[PATCH v3 2/2] virtio: pci support virtqueue reset

[Xuan Zhuo <xuanzhuo@linux.alibaba.com>]

PCI support virtqueue reset.

virtio_pci_common_cfg add "queue_reset" to support virtqueue reset.
The driver uses this to selectively reset the queue.

Signed-off-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
---
 content.tex | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/content.tex b/content.tex
index 603b1f1..35228dc 100644
--- a/content.tex
+++ b/content.tex
@@ -896,6 +896,7 @@ \subsubsection{Common configuration structure layout}\label{sec:Virtio Transport
         le64 queue_driver;              /* read-write */
         le64 queue_device;              /* read-write */
         le16 queue_notify_data;         /* read-only for driver */
+        le16 queue_reset;               /* read-write */
 };
 \end{lstlisting}
 
@@ -975,6 +976,12 @@ \subsubsection{Common configuration structure layout}\label{sec:Virtio Transport
         may benefit from providing another value, for example an internal virtqueue
         identifier, or an internal offset related to the virtqueue number.
         \end{note}
+
+\item[\field{queue_reset}]
+        The driver uses this to selectively reset the queue.
+        This field exists only if VIRTIO_F_RING_RESET has been
+        negotiated. (see \ref{sec:Virtqueues / Virtqueue Reset}).
+
 \end{description}
 
 \devicenormative{\paragraph}{Common configuration structure layout}{Virtio Transport Options / Virtio Over PCI Bus / PCI Device Layout / Common configuration structure layout}
@@ -1016,6 +1023,14 @@ \subsubsection{Common configuration structure layout}\label{sec:Virtio Transport
 
 The device MUST present a 0 in \field{queue_enable} on reset.
 
+The device MUST present a 0 in \field{queue_reset} after the virtqueue is
+enabled with \field{queue_enable}. The device MUST reset the queue when 1 is
+written to \field{queue_reset}, and present a 1 in \field{queue_reset} until the
+queue is enabled with \field{queue_enable}. (see \ref{sec:Virtqueues / Virtqueue Reset}).
+
+The device MUST present a 0 in \field{queue_enable} after the virtqueue is reset
+with \field{queue_reset}. (see \ref{sec:Virtqueues / Virtqueue Reset}).
+
 The device MUST present a 0 in \field{queue_size} if the virtqueue
 corresponding to the current \field{queue_select} is unavailable.
 
@@ -1040,6 +1055,12 @@ \subsubsection{Common configuration structure layout}\label{sec:Virtio Transport
 
 The driver MUST NOT write a 0 to \field{queue_enable}.
 
+If the VIRTIO_F_RING_RESET feature bit is negotiated, the driver can stop using
+the queue by writing a 1 to \field{queue_reset} and MUST read the value back to
+ensure synchronization. Then optionally re-enable the queue by writing a 1 to
+\field{queue_enable} after configuring the other virtqueue fields. (see
+\ref{sec:Virtqueues / Virtqueue Reset}).
+
 \subsubsection{Notification structure layout}\label{sec:Virtio Transport Options / Virtio Over PCI Bus / PCI Device Layout / Notification capability}
 
 The notification location is found using the VIRTIO_PCI_CAP_NOTIFY_CFG
-- 
2.31.0