From: Ilya Maximets <i.maximets@samsung.com>
To: Rich Lane <rich.lane@bigswitch.com>
Cc: dev@dpdk.org, Huawei Xie <huawei.xie@intel.com>,
Yuanhan Liu <yuanhan.liu@linux.intel.com>,
Dyasly Sergey <s.dyasly@samsung.com>,
Heetae Ahn <heetae82.ahn@samsung.com>,
Jianfeng Tan <jianfeng.tan@intel.com>
Subject: Re: [dpdk-dev] [PATCH] vhost: fix segfault on bad descriptor address.
Date: Thu, 02 Jun 2016 13:46:30 +0300 [thread overview]
Message-ID: <57500E86.3070104@samsung.com> (raw)
In-Reply-To: <CAGSMBPNMrvZ8JTUAU0A6MKVnATH9TZOKTCLaO=P=wvVPxmzwwA@mail.gmail.com>
Hi, Rich.
Thank you for testing and analysing.
On 01.06.2016 01:06, Rich Lane wrote:
> On Fri, May 20, 2016 at 5:50 AM, Ilya Maximets <i.maximets@samsung.com <mailto:i.maximets@samsung.com>> wrote:
>
> In current implementation guest application can reinitialize vrings
> by executing start after stop. In the same time host application
> can still poll virtqueue while device stopped in guest and it will
> crash with segmentation fault while vring reinitialization because
> of dereferencing of bad descriptor addresses.
>
>
> I see a performance regression with this patch at large packet sizes (> 768 bytes). rte_vhost_enqueue_burst is consuming 10% more cycles. Strangely, there's actually a ~1% performance improvement at small packet sizes.
>
> The regression happens with GCC 4.8.4 and 5.3.0, but not 6.1.1.
>
> AFAICT this is just the compiler generating bad code. One difference is that it's storing the offset on the stack instead of in a register. A workaround is to move the !desc_addr check outside the unlikely macros.
>
> --- a/lib/librte_vhost/vhost_rxtx.c
> +++ b/lib/librte_vhost/vhost_rxtx.c
> @@ -147,10 +147,10 @@ copy_mbuf_to_desc(struct virtio_net *dev, struct vhost_virtqueue *vq,
> struct virtio_net_hdr_mrg_rxbuf virtio_hdr = {{0, 0, 0, 0, 0, 0}, 0};
>
> desc = &vq->desc[desc_idx];
> - if (unlikely(desc->len < vq->vhost_hlen))
> + desc_addr = gpa_to_vva(dev, desc->addr);
> + if (unlikely(desc->len < vq->vhost_hlen || !desc_addr))
>
>
> Workaround: change to "if (unlikely(desc->len < vq->vhost_hlen) || !desc_addr)".
>
> return -1;
>
>
> - desc_addr = gpa_to_vva(dev, desc->addr);
> rte_prefetch0((void *)(uintptr_t)desc_addr);
>
> virtio_enqueue_offload(m, &virtio_hdr.hdr);
> @@ -184,6 +184,9 @@ copy_mbuf_to_desc(struct virtio_net *dev, struct vhost_virtqueue *vq,
>
> desc = &vq->desc[desc->next];
> desc_addr = gpa_to_vva(dev, desc->addr);
> + if (unlikely(!desc_addr))
>
>
> Workaround: change to "if (!desc_addr)".
>
>
> + return -1;
> +
> desc_offset = 0;
> desc_avail = desc->len;
> }
>
What about other places? Is there same issues or it's only inside copy_mbuf_to_desc() ?
Best regards, Ilya Maximets.
next prev parent reply other threads:[~2016-06-02 10:46 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-05-20 12:50 Ilya Maximets
2016-05-23 10:57 ` Yuanhan Liu
2016-05-23 11:04 ` Ilya Maximets
2016-05-30 11:05 ` Ilya Maximets
2016-05-30 14:25 ` Yuanhan Liu
2016-05-31 9:12 ` Ilya Maximets
2016-05-30 12:00 ` Tan, Jianfeng
2016-05-30 12:24 ` Ilya Maximets
2016-05-31 6:53 ` Tan, Jianfeng
2016-05-31 9:10 ` Ilya Maximets
2016-05-31 22:06 ` Rich Lane
2016-06-02 10:46 ` Ilya Maximets [this message]
2016-06-02 16:22 ` Rich Lane
2016-06-03 6:01 ` Ilya Maximets
2016-07-01 7:35 ` Yuanhan Liu
2016-07-06 11:19 ` Ilya Maximets
2016-07-06 12:24 ` Yuanhan Liu
2016-07-08 11:48 ` Ilya Maximets
2016-07-10 13:17 ` Yuanhan Liu
2016-07-11 8:38 ` Yuanhan Liu
2016-07-11 9:50 ` Ilya Maximets
2016-07-11 11:05 ` Yuanhan Liu
2016-07-11 11:47 ` Ilya Maximets
2016-07-12 2:43 ` Yuanhan Liu
2016-07-12 5:53 ` Ilya Maximets
2016-07-13 7:34 ` Ilya Maximets
2016-07-13 8:47 ` Yuanhan Liu
2016-07-13 15:54 ` Rich Lane
2016-07-14 1:42 ` Yuanhan Liu
2016-07-14 4:38 ` Ilya Maximets
2016-07-14 8:18 ` [dpdk-dev] [PATCH v2] " Ilya Maximets
2016-07-15 6:17 ` Yuanhan Liu
2016-07-15 7:23 ` Ilya Maximets
2016-07-15 8:40 ` Yuanhan Liu
2016-07-15 11:15 ` [dpdk-dev] [PATCH v3 0/2] " Ilya Maximets
2016-07-15 11:15 ` [dpdk-dev] [PATCH v3 1/2] vhost: fix using of bad return value on mergeable enqueue Ilya Maximets
2016-07-15 11:15 ` [dpdk-dev] [PATCH v3 2/2] vhost: do sanity check for ring descriptor address Ilya Maximets
2016-07-15 12:14 ` [dpdk-dev] [PATCH v3 0/2] vhost: fix segfault on bad " Yuanhan Liu
2016-07-15 19:37 ` Thomas Monjalon
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