[virtio-comment] [PATCH v8 4/4] transport-pci: Introduce group legacy group member config region access

[Parav Pandit <parav@nvidia.com>]

This patch links how in a PCI transport a group owner can access group
member (PCI VFs) legacy registers using a legacy registers access
commands using administration virtqueue infrastructure.

Additionally it extend the PCI notification capability through which a
PCI VF device indicates to the driver which PCI BAR region to be used
for driver notifications.

Fixes: https://github.com/oasis-tcs/virtio-spec/issues/167
Signed-off-by: Parav Pandit <parav@nvidia.com>
---
changelog:
v7->v8:
- addressed comments from Michael
- made bar offset 64-bit
- prefix legacy specific structure with _legacy
- moved generic normative from pci to generic section
- added link to virtio pci capabilities when referring to bar 0
- remove 'should' from generic description
v6->v7:
- addressed comments from Michael
- removed driver normative about I/O BAR emulation as it does not
  make much sense for the spec
- removed references to administration virtqueue
- rewrote driver legacy region access without guest and hypervisor
  wording
- added normative for notification region
- added normative for PCI IDs for device which support legacy commands
v5->v6:
- aligned pci capability to 4B as required by PCI spec
- added text for the PCI capability for the group member device
v4->v5:
- split pci transport and generic command section to new patch
- removed multiple references to the VF
- written the description of the command as generic with member
  and group device terminology
- reflected many section names to remove VF
v3->v4:
- moved noted to the conformance section details in next patch
- removed queue notify address query AQ command on Michael's suggestion,
  though it is fine. Instead replaced with extending virtio_pci_notify_cap
  to indicate that legacy queue notifications can be done on the
  notification location.
- fixed spelling errors.
- replaced administrative virtqueue to administration virtqueue
- added queue notification capability register to indicate legacy q
  notification supported
v2->v3:
- adddressed Jason and Michael's comment to split single register
  access command to common config and device specific commands.
- dropped the suggetion to introduce enable/disable command as
  admin command cap bit already covers it.
v1->v2:
- addressed comments from Michael
- added theory of operation
- grammar corrections
- removed group fields description from individual commands as
  it is already present in generic section
- added endianness normative for legacy device registers region
- renamed the file to drop vf and add legacy prefix

- added overview in commit log
- renamed subsection to reflect command
---
 admin-cmds-legacy-interface.tex |  4 ++--
 conformance.tex                 |  1 +
 transport-pci-legacy-regs.tex   | 41 +++++++++++++++++++++++++++++++++
 transport-pci.tex               |  2 ++
 4 files changed, 46 insertions(+), 2 deletions(-)
 create mode 100644 transport-pci-legacy-regs.tex

diff --git a/admin-cmds-legacy-interface.tex b/admin-cmds-legacy-interface.tex
index 8036a0b..f5d7d08 100644
--- a/admin-cmds-legacy-interface.tex
+++ b/admin-cmds-legacy-interface.tex
@@ -149,11 +149,11 @@ \subsubsection{Legacy Interfaces}\label{sec:Basic Facilities of a Virtio Device
 };
 \end{lstlisting}
 
-The driver should pick the suitable entry when multiple entries are supplied
+The driver picks the suitable entry when multiple entries are supplied
 by the device.
 
 Refer to the specific transport section for the definition of the
-\field{region_data}.
+\field{region_data}. For PCI transport refer to section \ref{sec:Virtio Transport Options / Virtio Over PCI Bus / Legacy Interface: Group Member Device Configuration Region Access}.
 
 \devicenormative{\paragraph}{Legacy Interface}{Basic Facilities of a Virtio Device / Device groups / Group administration commands / Legacy Interface}
 
diff --git a/conformance.tex b/conformance.tex
index dc00e84..b3f2c92 100644
--- a/conformance.tex
+++ b/conformance.tex
@@ -267,6 +267,7 @@ \section{Conformance Targets}\label{sec:Conformance / Conformance Targets}
 \item Section \ref{sec:Virtio Transport Options / Virtio Over PCI Bus / PCI Device Layout / Legacy Interfaces: A Note on PCI Device Layout}
 \item Section \ref{sec:Virtio Transport Options / Virtio Over PCI Bus / PCI-specific Initialization And Device Operation / Device Initialization / Virtio Device Configuration Layout Detection / Legacy Interface: A Note on Device Layout Detection}
 \item Section \ref{sec:Virtio Transport Options / Virtio Over PCI Bus / PCI-specific Initialization And Device Operation / Device Initialization / Virtqueue Configuration / Legacy Interface: A Note on Virtqueue Configuration}
+\item Section \ref{devicenormative:Virtio Transport Options / Virtio Over PCI Bus / Legacy Interface: Group Member Device Configuration Region Access}
 \item Section \ref{sec:Virtio Transport Options / Virtio Over MMIO / Legacy interface}
 \item Section \ref{sec:Virtio Transport Options / Virtio over channel I/O / Device Initialization / Setting the Virtio Revision / Legacy Interfaces: A Note on Setting the Virtio Revision}
 \item Section \ref{sec:Virtio Transport Options / Virtio over channel I/O / Device Initialization / Configuring a Virtqueue / Legacy Interface: A Note on Configuring a Virtqueue}
diff --git a/transport-pci-legacy-regs.tex b/transport-pci-legacy-regs.tex
new file mode 100644
index 0000000..e4f70c9
--- /dev/null
+++ b/transport-pci-legacy-regs.tex
@@ -0,0 +1,41 @@
+\subsection{Legacy Interface: Group member device Configuration Region Access}\label{sec:Virtio Transport Options / Virtio Over PCI Bus / Legacy Interface: Group Member Device Configuration Region Access}
+
+The PCI owner device or the member device or both supports driver notifications using
+a notification region defined in the \field{struct virtio_pci_notify_region}.
+
+In \field{struct virtio_virtio_admin_cmd_legacy_notify_query_entry},
+\field{region_data} is defined as following:
+
+\begin{lstlisting}
+struct virtio_pci_legacy_notify_region {
+        u8 owner;  /* When set to 1, notification region is of the owner device */
+        u8 bar;    /* BAR of the member or owner device */
+        u8 padding[6];
+        le64 offset; /* Offset within bar. */
+};
+\end{lstlisting}
+
+The group owner device hardwire VF BAR0 in the SR-IOV Extended capability.
+
+The group member device does not use PCI BAR0 in various Virtio PCI capabilities
+listed in section \ref{sec:Virtio Transport Options / Virtio Over PCI Bus / Virtio Structure PCI Capabilities}.
+
+\devicenormative{\subsubsection}{Legacy Interface: Group Member Device Legacy Configuration Region Access}{Virtio Transport Options / Virtio Over PCI Bus / Legacy Interface: Group Member Device Configuration Region Access}
+
+When a PCI SR-IOV group owner device supports
+VIRTIO_ADMIN_CMD_LEGACY_COMMON_CFG_READ,
+VIRTIO_ADMIN_CMD_LEGACY_COMMON_CFG_WRITE, VIRTIO_ADMIN_CMD_LEGACY_DEV_CFG_READ,
+VIRTIO_ADMIN_CMD_LEGACY_DEV_CFG_WRITE commands, the group owner device MUST
+hardwire VF BAR0 in the SR-IOV Extended capability and the group member device
+MUST NOT use BAR0 in any of the Virtio Structure PCI Capabilities.
+
+The group owner device or the group member device or both MAY support driver
+notifications region.
+
+For the SR-IOV group type, the owner device supporting
+VIRTIO_ADMIN_CMD_LEGACY_COMMON_CFG_READ,
+VIRTIO_ADMIN_CMD_LEGACY_COMMON_CFG_WRITE, VIRTIO_ADMIN_CMD_LEGACY_DEV_CFG_READ,
+VIRTIO_ADMIN_CMD_LEGACY_DEV_CFG_WRITE and VIRTIO_ADMIN_CMD_LEGACY_NOTIFY_QUERY
+commands and its member device SHOULD follow the rules for the PCI Device ID,
+Revision ID and Subsystem Device ID of the non-transitional devices documented in
+section \ref{sec:Virtio Transport Options / Virtio Over PCI Bus / PCI Device Discovery}.
diff --git a/transport-pci.tex b/transport-pci.tex
index a5c6719..72c78f6 100644
--- a/transport-pci.tex
+++ b/transport-pci.tex
@@ -1212,3 +1212,5 @@ \subsubsection{Driver Handling Interrupts}\label{sec:Virtio Transport Options /
         re-examine the configuration space to see what changed.
     \end{itemize}
 \end{itemize}
+
+\input{transport-pci-legacy-regs.tex}
-- 
2.26.2


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