* [virtio-dev] [PATCH v2] VIRTIO_F_IO_BARRIER: use I/O barriers in driver
@ 2018-05-04 2:44 Tiwei Bie
2018-05-10 9:49 ` Stefan Hajnoczi
0 siblings, 1 reply; 2+ messages in thread
From: Tiwei Bie @ 2018-05-04 2:44 UTC (permalink / raw)
To: mst, pbonzini, stefanha, jasowang, virtio-dev
Cc: dan.daly, cunming.liang, zhihong.wang
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 <tiwei.bie@intel.com>
---
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 | 16 ++++++++++++++++
1 file changed, 16 insertions(+)
diff --git a/content.tex b/content.tex
index 7a92cb1..d1a8b78 100644
--- a/content.tex
+++ b/content.tex
@@ -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:
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^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [virtio-dev] [PATCH v2] VIRTIO_F_IO_BARRIER: use I/O barriers in driver
2018-05-04 2:44 [virtio-dev] [PATCH v2] VIRTIO_F_IO_BARRIER: use I/O barriers in driver Tiwei Bie
@ 2018-05-10 9:49 ` Stefan Hajnoczi
0 siblings, 0 replies; 2+ messages in thread
From: Stefan Hajnoczi @ 2018-05-10 9:49 UTC (permalink / raw)
To: Tiwei Bie
Cc: mst, pbonzini, jasowang, virtio-dev, dan.daly, cunming.liang,
zhihong.wang
[-- Attachment #1: Type: text/plain, Size: 855 bytes --]
On Fri, May 04, 2018 at 10:44:36AM +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 <tiwei.bie@intel.com>
> ---
> 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 | 16 ++++++++++++++++
> 1 file changed, 16 insertions(+)
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
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2018-05-04 2:44 [virtio-dev] [PATCH v2] VIRTIO_F_IO_BARRIER: use I/O barriers in driver Tiwei Bie
2018-05-10 9:49 ` Stefan Hajnoczi
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