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Mon, 3 Feb 2020 17:46:38 +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> From: Auger Eric Message-ID: <5289913a-43fc-aaae-5b82-151922de93bf@redhat.com> Date: Mon, 3 Feb 2020 18:46:36 +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: <20200203151917.GD155875@xz-x1> Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 X-MC-Unique: F9XVggoSNdmWljG0Rg-KvQ-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, mst@redhat.com, quintela@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 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. Thanks Eric > > Thanks, >