From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-it0-x232.google.com (mail-it0-x232.google.com [IPv6:2607:f8b0:4001:c0b::232]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by ml01.01.org (Postfix) with ESMTPS id 5865621E49BAB for ; Tue, 22 Aug 2017 07:29:16 -0700 (PDT) Received: by mail-it0-x232.google.com with SMTP id o19so483473ito.0 for ; Tue, 22 Aug 2017 07:31:49 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; h=mime-version:in-reply-to:references:from:date:message-id:subject:to :cc; bh=PztR8fwMTq6EMGW4qYNWGSFFbxFBTzrlyRY1Y0MXqhs=; b=BOqMURHGu8pm0aUGiOBNSTQxgrPR/9pGjTfxAs6LJg6vowgW9lLQQN85yf6FBWa8uD pTROCgHoh3s6cJ7QwMR4jwAMacW5rlKuZxZHmve3hTPEiybZtEsCC2ap5DZqzqRxtoEl SxrGQAtdYN9U8AXZLpwgmfVQ/oiMRVLrocXGM= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:in-reply-to:references:from:date :message-id:subject:to:cc; bh=PztR8fwMTq6EMGW4qYNWGSFFbxFBTzrlyRY1Y0MXqhs=; b=mtEQQX/JaSr6U5QkV08ARhLqY3YoDG/RbTIEafKzLCIGkEyDnlJhUVfd970+KVZKlN UWEVQIrDrU7kCk5/ErGnspZFkVw4gz5EGCUH+1NLFFmnd1OxZO/B3PCJ99N864C13yO6 jHnKM9ZpqdgEa4n7akFPOf+IEsSg+Hfmj67Qy5eYDlo5rT4dHOlj8mgKYLX+jFlmVYyD W4EojKzf7USO2RUJ1Za9DxtvW3FTg1QHXgO+5koXh7/YEFdT3E9yOnXpm4MimHDE94ZB F0jIcrPylnH3Zracy/IIPpawgJq4o+eIAtA0cGC8QAyMLeOmVTEWDvk52ppRdd87RcVf MxMA== X-Gm-Message-State: AHYfb5i4pNyeD9CVbgFEFGZRo8KcfSkg/On/lASxf2uvUXHV1rU2K7a8 ltVsLlE9p4LxA4osHcjfxbDiU3kYFFcnIA4= X-Received: by 10.36.222.215 with SMTP id d206mr191529itg.63.1503412308504; Tue, 22 Aug 2017 07:31:48 -0700 (PDT) MIME-Version: 1.0 Received: by 10.107.162.1 with HTTP; Tue, 22 Aug 2017 07:31:47 -0700 (PDT) In-Reply-To: References: <20170818130243.4645-1-ard.biesheuvel@linaro.org> From: Ard Biesheuvel Date: Tue, 22 Aug 2017 15:31:47 +0100 Message-ID: To: Laszlo Ersek Cc: "edk2-devel@lists.01.org" , Leif Lindholm , Jordan Justen 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 14:29:16 -0000 Content-Type: text/plain; charset="UTF-8" [...] >> >> (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. 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) Laszlo: any ideas or suggestions you may want to share before I start working on this? -- Ard.