From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:57547) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Yxe88-0002jm-A1 for qemu-devel@nongnu.org; Wed, 27 May 2015 12:24:33 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Yxe84-0002UY-9E for qemu-devel@nongnu.org; Wed, 27 May 2015 12:24:32 -0400 Received: from mx1.redhat.com ([209.132.183.28]:55405) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Yxe84-0002UK-1a for qemu-devel@nongnu.org; Wed, 27 May 2015 12:24:28 -0400 Date: Wed, 27 May 2015 17:24:18 +0100 From: "Dr. David Alan Gilbert" Message-ID: <20150527162418.GF2130@work-vm> References: <555DE2EF.1000509@redhat.com> <20150522110136.GF14428@redhat.com> <20150522111259.GG14428@redhat.com> <55631B3A.7080803@redhat.com> <5564E4C9.8010906@codeaurora.org> <55658EAB.3010107@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <55658EAB.3010107@redhat.com> Subject: Re: [Qemu-devel] Announcing qboot, a minimal x86 firmware for QEMU List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Paolo Bonzini Cc: Peter Maydell , Christopher Covington , KVM list , qemu-devel * Paolo Bonzini (pbonzini@redhat.com) wrote: > > > On 26/05/2015 23:25, Christopher Covington wrote: > > On 05/25/2015 08:53 AM, Paolo Bonzini wrote: > >> > >> On 22/05/2015 13:12, Daniel P. Berrange wrote: > >>> In > >>> particular I don't see why we need to have a SATA controller and ISA/LPC > >>> bridge in every virt machine - root PCI bus only should be possible, as you > >>> can provide disks via virtio-blk or virtio-scsi and serial, parallel, mouse, > >>> floppy via PCI devices and/or by adding a USB bus in the cases where you > >>> really need one. > >> > >> I think removing the ISA/LPC bridge is hard. It includes the real-time > >> clock and fw_cfg, for example. > > > > Could VirtIO specified replacements make sense for these peripherals? > > Not really. virtio is too heavyweight and you'd be reinventing the > wheel unnecessarily. I see reasons to replace some but not all these components; and there's no point in replacing the ISA/LPC bridge since it's got nothing at all in it. > For example, ARM's "-M virt" uses a pl011 block for the RTC, and also > uses fw_cfg. Another commonly used ISA device is the UART, for which > again -M virt uses a pl031. I don't see much point in replacing the simple PC uart with anything virtio; I can imagine that you might want to go down to something really trivial with non of the bells and whistles; but a UART is pretty simple. The PC RTC though, it's a bit of a disaster that's had 30 years of random cruft added into it to hold random things that should never have been there. Dave > > Paolo > -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK