Re: [virtio-comment] vsock: define a maximum size for the packet data

["Loghin, Laura" <lauralg@amazon.com>]

Hi,

Sorry for the super late reply! I just sent the patch for the `len` description [1].

Regarding the max size for the packet data, the proposal for adding a field in the config space sounds good to me. What would be some next steps here? Should I send a patch for this one as well? From what I understand, we would define a new feature for the max size, and
add a new field in the config space. Did I misunderstand it?


Thanks,
Laura


[1] https://lists.oasis-open.org/archives/virtio-comment/202203/msg00073.html

 
________________________________________
From: Loghin, Laura
Sent: Wednesday, February 23, 2022 3:38 PM
To: Stefano Garzarella
Cc: Arseniy Krasnov; virtio-comment@lists.oasis-open.org
Subject: Re: [EXTERNAL] [virtio-comment] vsock: define a maximum size for the packet data

Hello,

Yes I'll send a patch next week, these days I'll be on vacation.

Thank you,
Laura
________________________________________
From: virtio-comment@lists.oasis-open.org <virtio-comment@lists.oasis-open.org> on behalf of Stefano Garzarella <sgarzare@redhat.com>
Sent: Wednesday, February 23, 2022 10:57 AM
To: Loghin, Laura
Cc: Arseniy Krasnov; virtio-comment@lists.oasis-open.org
Subject: RE: [EXTERNAL] [virtio-comment] vsock: define a maximum size for the packet data

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On Tue, Feb 22, 2022 at 08:46:29AM +0000, Loghin, Laura wrote:
>
>Hello,
>
>I was thinking that this limit would be used on the TX path (because on
>the RX, the device is considered to be trusted it will add a shorter
>buffer). The size of the TX buffer would still be the one from the
>header or from its descriptor (this is another thing that I think
>should be explicitly mentioned in the spec even though it's pretty
>obvious; there is no mention at this moment about what `len` is). The

The size of the TX buffers should be the one from the descriptor. (Now
we are using 2 buffers, one for the header and one for the payload, but
it is an implementation details).

Then the `len` field in the header contains the amount of bytes used for
the payload. So the buffer could be bigger then (hdr + payload).

For TX in the current implementation it never happens because of the way
the Linux driver is written, but for RX it happens just this, because
the driver allocates the buffer and the device can use only a part of
it.

However I agree that we could describe the `len` field better in the
specs, also because it's currently not really described.

If you want to send a patch, that would be great!

Thanks,
Stefano


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