From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:40955) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1W5FJ9-0007nh-7W for qemu-devel@nongnu.org; Mon, 20 Jan 2014 08:54:37 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1W5FJ2-0006BO-W8 for qemu-devel@nongnu.org; Mon, 20 Jan 2014 08:54:31 -0500 Received: from mx1.redhat.com ([209.132.183.28]:63374) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1W5FJ2-0006BK-Mi for qemu-devel@nongnu.org; Mon, 20 Jan 2014 08:54:24 -0500 Date: Mon, 20 Jan 2014 15:59:07 +0200 From: "Michael S. Tsirkin" Message-ID: <20140120135907.GB31950@redhat.com> References: <1387185088-16811-1-git-send-email-kraxel@redhat.com> <20131216115401.GA19233@redhat.com> <1387201577.28883.38.camel@nilsson.home.kraxel.org> <20131216192843.GB21330@redhat.com> <1387277686.12500.35.camel@nilsson.home.kraxel.org> <20131217115936.GA30168@redhat.com> <1387302966.12500.85.camel@nilsson.home.kraxel.org> <20140120112345.GA11565@redhat.com> <1390222725.11527.46.camel@nilsson.home.kraxel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1390222725.11527.46.camel@nilsson.home.kraxel.org> Subject: Re: [Qemu-devel] [PATCH v2] x86: gigabyte alignment for ram List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Gerd Hoffmann Cc: qemu-devel@nongnu.org, Anthony Liguori On Mon, Jan 20, 2014 at 01:58:45PM +0100, Gerd Hoffmann wrote: > On Mo, 2014-01-20 at 13:23 +0200, Michael S. Tsirkin wrote: > > On Tue, Dec 17, 2013 at 06:56:06PM +0100, Gerd Hoffmann wrote: > > > > I merged your patch but split it: q35 is separate and piix > > > > is separate. Would you like me to drop the q35 part then? > > > > > > If you are fine with q35 having only 2G lowmem keep it. It's safe. > > > > > > We can sort the mmconfig setup afterwards, then check if (and how) we'll > > > transition to 3G lowmem. Maybe we simply don't after all, with the > > > world moving to 64bit it doesn't matter that much whenever memory is > > > mapped above or below 4g. And for old 32bit guests there is always the > > > option to stick with piix which continues to offers up to 3.5G lowmem. > > > > > > cheers, > > > Gerd > > > > > > > Any update here? > > No time to investigate yet, still playing catch-up after xmas holidays & > being sick. > > > I'm worried 2G lowmem is a bit too aggressive, PAE still exists. > > piix (with up to 3.5g lowmem) exists too ;) Yes but I think it's preferable to keep features orthogonal. > > If we want to support old bios, one way would be to add > > a new register to enable 3g lowmem. > > Do we really want do this (allow guest change RAM mapping)? > > I think we should: > (1) reserve mmconf xbar as motherboard ressource, so it can live within > PCI0._CRS I don't think this is possible, PCI FW spec seems to outlaw this explicitly. > (2) make PCI0._CRS start at end of lowmem, like it does on piix This we can do. But we'll have to make a hole for the xbar. > Then maybe: > (3) update seabios to place xbar somewhere else > (4) adjust memory layout. > > (1)+(2) are useful anyway. (3)+(4) would allow for 3g lowmem, and > obviously have some compatibility issues: doing (4) requires a seabios > update. > > cheers, > Gerd Right. So you'll look into 4 then? I'm keeping these patches out of tree for now ...