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Subject: Re: [virtio-dev] Re: [PATCH v11] virtio-net: support inner header hash
On Wed, Mar 22, 2023 at 08:49:40PM +0800, Heng Qi wrote:
>
>
> å 2023/3/21 äå11:58, Michael S. Tsirkin åé:
> > On Tue, Mar 21, 2023 at 10:49:39PM +0800, Heng Qi wrote:
> > >
> > > å 2023/3/21 äå3:34, Michael S. Tsirkin åé:
> > > > On Tue, Mar 21, 2023 at 11:56:14AM +0800, Heng Qi wrote:
> > > > > å 2023/3/21 äå3:43, Michael S. Tsirkin åé:
> > > > > > On Mon, Mar 20, 2023 at 07:18:40PM +0800, Heng Qi wrote:
> > > > > > > 1. Currently, a received encapsulated packet has an outer and an inner header, but
> > > > > > > the virtio device is unable to calculate the hash for the inner header. Multiple
> > > > > > > flows with the same outer header but different inner headers are steered to the
> > > > > > > same receive queue. This results in poor receive performance.
> > > > > > >
> > > > > > > To address this limitation, a new feature VIRTIO_NET_F_HASH_TUNNEL has been
> > > > > > > introduced, which enables the device to advertise the capability to calculate the
> > > > > > > hash for the inner packet header. Compared with the out header hash, it regains
> > > > > > > better receive performance.
> > > > > > So this would be a very good argument however the cost would be it would
> > > > > > seem we have to keep extending this indefinitely as new tunneling
> > > > > > protocols come to light.
> > > > > > But I believe in fact we don't at least for this argument:
> > > > > > the standard way to address this is actually by propagating entropy
> > > > > > from inner to outer header.
> > > > > Yes, we don't argue with this.
> > > > >
> > > > > > So I'd maybe reorder the commit log and give the explanation 2 below
> > > > > > then say "for some legacy systems
> > > > > > including entropy in IP header
> > > > > > as done in modern protocols is not practical, resulting in
> > > > > > bad performance under RSS".
> > > > > I agree. But not necessarily the legacy system, some scenarios need to
> > > > > connect multiple tunnels, for compatibility, they will not use optional
> > > > > fields or choose the old tunnel protocol.
> > > > compatibility ... with legacy systems, no?
> > > >
> > > > > > > 2. The same flow can traverse through different tunnels, resulting in the encapsulated
> > > > > > > packets being spread across multiple receive queues (refer to the figure below).
> > > > > > > However, in certain scenarios, it becomes necessary to direct these encapsulated
> > > > > > > packets of the same flow to a single receive queue. This facilitates the processing
> > > > > > > of the flow by the same CPU to improve performance (warm caches, less locking, etc.).
> > > > > > >
> > > > > > > client1 client2
> > > > > > > | |
> > > > > > > | +-------+ |
> > > > > > > +------->|tunnels|<--------+
> > > > > > > +-------+
> > > > > > > | |
> > > > > > > | |
> > > > > > > v v
> > > > > > > +-----------------+
> > > > > > > | processing host |
> > > > > > > +-----------------+
> > > > > > necessary is too strong a word I feel.
> > > > > > All this is, is an optimization, we don't really know how strong it is
> > > > > > even.
> > > > > >
> > > > > > Here's how I understand this:
> > > > > >
> > > > > > Imagine two clients client1 and client2 talking to each other.
> > > > > > A copy of all packets is sent to a processing host over a virtio device.
> > > > > > Two directions of the same flow between two clients might be
> > > > > > encapsulated in two different tunnels, with current RSS
> > > > > > strategies they would land on two arbitrary, unrelated queues.
> > > > > > As an optimization, some hosts might wish to make sure both directions
> > > > > > of the encapsulated flow land on the same queue.
> > > > > >
> > > > > >
> > > > > > Is this a good summary?
> > > > > I think yes.
> > > > >
> > > > > > Now that things begin to be clearer, I kind of begin to agree with
> > > > > > Jason's suggestion that this is extremely narrow. And what if I want
> > > > > > one direction on queue1 and another one queue2 e.g. adjacent numbers for
> > > > > I don't understand why we need this, can you point out some usage scenarios?
> > > > If traffic is predominantly UDP, each queue can be processed in
> > > > parallel. If you need to look at the other side of the flow once
> > > > in a while, you can find it by doing ^1.
> > > I'm not sure if I align with you, but I try to answer. When we try to place
> > > traffic in one direction on a certain queue,
> > > it means that we have calculated the hash, we can record the five-tuple
> > > information and the queue number. When
> > > the traffic in the other direction comes, we can match what we just recorded
> > > information and place it on the ^1 queue.
> > >
> > > > > > the same flow? If enough people agree this is needed we can accept this
> > > > > > but did you at all consider using something programmable like BPF for
> > > > > I think the problem is that our virtio device cannot support ebpf, we can
> > > > > also ask Alvaro, Parav if their virtio devices can support ebpf offloading.
> > > > > :)
> > > > This isn't ebpf, more like classic bpf. Just math done on packets,
> > > > no tables.
> > > We would also really like to use simple bpf offloading, which is cool. But
> > > it still takes time, for example to
> > > support parsing of bpf instructions etc. on devices like fpga, which they
> > > can't do easily now. Few devices
> > > are supported right now, I only see support for the netronome iNIC in the
> > > kernel.
> > >
> > > ÂÂ #git grep XDP_SETUP_PROG_HW
> > > ÂÂ drivers/net/ethernet/netronome/nfp/nfp_net_common.c:ÂÂÂ case
> > > XDP_SETUP_PROG_HW:
> > > ÂÂ drivers/net/netdevsim/bpf.c:ÂÂÂ if (bpf->command == XDP_SETUP_PROG_HW &&
> > > !ns->bpf_xdpoffload_accept) {
> > > ÂÂ drivers/net/netdevsim/bpf.c:ÂÂÂ if (bpf->command == XDP_SETUP_PROG_HW) {
> > > ÂÂ drivers/net/netdevsim/bpf.c:ÂÂÂ case XDP_SETUP_PROG_HW:
> > > ÂÂ include/linux/netdevice.h:ÂÂÂÂÂ XDP_SETUP_PROG_HW,
> > > ÂÂ net/core/dev.c: xdp.command = mode == XDP_MODE_HW ? XDP_SETUP_PROG_HW :
> > > XDP_SETUP_PROG;
> > >
> > >
> > > >
> > > > > > this? Considering we are putting not insignificant amount of work into
> > > > > > this, making this widely useful would be better than a narrow
> > > > > > optimization for a very specific usecase.
> > > > > >
> > > > > >
> > > > > > > To achieve this, the device can calculate a symmetric hash based on the inner packet
> > > > > > > headers of the flow. The symmetric hash disregards the order of the 5-tuple when
> > > > > > > computing the hash.
> > > > > > when you say symmetric hash you really mean symmetric key for toeplitz, yes?
> > > > > > It's not that it disregards order, it just gives the same result if
> > > > > > you reverse source and destination, no?
> > > > > Yes, symmetric hashes can use the key with 2 same bytes repeated, and only
> > > > > support reverse source and destination.
> > > > So, this won't work if some inner flows are IPv4 and others IPv6, right?
> > > > You have to know the inner flow format?
> > > Yes, we need.
> > Ouch, even more narrow.
>
> I may have misunderstood what you meant earlier. For the device, the IP
> families of the inner payloads of the same flow are the same.
Yes. But my point is this. Some flows can be IPv4 others IPv6.
Do you see a way to have a key that will result in a symmetrical hash
for both IPv4 and IPv6? Can you give an example please?
> The device can calculate a symmetrical hash so that the flow can be placed
> to the same queue.
>
> > Maybe we need support for XOR hash then?
>
> I think we can. This is orthogonal to the inner header hash, I can start
> work on XOR hashing in another follow-up thread if you want.
Hmm can or should?
> >
> >
> > > > > > > Reviewed-by: Jason Wang <jasowang@redhat.com>
> > > > > > > Signed-off-by: Heng Qi <hengqi@linux.alibaba.com>
> > > > > > > Reviewed-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
> > > > > > > ---
> > > > > > > v10->v11:
> > > > > > > 1. Revise commit log for clarity for readers.
> > > > > > > 2. Some modifications to avoid undefined terms. @Parav Pandit
> > > > > > > 3. Change VIRTIO_NET_F_HASH_TUNNEL dependency. @Parav Pandit
> > > > > > > 4. Add the normative statements. @Parav Pandit
> > > > > > >
> > > > > > > v9->v10:
> > > > > > > 1. Removed hash_report_tunnel related information. @Parav Pandit
> > > > > > > 2. Re-describe the limitations of QoS for tunneling.
> > > > > > > 3. Some clarification.
> > > > > > >
> > > > > > > v8->v9:
> > > > > > > 1. Merge hash_report_tunnel_types into hash_report. @Parav Pandit
> > > > > > > 2. Add tunnel security section. @Michael S . Tsirkin
> > > > > > > 3. Add VIRTIO_NET_F_HASH_REPORT_TUNNEL.
> > > > > > > 4. Fix some typos.
> > > > > > > 5. Add more tunnel types. @Michael S . Tsirkin
> > > > > > >
> > > > > > > v7->v8:
> > > > > > > 1. Add supported_hash_tunnel_types. @Jason Wang, @Parav Pandit
> > > > > > > 2. Change hash_report_tunnel to hash_report_tunnel_types. @Parav Pandit
> > > > > > > 3. Removed re-definition for inner packet hashing. @Parav Pandit
> > > > > > > 4. Fix some typos. @Michael S . Tsirkin
> > > > > > > 5. Clarify some sentences. @Michael S . Tsirkin
> > > > > > >
> > > > > > > v6->v7:
> > > > > > > 1. Modify the wording of some sentences for clarity. @Michael S. Tsirkin
> > > > > > > 2. Fix some syntax issues. @Michael S. Tsirkin
> > > > > > >
> > > > > > > v5->v6:
> > > > > > > 1. Fix some syntax and capitalization issues. @Michael S. Tsirkin
> > > > > > > 2. Use encapsulated/encaptulation uniformly. @Michael S. Tsirkin
> > > > > > > 3. Move the links to introduction section. @Michael S. Tsirkin
> > > > > > > 4. Clarify some sentences. @Michael S. Tsirkin
> > > > > > >
> > > > > > > v4->v5:
> > > > > > > 1. Clarify some paragraphs. @Cornelia Huck
> > > > > > > 2. Fix the u8 type. @Cornelia Huck
> > > > > > >
> > > > > > > v3->v4:
> > > > > > > 1. Rename VIRTIO_NET_F_HASH_GRE_VXLAN_GENEVE_INNER to VIRTIO_NET_F_HASH_TUNNEL. @Jason Wang
> > > > > > > 2. Make things clearer. @Jason Wang @Michael S. Tsirkin
> > > > > > > 3. Keep the possibility to use inner hash for automatic receive steering. @Jason Wang
> > > > > > > 4. Add the "Tunnel packet" paragraph to avoid repeating the GRE etc. many times. @Michael S. Tsirkin
> > > > > > >
> > > > > > > v2->v3:
> > > > > > > 1. Add a feature bit for GRE/VXLAN/GENEVE inner hash. @Jason Wang
> > > > > > > 2. Chang \field{hash_tunnel} to \field{hash_report_tunnel}. @Jason Wang, @Michael S. Tsirkin
> > > > > > >
> > > > > > > v1->v2:
> > > > > > > 1. Remove the patch for the bitmask fix. @Michael S. Tsirkin
> > > > > > > 2. Clarify some paragraphs. @Jason Wang
> > > > > > > 3. Add \field{hash_tunnel} and VIRTIO_NET_HASH_REPORT_GRE. @Yuri Benditovich
> > > > > > >
> > > > > > > device-types/net/description.tex | 119 +++++++++++++++++++++++-
> > > > > > > device-types/net/device-conformance.tex | 1 +
> > > > > > > device-types/net/driver-conformance.tex | 1 +
> > > > > > > introduction.tex | 24 +++++
> > > > > > > 4 files changed, 144 insertions(+), 1 deletion(-)
> > > > > > >
> > > > > > > diff --git a/device-types/net/description.tex b/device-types/net/description.tex
> > > > > > > index 0500bb6..49dee2f 100644
> > > > > > > --- a/device-types/net/description.tex
> > > > > > > +++ b/device-types/net/description.tex
> > > > > > > @@ -83,6 +83,9 @@ \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_HASH_TUNNEL(52)] Device supports inner packet header hash
> > > > > > > + for tunnel-encapsulated packets.
> > > > > > > +
> > > > > > > \item[VIRTIO_NET_F_NOTF_COAL(53)] Device supports notifications coalescing.
> > > > > > > \item[VIRTIO_NET_F_GUEST_USO4 (54)] Driver can receive USOv4 packets.
> > > > > > > @@ -139,6 +142,7 @@ \subsubsection{Feature bit requirements}\label{sec:Device Types / Network Device
> > > > > > > \item[VIRTIO_NET_F_NOTF_COAL] Requires VIRTIO_NET_F_CTRL_VQ.
> > > > > > > \item[VIRTIO_NET_F_RSC_EXT] Requires VIRTIO_NET_F_HOST_TSO4 or VIRTIO_NET_F_HOST_TSO6.
> > > > > > > \item[VIRTIO_NET_F_RSS] Requires VIRTIO_NET_F_CTRL_VQ.
> > > > > > > +\item[VIRTIO_NET_F_HASH_TUNNEL] Requires VIRTIO_NET_F_CTRL_VQ along with VIRTIO_NET_F_RSS and/or VIRTIO_NET_F_HASH_REPORT.
> > > > > > > \end{description}
> > > > > > > \subsubsection{Legacy Interface: Feature bits}\label{sec:Device Types / Network Device / Feature bits / Legacy Interface: Feature bits}
> > > > > > > @@ -198,6 +202,7 @@ \subsection{Device configuration layout}\label{sec:Device Types / Network Device
> > > > > > > u8 rss_max_key_size;
> > > > > > > le16 rss_max_indirection_table_length;
> > > > > > > le32 supported_hash_types;
> > > > > > > + le32 supported_tunnel_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.
> > > > > > > @@ -212,6 +217,12 @@ \subsection{Device configuration layout}\label{sec:Device Types / Network Device
> > > > > > > Field \field{supported_hash_types} contains the bitmask of supported hash types.
> > > > > > > See \ref{sec:Device Types / Network Device / Device Operation / Processing of Incoming Packets / Hash calculation for incoming packets / Supported/enabled hash types} for details of supported hash types.
> > > > > > > +The next field, \field{supported_tunnel_hash_types} only exists if the device
> > > > > > > +supports inner packet header hash, i.e. if VIRTIO_NET_F_HASH_TUNNEL is set.
> > > > > > > +
> > > > > > > +Field \field{supported_tunnel_hash_types} contains the bitmask of supported tunnel hash types.
> > > > > > > +See \ref{sec:Device Types / Network Device / Device Operation / Processing of Incoming Packets / Hash calculation for incoming packets / Supported/enabled tunnel hash types} for details of supported tunnel hash types.
> > > > > > > +
> > > > > > > \devicenormative{\subsubsection}{Device configuration layout}{Device Types / Network Device / Device configuration layout}
> > > > > > > The device MUST set \field{max_virtqueue_pairs} to between 1 and 0x8000 inclusive,
> > > > > > > @@ -848,6 +859,7 @@ \subsubsection{Processing of Incoming Packets}\label{sec:Device Types / Network
> > > > > > > If the feature VIRTIO_NET_F_RSS was negotiated:
> > > > > > > \begin{itemize}
> > > > > > > \item The device uses \field{hash_types} of the virtio_net_rss_config structure as 'Enabled hash types' bitmask.
> > > > > > > +\item The device uses \field{hash_tunnel_types} of the virtio_net_rss_config structure as 'Enabled hash tunnel types' bitmask if VIRTIO_NET_F_HASH_TUNNEL was negotiated.
> > > > > > > \item The device uses a key as defined in \field{hash_key_data} and \field{hash_key_length} of the virtio_net_rss_config structure (see
> > > > > > > \ref{sec:Device Types / Network Device / Device Operation / Control Virtqueue / Receive-side scaling (RSS) / Setting RSS parameters}).
> > > > > > > \end{itemize}
> > > > > > > @@ -855,6 +867,7 @@ \subsubsection{Processing of Incoming Packets}\label{sec:Device Types / Network
> > > > > > > If the feature VIRTIO_NET_F_RSS was not negotiated:
> > > > > > > \begin{itemize}
> > > > > > > \item The device uses \field{hash_types} of the virtio_net_hash_config structure as 'Enabled hash types' bitmask.
> > > > > > > +\item The device uses \field{hash_tunnel_types} of the virtio_net_hash_config structure as 'Enabled hash tunnel types' bitmask if VIRTIO_NET_F_HASH_TUNNEL was negotiated.
> > > > > > > \item The device uses a key as defined in \field{hash_key_data} and \field{hash_key_length} of the virtio_net_hash_config structure (see
> > > > > > > \ref{sec:Device Types / Network Device / Device Operation / Control Virtqueue / Automatic receive steering in multiqueue mode / Hash calculation}).
> > > > > > > \end{itemize}
> > > > > > > @@ -870,6 +883,8 @@ \subsubsection{Processing of Incoming Packets}\label{sec:Device Types / Network
> > > > > > > \subparagraph{Supported/enabled hash types}
> > > > > > > \label{sec:Device Types / Network Device / Device Operation / Processing of Incoming Packets / Hash calculation for incoming packets / Supported/enabled hash types}
> > > > > > > +This paragraph relies on definitions from \hyperref[intro:IP]{[IP]},
> > > > > > > +\hyperref[intro:UDP]{[UDP]} and \hyperref[intro:TCP]{[TCP]}.
> > > > > > > Hash types applicable for IPv4 packets:
> > > > > > > \begin{lstlisting}
> > > > > > > #define VIRTIO_NET_HASH_TYPE_IPv4 (1 << 0)
> > > > > > > @@ -980,6 +995,99 @@ \subsubsection{Processing of Incoming Packets}\label{sec:Device Types / Network
> > > > > > > (see \ref{sec:Device Types / Network Device / Device Operation / Processing of Incoming Packets / Hash calculation for incoming packets / IPv6 packets without extension header}).
> > > > > > > \end{itemize}
> > > > > > > +\paragraph{Inner Packet Header Hash}
> > > > > > > +If the driver negotiates the VIRTIO_NET_F_HASH_TUNNEL feature, it can configure the
> > > > > > > +hash parameters (including \field{hash_tunnel_types}) for inner packet header hash
> > > > > > > +through the VIRTIO_NET_CTRL_MQ_HASH_CONFIG or the VIRTIO_NET_CTRL_RSS_CONFIG command.
> > > > > > > +If multiple commands are sent, the device configuration will be defined by the last command received.
> > > > > > > +
> > > > > > > +If a specific encapsulation type is set in \field{hash_tunnel_types}, the device will calculate the
> > > > > > > +hash on the inner packet header of the encapsulated packet (See \ref{sec:Device Types
> > > > > > > +/ Network Device / Device OperatiHn / Processing of Incoming Packets /
> > > > > > > +Hash calculation for incoming packets / Tunnel/Encapsulated packet}). If the encapsulation
> > > > > > > +type is not included in \field{hash_tunnel_types} or the value of \field{hash_tunnel_types}
> > > > > > > +is VIRTIO_NET_HASH_TUNNEL_TYPE_NONE, the device calculates the hash on the outer header.
> > > > > > > +
> > > > > > > +\field{hash_tunnel_types} is set to VIRTIO_NET_HASH_TUNNEL_TYPE_NONE by the device for non-encapsulated packets.
> > > > > > > +
> > > > > > > +\subparagraph{Tunnel/Encapsulated packet}
> > > > > > > +\label{sec:Device Types / Network Device / Device Operation / Processing of Incoming Packets / Hash calculation for incoming packets / Tunnel/Encapsulated packet}
> > > > > > > +A tunnel packet is encapsulated from the original packet based on the tunneling
> > > > > > > +protocol (only a single level of encapsulation is currently supported). The
> > > > > > > +encapsulated packet contains an outer header and an inner header, and the device
> > > > > > > +calculates the hash over either the inner header or the outer header.
> > > > > > > +
> > > > > > > +When the feature VIRTIO_NET_F_HASH_TUNNEL is negotiated and a received encapsulated
> > > > > > > +packet's outer header matches one of the supported \field{hash_tunnel_types},
> > > > > > > +the hash of the inner header is calculated. Supported encapsulation types are listed
> > > > > > > +in \ref{sec:Device Types / Network Device / Device Operation / Processing of Incoming
> > > > > > > +Packets / Hash calculation for incoming packets / Supported/enabled hash tunnel types}.
> > > > > > > +
> > > > > > > +Some encapsulated packet types: \hyperref[intro:GRE]{[GRE]}, \hyperref[intro:VXLAN]{[VXLAN]},
> > > > > > > +\hyperref[intro:GENEVE]{[GENEVE]}, \hyperref[intro:IPIP]{[IPIP]} and \hyperref[intro:NVGRE]{[NVGRE]}.
> > > > > > > +
> > > > > > > +\subparagraph{Supported/enabled tunnel hash types}
> > > > > > > +\label{sec:Device Types / Network Device / Device Operation / Processing of Incoming Packets / Hash calculation for incoming packets / Supported/enabled tunnel hash types}
> > > > > > > +If the feature VIRTIO_NET_F_HASH_TUNNEL is negotiated and \field{hash_tunnel_types}
> > > > > > > +is set to VIRTIO_NET_HASH_TUNNEL_TYPE_NONE, the device calculates the hash using the
> > > > > > > +outer header of the encapsulated packet.
> > > > > > > +\begin{lstlisting}
> > > > > > > +#define VIRTIO_NET_HASH_TUNNEL_TYPE_NONE (1 << 0)
> > > > > > > +\end{lstlisting}
> > > > > > > +
> > > > > > > +The encapsulation hash type below indicates that the hash is calculated over the
> > > > > > > +inner packet header:
> > > > > > > +Hash type applicable for inner payload of the gre-encapsulated packet
> > > > > > > +\begin{lstlisting}
> > > > > > > +#define VIRTIO_NET_HASH_TUNNEL_TYPE_GRE (1 << 1)
> > > > > > > +\end{lstlisting}
> > > > > > > +Hash type applicable for inner payload of the vxlan-encapsulated packet
> > > > > > > +\begin{lstlisting}
> > > > > > > +#define VIRTIO_NET_HASH_TUNNEL_TYPE_VXLAN (1 << 2)
> > > > > > > +\end{lstlisting}
> > > > > > > +Hash type applicable for inner payload of the geneve-encapsulated packet
> > > > > > > +\begin{lstlisting}
> > > > > > > +#define VIRTIO_NET_HASH_TUNNEL_TYPE_GENEVE (1 << 3)
> > > > > > > +\end{lstlisting}
> > > > > > > +Hash type applicable for inner payload of the ip-encapsulated packet
> > > > > > > +\begin{lstlisting}
> > > > > > > +#define VIRTIO_NET_HASH_TUNNEL_TYPE_IPIP (1 << 4)
> > > > > > > +\end{lstlisting}
> > > > > > > +Hash type applicable for inner payload of the nvgre-encapsulated packet
> > > > > > > +\begin{lstlisting}
> > > > > > > +#define VIRTIO_NET_HASH_TUNNEL_TYPE_NVGRE (1 << 5)
> > > > > > > +\end{lstlisting}
> > > > > > > +
> > > > > > > +\subparagraph{Tunnel QoS limitation}
> > > > > > > +When a specific receive queue is shared by multiple tunnels to receive encapsulated packets,
> > > > > > > +there is no quality of service (QoS) for these packets. For example, when the packets of certain
> > > > > > > +tunnels are spread across multiple receive queues, these receive queues may have an unbalanced
> > > > > > > +amount of packets. This can cause a specific receive queue to become full, resulting in packet loss.
> > > > > > > +
> > > > > > > +Possible mitigations:
> > > > > > > +\begin{itemize}
> > > > > > > +\item Use a tool with good forwarding performance to keep the receive queue from filling up.
> > > > > > > +\item If the QoS is unavailable, the driver can set \field{hash_tunnel_types} to VIRTIO_NET_HASH_TUNNEL_TYPE_NONE
> > > > > > > + to disable inner packet hash for encapsulated packets.
> > > > > > > +\item Choose a hash key that can avoid queue collisions.
> > > > > > > +\item Perform appropriate QoS before packets consume the receive buffers of the receive queues.
> > > > > > > +\end{itemize}
> > > > > > > +
> > > > > > > +The limitations mentioned above exist with/without the inner packer header hash.
> > > > > > > +
> > > > > > > +\devicenormative{\subparagraph}{Inner Packet Header Hash}{Device Types / Network Device / Device Operation / Control Virtqueue / Inner Packet Header Hash}
> > > > > > > +
> > > > > > > +The device MUST calculate the outer packet hash if the received encapsulated packet has an encapsulation type not in \field{supported_tunnel_hash_types}.
> > > > > > > +
> > > > > > > +The device MUST drop the encapsulated packet if the destination receive queue is being reset.
> > > > > > I'm not sure how this last one got here. It seems to have nothing to do
> > > > > > with encapsulation - if we want to we should require this for all
> > > > > > packets or none at all.
> > > > > Yes, you are right. It works for all packets.
> > > > >
> > > > > > > +\drivernormative{\subparagraph}{Inner Packet Header Hash}{Device Types / Network Device / Device Operation / Control Virtqueue / Inner Packet Header Hash}
> > > > > > > +
> > > > > > > +If the driver does not negotiate the VIRTIO_NET_F_HASH_TUNNEL feature, it MUST set \field{hash_tunnel_types}
> > > > > > > +to VIRTIO_NET_HASH_TUNNEL_TYPE_NONE before issuing the command VIRTIO_NET_CTRL_MQ_HASH_CONFIG or VIRTIO_NET_CTRL_RSS_CONFIG.
> > > > > > > +
> > > > > > > +The driver MUST set \field{hash_tunnel_types} to the encapsulation types supported by the device.
> > > > > > unclear. seems to mean all types must be approved
> > > > > > where you really mean "only those types". original for non tunnel is:
> > > > > >
> > > > > > A driver MUST NOT set any VIRTIO_NET_HASH_TYPE_ flags that are not supported by a device.
> > > > > >
> > > > > > which is clear though a bit verbose with two negations.
> > > > > Yes, we can use the same sentence structure to illustrate.
> > > > >
> > > > > > Also here it says "supported" but below it says "allowed".
> > > > > >
> > > > > >
> > > > > >
> > > > > > > \paragraph{Hash reporting for incoming packets}
> > > > > > > \label{sec:Device Types / Network Device / Device Operation / Processing of Incoming Packets / Hash reporting for incoming packets}
> > > > > > > @@ -1392,12 +1500,17 @@ \subsubsection{Control Virtqueue}\label{sec:Device Types / Network Device / Devi
> > > > > > > le16 reserved[4];
> > > > > > > u8 hash_key_length;
> > > > > > > u8 hash_key_data[hash_key_length];
> > > > > > > + le32 hash_tunnel_types;
> > > > > > > };
> > > > > > Hmm this fixed type after variable type is problematic - might
> > > > > > become unaligned. We could use some of reserved[4]
> > > > > > for this ...
> > > > > >
> > > > > This is a problem, and perhaps Parav's proposal of using a separate command
> > > > > and structure for inner hash is correct.
> > > > >
> > > > > > > \end{lstlisting}
> > > > > > > Field \field{hash_types} contains a bitmask of allowed hash types as
> > > > > > > defined in
> > > > > > > \ref{sec:Device Types / Network Device / Device Operation / Processing of Incoming Packets / Hash calculation for incoming packets / Supported/enabled hash types}.
> > > > > > > -Initially the device has all hash types disabled and reports only VIRTIO_NET_HASH_REPORT_NONE.
> > > > > > > +
> > > > > > > +Field \field{hash_tunnel_types} contains a bitmask of allowed hash tunnel types as
> > > > > > > +defined in \ref{sec:Device Types / Network Device / Device Operation / Processing of Incoming Packets / Hash calculation for incoming packets / Supported/enabled hash tunnel types}.
> > > > > > > +
> > > > > > > +Initially the device has all hash types and hash tunnel types disabled and reports only VIRTIO_NET_HASH_REPORT_NONE.
> > > > > > > Field \field{reserved} MUST contain zeroes. It is defined to make the structure to match the layout of virtio_net_rss_config structure,
> > > > > > > defined in \ref{sec:Device Types / Network Device / Device Operation / Control Virtqueue / Receive-side scaling (RSS)}.
> > > > > > > @@ -1421,6 +1534,7 @@ \subsubsection{Control Virtqueue}\label{sec:Device Types / Network Device / Devi
> > > > > > > le16 max_tx_vq;
> > > > > > > u8 hash_key_length;
> > > > > > > u8 hash_key_data[hash_key_length];
> > > > > > > + le32 hash_tunnel_types;
> > > > > > Same alignment problem here but I'm not sure how to solve it.
> > > > > > Suggestions?
> > > > > >
> > > > > > > };
> > > > > > > \end{lstlisting}
> > > > > > > Field \field{hash_types} contains a bitmask of allowed hash types as
> > > > > > > @@ -1441,6 +1555,9 @@ \subsubsection{Control Virtqueue}\label{sec:Device Types / Network Device / Devi
> > > > > > > Fields \field{hash_key_length} and \field{hash_key_data} define the key to be used in hash calculation.
> > > > > > > +Field \field{hash_tunnel_types} contains a bitmask of allowed hash tunnel types as
> > > > > > > +defined in \ref{sec:Device Types / Network Device / Device Operation / Processing of Incoming Packets / Hash calculation for incoming packets / Supported/enabled hash tunnel types}.
> > > > > > > +
> > > > > > > \drivernormative{\subparagraph}{Setting RSS parameters}{Device Types / Network Device / Device Operation / Control Virtqueue / Receive-side scaling (RSS) }
> > > > > > > A driver MUST NOT send the VIRTIO_NET_CTRL_MQ_RSS_CONFIG command if the feature VIRTIO_NET_F_RSS has not been negotiated.
> > > > > > > diff --git a/device-types/net/device-conformance.tex b/device-types/net/device-conformance.tex
> > > > > > > index 54f6783..0ff5944 100644
> > > > > > > --- a/device-types/net/device-conformance.tex
> > > > > > > +++ b/device-types/net/device-conformance.tex
> > > > > > > @@ -14,4 +14,5 @@
> > > > > > > \item \ref{devicenormative:Device Types / Network Device / Device Operation / Control Virtqueue / Automatic receive steering in multiqueue mode}
> > > > > > > \item \ref{devicenormative:Device Types / Network Device / Device Operation / Control Virtqueue / Receive-side scaling (RSS) / RSS processing}
> > > > > > > \item \ref{devicenormative:Device Types / Network Device / Device Operation / Control Virtqueue / Notifications Coalescing}
> > > > > > > +\item \ref{devicenormative:Device Types / Network Device / Device Operation / Control Virtqueue / Inner Packet Header Hash}
> > > > > > > \end{itemize}
> > > > > > > diff --git a/device-types/net/driver-conformance.tex b/device-types/net/driver-conformance.tex
> > > > > > > index 97d0cc1..951be89 100644
> > > > > > > --- a/device-types/net/driver-conformance.tex
> > > > > > > +++ b/device-types/net/driver-conformance.tex
> > > > > > > @@ -14,4 +14,5 @@
> > > > > > > \item \ref{drivernormative:Device Types / Network Device / Device Operation / Control Virtqueue / Offloads State Configuration / Setting Offloads State}
> > > > > > > \item \ref{drivernormative:Device Types / Network Device / Device Operation / Control Virtqueue / Receive-side scaling (RSS) }
> > > > > > > \item \ref{drivernormative:Device Types / Network Device / Device Operation / Control Virtqueue / Notifications Coalescing}
> > > > > > > +\item \ref{drivernormative:Device Types / Network Device / Device Operation / Control Virtqueue / Inner Packet Header Hash}
> > > > > > > \end{itemize}
> > > > > > > diff --git a/introduction.tex b/introduction.tex
> > > > > > > index 287c5fc..25c9d48 100644
> > > > > > > --- a/introduction.tex
> > > > > > > +++ b/introduction.tex
> > > > > > > @@ -99,6 +99,30 @@ \section{Normative References}\label{sec:Normative References}
> > > > > > > Standards for Efficient Cryptography Group(SECG), ``SEC1: Elliptic Cureve Cryptography'', Version 1.0, September 2000.
> > > > > > > \newline\url{https://www.secg.org/sec1-v2.pdf}\\
> > > > > > > + \phantomsection\label{intro:GRE}\textbf{[GRE]} &
> > > > > > > + Generic Routing Encapsulation
> > > > > > > + \newline\url{https://datatracker.ietf.org/doc/rfc2784/}\\
> > > > > > This is GRE over IPv4.
> > > > > > So we are not supporting GRE over IPv6?
> > > > > Yes. Do we need to add it?
> > > > > https://datatracker.ietf.org/doc/rfc7676/
> > > > If you want to support it, yes.
> > > >
> > > > > > And we do not support optional keys?
> > > > > We did not disallow optional fields.
> > > > >
> > > > > Thanks.
> > > > The spec you link to does not include this.
> > > I'll add this. :)
> > >
> > > Thanks!
> > Question is how common it is to support all three.
> > Do I understand it correctly that currently your use-case
> > is mostly with GRE?
>
> Our main use-cases are GRE(https://datatracker.ietf.org/doc/rfc2784), VXLAN
> and GENEVE.
>
> GRE needs to spread across multiple queues using the inner header hash.
> VXLAN and GENEVE require inner symmetric hashing to allow the same CPU to
> process and improve performance.
>
> Thanks.
>
>
> > > > > >
> > > > > > > + \phantomsection\label{intro:VXLAN}\textbf{[VXLAN]} &
> > > > > > > + Virtual eXtensible Local Area Network
> > > > > > > + \newline\url{https://datatracker.ietf.org/doc/rfc7348/}\\
> > > > > > > + \phantomsection\label{intro:GENEVE}\textbf{[GENEVE]} &
> > > > > > > + Generic Network Virtualization Encapsulation
> > > > > > > + \phantomsection\label{intro:IPIP}\textbf{[IPIP]} &
> > > > > > > + IP Encapsulation within IP
> > > > > > > + \newline\url{https://www.rfc-editor.org/rfc/rfc2003}\\
> > > > > > > + \phantomsection\label{intro:IPIP}\textbf{[NVGRE]} &
> > > > > > > + NVGRE: Network Virtualization Using Generic Routing Encapsulation
> > > > > > > + \newline\url{https://www.rfc-editor.org/rfc/rfc7637.html}\\
> > > > > > > + \newline\url{https://datatracker.ietf.org/doc/rfc8926/}\\
> > > > > > > + \phantomsection\label{intro:IP}\textbf{[IP]} &
> > > > > > > + INTERNET PROTOCOL
> > > > > > > + \newline\url{https://www.rfc-editor.org/rfc/rfc791}\\
> > > > > > > + \phantomsection\label{intro:UDP}\textbf{[UDP]} &
> > > > > > > + User Datagram Protocol
> > > > > > > + \newline\url{https://www.rfc-editor.org/rfc/rfc768}\\
> > > > > > > + \phantomsection\label{intro:TCP}\textbf{[TCP]} &
> > > > > > > + TRANSMISSION CONTROL PROTOCOL
> > > > > > > + \newline\url{https://www.rfc-editor.org/rfc/rfc793}\\
> > > > > > > \end{longtable}
> > > > > > > \section{Non-Normative References}
> > > > > > > --
> > > > > > > 2.19.1.6.gb485710b
> > > > > > ---------------------------------------------------------------------
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