From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: 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 745FC9863D4 for ; Wed, 10 Aug 2022 17:12:29 +0000 (UTC) Date: Wed, 10 Aug 2022 13:12:21 -0400 From: "Michael S. Tsirkin" Message-ID: <20220810131209-mutt-send-email-mst@kernel.org> References: <62920bd4-1070-a91a-baf8-659009e9f590@oracle.com> <20220810021320-mutt-send-email-mst@kernel.org> <20220810021427-mutt-send-email-mst@kernel.org> <20220810050219-mutt-send-email-mst@kernel.org> <20220810120440-mutt-send-email-mst@kernel.org> <20220810125749-mutt-send-email-mst@kernel.org> MIME-Version: 1.0 In-Reply-To: Subject: Re: [virtio-dev] [PATCH] virtio-net: use mtu size as buffer length for big packets Content-Type: text/plain; charset=us-ascii Content-Disposition: inline To: Parav Pandit Cc: Jason Wang , Si-Wei Liu , Gavin Li , "Hemminger, Stephen" , davem , virtualization , Virtio-Dev , "jesse.brandeburg@intel.com" , "alexander.h.duyck@intel.com" , "kubakici@wp.pl" , "sridhar.samudrala@intel.com" , "loseweigh@gmail.com" , Gavi Teitz List-ID: On Wed, Aug 10, 2022 at 05:06:33PM +0000, Parav Pandit wrote: > > > From: Michael S. Tsirkin > > Sent: Wednesday, August 10, 2022 12:59 PM > > > > On Wed, Aug 10, 2022 at 04:22:41PM +0000, Parav Pandit wrote: > > > > > > > From: Michael S. Tsirkin > > > > Sent: Wednesday, August 10, 2022 12:05 PM > > > > > > > > On Wed, Aug 10, 2022 at 04:00:08PM +0000, Parav Pandit wrote: > > > > > > > > > > > From: Michael S. Tsirkin > > > > > > Sent: Wednesday, August 10, 2022 5:03 AM > > > > > > > > > > > > > > > > Should we make this depend on the vq reset ability maybe? > > > > > > > > > > > > > > The advantage of this is to keep TX working. Or we can use > > > > > > > device reset as a fallback if there's no vq reset. > > > > > > > > > > > > > > Thanks > > > > > > > > > > > > Device reset is really annoying in that it loses all the state: > > > > > > rx filters etc etc. > > > > > > > > > > The elegant solution is let driver tell the new mtu to the device. > > > > > One way to do so is by using existing ctrl vq. > > > > > > > > That will need a new feature bit. > > > > > > > Yes. ctrl vq can tell what all configuration does it allow. :) Or you > > > prefer feature bit? > > > > We did feature bits for this in the past. > > > Ok. Will try to draft the update for future. > > Gavin should repost the patch to address comments unrelated to this future bit anyway. > Right? Right. > > > > > If merged buffer is done, and new mtu is > minimum posting size, > > > > > no need > > > > to undergo vq reset. > > > > > If merged buffer is not done, and buffer posted are smaller than > > > > > new mtu, > > > > undergo vq reset optionally. > > > > > > > > This can be done with or without sending mtu to device. > > > Yes, telling mtu to device helps device to optimize and adhere to the spec > > line " The device MUST NOT pass received packets that exceed mtu" in > > section 5.1.4.1. > > > > Again, that line refers to \field{mtu} which is the max mtu supported, > > irrespective to anything driver does. > > > > -- > > MST --------------------------------------------------------------------- To unsubscribe, e-mail: virtio-dev-unsubscribe@lists.oasis-open.org For additional commands, e-mail: virtio-dev-help@lists.oasis-open.org