From: "Wangyunjian(wangyunjian,TongTu)" <wangyunjian@huawei.com>
To: Stephen Hemminger <stephen@networkplumber.org>
Cc: "dev@dpdk.org" <dev@dpdk.org>,
"maxime.coquelin@redhat.com" <maxime.coquelin@redhat.com>,
"chenbox@nvidia.com" <chenbox@nvidia.com>,
"Lilijun (Jerry)" <jerry.lilijun@huawei.com>,
"xiawei (H)" <xiawei40@huawei.com>,
wangzengyuan <wangzengyuan@huawei.com>,
"stable@dpdk.org" <stable@dpdk.org>
Subject: RE: [PATCH 1/1] vhost: fix a double fetch when dequeue offloading
Date: Fri, 20 Dec 2024 02:17:12 +0000 [thread overview]
Message-ID: <f72d79f98e984283933a8955278bcee0@huawei.com> (raw)
In-Reply-To: <20241219081532.345c7536@hermes.local>
> -----Original Message-----
> From: Stephen Hemminger [mailto:stephen@networkplumber.org]
> Sent: Friday, December 20, 2024 12:16 AM
> To: Wangyunjian(wangyunjian,TongTu) <wangyunjian@huawei.com>
> Cc: dev@dpdk.org; maxime.coquelin@redhat.com; chenbox@nvidia.com;
> Lilijun (Jerry) <jerry.lilijun@huawei.com>; xiawei (H) <xiawei40@huawei.com>;
> wangzengyuan <wangzengyuan@huawei.com>; stable@dpdk.org
> Subject: Re: [PATCH 1/1] vhost: fix a double fetch when dequeue offloading
>
> On Thu, 19 Dec 2024 14:38:28 +0800
> Yunjian Wang <wangyunjian@huawei.com> wrote:
>
> > - hdr = (struct virtio_net_hdr *)((uintptr_t)buf_vec[0].buf_addr);
> > + rte_memcpy((void *)(uintptr_t)&tmp_hdr,
> > + (void *)(uintptr_t)buf_vec[0].buf_addr,
> > + sizeof(struct virtio_net_hdr));
> > }
>
> Do not introduce more rte_memcpy of a fixed size.
> You don't need that many casts!
> Why can you not use a structure assignment here.
The virtio_hdr is a shared component, and other fields within it are read
multiple times. This can potentially result in a double fetch scenario.
next prev parent reply other threads:[~2024-12-20 2:17 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-12-19 6:38 Yunjian Wang
2024-12-19 8:24 ` David Marchand
2024-12-19 11:02 ` Wangyunjian(wangyunjian,TongTu)
2024-12-19 16:15 ` Stephen Hemminger
2024-12-20 2:17 ` Wangyunjian(wangyunjian,TongTu) [this message]
2024-12-20 4:59 ` Stephen Hemminger
2024-12-20 3:49 ` [PATCH v2 " Yunjian Wang
2024-12-20 17:10 ` Stephen Hemminger
2024-12-20 16:35 ` [PATCH " Stephen Hemminger
2024-12-23 2:45 ` Wangyunjian(wangyunjian,TongTu)
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