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 DDF67EDE9A8 for ; Thu, 14 Sep 2023 11:35:26 +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 528762AEE4 for ; Thu, 14 Sep 2023 11:35:26 +0000 (UTC) Received: from lists.oasis-open.org (oasis-open.org [10.110.1.242]) by lists.oasis-open.org (Postfix) with ESMTP id 22851986641 for ; Thu, 14 Sep 2023 11:35:26 +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 06A3C986640; Thu, 14 Sep 2023 11:35:26 +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 083C3986639 for ; Thu, 14 Sep 2023 11:34:44 +0000 (UTC) X-Virus-Scanned: amavisd-new at kavi.com X-MC-Unique: h6kNeSVzOKOnucg7yzCNVg-1 X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1694691280; x=1695296080; h=in-reply-to:content-transfer-encoding:content-disposition :mime-version:references:message-id:subject:cc:to:from:date :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=roQQWJGP+CjOh4y3bJO70yqtkdteVlr7qjV+gxLBPfA=; b=HIxm8HXjaegFGwegzJLpk08DZM/fv+xkdIeSDtR38fAfAiBMGAyhGVIFif0QNFjeS8 XZM4yarb3T7MCBPh4gjrJH31zDBtxK2/QFRc9UQI4H69yUe+RRW2ysaXcPgDDZyZ0dEK SPZNM/CxoKl0lnkYO7F4KFdzbH/TZWCWxhEH2MuvxMR2FN7MpbBd7kciYymeY67hBiS8 4MtJRNs1/Gs1n6YU29BuhFmDWTTV+88exRu4nLl7CS0soQ2AfqkCaUMGzImpCpeO1xVf IHFgTd84OTDXRrMZen1jPYiTV5YHWfl0HRtBOcBso5eRgdFrg0yPtNUkjMxu2YUnugvl 3/hQ== X-Gm-Message-State: AOJu0YwZJ7JEIndKgtvL2ko6d0VATgKfVfTS7Fo+Xcikdiafhbiua3fJ ZZ5pC6lw3Qu7B/YuL1Cm2OlGwJaIr3UUxtn9epv9oTfuVNGXsyT3VVKQpFzr4UC5quaXoU/qdbV 3Qu73XHtHlLx1qk0FDoGH7I4nkopyfajzhR1R X-Received: by 2002:a17:906:53c5:b0:9a2:2842:f1c6 with SMTP id p5-20020a17090653c500b009a22842f1c6mr4246064ejo.28.1694691280316; Thu, 14 Sep 2023 04:34:40 -0700 (PDT) X-Google-Smtp-Source: AGHT+IFxGjcSg2xordJch72pu67Ol5RvNtPgyEdGRKBUex6yYa6U76xNGFSPk98vZYP5fiTlP9My6Q== X-Received: by 2002:a17:906:53c5:b0:9a2:2842:f1c6 with SMTP id p5-20020a17090653c500b009a22842f1c6mr4246053ejo.28.1694691279957; Thu, 14 Sep 2023 04:34:39 -0700 (PDT) Date: Thu, 14 Sep 2023 07:34:35 -0400 From: "Michael S. Tsirkin" To: Zhu Lingshan Cc: jasowang@redhat.com, eperezma@redhat.com, cohuck@redhat.com, stefanha@redhat.com, virtio-comment@lists.oasis-open.org, virtio-dev@lists.oasis-open.org Message-ID: <20230914073023-mutt-send-email-mst@kernel.org> References: <20230906081637.32185-1-lingshan.zhu@intel.com> <20230906081637.32185-3-lingshan.zhu@intel.com> MIME-Version: 1.0 In-Reply-To: <20230906081637.32185-3-lingshan.zhu@intel.com> X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit Subject: [virtio-dev] Re: [PATCH 2/5] virtio: introduce SUSPEND bit in device status On Wed, Sep 06, 2023 at 04:16:34PM +0800, Zhu Lingshan wrote: > This patch introduces a new status bit in the device status: SUSPEND. > > This SUSPEND bit can be used by the driver to suspend a device, > in order to stabilize the device states and virtqueue states. > > Its main use case is live migration. > > Signed-off-by: Zhu Lingshan > Signed-off-by: Jason Wang > Signed-off-by: Eugenio Pérez > --- > content.tex | 31 +++++++++++++++++++++++++++++++ > 1 file changed, 31 insertions(+) > > diff --git a/content.tex b/content.tex > index 0e492cd..0fab537 100644 > --- a/content.tex > +++ b/content.tex > @@ -47,6 +47,9 @@ \section{\field{Device Status} Field}\label{sec:Basic Facilities of a Virtio Dev > \item[DRIVER_OK (4)] Indicates that the driver is set up and ready to > drive the device. > > +\item[SUSPEND (16)] When VIRTIO_F_SUSPEND is negotiated, indicates that the > + device has been suspended by the driver. > + > \item[DEVICE_NEEDS_RESET (64)] Indicates that the device has experienced > an error from which it can't recover. > \end{description} > @@ -73,6 +76,10 @@ \section{\field{Device Status} Field}\label{sec:Basic Facilities of a Virtio Dev > recover by issuing a reset. > \end{note} > > +The driver SHOULD NOT set SUSPEND if FEATURES_OK is not set. > + > +When setting SUSPEND, the driver MUST re-read \field{device status} to ensure the SUSPEND bit is set. > + > \devicenormative{\subsection}{Device Status Field}{Basic Facilities of a Virtio Device / Device Status Field} > > The device MUST NOT consume buffers or send any used buffer > @@ -82,6 +89,26 @@ \section{\field{Device Status} Field}\label{sec:Basic Facilities of a Virtio Dev > that a reset is needed. If DRIVER_OK is set, after it sets DEVICE_NEEDS_RESET, the device > MUST send a device configuration change notification to the driver. > > +The device MUST ignore SUSPEND if FEATURES_OK is not set. > + > +The device MUST ignore SUSPEND if VIRTIO_F_SUSPEND is not negotiated. why? let's just forbid driver from setting it. > + > +The device SHOULD allow settings to \field{device status} even when SUSPEND is set. > + > +If VIRTIO_F_SUSPEND is negotiated and SUSPEND is set, the device SHOULD clear SUSPEND > +and resumes operation upon DRIVER_OK. > + sorry what? > +If VIRTIO_F_SUSPEND is negotiated, when the driver sets SUSPEND, > +the device SHOULD perform the following actions before presenting SUSPEND bit in the \field{device status}: > + > +\begin{itemize} > +\item Stop consuming buffers of any virtqueues and mark all finished descritors as used. > +\item Wait until all descriptors that being processed to finish and mark them as used. > +\item Flush all used buffer and send used buffer notifications to the driver. flush how? > +\item Record Virtqueue State of each enabled virtqueue, see section \ref{sec:Virtqueues / Virtqueue State} record where? > +\item Pause its operation except \field{device status} and preserve configurations in its Device Configuration Space, see \ref{sec:Basic Facilities of a Virtio Device / Device Configuration Space} pause in what sense? completely? this does not seem realistic. e.g. pci express link has to stay active or device will die. also, presumably here it is except a bunch of other fields. e.g. what about queue select and all related queue fields? > +\end{itemize} > + > \section{Feature Bits}\label{sec:Basic Facilities of a Virtio Device / Feature Bits} > > Each virtio device offers all the features it understands. During > @@ -937,6 +964,10 @@ \chapter{Reserved Feature Bits}\label{sec:Reserved Feature Bits} > \ref{devicenormative:Basic Facilities of a Virtio Device / Feature Bits} for > handling features reserved for future use. > > + \item[VIRTIO_F_SUSPEND(42)] This feature indicates that the driver can > + SUSPEND the device. > + See \ref{sec:Basic Facilities of a Virtio Device / Device Status Field}. > + > \end{description} > > \drivernormative{\section}{Reserved Feature Bits}{Reserved Feature Bits} > -- > 2.35.3 --------------------------------------------------------------------- To unsubscribe, e-mail: virtio-dev-unsubscribe@lists.oasis-open.org For additional commands, e-mail: virtio-dev-help@lists.oasis-open.org