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 0417DC4332F for ; Thu, 13 Oct 2022 11:00:40 +0000 (UTC) Received: from localhost ([::1]:36922 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1oivx9-0003xx-US for qemu-devel@archiver.kernel.org; Thu, 13 Oct 2022 07:00:39 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:40652) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1oiveJ-00052Y-V5 for qemu-devel@nongnu.org; Thu, 13 Oct 2022 06:41:13 -0400 Received: from frasgout.his.huawei.com ([185.176.79.56]:2727) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1oiveH-0000sC-VS for qemu-devel@nongnu.org; Thu, 13 Oct 2022 06:41:11 -0400 Received: from fraeml708-chm.china.huawei.com (unknown [172.18.147.207]) by frasgout.his.huawei.com (SkyGuard) with ESMTP id 4Mp5Zl45yvz688tX; Thu, 13 Oct 2022 18:38:07 +0800 (CST) Received: from lhrpeml500005.china.huawei.com (7.191.163.240) by fraeml708-chm.china.huawei.com (10.206.15.36) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.31; Thu, 13 Oct 2022 12:41:00 +0200 Received: from localhost (10.202.226.42) by lhrpeml500005.china.huawei.com (7.191.163.240) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.31; Thu, 13 Oct 2022 11:40:59 +0100 Date: Thu, 13 Oct 2022 11:40:58 +0100 To: Gregory Price CC: , Michael Tsirkin , Ben Widawsky , , Huai-Cheng Kuo , Chris Browy , , Subject: Re: [PATCH v7 4/5] hw/mem/cxl-type3: Add CXL CDAT Data Object Exchange Message-ID: <20221013114058.00003c8d@huawei.com> In-Reply-To: References: <20221007152156.24883-1-Jonathan.Cameron@huawei.com> <20221007152156.24883-5-Jonathan.Cameron@huawei.com> X-Mailer: Claws Mail 4.0.0 (GTK+ 3.24.29; i686-w64-mingw32) MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.202.226.42] X-ClientProxiedBy: lhrpeml100006.china.huawei.com (7.191.160.224) To lhrpeml500005.china.huawei.com (7.191.163.240) X-CFilter-Loop: Reflected Received-SPF: pass client-ip=185.176.79.56; envelope-from=jonathan.cameron@huawei.com; helo=frasgout.his.huawei.com 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, RCVD_IN_DNSWL_MED=-2.3, RCVD_IN_MSPIKE_H2=-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: 2.1.29 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" Reply-to: Jonathan Cameron From: Jonathan Cameron via On Wed, 12 Oct 2022 12:01:54 -0400 Gregory Price wrote: > This code contains heap corruption on free, and I think should be > refactored to pre-allocate all the entries we're interested in putting > into the table. Good point on the heap corruption.. (oops. Particularly as I raised that I didn't like the complexity of your free in your previous version and still failed to notice the current code was wrong...) > This would flatten the code and simplify the error > handling steps. I'm not so keen on this. Error handling is pretty trivial because of the autofree magic. It will get a tiny bit harder once we have two calls to the factored out function, but not too bad - we just need to free the handed off pointers in reverse from wherever we got to before the error. > > Also, should we consider making a union with all the possible entries to > make entry allocation easier? It may eat a few extra bytes of memory, > but it would simplify the allocation/cleanup code here further. An interesting point, though gets trickier once we have variable numbers of elements. I'm not sure it's worth the effort to save a few lines of code. > > Given that every allocation has to be checked, i'm also not convinced > the use of g_autofree is worth the potential footguns associated with > it. After rolling a version with some of your suggested changes incorporated the autofree logic is all nice and localized so I think it's well worth having. Only slightly messy bit is we end up with 4 separate pointers for the bandwidth and latency elements.