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 1D427EE49AA for ; Mon, 21 Aug 2023 10:32:34 +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 6738D2AD6B for ; Mon, 21 Aug 2023 10:32:33 +0000 (UTC) Received: from lists.oasis-open.org (oasis-open.org [10.110.1.242]) by lists.oasis-open.org (Postfix) with ESMTP id 53F1E986265 for ; Mon, 21 Aug 2023 10:32:33 +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 4433D983FE9; Mon, 21 Aug 2023 10:32:33 +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 3169898622C; Mon, 21 Aug 2023 10:32:32 +0000 (UTC) X-Virus-Scanned: amavisd-new at kavi.com X-IronPort-AV: E=McAfee;i="6600,9927,10808"; a="363714798" X-IronPort-AV: E=Sophos;i="6.01,189,1684825200"; d="scan'208";a="363714798" X-ExtLoop1: 1 X-IronPort-AV: E=McAfee;i="6600,9927,10808"; a="765319082" X-IronPort-AV: E=Sophos;i="6.01,189,1684825200"; d="scan'208";a="765319082" Message-ID: Date: Mon, 21 Aug 2023 18:32:19 +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 Content-Language: en-US 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> 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. OK, I can work out a patch in this series implementing it. And as discussed in another thread with Jason in this series, it is better to forbid resetting a vq after SUSPEND. 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