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Subject: Re: [virtio-comment] [PATCH v3] virtio-net: Add support for the flexible driver notification structure
On 2020/2/27 äå1:10, Michael S. Tsirkin wrote:
On Wed, Feb 26, 2020 at 02:54:36PM +0000, Vitaly Mireyno wrote:-----Original Message----- From: Jason Wang <jasowang@redhat.com> Sent: Wednesday, 26 February, 2020 5:13 To: Vitaly Mireyno <vmireyno@marvell.com>; virtio-comment@lists.oasis-open.org Cc: Michael S. Tsirkin <mst@redhat.com>; Ariel Elior <aelior@marvell.com> Subject: [EXT] Re: [virtio-comment] [PATCH v3] virtio-net: Add support for the flexible driver notification structure ---------------------------------------------------------------------- On 2020/2/26 äå12:30, Vitaly Mireyno wrote:Currently, the driver notification (available buffer notification) has a fixed structure. If VIRTIO_F_NOTIFICATION_DATA has been negotiated, it includes: vqn, next_off and next_wrap. If notify_off_multiplier > 0, the VQ number can be derived by the device from the Queue Notifyaddress, so vqn may be redundant.Some devices benefit from receiving an additional data with driver notifications. This data canoptionally replace the vqn field in the driver notification structure.In its simplest form, it would be sufficient for this data to be a per-device constant value. Changes from v2 - Defined a new feature flag instead of a PCI-specific flag. Signed-off-by: Vitaly Mireyno <vmireyno@marvell.com> --- content.tex | 34 ++++++++++++++++++++++++++++++++++ 1 file changed, 34 insertions(+) diff --git a/content.tex b/content.tex index b91a132..5223d5c 100644 --- a/content.tex +++ b/content.tex @@ -965,6 +965,8 @@ \subsubsection{Notification structure layout}\label{sec:Virtio TransportOptionsstruct virtio_pci_notify_cap { struct virtio_pci_cap cap; le32 notify_off_multiplier; /* Multiplier for queue_notify_off. */ + le16 notify_data; /* Data to be placed in the vqn field */ + le16 padding; /* Pad to a dword */ }; \end{lstlisting} @@ -984,6 +986,21 @@ \subsubsection{Notification structure layout}\label{sec:Virtio TransportOptionsthe same Queue Notify address for all queues. \end{note} +\field{notify_data} is the data that the driver will set in the +\field{vqn} field in the available buffer notification, if +VIRTIO_NET_F_NOTIF_EXTRA_DATA has been negotiated. + +\begin{note} +If \field{notify_off_multiplier} > 0, the virtqueue number can +potentially be derived by the device from the Queue Notify address, +so \field{vqn} may be redundant. Some devices benefit from receiving +the additional data with driver notifications. An example could be a +hardware device implementing multiple protocols (with virtio being +one of them), so extra notification data could serve as a notification type indication or a protocolindication.+Another example could be using shared hardware memory space for +driver notifications for multiple virtio devices in a trusted environment. +\end{note} + \devicenormative{\paragraph}{Notification capability}{Virtio Transport Options / Virtio Over PCI Bus/ PCI Device Layout / Notification capability}The device MUST present at least one notification capability. @@ -1020,6 +1037,10 @@ \subsubsection{Notification structure layout}\label{sec:Virtio TransportOptionscap.length >= queue_notify_off * notify_off_multiplier + 4 \end{lstlisting} +If VIRTIO_NET_F_NOTIF_EXTRA_DATA has been negotiated, the device MUST +set \field{notify_data} to a valid value, and SHOULD set +\field{notify_off_multiplier} > 0. + \subsubsection{ISR status capability}\label{sec:Virtio Transport Options / Virtio Over PCI Bus / PCI Device Layout / ISR status capability} The VIRTIO_PCI_CAP_ISR_CFG capability @@ -1519,6 +1540,14 @@ \subsubsection{Available Buffer Notifications}\label{sec:Virtio Transport Option See \ref{sec:Virtio Transport Options / Virtio Over PCI Bus / PCI Device Layout / Notificationcapability}for how to calculate the Queue Notify address. +\drivernormative{\paragraph}{Available Buffer Notifications}{Virtio +Transport Options / Virtio Over PCI Bus / PCI-specific Initialization +And Device Operation / Available Buffer Notifications} The driver SHOULD accept theVIRTIO_NET_F_NOTIF_EXTRA_DATA feature if it has been offered. I think we need use "MUST" here?Wouldnât it break the existing drivers then?I agree, we can't declare existing drivers non-conformant by fiat. Certainly not for a boutique feature like this.
I may miss something but I think device won't work correctly if this feature is not negotiated?
Thanks
Other looks good to me. Thanks+ +If VIRTIO_NET_F_NOTIF_EXTRA_DATA has been negotiated, the driver MUST +set the \field{vqn} field of the available buffer notification +structure to the \field{notify_data} value. + \subsubsection{Used Buffer Notifications}\label{sec:Virtio Transport Options / Virtio Over PCI Bus / PCI-specific Initialization And Device Operation / Used Buffer Notifications} If a used buffer notification is necessary for a virtqueue, the device would typically act as follows: @@ -2895,6 +2924,10 @@ \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_NOTIF_EXTRA_DATA(57)] Driver provides an extra data with + available buffer notifications, to aid in notification processing by the + device. + \item[VIRTIO_NET_F_GUEST_HDRLEN(59)] Driver can provide the exact \field{hdr_len} value. Device benefits from knowing the exact header length. @@ -2934,6 +2967,7 @@ \subsubsection{Feature bit requirements}\label{sec:Device Types /Network Device\item[VIRTIO_NET_F_CTRL_MAC_ADDR] Requires VIRTIO_NET_F_CTRL_VQ. \item[VIRTIO_NET_F_RSC_EXT] Requires VIRTIO_NET_F_HOST_TSO4 orVIRTIO_NET_F_HOST_TSO6.\item[VIRTIO_NET_F_RSS] Requires VIRTIO_NET_F_CTRL_VQ. +\item[VIRTIO_NET_F_NOTIF_EXTRA_DATA] Requires VIRTIO_F_NOTIFICATION_DATA. \end{description} \subsubsection{Legacy Interface: Feature bits}\label{sec:Device Types / Network Device / Feature bits / Legacy Interface: Feature bits} -- This publicly archived list offers a means to provide input to the OASIS Virtual I/O Device (VIRTIO) TC. In order to verify user consent to the Feedback License terms and to minimize spam in the list archive, subscription is required before posting. Subscribe: virtio-comment-subscribe@lists.oasis-open.org Unsubscribe: virtio-comment-unsubscribe@lists.oasis-open.org List help: virtio-comment-help@lists.oasis-open.org List archive: https://urldefense.proofpoint.com/v2/url?u=https-3A__lists.oasis-2Dope n.org_archives_virtio-2Dcomment_&d=DwIFaQ&c=nKjWec2b6R0mOyPaz7xtfQ&r=l DHJ2FW52oJ3lqqsArgFRdcevq01tbLQAw4A_NO7xgI&m=94BRvyqIARqVJ-yydsIqG25_z AUHjeENww-NxeMs_s8&s=fspKS4uA_CyM-S4HrR6GdJbvttjkX5iCygZvcybe_qs&e= Feedback License: https://urldefense.proofpoint.com/v2/url?u=https-3A__www.oasis-2Dopen. org_who_ipr_feedback-5Flicense.pdf&d=DwIFaQ&c=nKjWec2b6R0mOyPaz7xtfQ&r =lDHJ2FW52oJ3lqqsArgFRdcevq01tbLQAw4A_NO7xgI&m=94BRvyqIARqVJ-yydsIqG25 _zAUHjeENww-NxeMs_s8&s=sskV_Q0nV6odmu9tb3_QO4sJgxQQfA7SDNkDbhCPgZ0&e= List Guidelines: https://urldefense.proofpoint.com/v2/url?u=https-3A__www.oasis-2Dopen. org_policies-2Dguidelines_mailing-2Dlists&d=DwIFaQ&c=nKjWec2b6R0mOyPaz 7xtfQ&r=lDHJ2FW52oJ3lqqsArgFRdcevq01tbLQAw4A_NO7xgI&m=94BRvyqIARqVJ-yy dsIqG25_zAUHjeENww-NxeMs_s8&s=0FDuoPUSirLgEwBf7ATkyVMaalFeB6N0-vhpOnkB vWY&e= Committee: https://urldefense.proofpoint.com/v2/url?u=https-3A__www.oasis-2Dopen. org_committees_virtio_&d=DwIFaQ&c=nKjWec2b6R0mOyPaz7xtfQ&r=lDHJ2FW52oJ 3lqqsArgFRdcevq01tbLQAw4A_NO7xgI&m=94BRvyqIARqVJ-yydsIqG25_zAUHjeENww- NxeMs_s8&s=raC15yZMnr9y9Iv5_woorP7Bq2OQiO-uybPhgqzNtlE&e= Join OASIS: https://urldefense.proofpoint.com/v2/url?u=https-3A__www.oasis-2Dopen. org_join_&d=DwIFaQ&c=nKjWec2b6R0mOyPaz7xtfQ&r=lDHJ2FW52oJ3lqqsArgFRdce vq01tbLQAw4A_NO7xgI&m=94BRvyqIARqVJ-yydsIqG25_zAUHjeENww-NxeMs_s8&s=Gw VYWNwNZr7MFb5jJ7acLULJni1uMlwLgWBgiTSrp74&e=This publicly archived list offers a means to provide input to the OASIS Virtual I/O Device (VIRTIO) TC. In order to verify user consent to the Feedback License terms and to minimize spam in the list archive, subscription is required before posting. Subscribe: virtio-comment-subscribe@lists.oasis-open.org Unsubscribe: virtio-comment-unsubscribe@lists.oasis-open.org List help: virtio-comment-help@lists.oasis-open.org List archive: https://lists.oasis-open.org/archives/virtio-comment/ Feedback License: https://www.oasis-open.org/who/ipr/feedback_license.pdf List Guidelines: https://www.oasis-open.org/policies-guidelines/mailing-lists Committee: https://www.oasis-open.org/committees/virtio/ Join OASIS: https://www.oasis-open.org/join/
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