From 74f052de33cb14d7a1656079a53102a7cbbb6e75 Mon Sep 17 00:00:00 2001
From: jiangdongxu <jiangdongxu1@huawei.com>
Date: Fri, 11 Feb 2022 16:16:05 +0800
Subject: [PATCH 2/6] seabios: do not give back high ram

Oracle 6 and 7 series virtual machines will use the high ram returned by
sebios. Since these high ram will not be initialized before kernel used,
this will cause a system exception. This patch removes the logic for
returning high ram, making the virtual machine will not use this part
of the memory, thus avoiding this kernel bug.

Signed-off-by: wangxin <wangxinxin.wang@huawei.com>
Signed-off-by: Fangyi <eric.fangyi@huawei.com>
Signed-off-by: jiangdongxu <jiangdongxu1@huawei.com>
---
 roms/seabios/src/malloc.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/roms/seabios/src/malloc.c b/roms/seabios/src/malloc.c
index 3733855caf..5827a6523a 100644
--- a/roms/seabios/src/malloc.c
+++ b/roms/seabios/src/malloc.c
@@ -549,6 +549,9 @@ malloc_prepboot(void)
     dprintf(1, "Space available for UMB: %x-%x, %x-%x\n"
             , RomEnd, base, info->range_start, info->range_end);
 
+    // We should not give back unused high ram, to support some special
+    // guest OS, like oracle linux series.
+#ifdef HIGH_MEM_BACK
     // Give back unused high ram.
     info = alloc_find_lowest(&ZoneHigh);
     if (info) {
@@ -556,6 +559,7 @@ malloc_prepboot(void)
         e820_add(info->range_start, giveback, E820_RAM);
         dprintf(1, "Returned %d bytes of ZoneHigh\n", giveback);
     }
+#endif
 
     calcRamSize();
 }
-- 
2.27.0