LKML Archive on lore.kernel.org
help / color / mirror / Atom feed
From: Jason Wang <jasowang@redhat.com>
To: Tiwei Bie <tiwei.bie@intel.com>,
mst@redhat.com, virtualization@lists.linux-foundation.org,
linux-kernel@vger.kernel.org, netdev@vger.kernel.org
Cc: wexu@redhat.com
Subject: Re: [RFC v3 3/5] virtio_ring: add packed ring support
Date: Thu, 10 May 2018 15:34:50 +0800 [thread overview]
Message-ID: <5885acac-e9e3-3abf-b6a2-7347f4d55be2@redhat.com> (raw)
In-Reply-To: <927f4478-5a81-31d4-ac69-f9ec26248591@redhat.com>
On 2018年05月10日 15:32, Jason Wang wrote:
>
>
> On 2018年04月25日 13:15, Tiwei Bie wrote:
>> + /* We're using some buffers from the free list. */
>> + vq->vq.num_free -= descs_used;
>> +
>> + /* Update free pointer */
>> + if (indirect) {
>> + n = head + 1;
>> + if (n >= vq->vring_packed.num) {
>> + n = 0;
>> + vq->wrap_counter ^= 1;
>> + }
>> + vq->next_avail_idx = n;
>> + } else
>> + vq->next_avail_idx = i;
>
> During testing zerocopy (out of order completion), I found driver may
> submit two identical buffer id to vhost. So the above code may not
> work well.
>
> Consider the case that driver adds 3 buffer and virtqueue size is 8.
>
> a) id = 0,count = 2,next_avail = 2
>
> b) id = 2,count = 4,next_avail = 2
next_avail should be 6 here.
>
> c) id = 4,count = 2,next_avail = 0
>
id should be 6 here.
Thanks
> if packet b is done before packet a, driver may think buffer id 0 is
> available and try to use it if even if the real buffer 0 was not done.
>
> Thanks
> _______________________________________________
> Virtualization mailing list
> Virtualization@lists.linux-foundation.org
> https://lists.linuxfoundation.org/mailman/listinfo/virtualization
next prev parent reply other threads:[~2018-05-10 7:34 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-04-25 5:15 [RFC v3 0/5] virtio: support packed ring Tiwei Bie
2018-04-25 5:15 ` [RFC v3 1/5] virtio: add packed ring definitions Tiwei Bie
2018-04-25 5:15 ` [RFC v3 2/5] virtio_ring: support creating packed ring Tiwei Bie
2018-04-25 5:15 ` [RFC v3 3/5] virtio_ring: add packed ring support Tiwei Bie
2018-05-10 7:32 ` Jason Wang
2018-05-10 7:34 ` Jason Wang [this message]
2018-05-10 8:56 ` Tiwei Bie
2018-05-10 9:49 ` Jason Wang
2018-05-10 10:50 ` Tiwei Bie
2018-04-25 5:15 ` [RFC v3 4/5] virtio_ring: add event idx support in packed ring Tiwei Bie
2018-05-02 2:51 ` Jason Wang
2018-05-02 7:28 ` Tiwei Bie
2018-05-02 13:51 ` Michael S. Tsirkin
2018-05-02 15:12 ` Tiwei Bie
2018-05-02 15:42 ` Michael S. Tsirkin
2018-05-03 1:11 ` Tiwei Bie
2018-05-03 1:44 ` Michael S. Tsirkin
2018-05-03 2:09 ` Tiwei Bie
2018-05-03 7:25 ` Jason Wang
2018-05-03 13:54 ` Tiwei Bie
2018-05-08 3:05 ` Jason Wang
2018-05-08 5:40 ` Jason Wang
2018-05-08 6:44 ` Tiwei Bie
2018-05-08 7:16 ` Jason Wang
2018-05-08 9:16 ` Tiwei Bie
2018-05-08 9:34 ` Jason Wang
2018-05-08 9:44 ` Tiwei Bie
2018-05-09 3:43 ` Jason Wang
2018-05-16 5:01 ` Jason Wang
2018-05-16 5:55 ` Tiwei Bie
2018-04-25 5:15 ` [RFC v3 5/5] virtio_ring: enable " Tiwei Bie
2018-04-27 3:56 ` [RFC v3 0/5] virtio: support " Jason Wang
2018-04-27 4:18 ` Michael S. Tsirkin
2018-04-27 6:17 ` Jason Wang
2018-04-27 9:12 ` Tiwei Bie
2018-04-28 2:45 ` Jason Wang
2018-05-02 3:49 ` Jason Wang
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=5885acac-e9e3-3abf-b6a2-7347f4d55be2@redhat.com \
--to=jasowang@redhat.com \
--cc=linux-kernel@vger.kernel.org \
--cc=mst@redhat.com \
--cc=netdev@vger.kernel.org \
--cc=tiwei.bie@intel.com \
--cc=virtualization@lists.linux-foundation.org \
--cc=wexu@redhat.com \
--subject='Re: [RFC v3 3/5] virtio_ring: add packed ring support' \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).