/test/tmpd.hpp"
+
+#include <cassert>
+#include <cstring>
+#include <experimental/filesystem>
+#include <fstream>
+#include <vector>
+
+#include "vpnor/backend.h"
+
+// A read window assumes that the toc is located at offset 0,
+// so create dummy partition at arbitrary offset 0x1000.
+const std::string toc[] = {
+    "partition01=HBB,00001000,00002000,80,ECC,READONLY",
+    "partition05=DJVPD,0x000e5000,0x0022d000,00,ECC,PRESERVED",
+};
+
+static const auto BLOCK_SIZE = 4096;
+static const auto ERASE_SIZE = BLOCK_SIZE;
+static const auto N_WINDOWS = 1;
+static const auto WINDOW_SIZE = 1024 * 1024;
+static const auto MEM_SIZE = WINDOW_SIZE * 3;
+
+static const uint8_t get_info[] = {0x02, 0x00, 0x02, 0x00, 0x00, 0x00,
+                                   0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+                                   0x00, 0x00, 0x00, 0x00};
+
+// Used to check the alignment
+static const uint8_t create_read_window1[] = {
+    0x04, 0x01, 0xe7, 0x00, 0x01, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00};
+
+static const uint8_t response1[] = {0x04, 0x01, 0x00, 0xfd, 0x00, 0x01, 0xe5,
+                                    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01};
+
+static const uint8_t create_read_window2[] = {
+    0x04, 0x02, 0xe5, 0x01, 0x01, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00};
+
+static const uint8_t response2[] = {0x04, 0x02, 0x00, 0xfd, 0x48, 0x00, 0xe5,
+                                    0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01};
+
+namespace test = openpower::virtual_pnor::test;
+
+int main()
+{
+    struct mbox_context* ctx;
+
+    system_set_reserved_size(MEM_SIZE);
+    system_set_mtd_sizes(MEM_SIZE, ERASE_SIZE);
+
+    ctx = mbox_create_frontend_context(N_WINDOWS, WINDOW_SIZE);
+
+    test::VpnorRoot root(&ctx->backend, toc, BLOCK_SIZE);
+
+    int rc = mbox_command_dispatch(ctx, get_info, sizeof(get_info));
+    assert(rc == 1);
+
+    // send the request for partition5
+    rc = mbox_command_dispatch(ctx, create_read_window1,
+                               sizeof(create_read_window1));
+    assert(rc == 1);
+    rc = mbox_cmp(ctx, response1, sizeof(response1));
+    assert(rc == 0);
+
+    // send the request for partition5
+    rc = mbox_command_dispatch(ctx, create_read_window2,
+                               sizeof(create_read_window2));
+    assert(rc == 1);
+    rc = mbox_cmp(ctx, response2, sizeof(response2));
+    assert(rc == 0);
+
+    return rc;
+}