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 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 smtp.lore.kernel.org (Postfix) with ESMTPS id 84C3FC433EF for ; Fri, 13 May 2022 10:05:58 +0000 (UTC) Received: from localhost ([::1]:37878 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1npSBJ-00081Z-IR for qemu-devel@archiver.kernel.org; Fri, 13 May 2022 06:05:57 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:52844) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1npS5y-00005K-QC for qemu-devel@nongnu.org; Fri, 13 May 2022 06:00:29 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:54514) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1npS5t-00075C-T9 for qemu-devel@nongnu.org; Fri, 13 May 2022 06:00:24 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1652436018; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:mime-version:mime-version:content-type:content-type; bh=k9rU5wyMgrkt2hOOpl/7uNBhB/nIMMuiSw7ffSLudho=; b=T94QW26xpgFwsqpBRyNx+6+0Td1IqSPYvqMayPJzJvr65qDgRM297W9tGRIUVFQK6YZvRY kMzELKtdDiW87F4hQgenaqM+qSHlOd71cbMBLTAG+COwkiLJU82WJOuMTevC8tb4gfycuJ VL+m2ARKv+MifgpFZebTP4jTe0NNhmw= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-574-ev5xSy0nOEiQn2U1XuYQ2A-1; Fri, 13 May 2022 06:00:17 -0400 X-MC-Unique: ev5xSy0nOEiQn2U1XuYQ2A-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.rdu2.redhat.com [10.11.54.2]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 1855E803792 for ; Fri, 13 May 2022 10:00:17 +0000 (UTC) Received: from oldenburg.str.redhat.com (unknown [10.39.192.147]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 71CF040D2820 for ; Fri, 13 May 2022 10:00:16 +0000 (UTC) From: Florian Weimer To: qemu-devel@nongnu.org Subject: Emulating CPUs with larger atomic accesses Date: Fri, 13 May 2022 12:00:14 +0200 Message-ID: <87k0apeor5.fsf@oldenburg.str.redhat.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.2 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-Scanned-By: MIMEDefang 2.84 on 10.11.54.2 Received-SPF: pass client-ip=170.10.133.124; envelope-from=fweimer@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -28 X-Spam_score: -2.9 X-Spam_bar: -- X-Spam_report: (-2.9 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.082, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" What's QEMU's approach to emulating CPU instructions that atomatically operate on values larger than what is supported by the host CPU? I assume that for full system emulation, this is not a problem, but qemu-user will not achieve atomic behavior on shared memory mappings. How much of a problem is this in practice? Thanks, Florian