From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:35137) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1alvCX-0005hg-Fk for qemu-devel@nongnu.org; Fri, 01 Apr 2016 05:17:10 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1alvCS-00078p-FO for qemu-devel@nongnu.org; Fri, 01 Apr 2016 05:17:09 -0400 Received: from mx1.redhat.com ([209.132.183.28]:55861) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1alvCS-00078c-9z for qemu-devel@nongnu.org; Fri, 01 Apr 2016 05:17:04 -0400 Date: Fri, 1 Apr 2016 10:16:59 +0100 From: "Dr. David Alan Gilbert" Message-ID: <20160401091658.GC2242@work-vm> References: <20160331092125.GH32185@stefanha-x1.localdomain> <20160331162222.GA17533@morn.lan> <20160331221039.GA32728@redhat.com> <20160331221730.GA5637@redhat.com> <20160331224432.GA4583@morn.lan> <20160401080222.GC32728@redhat.com> <56FE2D42.5020607@redhat.com> <20160401081417.GD32728@redhat.com> <56FE3045.2030003@redhat.com> <20160401084456.GF32728@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20160401084456.GF32728@redhat.com> Subject: Re: [Qemu-devel] Why is SeaBIOS used with -kernel? List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Richard W.M. Jones" Cc: marc.mari.barcelo@gmail.com, Paolo Bonzini , Kevin O'Connor , qemu-devel@nongnu.org, Stefan Hajnoczi * Richard W.M. Jones (rjones@redhat.com) wrote: > On Fri, Apr 01, 2016 at 10:24:37AM +0200, Paolo Bonzini wrote: > > On 01/04/2016 10:14, Richard W.M. Jones wrote: > > > Found it: only CONFIG_MPTABLE=y was necessary. It boots with: > > > > > > # CONFIG_PIRTABLE is not set > > > CONFIG_MPTABLE=y > > > # CONFIG_SMBIOS is not set > > > # CONFIG_ACPI is not set > > > > If you add all three it should not give any slowdown and will provide > > full hardware features to the kernel. qboot does ACPI and PCI bus > > assignment (it doesn't do SMBIOS because I got bored debugging it. :)) > > Enabling all 4 adds about 2ms. > > However the overhead of SeaBIOS is still down from 68ms to 18ms > (4.0% of total boot time down to 1.1%) so it's still a big gain. > > I wonder how we can make use of this in qemu and downstream distros? > Can we have a bios-min.bin which is used with -kernel boots? Could we pass a flag at runtime that gets the standard image to skip a lot of the stuff you don't want? Or is there anything else qemu could provide (e.g. a fast way to get to PCI config space?) Dave -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK