From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:36984) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Zr00J-0003Ts-4o for qemu-devel@nongnu.org; Tue, 27 Oct 2015 04:53:15 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Zr00F-0004ep-Vc for qemu-devel@nongnu.org; Tue, 27 Oct 2015 04:53:15 -0400 Received: from mx1.redhat.com ([209.132.183.28]:46314) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Zr00F-0004eU-Q0 for qemu-devel@nongnu.org; Tue, 27 Oct 2015 04:53:11 -0400 Received: from int-mx13.intmail.prod.int.phx2.redhat.com (int-mx13.intmail.prod.int.phx2.redhat.com [10.5.11.26]) by mx1.redhat.com (Postfix) with ESMTPS id 65DE78F2FE for ; Tue, 27 Oct 2015 08:53:11 +0000 (UTC) Date: Tue, 27 Oct 2015 10:53:08 +0200 From: "Michael S. Tsirkin" Message-ID: <20151027105059-mutt-send-email-mst@redhat.com> References: <1445852815-85168-1-git-send-email-imammedo@redhat.com> <20151026120943-mutt-send-email-mst@redhat.com> <20151026142432.4a8ca282@nial.brq.redhat.com> <20151027084706-mutt-send-email-mst@redhat.com> <20151027094837.65185c94@nial.brq.redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20151027094837.65185c94@nial.brq.redhat.com> Subject: Re: [Qemu-devel] [PATCH v2] pc: memhp: enforce minimal 128Mb alignment for pc-dimm List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Igor Mammedov Cc: pbonzini@redhat.com, qemu-devel@nongnu.org, ehabkost@redhat.com On Tue, Oct 27, 2015 at 09:48:37AM +0100, Igor Mammedov wrote: > On Tue, 27 Oct 2015 10:31:21 +0200 > "Michael S. Tsirkin" wrote: > > > On Mon, Oct 26, 2015 at 02:24:32PM +0100, Igor Mammedov wrote: > > > Yep it's workaround but it works around QEMU's broken virtio > > > implementation in a simple way without need for guest side changes. > > > > > > Without foreseeable virtio fix it makes memory hotplug unusable and even > > > more so if there were a virtio fix it won't fix old guests since you've > > > said that virtio fix would require changes of both QEMU and guest sides. > > > > What makes it not foreseeable? > > Apparently only the fact that we have a work-around in place so no one > > works on it. I can code it up pretty quickly, but I'm flat out of time > > for testing as I'm going on vacation soon, and hard freeze is pretty > > close. > I can lend a hand for testing part. > > > > > GPA space is kind of cheap, but wasting it in chunks of 512M > > seems way too aggressive. > hotplug region is sized with 1Gb alignment reserve per DIMM so we aren't > actually wasting anything here. > If I allocate two 1G DIMMs, what will be the gap size? 512M? 1G? It's too much either way. -- MST