VIRTIO_F_IO_BARRIER: use I/O barriers in driver
PATCH v2 1/1 VIRTIO_F_IO_BARRIER: use I/O barriers in driver
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.
---
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(+)
content.tex +16 -0
@@ -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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Quoted 15 lines · Tiwei Bie
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 <[email protected]>---
v1 -> v2:
- Rebase to the latest spec (MST);
- Use a smaller textwidth (according to_vimrc);
Quoted 6 lines
RFC -> v1:
- Use plural (Stefan);
- Add more details (Stefan);content.tex | 16 ++++++++++++++++ 1 file changed, 16 insertions(+)