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virtio-net: Improve dev config layout

PATCH New Parav Pandit 1 participant 3 messages Feb 23, 2023

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Parav Pandit

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#0 lore raw

v5 cover virtio-net: Improve dev config layout

This two patches improve dev configuration layout in two ways.

1. Define device configuration layout before describing it fields
2. Avoid duplicate description of its read only fields and whole layout

Patch summary:
patch-1: consolidate read only field at one place in driver requirements
patch-2: define device configuration layout before describing its fields.

changelog:
v4->v5:
- grammar correction
- smaller commit message
v3->v4:
- wrote driver requirement as normative statement
- moved read only line to description section v2->v3:
- split into two patches
- move read only description to driver requirements section

Parav Pandit (2):
virtio-net: Describe dev cfg fields read only
virtio-net: Define cfg fields before description

 device-types/net/description.tex | 49 ++++++++++++++++++--------------
 1 file changed, 28 insertions(+), 21 deletions(-)
Signature · 18 lines
2.26.2


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author
#1 lore raw

PATCH v5 1/2 virtio-net: Describe dev cfg fields read only

Device configuration fields are read only. Avoid duplicating this description for multiple fields.

Instead describe it one time and do it in the driver requirements section.

Fixes https://github.com/oasis-tcs/virtio-spec/issues/161
Reviewed-by David Edmondson <[email protected]>
Signed-off-by Parav Pandit <[email protected]>

---
changelog:
v4->v5:
- grammer correction
v3->v4:
- write driver requirement as normative statement
- add back read only wording in the description
v2->v3:
- split as new patch

---
 device-types/net/description.tex | 21 +++++++++++++--------
 1 file changed, 13 insertions(+), 8 deletions(-)
device-types/net/description.tex +13 -8
index 73501b6..75ebe98 100644
@@ -156,25 +156,28 @@ \subsubsection{Legacy Interface: Feature bits}\label{sec:Device Types / Network
 \subsection{Device configuration layout}\label{sec:Device Types / Network Device / Device configuration layout}
 \label{sec:Device Types / Block Device / Feature bits / Device configuration layout}
 
-Device configuration fields are listed below, they are read-only for a driver. The \field{mac} address field
-always exists (though is only valid if VIRTIO_NET_F_MAC is set), and
-\field{status} only exists if VIRTIO_NET_F_STATUS is set. Two
-read-only bits (for the driver) are currently defined for the status field:
-VIRTIO_NET_S_LINK_UP and VIRTIO_NET_S_ANNOUNCE.
+Device configuration fields are listed below. All of the device
+configuration fields are read-only for the driver.
+
+The \field{mac} address field always exists (though is only
+valid if VIRTIO_NET_F_MAC is set), and \field{status} only
+exists if VIRTIO_NET_F_STATUS is set. Two bits are currently
+defined for the status field: VIRTIO_NET_S_LINK_UP and
+VIRTIO_NET_S_ANNOUNCE.
 
 \begin{lstlisting}
 #define VIRTIO_NET_S_LINK_UP     1
 #define VIRTIO_NET_S_ANNOUNCE    2
 \end{lstlisting}
 
-The following driver-read-only field, \field{max_virtqueue_pairs} only exists if
+The following field, \field{max_virtqueue_pairs} only exists if
 VIRTIO_NET_F_MQ or VIRTIO_NET_F_RSS is set. This field specifies the maximum number
 of each of transmit and receive virtqueues (receiveq1\ldots receiveqN
 and transmitq1\ldots transmitqN respectively) that can be configured once at least one of these features
 is negotiated.
 
-The following driver-read-only field, \field{mtu} only exists if
-VIRTIO_NET_F_MTU is set. This field specifies the maximum MTU for the driver to
+The following field, \field{mtu} only exists if VIRTIO_NET_F_MTU
+is set. This field specifies the maximum MTU for the driver to
 use.
 
 The following two fields, \field{speed} and \field{duplex}, only

@@ -264,6 +267,8 @@ \subsection{Device configuration layout}\label{sec:Device Types / Network Device
 
 \drivernormative{\subsubsection}{Device configuration layout}{Device Types / Network Device / Device configuration layout}
 
+The driver MUST NOT write to any of the device configuration fields.
+
 A driver SHOULD negotiate VIRTIO_NET_F_MAC if the device offers it.
 If the driver negotiates the VIRTIO_NET_F_MAC feature, the driver MUST set
 the physical address of the NIC to \field{mac}.  Otherwise, it SHOULD
Signature · 1 line
2.26.2
author
#2 lore raw

PATCH v5 2/2 virtio-net: Define cfg fields before description

In reply to Parav Pandit

Currently some fields of the virtio_net_config structure are defined before introducing the structure and some are defined after. Better to define the configuration layout first followed by description of all the fields.

Device configuration fields are described in the section. Change wording from 'listed' to 'described' as suggested in patch [1].

[1] https://lists.oasis-open.org/archives/virtio-dev/202302/msg00004.html

Fixes https://github.com/oasis-tcs/virtio-spec/issues/161
Reviewed-by David Edmondson <[email protected]>
Signed-off-by Parav Pandit <[email protected]>

---
changelog:
v4->v5:
- rebase
- updated commit msg
v2->v3:
- split the patch for read only description as prepration patch
- rebased
v1->v2:
- remove read-only wording from multiple places v0->v1:
- Change wording about device configuration field introduction
- remove duplicate read-only wording for status field
- reword sentence to read it better

---
 device-types/net/description.tex | 42 +++++++++++++++++---------------
 1 file changed, 22 insertions(+), 20 deletions(-)
device-types/net/description.tex +22 -20
index 75ebe98..f6d0479 100644
@@ -156,14 +156,29 @@ \subsubsection{Legacy Interface: Feature bits}\label{sec:Device Types / Network
 \subsection{Device configuration layout}\label{sec:Device Types / Network Device / Device configuration layout}
 \label{sec:Device Types / Block Device / Feature bits / Device configuration layout}
 
-Device configuration fields are listed below. All of the device
-configuration fields are read-only for the driver.
+The network device has the following device configuration layout.
+All of the device configuration fields are read-only for the driver.
 
-The \field{mac} address field always exists (though is only
-valid if VIRTIO_NET_F_MAC is set), and \field{status} only
-exists if VIRTIO_NET_F_STATUS is set. Two bits are currently
-defined for the status field: VIRTIO_NET_S_LINK_UP and
-VIRTIO_NET_S_ANNOUNCE.
+\begin{lstlisting}
+struct virtio_net_config {
+        u8 mac[6];
+        le16 status;
+        le16 max_virtqueue_pairs;
+        le16 mtu;
+        le32 speed;
+        u8 duplex;
+        u8 rss_max_key_size;
+        le16 rss_max_indirection_table_length;
+        le32 supported_hash_types;
+};
+\end{lstlisting}
+
+The \field{mac} address field always exists (although it is only
+valid if VIRTIO_NET_F_MAC is set).
+
+The \field{status} only exists if VIRTIO_NET_F_STATUS is set.
+Two bits are currently defined for the status field: VIRTIO_NET_S_LINK_UP
+and VIRTIO_NET_S_ANNOUNCE.
 
 \begin{lstlisting}
 #define VIRTIO_NET_S_LINK_UP     1

@@ -193,19 +208,6 @@ \subsection{Device configuration layout}\label{sec:Device Types / Network Device
 is expected to re-read these values after receiving a
 configuration change notification.
 
-\begin{lstlisting}
-struct virtio_net_config {
-        u8 mac[6];
-        le16 status;
-        le16 max_virtqueue_pairs;
-        le16 mtu;
-        le32 speed;
-        u8 duplex;
-        u8 rss_max_key_size;
-        le16 rss_max_indirection_table_length;
-        le32 supported_hash_types;
-};
-\end{lstlisting}
 The following field, \field{rss_max_key_size} only exists if VIRTIO_NET_F_RSS or VIRTIO_NET_F_HASH_REPORT is set.
 It specifies the maximum supported length of RSS key in bytes.
Signature · 1 line
2.26.2