From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43) id 1NZprF-0004a8-RR for qemu-devel@nongnu.org; Tue, 26 Jan 2010 13:09:46 -0500 Received: from exim by lists.gnu.org with spam-scanned (Exim 4.43) id 1NZpr8-0004PF-Sm for qemu-devel@nongnu.org; Tue, 26 Jan 2010 13:09:43 -0500 Received: from [199.232.76.173] (port=34104 helo=monty-python.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1NZpr8-0004Oq-BW for qemu-devel@nongnu.org; Tue, 26 Jan 2010 13:09:38 -0500 Received: from david.siemens.de ([192.35.17.14]:15339) by monty-python.gnu.org with esmtps (TLS-1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.60) (envelope-from ) id 1NZpr7-0008VF-OB for qemu-devel@nongnu.org; Tue, 26 Jan 2010 13:09:38 -0500 Message-ID: <4B5F2FDD.1030802@siemens.com> Date: Tue, 26 Jan 2010 19:09:33 +0100 From: Jan Kiszka MIME-Version: 1.0 Subject: Re: [Qemu-devel] CONFIG_FB_CIRRUS for Linux guests References: <4B5EFFBC.8020703@siemens.com> <4B5F1E39.1000909@codemonkey.ws> In-Reply-To: <4B5F1E39.1000909@codemonkey.ws> Content-Type: text/plain; charset=ISO-8859-15 Content-Transfer-Encoding: 7bit List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Anthony Liguori Cc: Glauber Costa , Marcelo Tosatti , qemu-devel Anthony Liguori wrote: > On 01/26/2010 08:44 AM, Jan Kiszka wrote: >> Hi, >> >> just received some Linux guest kernel that refuses to properly use its >> framebuffer console under QEMU (probably any version, tried down to some >> 0.10.x). It turned out that it has CONFIG_FB_CIRRUS enabled and fails to >> initialize the display when this is actually used. Anyone came across >> this before or has some idea what goes wrong? >> > > Looks like it worked at some point: > > commit ca896ef389fc44c7a673d1bd2b94823e28da37a1 > Author: aurel32 > Date: Thu May 8 12:21:27 2008 +0000 > > cirrusfb: proper "Attribute Controller Toggle Readback" register > behaviour > > (Marcelo Tosatti) > > > git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@4386 > c046a42c-6fe2-441c > > The cirrusfb Linux driver uses the toggle readback register to determine > whether to flip 0xC30 to data/address mode. > > Without proper implementation the VGA mode will be erroneously set to > blank resulting in crashes when starting BITBLT. > > 3d4h index 24h (R): Attribute Controller Toggle Readback Register > bit 7 If set the Attribute Controller will next access a data register, if > clear it'll access the index register > > > Signed-off-by: Marcelo Tosatti > Yep, and 2bec46dc97571a3c34b18fe4ca198e7bfbdca41f broke it again. Unless Glauber immediately confesses the crime and removes the bug he left behind, I will try to understand the reason later. Jan -- Siemens AG, Corporate Technology, CT T DE IT 1 Corporate Competence Center Embedded Linux