From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: virtio-dev-return-4085-cohuck=redhat.com@lists.oasis-open.org Sender: List-Post: List-Help: List-Unsubscribe: List-Subscribe: Received: from lists.oasis-open.org (oasis-open.org [66.179.20.138]) by lists.oasis-open.org (Postfix) with ESMTP id 00735581912A for ; Tue, 15 May 2018 18:38:24 -0700 (PDT) Date: Wed, 16 May 2018 09:38:38 +0800 From: Tiwei Bie Message-ID: <20180516013838.GA7589@debian> References: <20180510154126.4062-1-tiwei.bie@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20180510154126.4062-1-tiwei.bie@intel.com> Subject: Re: [virtio-dev] [PATCH v3] VIRTIO_F_IO_BARRIER: use I/O barriers in driver To: mst@redhat.com, pbonzini@redhat.com, stefanha@redhat.com, jasowang@redhat.com, virtio-dev@lists.oasis-open.org Cc: dan.daly@intel.com, cunming.liang@intel.com, zhihong.wang@intel.com List-ID: On Thu, May 10, 2018 at 11:41:26PM +0800, Tiwei Bie wrote: > There will be hardware virtio devices in the future, which > require drivers to use the barriers suitable for I/O devices, > compared with software virtio devices which just require > drivers to use the barriers suitable for CPU cores. > > To fix the ordering issue for hardware virtio devices, add > a new feature: VIRTIO_F_IO_BARRIER. When negotiated, driver > will use the barriers suitable for I/O devices. > > Signed-off-by: Tiwei Bie > Reviewed-by: Stefan Hajnoczi I have opened an issue for this: Fixes: https://github.com/oasis-tcs/virtio-spec/issues/10 Please start the voting. Thanks! Best regards, Tiwei Bie > --- > v2 -> v3: > - Update the feature bits allocation (Stefan); > > v1 -> v2: > - Rebase to the latest spec (MST); > - Use a smaller textwidth (according to _vimrc); > > RFC -> v1: > - Use plural (Stefan); > - Add more details (Stefan); > > content.tex | 20 ++++++++++++++++++-- > 1 file changed, 18 insertions(+), 2 deletions(-) > > diff --git a/content.tex b/content.tex > index 7a92cb1..95c243f 100644 > --- a/content.tex > +++ b/content.tex > @@ -95,10 +95,10 @@ Feature bits are allocated as follows: > \begin{description} > \item[0 to 23] Feature bits for the specific device type > > -\item[24 to 33] Feature bits reserved for extensions to the queue and > +\item[24 to 36] Feature bits reserved for extensions to the queue and > feature negotiation mechanisms > > -\item[34 and above] Feature bits reserved for future extensions. > +\item[37 and above] Feature bits reserved for future extensions. > \end{description} > > \begin{note} > @@ -5348,6 +5348,15 @@ Descriptors} and \ref{sec:Packed Virtqueues / Indirect Flag: Scatter-Gather Supp > \item[VIRTIO_F_IN_ORDER(35)] This feature indicates > that all buffers are used by the device in the same > order in which they have been made available. > + \item[VIRTIO_F_IO_BARRIER(36)] This feature indicates > + that the device needs the driver to use the barriers > + suitable for hardware devices. Some transports require > + barriers to ensure devices have a consistent view of > + memory. When devices are implemented in software a > + weaker form of barrier may be sufficient and yield > + better performance. This feature indicates whether > + a stronger form of barrier suitable for hardware > + devices is necessary. > \end{description} > > \drivernormative{\section}{Reserved Feature Bits}{Reserved Feature Bits} > @@ -5363,6 +5372,10 @@ addresses to the device. > > A driver SHOULD accept VIRTIO_F_RING_PACKED if it is offered. > > +A driver SHOULD accept VIRTIO_F_IO_BARRIER if it is offered. > +If VIRTIO_F_IO_BARRIER has been negotiated, a driver MUST use > +the barriers suitable for hardware devices. > + > \devicenormative{\section}{Reserved Feature Bits}{Reserved Feature Bits} > > A device MUST offer VIRTIO_F_VERSION_1. A device MAY fail to operate further > @@ -5376,6 +5389,9 @@ accepted. > If VIRTIO_F_IN_ORDER has been negotiated, a device MUST use > buffers in the same order in which they have been available. > > +A device MAY fail to operate further if VIRTIO_F_IO_BARRIER > +is not accepted. > + > \section{Legacy Interface: Reserved Feature Bits}\label{sec:Reserved Feature Bits / Legacy Interface: Reserved Feature Bits} > > Transitional devices MAY offer the following: > -- > 2.11.0 > > > --------------------------------------------------------------------- > To unsubscribe, e-mail: virtio-dev-unsubscribe@lists.oasis-open.org > For additional commands, e-mail: virtio-dev-help@lists.oasis-open.org > --------------------------------------------------------------------- To unsubscribe, e-mail: virtio-dev-unsubscribe@lists.oasis-open.org For additional commands, e-mail: virtio-dev-help@lists.oasis-open.org