virtio — archive

[Michael S. Tsirkin]

--- content.tex 15 ++++++++++ ----- 1 file changed, 10 insertions(+), 5 deletions(-) diff --git a/content.tex b/content.tex index 2de0644..58402f3 100644 --- a/content.tex +++ b/content.tex @@ -4352,20 +4352,25 @@ and should not be used. section{Legacy Interface: Reserved Feature Bits}label{sec:Reserved Feature Bits / Legacy Interface: Reserved Feature Bits} -Legacy or transitional devices may offer the following: - +Transitional devices MAY offer the following: egin{description} -item[VIRTIO_F_NOTIFY_ON_EMPTY (24)] Negotiating this feature - indicates that the driver wants an interrupt if the device runs +item[VIRTIO_F_NOTIFY_ON_EMPTY (24)] If this feature + has been negotiated by driver, the device MUST issue + an interrupt if the device runs out of available descriptors on a virtqueue, even though interrupts are suppressed using the VRING_AVAIL_F_NO_INTERRUPT - flag or the field{used_event} field. An example of this is the + flag or the field{used_event} field. An example of a driver + using this feature is the legacy networking driver: it doesn't need to know every time a packet is transmitted, but it does need to free the transmitted packets a finite time after they are transmitted. It can avoid using a timer if the device interrupts it when all the packets are transmitted. +end{description} +Transitional devices MUST offer, and if offered by the device +traditional drivers MUST negotiate the following: +egin{description} item[VIRTIO_F_ANY_LAYOUT (27)] This feature indicates that the device accepts arbitrary descriptor layouts, as described in Section ef{sec:Basic Facilities of a Virtio Device / Virtqueues / Message Framing / Legacy Interface: Message Framing}~ ameref{sec:Basic Facilities of a Virtio Device / Virtqueues / Message Framing / Legacy Interface: Message Framing}. -- MST