patches for DPDK stable branches
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From: yang_y_yi  <yang_y_yi@163.com>
To: "Olivier Matz" <olivier.matz@6wind.com>
Cc: dev@dpdk.org, "Maxime Coquelin" <maxime.coquelin@redhat.com>,
	 "Chenbo Xia" <chenbo.xia@intel.com>,
	 "Zhihong Wang" <zhihong.wang@intel.com>,
	 "Flavio Leitner" <fbl@sysclose.org>,
	stable@dpdk.org
Subject: Re: [dpdk-stable] [PATCH] vhost: fix external mbuf creation
Date: Fri, 9 Oct 2020 17:04:25 +0800 (CST)
Message-ID: <68560945.61c2.1750c9aaf0e.Coremail.yang_y_yi@163.com> (raw)
In-Reply-To: <20201007125318.9850-1-olivier.matz@6wind.com>

Thanks Oliver for posting this patch, it clearly explain his concern, I totally agree this change. I tested it by OVS DPDK, it works well.

At 2020-10-07 20:53:18, "Olivier Matz" <olivier.matz@6wind.com> wrote:
>In virtio_dev_extbuf_alloc(), the shinfo structure used to store
>the reference counter and the free callback of the external buffer
>is by default stored inside the mbuf data.
>
>This is wrong because the mbuf (and its data) can be freed before
>the external buffer, for instance in the following situation:
>
>  pkt2 = rte_pktmbuf_alloc(mp);
>  rte_pktmbuf_attach(pkt2, pkt);
>  rte_pktmbuf_free(pkt);
>
>After this, pkt is freed, but it still contains shinfo, which is
>referenced by pkt2.
>
>Fix this by always storing the shinfo beside the external buffer.
>
>Fixes: c3ff0ac70acb ("vhost: improve performance by supporting large buffer")
>Cc: stable@dpdk.org
>
>Signed-off-by: Olivier Matz <olivier.matz@6wind.com>
>---
>
>Hi,
>
>I found this issue by code review while discussing about this
>patchset [1]. I did not tested the patch, but as I'm only removing
>one path among the two, I don't expect that it breaks anything.
>
>[1] http://inbox.dpdk.org/dev/20200730120900.108232-1-yang_y_yi@163.com/
>
>Regards,
>Olivier
>
> lib/librte_vhost/virtio_net.c | 30 ++++++++----------------------
> 1 file changed, 8 insertions(+), 22 deletions(-)
>
>diff --git a/lib/librte_vhost/virtio_net.c b/lib/librte_vhost/virtio_net.c
>index 0a0bea1a5a..008f5ceb04 100644
>--- a/lib/librte_vhost/virtio_net.c
>+++ b/lib/librte_vhost/virtio_net.c
>@@ -2098,16 +2098,8 @@ virtio_dev_extbuf_alloc(struct rte_mbuf *pkt, uint32_t size)
> 	rte_iova_t iova;
> 	void *buf;
> 
>-	/* Try to use pkt buffer to store shinfo to reduce the amount of memory
>-	 * required, otherwise store shinfo in the new buffer.
>-	 */
>-	if (rte_pktmbuf_tailroom(pkt) >= sizeof(*shinfo))
>-		shinfo = rte_pktmbuf_mtod(pkt,
>-					  struct rte_mbuf_ext_shared_info *);
>-	else {
>-		total_len += sizeof(*shinfo) + sizeof(uintptr_t);
>-		total_len = RTE_ALIGN_CEIL(total_len, sizeof(uintptr_t));
>-	}
>+	total_len += sizeof(*shinfo) + sizeof(uintptr_t);
>+	total_len = RTE_ALIGN_CEIL(total_len, sizeof(uintptr_t));
> 
> 	if (unlikely(total_len > UINT16_MAX))
> 		return -ENOSPC;
>@@ -2118,18 +2110,12 @@ virtio_dev_extbuf_alloc(struct rte_mbuf *pkt, uint32_t size)
> 		return -ENOMEM;
> 
> 	/* Initialize shinfo */
>-	if (shinfo) {
>-		shinfo->free_cb = virtio_dev_extbuf_free;
>-		shinfo->fcb_opaque = buf;
>-		rte_mbuf_ext_refcnt_set(shinfo, 1);
>-	} else {
>-		shinfo = rte_pktmbuf_ext_shinfo_init_helper(buf, &buf_len,
>-					      virtio_dev_extbuf_free, buf);
>-		if (unlikely(shinfo == NULL)) {
>-			rte_free(buf);
>-			VHOST_LOG_DATA(ERR, "Failed to init shinfo\n");
>-			return -1;
>-		}
>+	shinfo = rte_pktmbuf_ext_shinfo_init_helper(buf, &buf_len,
>+						virtio_dev_extbuf_free, buf);
>+	if (unlikely(shinfo == NULL)) {
>+		rte_free(buf);
>+		VHOST_LOG_DATA(ERR, "Failed to init shinfo\n");
>+		return -1;
> 	}
> 
> 	iova = rte_malloc_virt2iova(buf);
>-- 
>2.25.1

      parent reply	other threads:[~2020-10-09  9:04 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-10-07 12:53 Olivier Matz
2020-10-09  7:15 ` Maxime Coquelin
2020-10-09  7:24 ` Maxime Coquelin
2020-10-09  8:47 ` yang_y_yi
2020-10-09  9:04 ` yang_y_yi [this message]

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