From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43) id 1N9mlH-0001Xu-3i for qemu-devel@nongnu.org; Sun, 15 Nov 2009 16:35:55 -0500 Received: from exim by lists.gnu.org with spam-scanned (Exim 4.43) id 1N9mlC-0001XJ-Mu for qemu-devel@nongnu.org; Sun, 15 Nov 2009 16:35:54 -0500 Received: from [199.232.76.173] (port=57697 helo=monty-python.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1N9mlC-0001XG-Hx for qemu-devel@nongnu.org; Sun, 15 Nov 2009 16:35:50 -0500 Received: from mail-yx0-f188.google.com ([209.85.210.188]:34833) by monty-python.gnu.org with esmtp (Exim 4.60) (envelope-from ) id 1N9mlC-00082t-5C for qemu-devel@nongnu.org; Sun, 15 Nov 2009 16:35:50 -0500 Received: by yxe26 with SMTP id 26so4116101yxe.4 for ; Sun, 15 Nov 2009 13:35:49 -0800 (PST) MIME-Version: 1.0 In-Reply-To: References: <20091115152858.GH7392@redhat.com> <4B0061B2.2070207@mail.berlios.de> From: Blue Swirl Date: Sun, 15 Nov 2009 23:35:29 +0200 Message-ID: Subject: Re: [Qemu-devel] Standard vga breakage Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: malc Cc: qemu-devel , Gleb Natapov On Sun, Nov 15, 2009 at 11:21 PM, malc wrote: > On Sun, 15 Nov 2009, Stefan Weil wrote: > >> malc schrieb: >> > On Sun, 15 Nov 2009, Gleb Natapov wrote: > > [..snip..] > >> >> Here is a summary of my analysis of this problem: >> >> Graphics mode memory (ram 0xe0000000 ...) is not mapped >> in QEMU address space (which results in unassigned >> memory writes) for standard pci vga (-vga std), so users >> don't get vga display output with grub (in graphical mode), >> debian installer (in graphical mode) or similar boot software. >> >> This happens for PC system emulation using SeaBIOS. >> It won't happen when using Bochs BIOS. >> >> Other system emulations which can run standard pci vga >> seem to suffer from the same problem: when I run mips >> malta using -vga std, it won't display anything on the vga >> screen (it works with cirrus pci vga). >> >> Malta has no vga bios, so the error might be in QEMU's >> vga code (hw/vga-pci.c). Maybe wrong initial PCI mappings? >> Maybe this has always be wrong (which would explain why >> git bisect does not work). > > git bisect doesn't work because most of the time: > > a. Compilation fails > b. Compilation succeeds but qemu segfaults before even trying to > =C2=A0 execute any guest code With infinite time and resources, we could construct a fully bisectable tree with the following properties: - buggy commits (especially commits that break build or require manual reconfiguration) are replaced with corrected commits by changing the history - no merges, linear history - compound commits are broken down to simple, atomic versions - documentation is added by the first commit to reduce the number of commit= s - spelling fixes applied by changing history, not as a separate commit - each commit should still have some relation to some real tree commit