From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mga14.intel.com (mga14.intel.com [192.55.52.115]) (using TLSv1 with cipher CAMELLIA256-SHA (256/256 bits)) (No client certificate requested) by ml01.01.org (Postfix) with ESMTPS id 650031A1E76 for ; Thu, 1 Sep 2016 13:52:41 -0700 (PDT) Received: from orsmga002.jf.intel.com ([10.7.209.21]) by fmsmga103.fm.intel.com with ESMTP; 01 Sep 2016 13:52:40 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.30,268,1470726000"; d="scan'208";a="1044585396" Received: from danyzest-mobl.amr.corp.intel.com (HELO localhost) ([10.252.141.10]) by orsmga002.jf.intel.com with ESMTP; 01 Sep 2016 13:52:40 -0700 MIME-Version: 1.0 To: Ard Biesheuvel , Message-ID: <147276316057.22179.17432934377065931050@jljusten-ivb> From: Jordan Justen In-Reply-To: Cc: "Laszlo Ersek" , "edk2-devel-01" References: <20160819124932.29711-1-lersek@redhat.com> <147267618723.12178.11385591212119668150@jljusten-ivb> <2c5b6038-a51a-9206-392b-d391c0aabf51@redhat.com> <147275300806.20661.4606850370467291385@jljusten-ivb> <0500cc50-86f9-ab97-f22d-012ac1857ad0@redhat.com> <147275957055.21562.7750188759462698423@jljusten-ivb> User-Agent: alot/0.3.7 Date: Thu, 01 Sep 2016 13:52:40 -0700 Subject: Re: [PATCH 00/11] OvmfPkg, ArmVirtPkg: GOP driver for the VirtIo GPU (virtio-gpu-pci) X-BeenThere: edk2-devel@lists.01.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: EDK II Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 01 Sep 2016 20:52:41 -0000 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Points taken. Oh well. :\ On 2016-09-01 13:23:27, Ard Biesheuvel wrote: > On 1 September 2016 at 20:52, Jordan Justen w= rote: > > On 2016-09-01 11:46:04, Laszlo Ersek wrote: > >> On 09/01/16 20:03, Jordan Justen wrote: > >> > >> > I think there would be value to have a non-VGA device that could sti= ll > >> > configure a simple framebuffer. VGA does bring a fair amount of other > >> > baggage. > >> > >> Ah, I see your point. You distinguish "VGA" from "non-VGA device with > >> framebuffer". > >> > >> For this discussion however, this distinction makes no difference. The > >> suggested "non-VGA device with framebuffer" would be broken exactly the > >> same way. In other words, it's not the "other baggage" that is broken, > >> it is the framebuffer. > >> > > > > This is only focusing on the current ARM issue. I'm just pointing out > > that I think virtio gpu without VGA, but with a framebuffer could be > > useful on IA32/X64 as well. > > > > 1. You don't have to deal with the PCI bus > > > > 2. The OS re-enumerating the PCI bus would not break the framebuffer > > > = > How does adding a framebuffer to virtio-gpu solve any of that? > virtio-gpu is a PCI device as well > = > > Is there no chance that ARM KVM might someday also be able to support > > a framebuffer? > > > = > There are workarounds imaginable, but none of them are feasible in > terms. A new revision of the architecture may address this, but that > will take years to turn up in real hardware. > = > > Obviously this is not too important for IA32/X64 OVMF, because we have > > reasonable alternatives. But, it seems like virtio gpu could be a > > significantly better option for IA32/X64 OVMF if an optional > > framebuffer was possible. > > > = > IIUC, not having a linear framebuffer was one of the design goals, > since it is essentially a layering violation in the virtio stack. > virtio-gpu is strictly ring based, like other virtio devices. > = > If you want a framebuffer, you should use virtio-vga. Adding a > framebuffer to virtio-gpu is a step back rather than a step forward. > = > Also, the loader->OS handover already suffers from the issues you > mention, since the PCI reconfiguration breaks GOP on almost every > platform. The reason that it is less of a concern on ARM is that most > systems use UART as the primary console.