From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([209.51.188.92]:34998) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1hCDkf-0008Fv-9R for qemu-devel@nongnu.org; Thu, 04 Apr 2019 21:34:42 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1hCDke-0002d0-Ac for qemu-devel@nongnu.org; Thu, 04 Apr 2019 21:34:41 -0400 Received: from mail-oi1-x244.google.com ([2607:f8b0:4864:20::244]:37692) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_128_CBC_SHA1:16) (Exim 4.71) (envelope-from ) id 1hCDke-0002Zf-2W for qemu-devel@nongnu.org; Thu, 04 Apr 2019 21:34:40 -0400 Received: by mail-oi1-x244.google.com with SMTP id v84so3586455oif.4 for ; Thu, 04 Apr 2019 18:34:39 -0700 (PDT) MIME-Version: 1.0 References: <20190404185730.GA22512@ls3530.dellerweb.de> In-Reply-To: <20190404185730.GA22512@ls3530.dellerweb.de> From: Peter Maydell Date: Fri, 5 Apr 2019 08:34:26 +0700 Message-ID: Content-Type: text/plain; charset="UTF-8" Subject: Re: [Qemu-devel] [PATCH] configure: Automatically fall back to TCI on non-release architectures List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Helge Deller Cc: QEMU Developers On Fri, 5 Apr 2019 at 01:59, Helge Deller wrote: > If a non-release architecture is found, and it's known that there is no > native TCG support for that CPU, automatically fall back to the TCI > implementation instead of requesting the user to run configure again > with the --enable-tcg-interpreter option. > > This change simplifies building qemu in automatic build environments > (like in my case the debian buildds) because one does not need to > special case on the architectures. I don't think we should do this. TCI is unmaintained, has several known flaws, does not provide the level of performance that people expect from QEMU, and we've talked about removing it altogether. In particular, distros should not automatically ship a TCI QEMU -- it's something that a user can use if they explicitly opt into but which I don't think we want to surprise anybody with. If we care about a host architecture we should support it with a proper TCG backend. If we don't care that much we shouldn't support it. thanks -- PMM From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-1.0 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS, URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id BB6CFC4360F for ; Fri, 5 Apr 2019 01:35:33 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 825672171F for ; Fri, 5 Apr 2019 01:35:33 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=linaro.org header.i=@linaro.org header.b="KJ9SMmyo" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 825672171F Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linaro.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([127.0.0.1]:33732 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1hCDlU-000080-MR for qemu-devel@archiver.kernel.org; Thu, 04 Apr 2019 21:35:32 -0400 Received: from eggs.gnu.org ([209.51.188.92]:34998) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1hCDkf-0008Fv-9R for qemu-devel@nongnu.org; Thu, 04 Apr 2019 21:34:42 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1hCDke-0002d0-Ac for qemu-devel@nongnu.org; Thu, 04 Apr 2019 21:34:41 -0400 Received: from mail-oi1-x244.google.com ([2607:f8b0:4864:20::244]:37692) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_128_CBC_SHA1:16) (Exim 4.71) (envelope-from ) id 1hCDke-0002Zf-2W for qemu-devel@nongnu.org; Thu, 04 Apr 2019 21:34:40 -0400 Received: by mail-oi1-x244.google.com with SMTP id v84so3586455oif.4 for ; Thu, 04 Apr 2019 18:34:39 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=R7LhU1mUZhzaAg1dgTFUmoo1SX8T+A7gYbFE93tsQug=; b=KJ9SMmyo0e5RzjwKjGiM+I6MeR71f5Y5BgtJZ3msRv/4dXEyj3hKEK1ZiDtJ+sbJXz HhnLmgThBNvcrq8Pbe0pPysSfqxeSep4P8EyKofUW2bLrf89e1qS54J1zY40irc5eztT PAfzY+S53mg0gEfhDol5ufKV4k4GM7a7dNk/Eu0AioETzZpSqxWJ7snEUX7tc0WQIwrl ycWkNhNbpBSvOkGgPbmh9x1COLBALzChCSkQrSC0NVeDbkmlFzeToqGEcnSWrYOWEbCK wDKHIK3hswxy/o+qDquSEBTgvcPn3qk2oTYdHpx0YYio+QFJ3pfM/+zsTDV8uObTCfA8 TKpQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=R7LhU1mUZhzaAg1dgTFUmoo1SX8T+A7gYbFE93tsQug=; b=qYpBQ6slBb1Hhs+owrc5EPEd2DvEFkxZiHrUHnwAA6WJ3YyX7+SeSbygCajcAG80Ng pYpMgWT+TxbEmCRl+OcfLsNLhYNIdF+WajylH9sVCW3fCo/QPObguFC5kXsP7Gy772J+ 6pInmeveeTDrqWM6pU3fIIWSw91B/UWikux7+FQijdgKSbusF94TETKqsIrhNbrRDCaU ApP8ar31G6WQ7GgSMvKSrrWe9X1AN2QBZi0m+LosSlUWF92B8cOtcZ3hOs9DpS7tZETh Wt0FKieUgqHBc1dWWb/83xsvKkJn/ERC9n2DCSq35vaKqsW7ZyqFWU5Rc1iiO/hUupjp lBig== X-Gm-Message-State: APjAAAVvat5cKOORSEBNQ92hrKMx6etF8JaY5qNkUzT4MgKT0TuxvdSL aRhwYzBLTurdeV2iSmybH1PpCgOO9kKxwUb1C5pwEw== X-Google-Smtp-Source: APXvYqx3ET4q6jlkmufyHt4C38Qgi3+2qvHgweVrwu8SK/PE8KNOEHdXQnj5qwedkS19wVoTitSSJq4zLhK68hLf7u4= X-Received: by 2002:aca:4c88:: with SMTP id z130mr5565753oia.170.1554428077941; Thu, 04 Apr 2019 18:34:37 -0700 (PDT) MIME-Version: 1.0 References: <20190404185730.GA22512@ls3530.dellerweb.de> In-Reply-To: <20190404185730.GA22512@ls3530.dellerweb.de> From: Peter Maydell Date: Fri, 5 Apr 2019 08:34:26 +0700 Message-ID: To: Helge Deller Content-Type: text/plain; charset="UTF-8" X-detected-operating-system: by eggs.gnu.org: Genre and OS details not recognized. X-Received-From: 2607:f8b0:4864:20::244 Subject: Re: [Qemu-devel] [PATCH] configure: Automatically fall back to TCI on non-release architectures X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: QEMU Developers Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Message-ID: <20190405013426.eW_LXEYM-fhFyoEXeBJXwah6_2dumSjOUN-ZTtoSlaU@z> On Fri, 5 Apr 2019 at 01:59, Helge Deller wrote: > If a non-release architecture is found, and it's known that there is no > native TCG support for that CPU, automatically fall back to the TCI > implementation instead of requesting the user to run configure again > with the --enable-tcg-interpreter option. > > This change simplifies building qemu in automatic build environments > (like in my case the debian buildds) because one does not need to > special case on the architectures. I don't think we should do this. TCI is unmaintained, has several known flaws, does not provide the level of performance that people expect from QEMU, and we've talked about removing it altogether. In particular, distros should not automatically ship a TCI QEMU -- it's something that a user can use if they explicitly opt into but which I don't think we want to surprise anybody with. If we care about a host architecture we should support it with a proper TCG backend. If we don't care that much we shouldn't support it. thanks -- PMM