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=-5.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 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 9450CC433E0 for ; Tue, 2 Mar 2021 12:05:37 +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 0268264F09 for ; Tue, 2 Mar 2021 12:05:36 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 0268264F09 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=suse.de Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:40306 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1lH3mR-0003Wm-R0 for qemu-devel@archiver.kernel.org; Tue, 02 Mar 2021 07:05:35 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:51876) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lH3l7-0002L3-Dp for qemu-devel@nongnu.org; Tue, 02 Mar 2021 07:04:13 -0500 Received: from mx2.suse.de ([195.135.220.15]:60060) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lH3l3-0006CK-Ra for qemu-devel@nongnu.org; Tue, 02 Mar 2021 07:04:13 -0500 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 2F3B4ABF4; Tue, 2 Mar 2021 12:04:08 +0000 (UTC) Subject: Re: target/arm: "define_arm_cp_regs" and similar for KVM To: Peter Maydell References: <7360ab6a-0613-8300-ef8d-b0c641fbaed1@suse.de> From: Claudio Fontana Message-ID: <1bd1bf6c-7139-74f1-7579-78895f5f554d@suse.de> Date: Tue, 2 Mar 2021 13:04:07 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.12.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=195.135.220.15; envelope-from=cfontana@suse.de; helo=mx2.suse.de X-Spam_score_int: -41 X-Spam_score: -4.2 X-Spam_bar: ---- X-Spam_report: (-4.2 / 5.0 requ) BAYES_00=-1.9, NICE_REPLY_A=-0.001, RCVD_IN_DNSWL_MED=-2.3, RCVD_IN_MSPIKE_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-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: qemu-devel Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 3/2/21 1:02 PM, Peter Maydell wrote: > On Fri, 26 Feb 2021 at 17:27, Claudio Fontana wrote: >> >> Hi Peter, >> >> I am trying to find out how to split properly KVM and TCG in target/arm, among other things. >> >> I skipped or stubbed all define_arm_cp_regs and similar functions, >> >> and made a cpregs module that is TCG-only. >> >> Thought it is fine, as we have a kvm_arm_init_cpreg_list that throws away everything TCG-related anyway later: >> >> target/arm/kvm.c: >> >> /* Initialize the ARMCPU cpreg list according to the kernel's >> * definition of what CPU registers it knows about (and throw away >> * the previous TCG-created cpreg list). >> */ >> int kvm_arm_init_cpreg_list(ARMCPU *cpu) > > It throws away the cpreg *list*, but not the cpreg hash table. > That is, we trust KVM for "what sysregs exist and need to be migrated" > but we still > use the hashtable to find out what QEMU thinks about them and where it stores > them in the CPU state structure if it knows about them. So you still > need to keep the > define_arm_cp_regs stuff to register sysregs. Not doing so will break > any bits of the > code which rely on being able to do "synchronize kernel's idea of > sysreg state to > QEMU" and then "read the register value out of the CPU state struct". It'll also > break visibility of sysregs in the gdbstub. > > thanks > -- PMM > Thanks for the confirmation Peter, I ended up doing that. Thanks, Claudio