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=-2.1 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, 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 EF9C7C2D0B1 for ; Tue, 4 Feb 2020 12:27:25 +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 BA9862084E for ; Tue, 4 Feb 2020 12:27:25 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="bLZN1XkL" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org BA9862084E Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:57400 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1iyxIa-0007n5-WB for qemu-devel@archiver.kernel.org; Tue, 04 Feb 2020 07:27:25 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:37272) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1iyxHj-0007AN-LL for qemu-devel@nongnu.org; Tue, 04 Feb 2020 07:26:33 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1iyxHh-0002fb-0q for qemu-devel@nongnu.org; Tue, 04 Feb 2020 07:26:30 -0500 Received: from us-smtp-2.mimecast.com ([207.211.31.81]:43544 helo=us-smtp-delivery-1.mimecast.com) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1iyxHg-0002Yt-K6 for qemu-devel@nongnu.org; Tue, 04 Feb 2020 07:26:28 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1580819187; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=MszlNI7YNZV2jQRy7qH0Q4vUrqQZS2e1Cn9y39/Qy5g=; b=bLZN1XkL5XL07oCgVYtpaDAHn2VpsZ+tLQg5OKXptC451Jg2oaNWs9orAIMdWTQ1yjVcgC n7DpBPWCc6g0DFtNUReDZxkwbecm+SbpNhZ9SJx5dRdjCju/7wH1eLfIthRIwYemkamWVg SZTlaogHfnhYYaB3FzS+xb2WrjBQ8TU= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-295-IKb5SNlgMcyyescI_bQdWw-1; Tue, 04 Feb 2020 07:26:23 -0500 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 51FA51137846; Tue, 4 Feb 2020 12:26:21 +0000 (UTC) Received: from [10.36.116.37] (ovpn-116-37.ams2.redhat.com [10.36.116.37]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 06D4C86C4A; Tue, 4 Feb 2020 12:26:11 +0000 (UTC) Subject: Re: [PATCH v13 03/10] virtio-iommu: Implement attach/detach command To: Peter Xu References: <20200125171955.12825-1-eric.auger@redhat.com> <20200125171955.12825-4-eric.auger@redhat.com> <20200203134915.GA155875@xz-x1> <20200203151917.GD155875@xz-x1> <5289913a-43fc-aaae-5b82-151922de93bf@redhat.com> <20200203181938.GE155875@xz-x1> From: Auger Eric Message-ID: <75625c27-88da-c26b-7ee6-ab3f57b55906@redhat.com> Date: Tue, 4 Feb 2020 13:26:09 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.4.0 MIME-Version: 1.0 In-Reply-To: <20200203181938.GE155875@xz-x1> Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 X-MC-Unique: IKb5SNlgMcyyescI_bQdWw-1 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 207.211.31.81 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: peter.maydell@linaro.org, kevin.tian@intel.com, tnowicki@marvell.com, quintela@redhat.com, mst@redhat.com, qemu-devel@nongnu.org, dgilbert@redhat.com, bharatb.linux@gmail.com, qemu-arm@nongnu.org, jean-philippe@linaro.org, eric.auger.pro@gmail.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Hi Peter, On 2/3/20 7:19 PM, Peter Xu wrote: > On Mon, Feb 03, 2020 at 06:46:36PM +0100, Auger Eric wrote: >> Hi Peter, >> >> On 2/3/20 4:19 PM, Peter Xu wrote: >>> On Mon, Feb 03, 2020 at 03:59:00PM +0100, Auger Eric wrote: >>> >>> [...] >>> >>>>>> +static void virtio_iommu_detach_endpoint_from_domain(VirtIOIOMMUEndpoint *ep) >>>>>> +{ >>>>>> + QLIST_REMOVE(ep, next); >>>>>> + g_tree_unref(ep->domain->mappings); >>>>> >>>>> Here domain->mapping is unreferenced for each endpoint, while at [1] >>>>> below you only reference the domain->mappings if it's the first >>>>> endpoint. Is that problematic? >>>> in [1] I take a ref to the domain->mappings if it is *not* the 1st >>>> endpoint. This aims at deleting the mappings gtree when the last EP is >>>> detached from the domain. >>>> >>>> This fixes the issue reported by Jean in: >>>> https://patchwork.kernel.org/patch/11258267/#23046313 >>> >>> Ah OK. :) >>> >>> However this is tricky. How about do explicit g_tree_destroy() in >>> virtio_iommu_detach() when it's the last endpoint? I see that you >>> have: >>> >>> /* >>> * when the last EP is detached, simply remove the domain for >>> * the domain list and destroy it. Note its mappings were already >>> * freed by the ref count mechanism. Next operation involving >>> * the same domain id will re-create one domain object. >>> */ >>> if (QLIST_EMPTY(&domain->endpoint_list)) { >>> g_tree_remove(s->domains, GUINT_TO_POINTER(domain->id)); >>> } >>> >>> Then it becomes: >>> >>> if (QLIST_EMPTY(&domain->endpoint_list)) { >>> g_tree_destroy(domain->mappings); >>> g_tree_remove(s->domains, GUINT_TO_POINTER(domain->id)); >>> } >>> >>> And also remove the trick in attach() so you take the domain ref >>> unconditionally. Would that work? >> Yes I think so. On the other hand this ref counting mechanism is also >> made for that purpose of destroying objects without being forced to >> explicitly call the destroy function. > > IMHO that's two different things. g_tree_destroy() should be the same > as g_tree_unref() here when the tree is empty. It's really a matter > of easy reading of code: > > void > g_tree_destroy (GTree *tree) > { > g_return_if_fail (tree != NULL); > > g_tree_remove_all (tree); > g_tree_unref (tree); > } > > What we really changed here is to allow the ref/unref to be clearly > paired, i.e., for each EP it'll ref once and unref once. The prvious > solution has the trick in that the 1st EP don't ref, the latter EPs > ref, and when the domain quits it doesn't unref to match the first > ref. It's error prone to me. Then, if we can do it in the paired way > easily, I don't see why not... OK. I will respin according to your suggestion. Thanks Eric > > Thanks, >