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Mon, 23 Dec 2019 09:14:11 +0000 (UTC) Subject: Re: [PATCH for-5.0 v11 06/20] virtio-iommu: Implement attach/detach command To: Jean-Philippe Brucker References: <20191122182943.4656-1-eric.auger@redhat.com> <20191122182943.4656-7-eric.auger@redhat.com> <20191210164156.GE277340@myrica> From: Auger Eric Message-ID: <531cb6d7-6a2b-1278-a4d2-f4ea11442967@redhat.com> Date: Mon, 23 Dec 2019 10:14:09 +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: <20191210164156.GE277340@myrica> Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 X-MC-Unique: 1rjFu8BaP1OQ4D2Lz402PA-1 X-Mimecast-Spam-Score: 0 Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 207.211.31.120 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: yang.zhong@intel.com, peter.maydell@linaro.org, kevin.tian@intel.com, tnowicki@marvell.com, mst@redhat.com, jean-philippe.brucker@arm.com, quintela@redhat.com, qemu-devel@nongnu.org, peterx@redhat.com, armbru@redhat.com, bharatb.linux@gmail.com, qemu-arm@nongnu.org, dgilbert@redhat.com, eric.auger.pro@gmail.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Hi Jean, On 12/10/19 5:41 PM, Jean-Philippe Brucker wrote: > On Fri, Nov 22, 2019 at 07:29:29PM +0100, Eric Auger wrote: >> diff --git a/hw/virtio/virtio-iommu.c b/hw/virtio/virtio-iommu.c >> index 235bde2203..138d5b2a9c 100644 >> --- a/hw/virtio/virtio-iommu.c >> +++ b/hw/virtio/virtio-iommu.c >> @@ -77,11 +77,12 @@ static gint interval_cmp(gconstpointer a, gconstpointer b, gpointer user_data) >> static void virtio_iommu_detach_endpoint_from_domain(viommu_endpoint *ep) >> { >> QLIST_REMOVE(ep, next); >> + g_tree_unref(ep->domain->mappings); >> ep->domain = NULL; >> } >> >> -viommu_endpoint *virtio_iommu_get_endpoint(VirtIOIOMMU *s, uint32_t ep_id); >> -viommu_endpoint *virtio_iommu_get_endpoint(VirtIOIOMMU *s, uint32_t ep_id) >> +static viommu_endpoint *virtio_iommu_get_endpoint(VirtIOIOMMU *s, >> + uint32_t ep_id) >> { >> viommu_endpoint *ep; >> >> @@ -102,15 +103,14 @@ static void virtio_iommu_put_endpoint(gpointer data) >> >> if (ep->domain) { >> virtio_iommu_detach_endpoint_from_domain(ep); >> - g_tree_unref(ep->domain->mappings); >> } >> >> trace_virtio_iommu_put_endpoint(ep->id); >> g_free(ep); >> } >> >> -viommu_domain *virtio_iommu_get_domain(VirtIOIOMMU *s, uint32_t domain_id); >> -viommu_domain *virtio_iommu_get_domain(VirtIOIOMMU *s, uint32_t domain_id) >> +static viommu_domain *virtio_iommu_get_domain(VirtIOIOMMU *s, >> + uint32_t domain_id) > > Looks like the above change belong to patch 5? virtio_iommu_get_domain was not used yet in last patch. I turn it into static now it gets used. > >> { >> viommu_domain *domain; >> >> @@ -137,7 +137,6 @@ static void virtio_iommu_put_domain(gpointer data) >> QLIST_FOREACH_SAFE(iter, &domain->endpoint_list, next, tmp) { >> virtio_iommu_detach_endpoint_from_domain(iter); >> } >> - g_tree_destroy(domain->mappings); > > When created by virtio_iommu_get_domain(), mappings has one reference. > Then for each attach (including the first one) an additional reference is > taken, and freed by virtio_iommu_detach_endpoint_from_domain(). So I think > there are two problems: > > * virtio_iommu_put_domain() drops one ref for each endpoint, but we still > have one reference to mappings, so they're not freed. We do need this > g_tree_destroy() > > * After detaching all the endpoints, the guest may reuse the domain ID for > another domain, but the previous mappings haven't been erased. Not sure > how to fix this using the g_tree refs, because dropping all the > references will free the internal tree data and it won't be reusable. You're perfectly right, mappings were not destroyed and I missed that. So I made 2 modifications: - do not increment the ref count on the first EP addition - destroy the domain when its EP list get empty. Thanks Eric > > Thanks, > Jean >