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=-10.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 88E97C433ED for ; Tue, 20 Apr 2021 07:23:40 +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 E82A160FEA for ; Tue, 20 Apr 2021 07:23:39 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org E82A160FEA Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=ilande.co.uk Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:36964 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1lYkjT-0002ZQ-0V for qemu-devel@archiver.kernel.org; Tue, 20 Apr 2021 03:23:39 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:34984) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lYkiS-00027P-9J for qemu-devel@nongnu.org; Tue, 20 Apr 2021 03:22:36 -0400 Received: from mail.ilande.co.uk ([2001:41c9:1:41f::167]:54786 helo=mail.default.ilande.uk0.bigv.io) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lYkiQ-0004WD-Ij for qemu-devel@nongnu.org; Tue, 20 Apr 2021 03:22:36 -0400 Received: from host86-132-83-131.range86-132.btcentralplus.com ([86.132.83.131] helo=[192.168.1.110]) by mail.default.ilande.uk0.bigv.io with esmtpsa (TLS1.3:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.92) (envelope-from ) id 1lYkif-0000KL-Gl; Tue, 20 Apr 2021 08:22:49 +0100 To: =?UTF-8?Q?Philippe_Mathieu-Daud=c3=a9?= , "qemu-devel@nongnu.org Developers" , Peter Maydell References: <20210417140206.673885-1-f4bug@amsat.org> <8f59bd60-3588-3be0-c44c-1ebfbefd78bd@ilande.co.uk> <67955dd0-dfc7-271f-009f-cf7247f3b6c2@amsat.org> From: Mark Cave-Ayland Message-ID: Date: Tue, 20 Apr 2021 08:22:28 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.9.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit X-SA-Exim-Connect-IP: 86.132.83.131 X-SA-Exim-Mail-From: mark.cave-ayland@ilande.co.uk Subject: Re: [PATCH v3] memory: Directly dispatch alias accesses on origin memory region X-SA-Exim-Version: 4.2.1 (built Wed, 08 May 2019 21:11:16 +0000) X-SA-Exim-Scanned: Yes (on mail.default.ilande.uk0.bigv.io) Received-SPF: pass client-ip=2001:41c9:1:41f::167; envelope-from=mark.cave-ayland@ilande.co.uk; helo=mail.default.ilande.uk0.bigv.io 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, NICE_REPLY_A=-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: Paolo Bonzini , Richard Henderson , Peter Xu Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 19/04/2021 22:11, Philippe Mathieu-Daudé wrote: >> My patch might not be the proper fix, but we need to figure out how >> to avoid others to hit the same problem, as it is very hard to debug. >> >> At least an assertion and a comment. > > Something like: > > -- >8 -- > diff --git a/softmmu/memory.c b/softmmu/memory.c > index d4493ef9e43..e031ac6e074 100644 > --- a/softmmu/memory.c > +++ b/softmmu/memory.c > @@ -1442,6 +1442,7 @@ MemTxResult memory_region_dispatch_read(MemoryRegion *mr, > unsigned size = memop_size(op); > MemTxResult r; > > + assert(!(mr->alias && !mr>alias_offset)); /* Use AddressSpace API > instead */ > if (!memory_region_access_valid(mr, addr, size, false, attrs)) { > *pval = unassigned_mem_read(mr, addr, size); > return MEMTX_DECODE_ERROR; AFAICT the dispatch functions don't handle rom/ram or aliases so you might need to go a bit stronger. The check is further complicated by the fact that you can have rom/ram devices which do define the underlying mr->ops. I'm wondering for memory_region_dispatch_read() if this would work? assert(!mr->alias && !memory_access_is_direct(mr, false)); ATB, Mark.