From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: virtio-comment-return-1077-cohuck=redhat.com@lists.oasis-open.org Sender: List-Post: List-Help: List-Unsubscribe: List-Subscribe: Received: from lists.oasis-open.org (oasis-open.org [10.110.1.242]) by lists.oasis-open.org (Postfix) with ESMTP id A39E5985EF2 for ; Thu, 20 Feb 2020 07:41:14 +0000 (UTC) Date: Thu, 20 Feb 2020 02:41:03 -0500 (EST) From: Yuri Benditovich Message-ID: <893990295.7352578.1582184463424.JavaMail.zimbra@redhat.com> In-Reply-To: <623f76be-bf87-c473-350e-87fe53b41261@redhat.com> References: <20200219075337.23191-1-yuri.benditovich@daynix.com> <20200219075337.23191-2-yuri.benditovich@daynix.com> <86420fd1-cbb4-0105-4114-ca2d6cb3b8ff@redhat.com> <20200219092244-mutt-send-email-mst@kernel.org> <623f76be-bf87-c473-350e-87fe53b41261@redhat.com> MIME-Version: 1.0 Subject: Re: [virtio-comment] [PATCH v4 1/1] virtio-net: Define per-packet hash reporting feature Content-Type: multipart/alternative; boundary="----=_Part_7352577_161686250.1582184463423" To: Jason Wang Cc: "Michael S. Tsirkin" , Yuri Benditovich , virtio-comment@lists.oasis-open.org List-ID: ------=_Part_7352577_161686250.1582184463423 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable ----- Original Message ----- > From: "Jason Wang" > To: "Michael S. Tsirkin" > Cc: "Yuri Benditovich" , > virtio-comment@lists.oasis-open.org > Sent: Thursday, February 20, 2020 8:38:50 AM > Subject: Re: [virtio-comment] [PATCH v4 1/1] virtio-net: Define per-packe= t > hash reporting feature > On 2020/2/19 =E4=B8=8B=E5=8D=8810:23, Michael S. Tsirkin wrote: > > On Wed, Feb 19, 2020 at 08:27:10PM +0800, Jason Wang wrote: > >> On 2020/2/19 =E4=B8=8B=E5=8D=883:53, Yuri Benditovich wrote: > >>> The device MUST set \field{rss_max_indirection_table_length} to at le= ast > >>> 128, if it offers > >>> VIRTIO_NET_F_RSS. > >>> @@ -3195,6 +3180,8 @@ \subsection{Device Operation}\label{sec:Device > >>> Types / Network Device / Device O > >>> le16 csum_start; > >>> le16 csum_offset; > >>> le16 num_buffers; > >>> + le32 hash_value; (Only if VIRTIO_NET_F_HASH_REPORT negotiated) > >>> + le16 hash_type; (Only if VIRTIO_NET_F_HASH_REPORT negotiated) > >>> }; > >>> \end{lstlisting} > >> A question here: > >> > >> Consider we introduce VIRTIO_NET_F_FEATURE_INFORMATION in the future: > >> > >> le32 hash_type; // VIRTIO_NET_F_HASH_REPORT > >> le32 feature_information; // VIRTIO_NET_F_FEATURE_INFORMATION > >> > >> What happens if HASH_REPORT is not negotiated, I believe we expect a > >> stable > >> ABI(offset) here for feature_information? > >> > >> Thanks > >> > > We'll have to decide at that point ... any better ideas? > Not sure but something that is self descriptive? (which could be an > overkill for fields that only need few bytes). The problem is that the driver typically wants to know the header size from= the beginning to configure SG table.=20 So any self-descriptive layout seems good but in practice not so usable, IM= O.=20 > Thanks > This publicly archived list offers a means to provide input to the > OASIS Virtual I/O Device (VIRTIO) TC. > In order to verify user consent to the Feedback License terms and > to minimize spam in the list archive, subscription is required > before posting. > Subscribe: virtio-comment-subscribe@lists.oasis-open.org > Unsubscribe: virtio-comment-unsubscribe@lists.oasis-open.org > List help: virtio-comment-help@lists.oasis-open.org > List archive: https://lists.oasis-open.org/archives/virtio-comment/ > Feedback License: https://www.oasis-open.org/who/ipr/feedback_license.pdf > List Guidelines: https://www.oasis-open.org/policies-guidelines/mailing-l= ists > Committee: https://www.oasis-open.org/committees/virtio/ > Join OASIS: https://www.oasis-open.org/join/ ------=_Part_7352577_161686250.1582184463423 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable


To: "Mich= ael S. Tsirkin" <mst@redhat.com>
Cc: "Yuri Benditovich" <= ;yuri.benditovich@daynix.com>, virtio-comment@lists.oasis-open.org
Sent: Thursday, February 20, 2020 8:38:50 AM
Subject: Re: [v= irtio-comment] [PATCH v4 1/1] virtio-net: Define per-packet hash reporting = feature


On 2020/2/19 =E4=B8=8B=E5=8D=8810:23, Michael= S. Tsirkin wrote:
> On Wed, Feb 19, 2020 at 08:27:10PM +0800, Jason = Wang wrote:
>> On 2020/2/19 =E4=B8=8B=E5=8D=883:53, Yuri Benditovi= ch wrote:
>>>    The device MUST set \field{rss_max_i= ndirection_table_length} to at least 128, if it offers
>>> &nbs= p;  VIRTIO_NET_F_RSS.
>>> @@ -3195,6 +3180,8 @@ \subsectio= n{Device Operation}\label{sec:Device Types / Network Device / Device O
&= gt;>>            le16 csum_start;
&g= t;>>            le16 csum_offset;
&g= t;>>            le16 num_buffers;
&g= t;>> +        le32 hash_value; (Only if VIRTIO_NE= T_F_HASH_REPORT negotiated)
>>> +        le= 16 hash_type;  (Only if VIRTIO_NET_F_HASH_REPORT negotiated)
>&g= t;>    };
>>>    \end{lstlisting}
>= ;> A question here:
>>
>> Consider we introduce VIRTIO= _NET_F_FEATURE_INFORMATION in the future:
>>
>> le32 hash= _type; // VIRTIO_NET_F_HASH_REPORT
>> le32 feature_information; //= VIRTIO_NET_F_FEATURE_INFORMATION
>>
>> What happens if H= ASH_REPORT is not negotiated, I believe we expect a stable
>> ABI(= offset) here for feature_information?
>>
>> Thanks
>= ;>
> We'll have to decide at that point ... any better ideas?
<= div>

Not sure but something that is self descriptive? (which c= ould be an
overkill for fields that only need few bytes).
The problem is that the driver typically wants to know the header s= ize from the beginning to configure SG table.
So any self-des= criptive layout seems good but in practice not so usable, IMO.


Thanks


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OASIS Virtual I/O Device (VIRTIO) TC.

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