On Mon, Dec 09, 2013 at 10:57:25AM -0500, Kevin O'Connor wrote:
On Mon, Dec 09, 2013 at 02:20:59PM +0100, Gerd Hoffmann wrote:
On Mo, 2013-12-09 at 14:18 +0200, Gal Hammer wrote:
A Windows 7 (32-bit) VM running with QXL device fails to start with the new updated vgabios binaries (commit
Tracked down to the new vgabios stack switching. With CONFIG_VGA_ALLOCATE_EXTRA_STACK=n everything is fine again.
Ughh. WinXP doesn't have the problem, but I can also reproduce on Win7 beta.
I'll change the default for CONFIG_VGA_ALLOCATE_EXTRA_STACK to off.
I tracked this down further. The problem is the Windows x86 emulator doesn't correctly handle memory accesses relative to the %esp register. Julian reported this some time back and we worked around it then. However, the recent "extra stack" assembler code inserted a few of these instructions.
I think the proper fix is to leave CONFIG_VGA_ALLOCATE_EXTRA_STACK on and use slightly different assembler so as not to aggravate win7.
I tested the seabios patch below and my win7 beta now boots okay.
-Kevin
--- a/vgasrc/vgaentry.S +++ b/vgasrc/vgaentry.S @@ -97,12 +97,9 @@ entry_10_extrastack: movl %ecx, BREGS_ecx(%eax) movw %es, BREGS_es(%eax) movl %esp, BREGS_size+0(%eax) - movzwl %sp, %esp movw %ss, BREGS_size+4(%eax) - movl (%esp), %edx - movl %edx, BREGS_code(%eax) - movw 4(%esp), %dx - movw %dx, BREGS_flags(%eax) + popl BREGS_code(%eax) + popw BREGS_flags(%eax)
movw %ds, %dx // Setup %ss/%esp and call function movw %dx, %ss