From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_NEOMUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id EF2A6C31E44 for ; Fri, 14 Jun 2019 04:49:33 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id BB17420851 for ; Fri, 14 Jun 2019 04:49:33 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org BB17420851 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:48310 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.86_2) (envelope-from ) id 1hbe9c-0001vw-M2 for qemu-devel@archiver.kernel.org; Fri, 14 Jun 2019 00:49:32 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:35963) by lists.gnu.org with esmtp (Exim 4.86_2) (envelope-from ) id 1hbe8l-0001Wx-Mv for qemu-devel@nongnu.org; Fri, 14 Jun 2019 00:48:40 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1hbe8k-0006Cp-Nr for qemu-devel@nongnu.org; Fri, 14 Jun 2019 00:48:39 -0400 Received: from mx1.redhat.com ([209.132.183.28]:48464) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1hbe3q-00021B-H9; Fri, 14 Jun 2019 00:43:34 -0400 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id E8E1B8762F; Fri, 14 Jun 2019 04:43:13 +0000 (UTC) Received: from sirius.home.kraxel.org (ovpn-116-33.ams2.redhat.com [10.36.116.33]) by smtp.corp.redhat.com (Postfix) with ESMTP id 557D219C67; Fri, 14 Jun 2019 04:43:11 +0000 (UTC) Received: by sirius.home.kraxel.org (Postfix, from userid 1000) id 5A7C311AA3; Fri, 14 Jun 2019 06:43:10 +0200 (CEST) Date: Fri, 14 Jun 2019 06:43:10 +0200 From: Gerd Hoffmann To: Sam Eiderman Message-ID: <20190614044310.wxnkwxagr23d5cbt@sirius.home.kraxel.org> References: <20190612115939.23825-1-shmuel.eiderman@oracle.com> <20190612130650.xftda65kgnsefyvs@sirius.home.kraxel.org> <20190612191817.5bilt2abif2xvcbv@sirius.home.kraxel.org> <02844D7D-ED79-4744-A203-8E713DE7A717@oracle.com> <20190613093850.5k7prawn6x4qt3fi@sirius.home.kraxel.org> <730C65DE-A9B4-4553-B6A0-7A3B81A1FA12@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <730C65DE-A9B4-4553-B6A0-7A3B81A1FA12@oracle.com> User-Agent: NeoMutt/20180716 X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.26]); Fri, 14 Jun 2019 04:43:27 +0000 (UTC) X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 209.132.183.28 Subject: Re: [Qemu-devel] [QEMU] [PATCH v2 0/8] Add Qemu to SeaBIOS LCHS interface X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: kwolf@redhat.com, qemu-block@nongnu.org, arbel.moshe@oracle.com, seabios@seabios.org, QEMU , Max Reitz , Kevin O'Connor , liran.alon@oracle.com, Karl Heubaum Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Hi, > Can there be a guest that will fail the MBR in such a way? Yes. > Look at the following MBR partition table of a Windows XP guest in our production > environment: > > Disk size in sectors: 16777216 > > Binary (only one partition 16 bytes): 80 01 01 00 07 fe ff ff 3f 00 00 00 d5 ea ff 00 > Start: (0, 1, 1, 63) > End: (1023, 254, 63, 16771859) > > As can be easily seen, any MBR guessing algorithm should guess: > > 255 heads (since a value of 254 appears), 63 spt (since a value of 63 appears) > > Turns out that this image does not work with 255, 63 but actually requires > > 16 heads, 63 spt > > to boot. > > So relying on MBR partitions alone is not always enough and sometimes manual intervention > is required. Ok, given that seabios has no setup any manual configuration needs to be done via qemu. But why do we need a new interface for that? IDE can pass the geometry to the guest. virtio-blk has support too (VIRTIO_BLK_F_GEOMETRY). Likewise scsi (MODE_PAGE_HD_GEOMETRY). So this should be doable without any qemu changes. cheers, Gerd