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cl-os.tex
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540 & 11 Oct 2015 & Greg Kurz & {virtqueues: fix
trivial typo
See
\ref{sec:Basic Facilities of a Virtio Device / Virtqueues / Virtqueue Interrupt Suppression}.
} \\
\hline
541 & 11 Oct 2015 & Paolo Bonzini & {virtio-blk: fix typo
in legacy framing requirements section
See
\ref{sec:Device Types / Block Device / Legacy Interface: Framing Requirements}.
} \\
\hline
545 & 18 Oct 2015 & Paolo Bonzini & {virtio-blk: restore VIRTIO_BLK_F_FLUSH and VIRTIO_BLK_F_CONFIG_WCE
VIRTIO_BLK_F_CONFIG_WCE is important in order to achieve good performance
(up to 2x, though more realistically +30-40\%) in latency-bound workloads.
However, it was removed by mistake together with VIRTIO_BLK_F_FLUSH.
In addition, even removing VIRTIO_BLK_F_FLUSH was probably not a great
idea, because it simplifies simple drivers (e.g. firmware) that are okay
with a writethrough cache but still need data to persist after power loss.
What really should have been removed is just the possibility that devices
not propose VIRTIO_BLK_F_FLUSH, but even that only deserves a "SHOULD" in
the new world of conformance statements.
Restore these, with the following changes:
* clarify and use conformance statements in order to define writeback
and writethrough caching according to what is commonly done by high-end
storage.
* clarify (with conformance statements) the influence of the
VIRTIO_BLK_F_FLUSH feature on caching and how to proceed if only one of
VIRTIO_BLK_F_FLUSH and VIRTIO_BLK_F_CONFIG_WCE is negotiated.
* strengthen the requirement for persisting writes to MUST after
a VIRTIO_BLK_T_FLUSH request (and in other cases too involving the
new features).
The suggested behavior upon feature negotiation is okay for the Linux
implementation of virtio1, even after the implementation is modified to
support the two new features.
This fixes VIRTIO-144.
See \ref{sec:Device Types / Block Device},
\ref{sec:Conformance / Driver Conformance / Block Driver Conformance} and
\ref{sec:Conformance / Device Conformance / Block Device Conformance}.
} \\
\hline
546 & 18 Oct 2015 & Michael S. Tsirkin & {pci: clarify configuration access capability rules
The point of the configuration access capability is to enable
access to other capabilities. The intent never was to allow
writes to a random place within device BARs.
Limiting drivers simplifies devices - and devices can always
add another capability if drivers ever want to access
some other range.
This resolves VIRTIO-145.
See \ref{drivernormative:Virtio Transport Options / Virtio Over
PCI Bus / PCI Device Layout / PCI configuration access
capability}.
} \\
\hline
547 & 18 Oct 2015 & Michael S. Tsirkin & {add advice on transition from legacy interfaces
Reading legacy chapters gives a hint about what changed,
let's help readers discover this useful shortcut.
This resolves VIRTIO-146.
See \ref{sec:Transition from earlier specification drafts}.
} \\
\hline
554 & 16 Feb 2016 & Thomas Huth & {virtio-net: fix inconsistent legacy header size
Current text says:
The legacy driver only presented num_buffers in the struct
virtio_net_hdr when VIRTIO_NET_F_MRG_RXBUF was not negotiated;
Should be:
"\dots was negotiated \dots" instead of "\dots was not negotiated \dots"
To be consistent with the following:
without that feature the structure was 2 bytes shorter.
See \ref{sec:Device Types / Network Device / Device Operation / Legacy Interface: Device Operation}.
} \\
\hline
555 & 16 Feb 2016 & Michael S. Tsirkin & {virtio header: tweak
change motivation
The changes are not just to remove Linux assumptions,
we have also renamed ring->queue.
Tweak the header description accordingly.
See \ref{sec:Basic Facilities of a Virtio Device / Virtqueues / Helpers for Operating Virtqueues}.
} \\
\hline
558 & 16 Feb 2016 & Michael S. Tsirkin & {rename virtio_ring.h to virtio_queue.h
Since vring* and VRING* have been replaced with virtq* and VIRTQ*
respectively, rename the header virtio_ring.h to virtio_queue.h.
See \ref{sec:virtio-queue.h}.
} \\
\hline
559 & 16 Feb 2016 & Michael S. Tsirkin & {init: sort status bits
Status bit order is inconsistent: they are neither in increasing
order nor in the order they are likely to be used.
The second approach seems more useful since there aren't
that many bits, so the numerical order does not help much.
A typical order of use would be:
\begin{itemize}
\item ACKNOWLEDGE
\item DRIVER
\item then either FAILED or FEATURES_OK
\item then either FAILED or DRIVER_OK
\item then DEVICE_NEEDS_RESET (if device detects an error)
\end{itemize}
Sort the bits accordingly.
See \ref{sec:Basic Facilities of a Virtio Device / Device Status Field}.
} \\
\hline