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COMMENTS FOR virtio-v1.0-csprd01
================================
Number: 1
Date: Fri, 10 Jan 2014 11:01:44 +0100
Link to Mail: https://lists.oasis-open.org/archives/virtio-comment/201401/msg00000.html
Commenter name: Thomas Huth <thuth@linux.vnet.ibm.com>
- The first three chapters sometimes uses the pronoun "we" in sentences.
I think this should be avoided, since it is not always clear who is
meant with this pronoun: The reader? The driver? The device?
- Some of the generic sections still use the term "PCI" though they
should not.
I tried to mention the related spots below, but I'd like to suggest to
scan again the whole document for "we" and "PCI" to be sure to get
everything right.
Page 8 / Introduction:
- "Extensible: Virtio PCI devices contain feature bits ..."
=> Remove the "PCI" in above sentence.
Page 10 / Configuration Space:
- "... nor or reads from multiple fields"
=> that's difficult to parse, is this sentence right?
Page 14 / The Virtqueue Available Ring
- "The available ring refers to what descriptor chains the driver is
offering the device"
=> Somewhat hard to read, maybe better something like this:
"The available ring refers to the descriptor chains that the driver
is offering to the device" ?
- "The "idx" field indicates where we would put the next descriptor
entry in the ring"
=> "The "idx" field indicates where the driver would put the next
descriptor entry in the ring"
Page 16 / Device Initialization:
- "2. Set the ACKNOWLEDGE status bit: we have noticed the device."
=> "2. The guest OS sets the ACKNOWLEDGE status bit to indicate
that it has noticed the device."
- "3. Set the DRIVER status bit: we know how to drive the device."
=> "3. The driver sets the DRIVER status bit to indicate that
it knows how to drive the device"
Page 18 / Notifying the device:
- "... we go ahead and write to the PCI configuration space."
=> "... the driver can go ahead and write to the configuration space."
- "The avail_event field wraps naturally at 65536 as well, iving the
following algorithm ..."
=> What does "iving" mean? I did not find that in my dictionary.
Page 19:
- "It can then process used ring entries finally enabling interrupts ..."
=> This sentence is hard to parse ... is there missing something
before "finally"?
Proposal:
diff --git a/content.tex b/content.tex
index 803615d..8850c1a 100644
--- a/content.tex
+++ b/content.tex
@@ -145,7 +145,7 @@ Interface' in the section title.
Configuration space is generally used for rarely-changing or
initialization-time parameters. Drivers MUST NOT assume reads from
-fields greater than 32 bits wide are atomic, nor or reads from
+fields greater than 32 bits wide are atomic, nor reads from
multiple fields.
Each transport provides a generation count for the configuration
@@ -418,11 +418,11 @@ the device MUST ignore the write-only flag (flags\&VRING_DESC_F_WRITE) in the de
};
\end{lstlisting}
-The available ring refers to what descriptor chains the driver is offering the
+The driver uses the available ring to offer buffers to the
device: each ring entry refers to the head of a descriptor chain. It is only
written by the driver and read by the device.
-The “idx” field indicates where we would put the next descriptor
+The “idx” field indicates where the driver would put the next descriptor
entry in the ring (modulo the queue size). This starts at 0, and increases.
If the VIRTIO_RING_F_INDIRECT_DESC feature bit is not negotiated, the
@@ -515,9 +515,9 @@ The driver MUST follow this sequence to initialize a device:
\begin{enumerate}
\item Reset the device.
-\item Set the ACKNOWLEDGE status bit: we have noticed the device.
+\item Set the ACKNOWLEDGE status bit: the guest OS has notice the device.
-\item Set the DRIVER status bit: we know how to drive the device.
+\item Set the DRIVER status bit: the guest OS knows how to drive the device.
\item Read device feature bits, and write the subset of feature bits
understood by the OS and driver to the device.
@@ -686,7 +686,7 @@ we use a memory barrier here before reading the flags or the
avail_event field.
If the VIRTIO_F_RING_EVENT_IDX feature is not negotiated, and if the
-VRING_USED_F_NOTIFY flag is not set, we go ahead and notify the
+VRING_USED_F_NOTIFY flag is not set, the driver SHOULD notify the
device.
If the VIRTIO_F_RING_EVENT_IDX feature is negotiated, we read the
@@ -694,7 +694,7 @@ avail_event field in the available ring structure. If the
available index crossed_the avail_event field value since the
last notification, we go ahead and write to the PCI configuration
space. The avail_event field wraps naturally at 65536 as well,
-iving the following algorithm for calculating whether a device needs
+giving the following algorithm for calculating whether a device needs
notification:
\begin{lstlisting}
@@ -705,7 +705,7 @@ notification:
Once the device has used a buffer (read from or written to it, or
parts of both, depending on the nature of the virtqueue and the
-device), it sends an interrupt, following an algorithm very
+device), it SHOULD send an interrupt, following an algorithm very
similar to the algorithm used for the driver to send the device a
buffer:
@@ -732,11 +732,11 @@ buffer:
\end{enumerate}
\end{enumerate}
-For each ring, the driver should then disable interrupts by writing
+For each ring, the driver MAY then disable interrupts by writing
VRING_AVAIL_F_NO_INTERRUPT flag in avail structure, if required.
-It can then process used ring entries finally enabling interrupts
-by clearing the VRING_AVAIL_F_NO_INTERRUPT flag or updating the
-EVENT_IDX field in the available structure. The driver should then
+Once it has processed the ring entries, it SHOULD re-enable
+interrupts by clearing the VRING_AVAIL_F_NO_INTERRUPT flag or updating the
+EVENT_IDX field in the available structure. The driver SHOULD then
execute a memory barrier, and then recheck the ring empty
condition. This is necessary to handle the case where after the
last check and before enabling interrupts, an interrupt has been
Decision:
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