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Mon, 05 Feb 2024 05:00:54 -0500 X-MC-Unique: VkHGbA1rOZC70o8FSOK_SA-1 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.rdu2.redhat.com [10.11.54.7]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 933A238562CB; Mon, 5 Feb 2024 10:00:53 +0000 (UTC) Received: from [10.39.208.18] (unknown [10.39.208.18]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 04B791C060B1; Mon, 5 Feb 2024 10:00:51 +0000 (UTC) Message-ID: <1df1c558-c101-405a-bdc2-cf342a3771ce@redhat.com> Date: Mon, 5 Feb 2024 11:00:50 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2] vhost: fix deadlock during software live migration of VDPA in a nested virtualization environment To: Hao Chen , dev@dpdk.org Cc: david.marchand@redhat.com, zy@yusur.tech, huangml@yusur.tech, stable@dpdk.org, Chenbo Xia , Xiao Wang References: <20240118103344.50739-1-chenh@yusur.tech> <20240122032746.2749586-1-chenh@yusur.tech> From: Maxime Coquelin Autocrypt: addr=maxime.coquelin@redhat.com; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: DPDK patches and discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces@dpdk.org Hi Hao, On 1/22/24 04:27, Hao Chen wrote: > In a nested virtualization environment, running dpdk-vdpa in QEMU-L1 for > software live migration will result in a deadlock between dpdke-vdpa and > QEMU-L2 processes. > 'rte_vdpa_relay_vring_used'-> > '__vhost_iova_to_vva'-> > 'vhost_user_iotlb_rd_unlock(vq)'-> > 'vhost_user_iotlb_miss'-> send vhost message 'VHOST_USER_SLAVE_IOTLB_MSG' > to QEMU-L2's vdpa socket, > then call 'vhost_user_iotlb_rd_lock(vq)' to hold the read lock `iotlb_lock`. > But there is no place to release this read lock. > > QEMU-L2 get the 'VHOST_USER_SLAVE_IOTLB_MSG', > then call 'vhost_user_send_device_iotlb_msg' to send 'VHOST_USER_IOTLB_MSG' > messages to dpdk-vdpa. > Dpdk-vdpa will call vhost_user_iotlb_msg-> > vhost_user_iotlb_cache_insert, here, will obtain the write lock > `iotlb_lock`, but the read lock `iotlb_lock` has not been released and > will block here. > > This patch add lock and unlock function to fix the deadlock. > > Fixes: b13ad2decc83 ("vhost: provide helpers for virtio ring relay") > Cc: stable@dpdk.org > > Signed-off-by: Hao Chen > --- > Changes v1 ... v2: > - protect the vhost_alloc_copy_ind_table() call too. > > lib/vhost/vdpa.c | 11 +++++++++-- > 1 file changed, 9 insertions(+), 2 deletions(-) > > diff --git a/lib/vhost/vdpa.c b/lib/vhost/vdpa.c > index 9776fc07a9..a1dd5a753b 100644 > --- a/lib/vhost/vdpa.c > +++ b/lib/vhost/vdpa.c > @@ -19,6 +19,7 @@ > #include "rte_vdpa.h" > #include "vdpa_driver.h" > #include "vhost.h" > +#include "iotlb.h" > > /** Double linked list of vDPA devices. */ > TAILQ_HEAD(vdpa_device_list, rte_vdpa_device); > @@ -147,7 +148,6 @@ rte_vdpa_unregister_device(struct rte_vdpa_device *dev) > > int > rte_vdpa_relay_vring_used(int vid, uint16_t qid, void *vring_m) > - __rte_no_thread_safety_analysis /* FIXME: requires iotlb_lock? */ > { > struct virtio_net *dev = get_device(vid); > uint16_t idx, idx_m, desc_id; > @@ -193,17 +193,21 @@ rte_vdpa_relay_vring_used(int vid, uint16_t qid, void *vring_m) > if (unlikely(nr_descs > vq->size)) > return -1; > > + vhost_user_iotlb_rd_lock(vq); > desc_ring = (struct vring_desc *)(uintptr_t) > vhost_iova_to_vva(dev, vq, > vq->desc[desc_id].addr, &dlen, > VHOST_ACCESS_RO); > + vhost_user_iotlb_rd_unlock(vq); > if (unlikely(!desc_ring)) > return -1; > > if (unlikely(dlen < vq->desc[desc_id].len)) { > + vhost_user_iotlb_rd_lock(vq); > idesc = vhost_alloc_copy_ind_table(dev, vq, > vq->desc[desc_id].addr, > vq->desc[desc_id].len); > + vhost_user_iotlb_rd_unlock(vq); > if (unlikely(!idesc)) > return -1; > > @@ -220,9 +224,12 @@ rte_vdpa_relay_vring_used(int vid, uint16_t qid, void *vring_m) > if (unlikely(nr_descs-- == 0)) > goto fail; > desc = desc_ring[desc_id]; > - if (desc.flags & VRING_DESC_F_WRITE) > + if (desc.flags & VRING_DESC_F_WRITE) { > + vhost_user_iotlb_rd_lock(vq); > vhost_log_write_iova(dev, vq, desc.addr, > desc.len); > + vhost_user_iotlb_rd_unlock(vq); > + } > desc_id = desc.next; > } while (desc.flags & VRING_DESC_F_NEXT); > Thanks for the fix, looks good to me. There's one minor checkpatch issue I'll fix while applying. Reviewed-by: Maxime Coquelin Thanks, Maxime