[Qemu-devel] Motivation of BIOS patch?

[Qemu-devel] Motivation of BIOS patch?

[H. Peter Anvin]

I saw the following patch in the Qemu source:

Index: rombios.c
===================================================================
RCS file: /cvsroot/bochs/bochs/bios/rombios.c,v
retrieving revision 1.174
diff -u -w -r1.174 rombios.c
--- rombios.c   17 Oct 2006 16:48:05 -0000      1.174
+++ rombios.c   8 Feb 2007 21:57:48 -0000
@@ -9472,6 +9472,14 @@
    mov eax, #0x00040000
    call eax

+  ;; reset the memory (some boot loaders such as syslinux suppose
+  ;; that the memory is set to zero)
+  mov edi, #0x00040000
+  mov ecx, #0x40000 / 4
+  xor eax, eax
+  rep
+    stosd
+
    ;; return to 16 bit protected mode first
    db 0xea
    dd rombios32_10

Being the SYSLINUX author I'm more than a little surprised about this; 
this is probably indicative of a serious bug (possibly now fixed). 
Anyone who has any information about this?

	-hpa