From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:44014) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1VqK2p-0000Z6-86 for qemu-devel@nongnu.org; Tue, 10 Dec 2013 04:56:03 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1VqK2l-0000xh-41 for qemu-devel@nongnu.org; Tue, 10 Dec 2013 04:55:59 -0500 Received: from mx3-phx2.redhat.com ([209.132.183.24]:49757) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1VqK2k-0000xT-Ri for qemu-devel@nongnu.org; Tue, 10 Dec 2013 04:55:55 -0500 Date: Tue, 10 Dec 2013 04:55:36 -0500 (EST) From: Gal Hammer Message-ID: <1177689370.4553974.1386669336686.JavaMail.root@redhat.com> In-Reply-To: <20131209221251.GA5135@morn.localdomain> References: <52A5B531.9020507@redhat.com> <1386595259.8684.47.camel@nilsson.home.kraxel.org> <20131209155725.GA12684@morn.localdomain> <20131209221251.GA5135@morn.localdomain> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [SeaBIOS] [BUG] Windows 7 fails to start with new vgabios binaries Reply-To: Gal Hammer List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Kevin O'Connor Cc: seabios , Julian Pidancet , Gerd Hoffmann , qemu-devel@nongnu.org Kevin, The patch was verified and it solves the problem on Windows 7 official release as well. Thanks! Gal. ----- Original Message ----- From: "Kevin O'Connor" To: "Gerd Hoffmann" Cc: "Gal Hammer" , "seabios" , qemu-devel@nongnu.org, "Julian Pidancet" Sent: Tuesday, December 10, 2013 12:12:51 AM Subject: Re: [SeaBIOS] [BUG] Windows 7 fails to start with new vgabios binaries 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