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=-0.7 required=3.0 tests=BAYES_00, FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no 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 36687C4361B for ; Tue, 8 Dec 2020 22:44:46 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id C45CB23AFE for ; Tue, 8 Dec 2020 22:44:45 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org C45CB23AFE Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=free.fr Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:51052 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1kmliu-0002St-UJ for qemu-devel@archiver.kernel.org; Tue, 08 Dec 2020 17:44:44 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:35130) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1kmleV-0006HP-SG for qemu-devel@nongnu.org; Tue, 08 Dec 2020 17:40:13 -0500 Received: from smtp4-g21.free.fr ([2a01:e0c:1:1599::13]:52442) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1kmleR-0006pF-TP for qemu-devel@nongnu.org; Tue, 08 Dec 2020 17:40:11 -0500 Received: from wise (unknown [78.207.163.35]) (Authenticated sender: stephane.duverger@free.fr) by smtp4-g21.free.fr (Postfix) with ESMTPSA id 9208E19F57B; Tue, 8 Dec 2020 23:39:59 +0100 (CET) Date: Tue, 8 Dec 2020 23:39:52 +0100 From: Stephane Duverger To: Richard Henderson , qemu-devel@nongnu.org Subject: Re: x86 TCG helpers clobbered registers Message-ID: <20201208223952.GA36560@wise> References: <20201204153446.GA66154@wise> <1d246e29-b364-099f-440c-5b644087b55f@linaro.org> <20201205013402.GA69224@wise> <5718f49e-8e17-17ae-45ec-94347f0a009d@linaro.org> <20201207101029.GA96540@wise> <4ee3b75a-c778-3cf5-2516-9c9290d96b44@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4ee3b75a-c778-3cf5-2516-9c9290d96b44@linaro.org> Received-SPF: none client-ip=2a01:e0c:1:1599::13; envelope-from=stephane.duverger@free.fr; helo=smtp4-g21.free.fr X-Spam_score_int: -18 X-Spam_score: -1.9 X-Spam_bar: - X-Spam_report: (-1.9 / 5.0 requ) BAYES_00=-1.9, FREEMAIL_FROM=0.001, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_NONE=0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Paolo Bonzini Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Tue, Dec 08, 2020 at 03:18:54PM -0600, Richard Henderson wrote: > As for modifying the fast path cases, the code is quite delicate, > and you run into problems with live registers. Which could be > worked around in each backend, but... why? Perhaps thinking that working at IR level would prevent these live registers issues, seconded by the fact that vCPU TLBs handling seem to be tcg-target agnostic. But I do understand your position, have no patch suggesting a viable alternative implementation, and most of all don't want to take more of your time. I appreciated the discussion and your help Richard. Thanks again.