From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from ws5-mx01.kavi.com (ws5-mx01.kavi.com [34.193.7.191]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id B1124CA0FF3 for ; Tue, 5 Sep 2023 09:08:42 +0000 (UTC) Received: from lists.oasis-open.org (oasis.ws5.connectedcommunity.org [10.110.1.242]) by ws5-mx01.kavi.com (Postfix) with ESMTP id 55928C6396 for ; Tue, 5 Sep 2023 09:08:40 +0000 (UTC) Received: from lists.oasis-open.org (oasis-open.org [10.110.1.242]) by lists.oasis-open.org (Postfix) with ESMTP id 42F589864B0 for ; Tue, 5 Sep 2023 09:08:40 +0000 (UTC) Received: from host09.ws5.connectedcommunity.org (host09.ws5.connectedcommunity.org [10.110.1.97]) by lists.oasis-open.org (Postfix) with QMQP id 32A5D983E51; Tue, 5 Sep 2023 09:08:40 +0000 (UTC) Mailing-List: contact virtio-dev-help@lists.oasis-open.org; run by ezmlm List-ID: Sender: Precedence: bulk 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 20829986410; Tue, 5 Sep 2023 09:08:38 +0000 (UTC) X-Virus-Scanned: amavisd-new at kavi.com X-IronPort-AV: E=McAfee;i="6600,9927,10823"; a="374135959" X-IronPort-AV: E=Sophos;i="6.02,229,1688454000"; d="scan'208";a="374135959" X-ExtLoop1: 1 X-IronPort-AV: E=McAfee;i="6600,9927,10823"; a="1071900141" X-IronPort-AV: E=Sophos;i="6.02,229,1688454000"; d="scan'208";a="1071900141" Message-ID: <4f88bf69-7436-4f26-6be8-76347355d59c@intel.com> Date: Tue, 5 Sep 2023 17:08:30 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:102.0) Gecko/20100101 Firefox/102.0 Thunderbird/102.14.0 To: Eugenio Perez Martin Cc: Jason Wang , mst@redhat.com, cohuck@redhat.com, virtio-comment@lists.oasis-open.org, virtio-dev@lists.oasis-open.org, Si-Wei Liu , Dragos Tatulea References: <20230814192904.30062-1-lingshan.zhu@intel.com> <20230814192904.30062-5-lingshan.zhu@intel.com> <8ce92e00-39f9-3e99-96e2-5599588869e3@intel.com> <23b9082d-050a-6f82-754e-d309c48972d5@intel.com> Content-Language: en-US From: "Zhu, Lingshan" In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Subject: [virtio-dev] Re: [virtio-comment] Re: [RFC PATCH 4/5] virtqueue: constraints for virtqueue state On 8/21/2023 5:26 PM, Eugenio Perez Martin wrote: > On Fri, Aug 18, 2023 at 11:44 AM Zhu, Lingshan wrote: >> >> >> On 8/17/2023 11:19 PM, Eugenio Perez Martin wrote: >>> On Tue, Aug 15, 2023 at 1:30 PM Zhu, Lingshan wrote: >>>> >>>> On 8/15/2023 8:34 AM, Jason Wang wrote: >>>>> On Mon, Aug 14, 2023 at 7:29 PM Zhu Lingshan wrote: >>>>>> This commit specifies the constraints of the virtqueue state, >>>>>> and the actions should be taken by the device when SUSPEND >>>>>> and DRIVER_OK is set >>>>>> >>>>>> Signed-off-by: Jason Wang >>>>>> Signed-off-by: Zhu Lingshan >>>>>> --- >>>>>> content.tex | 31 +++++++++++++++++++++++++++++++ >>>>>> 1 file changed, 31 insertions(+) >>>>>> >>>>>> diff --git a/content.tex b/content.tex >>>>>> index 43bd5de..f6ac581 100644 >>>>>> --- a/content.tex >>>>>> +++ b/content.tex >>>>>> @@ -587,6 +587,37 @@ \subsection{\field{Used State} Field} >>>>>> >>>>>> See also \ref{sec:Packed Virtqueues / Driver and Device Ring Wrap Counters}. >>>>>> >>>>>> +\drivernormative{\subsection}{Virtqueue State}{Basic Facilities of a Virtio Device / Virtqueue State} >>>>>> + >>>>>> +If VIRTIO_F_QUEUE_STATE has been negotiated, the driver MUST set SUSPEND in \field{device status} >>>>>> +first before getting or setting Virtqueue State of any virtqueues. >>>>> I don't get why this is a must. It could be useful for debugging. >>>> To avoid race conditions with the device and make the device >>>> implementation easier >>>>>> + >>>>>> +If VIRTIO_F_QUEUE_STATE has been negotiaged but VIRTIO_RING_F_PACKED not been negotiated, >>>>> typo >>>> yes >>>>>> +the driver MUST NOT access \field{Used State} of any virtqueues, it should use the >>>>>> +used index in the used ring. >>>>>> + >>>>>> +\devicenormative{\subsection}{Virtqueue State}{Basic Facilities of a Virtio Device / Virtqueue State} >>>>>> + >>>>>> +If VIRTIO_F_QUEUE_STATE has been negotiated but SUSPEND is not set in \field{device status}, >>>>>> +the device MUST ignore any accesses against Virtqueue State of any virtqueues. >>>>> Btw, do we need to clarify the behavior of ring reset after suspending? >>>> I think once suspended, the device should ignore resetting a queue >>> Actually shadow virtqueue could benefit from the ability to change vq >>> properties (addresses) while the device is suspended, and then just >>> resume it. I've been told that ring reset is overkill for that. >> If ring reset is overkill, is SUSPEND even more overkill? > It depends on the cost of recreating the vq in the device I think. But > it has more to do with *what* is changed in the vq, as it seems some > parameters (vq size) has more impact than others like vq address. The > way to stop the device does not affect, but ring reset offers the > possibility of change all of the parameters already. > > Adding Si-Wei and Dragos here, as they pointed it out in the > virtio-networking upstream meeting. > >>> But probably it is better to address it on top, with another feature flag. >> I think if we want to changing the vq properties, there must be a >> mechanism to >> stop the queue then resume the queue. >> >> How about allow setting queue_enable = 0 to stop it and =1 to resume and >> force it reinitialize? >> > Yes, I think that is better suited. But maybe this is better to be > added on top, so we maintain this series small. Hi Eugenio, I have a second thought while implementing above queue_enable = 0, it doesn't provide more advantages over queue_reset: 1) queue_reset can help to stop a queue and the vq properties can be reconfigured during queue_reset --> queue_enable. 2) once the driver sees SUSPEND presented by the device, it assume the device states and vq states are stable, at that point the driver can read reliable device configurations. So vq reset should be ignored once SUSPEND is present and if we implement queue stop, it should be ignored too when SUSPEND. 3) the device should only accept resetting a queue when !SUSPEND and the driver can flush the queue buffers before resetting it to avoid losing buffers, and we will have tracker for in-flight descriptors later. Any thoughts? Thanks > > Thanks! > >> Thanks >> Zhu Lingshan >>>>>> + >>>>>> +When VIRTIO_F_QUEUE_STATE has been negotiated but VIRTIO_RING_F_PACKED is not, >>>>>> +the device MUST ignore any accesses against \field{Used State}. >>>>>> + >>>>>> +If VIRTIO_F_QUEUE_STATE has been negotiaged, the device MUST reset >>>>>> +the Virtqueue State of every virtqueue upon a reset. >>>>> Need to define the meaning of "reset" this is important for packed virtqueue. >>>> I will remove this as Stefan suggested. >>>>>> + >>>>>> +If VIRTIO_F_QUEUE_STATE and VIRTIO_RING_F_PACKED have been negotiaged, when SUSPEND is set, >>>>>> +the device MUST record the Virtqueue State of every enabled virtqueue >>>>>> +in \field{Available State} and \field{Used State} respectively, >>>>>> +and correspondingly restore the Virtqueue State of every enabled virtqueue >>>>>> +from \field{Avaiable State} and \field{Used State} when DRIVER_OK is set. >>>>> We can just let the device report those states in any case then we >>>>> don't need to care about those details, or did you see any blockers? >>>> Agree, I will add the definition of used_state of splitted vq in the >>>> next version >>>> >>>> Thanks >>>>> Thanks >>>>> >>>>>> + >>>>>> +If VIRTIO_F_QUEUE_STATE has been negotiated but VIRTIO_RING_F_PACKED has been not, when SUSPEND is set, >>>>>> +the device MUST record the available state of every enabled virtqueue in \field{Available State}, >>>>>> +and restore the available state of every enabled virtqueue from \field{Avaiable State} >>>>>> +when DRIVER_OK is set. >>>>>> + >>>>>> \input{admin.tex} >>>>>> >>>>>> \chapter{General Initialization And Device Operation}\label{sec:General Initialization And Device Operation} >>>>>> -- >>>>>> 2.35.3 >>>>>> > > 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-lists > > Committee: https://www.oasis-open.org/committees/virtio/ > > Join OASIS: https://www.oasis-open.org/join/ > --------------------------------------------------------------------- To unsubscribe, e-mail: virtio-dev-unsubscribe@lists.oasis-open.org For additional commands, e-mail: virtio-dev-help@lists.oasis-open.org