X-Git-Url: https://gerrit.opnfv.org/gerrit/gitweb?a=blobdiff_plain;f=qemu%2Froms%2Fseabios%2Fvgasrc%2Fvgaentry.S;h=53be2b38ca520c691a4fde927bd8e0c5415a8919;hb=a14b48d18a9ed03ec191cf16b162206998a895ce;hp=d9ebdb93ca39aa258961f9a9712097cbe40a5827;hpb=e44e3482bdb4d0ebde2d8b41830ac2cdb07948fb;p=kvmfornfv.git

diff --git a/qemu/roms/seabios/vgasrc/vgaentry.S b/qemu/roms/seabios/vgasrc/vgaentry.S
index d9ebdb93c..53be2b38c 100644
--- a/qemu/roms/seabios/vgasrc/vgaentry.S
+++ b/qemu/roms/seabios/vgasrc/vgaentry.S
@@ -86,14 +86,23 @@ entry_10:
         ENTRY_ARG_VGA handle_10
         iretw
 
+#define VGA_CUSTOM_BDA_FLAGS 0xb9
+#define BF_EXTRA_STACK 0x40
+
         // Entry point using extra stack
         DECLFUNC entry_10_extrastack
 entry_10_extrastack:
         cli
         cld
-        pushw %ds               // Set %ds:%eax to space on ExtraStack
+        pushw %ds
         pushl %eax
-        movw %cs:ExtraStackSeg, %ds
+
+        movw $SEG_BDA, %ax      // Check if extra stack is enabled
+        movw %ax, %ds
+        testb $BF_EXTRA_STACK, VGA_CUSTOM_BDA_FLAGS
+        jz 1f
+
+        movw %cs:ExtraStackSeg, %ds // Set %ds:%eax to space on ExtraStack
         movl $(CONFIG_VGA_EXTRA_STACK_SIZE-PUSHBREGS_size-16), %eax
         SAVEBREGS_POP_DSEAX     // Save registers on extra stack
         movl %esp, PUSHBREGS_size+8(%eax)
@@ -116,6 +125,11 @@ entry_10_extrastack:
         RESTOREBREGS_DSEAX
         iretw
 
+1:      // Use regular entry point if the extra stack is disabled
+        popl %eax
+        popw %ds
+        jmp entry_10
+
         // Timer irq handling
         DECLFUNC entry_timer_hook
 entry_timer_hook: