[Date Prev] | [Thread Prev] | [Thread Next] | [Date Next] -- [Date Index] | [Thread Index] | [List Home]
Subject: Re: [PATCH] virtio-net: Add an optional device control over the receive buffers length
On Mon, Dec 30, 2019 at 01:59:17PM +0000, Vitaly Mireyno wrote: > This patch gives devices some level of control over the receive buffers length. > The driver declares the minimum receive buffer length, and the device requests max/min buffer length ratio. > This is a follow-up to the "[PATCH] virtio-net: Add equal-sized receive buffers feature" discussion: https://lists.oasis-open.org/archives/virtio-comment/201912/msg00007.html > > > Signed-off-by: Vitaly Mireyno <vmireyno@marvell.com> > --- > content.tex | 41 +++++++++++++++++++++++++++++++++++++++-- > 1 file changed, 39 insertions(+), 2 deletions(-) > > diff --git a/content.tex b/content.tex > index d68cfaf..0a4cfba 100644 > --- a/content.tex > +++ b/content.tex > @@ -2815,6 +2815,13 @@ \subsection{Feature bits}\label{sec:Device Types / Network Device / Feature bits > \item[VIRTIO_NET_F_CTRL_MAC_ADDR(23)] Set MAC address through control > channel. > > +\item[VIRTIO_NET_F_RXBUF_LEN_RATIO(57)] Device requests to limit the > + maximum/minimum receive buffers length ratio. > + So VIRTIO_NET_F_RXBUF_LEN_RATIO only makes sense with VIRTIO_NET_F_RXBUF_MIN_LEN, right? I think we can just use a single feature bit then, and just set ratio to 0 to mean "infinity". > +\item[VIRTIO_NET_F_RXBUF_MIN_LEN(58)] Device requests to know the minimum > + receive buffers length. Driver declares the minimum receive buffers > + length. > + > \item[VIRTIO_NET_F_GUEST_HDRLEN(59)] Driver can provide the exact \field{hdr_len} > value. Device benefits from knowing the exact header length. > > @@ -2861,8 +2868,8 @@ \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} > > -Three driver-read-only configuration fields are currently defined. The \field{mac} address field > -always exists (though is only valid if VIRTIO_NET_F_MAC is set), and > +The driver-read-only \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. > @@ -2882,12 +2889,22 @@ \subsection{Device configuration layout}\label{sec:Device Types / Network Device > VIRTIO_NET_F_MTU is set. This field specifies the maximum MTU for the driver to > use. > > +The device-read-only field \field{min_rx_buf_len} only exists if > +VIRTIO_NET_F_RXBUF_MIN_LEN is set. This field specifies the minimum receive > +buffers length. > + > +The driver-read-only field \field{rx_buf_len_ratio} only exists if > +VIRTIO_NET_F_RXBUF_LEN_RATIO is set. This field specifies the maximum/minimum receive > +buffers length ratio. Actually shouldn't all of these always exist and only be valid if a flag is set? I think existing text should be fixed too. > + > \begin{lstlisting} > struct virtio_net_config { > u8 mac[6]; > le16 status; > le16 max_virtqueue_pairs; > le16 mtu; > + le32 min_rx_buf_len; > + le16 rx_buf_len_ratio; > }; > \end{lstlisting} > > @@ -2916,6 +2933,15 @@ \subsection{Device configuration layout}\label{sec:Device Types / Network Device > If the driver negotiates the VIRTIO_NET_F_STANDBY feature, the device MAY act > as a standby device for a primary device with the same MAC address. > > +A driver SHOULD accept the VIRTIO_NET_F_RXBUF_MIN_LEN feature if offered. > + > +If VIRTIO_NET_F_RXBUF_MIN_LEN feature has been negotiated, the driver MUST > +set \field{min_rx_buf_len}. > + > +A driver MUST NOT modify \field{min_rx_buf_len} once it has been set. > + > +A driver SHOULD accept the VIRTIO_NET_F_RXBUF_LEN_RATIO feature if offered. > + > \drivernormative{\subsubsection}{Device configuration layout}{Device Types / Network Device / Device configuration layout} > > A driver SHOULD negotiate VIRTIO_NET_F_MAC if the device offers it. > @@ -3281,6 +3307,17 @@ \subsubsection{Setting Up Receive Buffers}\label{sec:Device Types / Network Devi > If VIRTIO_NET_F_MQ is negotiated, each of receiveq1\ldots receiveqN > that will be used SHOULD be populated with receive buffers. > > +If VIRTIO_NET_F_RXBUF_MIN_LEN feature has been negotiated, the driver > +MUST initialize all receive virtqueue descriptors \field{len} field with > +the value greater than or equal to the value configured in the > +\field{min_rx_buf_len} device configuration field, and allocate receive > +buffers accordingly. I think above should talk about buffer length, discussion about descriptors doesn't belong in devices, it's a way to describe buffers. If we want to limit descriptors per rx buffer, I think it's a separate feature similar to max_sg for blk/scsi. > +If VIRTIO_NET_F_RXBUF_LEN_RATIO feature has been negotiated, the driver > +MUST initialize all receive virtqueue descriptors \field{len} field with > +the value less than or equal to (\field{min_rx_buf_len} * \field{rx_buf_len_ratio}), > +and allocate receive buffers accordingly. > + > \devicenormative{\paragraph}{Setting Up Receive Buffers}{Device Types / Network Device / Device Operation / Setting Up Receive Buffers} > > The device MUST set \field{num_buffers} to the number of descriptors used to > --
[Date Prev] | [Thread Prev] | [Thread Next] | [Date Next] -- [Date Index] | [Thread Index] | [List Home]