From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx1.redhat.com (mx1.redhat.com [209.132.183.28]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ml01.01.org (Postfix) with ESMTPS id 76B8621E49BA7 for ; Tue, 22 Aug 2017 08:41:53 -0700 (PDT) Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id D2099155B9; Tue, 22 Aug 2017 15:44:25 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mx1.redhat.com D2099155B9 Authentication-Results: ext-mx05.extmail.prod.ext.phx2.redhat.com; dmarc=none (p=none dis=none) header.from=redhat.com Authentication-Results: ext-mx05.extmail.prod.ext.phx2.redhat.com; spf=fail smtp.mailfrom=lersek@redhat.com Received: from lacos-laptop-7.usersys.redhat.com (ovpn-116-92.phx2.redhat.com [10.3.116.92]) by smtp.corp.redhat.com (Postfix) with ESMTP id D7A9977D5A; Tue, 22 Aug 2017 15:44:24 +0000 (UTC) To: Ard Biesheuvel Cc: "edk2-devel@lists.01.org" , Leif Lindholm , Jordan Justen References: <20170818130243.4645-1-ard.biesheuvel@linaro.org> From: Laszlo Ersek Message-ID: Date: Tue, 22 Aug 2017 17:44:23 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.3.0 MIME-Version: 1.0 In-Reply-To: X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.29]); Tue, 22 Aug 2017 15:44:26 +0000 (UTC) Subject: Re: [PATCH] OvmfPkg/QemuVideoDxe: map framebuffer as write-combining/non-executable X-BeenThere: edk2-devel@lists.01.org X-Mailman-Version: 2.1.22 Precedence: list List-Id: EDK II Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 22 Aug 2017 15:41:53 -0000 Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit On 08/22/17 16:31, Ard Biesheuvel wrote: > [...] >>> >>> (1) When we added VirtioGpuDxe to the ArmVirtPkg platforms, the only >>> reason I didn't propose removing QemuVideoDxe from the same platforms >>> was that QemuVideoDxe was usable on QEMU/TCG, and I figured it wouldn't >>> hurt to keep it. >>> >>> Other than that, I see zero point in using this driver on ARM. (And, >>> apparently, it does hurt to keep it.) >>> >>> Can we please consider simply removing this driver from the ArmVirtPkg >>> platforms? (And then some now-conditional compilation could be >>> simplified in the driver too!) >>> >> >> It is actually quite useful in TCG mode, and the fact that QEMU >> currently allows unaligned accesses to device memory is not something >> we should be relying upon. >> > > Actually, I managed to confuse myself here. The only thing lacking > when running with virtio-gpu rather than VGA is efifb support, due to > the fact that the framebuffer is no longer directly addressable. efifb > is a useful hack on bare metal systems that lack a real framebuffer > driver, but it is hardly something to care deeply about on VMs. (Some side thoughts: The "virtiodrmfb" driver in the Linux guest works fine with virtio-gpu-pci. It does not activate itself as soon into the boot process as efifb, but it does provide a fully functional character console. And X11 works fine too, with the kernel modesetting driver. Even if efifb had a chance to work (inheriting a framebuffer), it would be supplanted during boot really quickly by virtiodrmfb. So the only consequence of "efifb" not working is that the character console comes to life a bit later, and some early messages are not shown on the VT.) > So I am going to change my mind, and agree with Laszlo: let's remove > QemuVideoDxe from ArmVirtQemu; the longer we wait, the more difficult > it becomes, and only TCG users that rely on a GOP protocol being > exposed with direct framebuffer access are going to be affected in the > first place (if any such use cases exist) I expect this set of users to be empty already. > Laszlo: any ideas or suggestions you may want to share before I start > working on this? Just the above musings. Please go ahead with the QemuVideoDxe removal! Thank you! Laszlo