From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:40640) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1aTAbN-0000x6-OP for qemu-devel@nongnu.org; Tue, 09 Feb 2016 10:53:18 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1aTAbJ-0007AQ-Hm for qemu-devel@nongnu.org; Tue, 09 Feb 2016 10:53:17 -0500 Received: from mx2.parallels.com ([199.115.105.18]:52524) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1aTAbJ-00078W-CQ for qemu-devel@nongnu.org; Tue, 09 Feb 2016 10:53:13 -0500 Date: Tue, 9 Feb 2016 18:52:50 +0300 From: Roman Kagan Message-ID: <20160209155249.GA13787@rkaganb.sw.ru> References: <1454612376-7072-1-git-send-email-mst@redhat.com> <1454612376-7072-49-git-send-email-mst@redhat.com> <20160205192507.41fc6024@nial.brq.redhat.com> <20160208131443.GC6420@rkaganb.sw.ru> <56B8F89F.3090603@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: <56B8F89F.3090603@redhat.com> Subject: Re: [Qemu-devel] [PULL 48/49] i386: populate floppy drive information in DSDT List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: John Snow Cc: Peter Maydell , Eduardo Habkost , "Michael S. Tsirkin" , qemu-devel@nongnu.org, Paolo Bonzini , Igor Mammedov , Richard Henderson On Mon, Feb 08, 2016 at 03:20:47PM -0500, John Snow wrote: > On 02/08/2016 08:14 AM, Roman Kagan wrote: > > On Fri, Feb 05, 2016 at 07:25:07PM +0100, Igor Mammedov wrote: > >>> + aml_append(fdi, > >>> + aml_int(cylinders - 1)); /* Maximum Cylinder Number */ > >> this puts uint64_t(-1) in AML i.e. cylinders == 0 and overflow happens here > >> > >> CCing Jon > > > > I guess this is the effect of John's fdc rework. I used to think zero > > geometry was impossible at the time this patch was developed. > > > > I wonder if it hasn't been fixed already by > > > > commit fd9bdbd3459e5b9d51534f0747049bc5b6145e07 > > Author: John Snow > > Date: Wed Feb 3 11:28:55 2016 -0500 > > > > fdc: fix detection under Linux > > Yes, hopefully solved on my end. The geometry values for an empty disk > are not well defined (they certainly don't have any *meaning*) so if you > are populating tables based on an empty drive, I just hope you also have > the mechanisms needed to update said tables when the media changes. I don't. At the time the patch was developed there basically were no mechanisms to update the geometry at all (and this was what you patchset addressed, in particular, wasn't it?) so I didn't care. Now if it actually has to be fully dynamic it's gonna be more involved... > What do the guests use these values for? Are they fixed at boot? Only Windows guests use it so it's hard to tell. I can only claim that if I stick bogus values into that ACPI object the guest fails to read the floppy. Roman.