[RFC PATCH v3 0/2] Cross-device resource sharing

[RFC PATCH v3 0/2] Cross-device resource sharing

[David Stevens]

Hi all,

This is the next iteration of patches for adding support for sharing
resources between different virtio devices. In addition to these
patches, the most recent virtio-video patchset includes a patch for
importing objects into that device [1].

[1] https://markmail.org/message/wxdne5re7aaugbjg

Changes v2 -> v3:
* Replace references to guest/host
* Remove unnecessary paragraph and field in exported object section
* Recommend RFC4122 version 4 UUIDs
* Represent UUID as u8[16] instead of le64 pair

David Stevens (2):
  content: define what an exported object is
  virtio-gpu: add the ability to export resources

 content.tex      | 12 ++++++++++++
 introduction.tex |  4 ++++
 virtio-gpu.tex   | 29 +++++++++++++++++++++++++++++
 3 files changed, 45 insertions(+)

-- 
2.25.0.341.g760bfbb309-goog

[RFC PATCH v3 1/2] content: define what an exported object is

[David Stevens]

Define a mechanism for sharing objects between different virtio
devices.

Signed-off-by: David Stevens <stevensd@chromium.org>
---
 content.tex      | 12 ++++++++++++
 introduction.tex |  4 ++++
 2 files changed, 16 insertions(+)

diff --git a/content.tex b/content.tex
index b1ea9b9..ad3723c 100644
--- a/content.tex
+++ b/content.tex
@@ -373,6 +373,18 @@ \section{Driver Notifications} \label{sec:Virtqueues / Driver notifications}
 
 \input{shared-mem.tex}
 
+\section{Exporting Objects}\label{sec:Basic Facilities of a Virtio Device / Exporting Objects}
+
+When an object created by one virtio device needs to be
+shared with a seperate virtio device, the first device can
+export the object by generating a UUID which can then
+be passed to the second device to identify the object.
+
+What constitutes an object, how to export objects, and
+how to import objects are defined by the individual device
+types. It is RECOMMENDED that devices generate version 4
+UUIDs as specified by \hyperref[intro:rfc4122]{[RFC4122]}.
+
 \chapter{General Initialization And Device Operation}\label{sec:General Initialization And Device Operation}
 
 We start with an overview of device initialization, then expand on the
diff --git a/introduction.tex b/introduction.tex
index 40f16f8..fc2aa50 100644
--- a/introduction.tex
+++ b/introduction.tex
@@ -40,6 +40,10 @@ \section{Normative References}\label{sec:Normative References}
 	\phantomsection\label{intro:rfc2119}\textbf{[RFC2119]} &
 Bradner S., ``Key words for use in RFCs to Indicate Requirement
 Levels'', BCP 14, RFC 2119, March 1997. \newline\url{http://www.ietf.org/rfc/rfc2119.txt}\\
+	\phantomsection\label{intro:rfc4122}\textbf{[RFC4122]} &
+Leach, P., Mealling, M., and R. Salz, ``A Universally Unique
+IDentifier (UUID) URN Namespace'', RFC 4122, DOI 10.17487/RFC4122,
+July 2005. \newline\url{http://www.ietf.org/rfc/rfc4122.txt}\\
 	\phantomsection\label{intro:S390 PoP}\textbf{[S390 PoP]} & z/Architecture Principles of Operation, IBM Publication SA22-7832, \newline\url{http://publibfi.boulder.ibm.com/epubs/pdf/dz9zr009.pdf}, and any future revisions\\
 	\phantomsection\label{intro:S390 Common I/O}\textbf{[S390 Common I/O]} & ESA/390 Common I/O-Device and Self-Description, IBM Publication SA22-7204, \newline\url{http://publibfp.dhe.ibm.com/cgi-bin/bookmgr/BOOKS/dz9ar501/CCONTENTS}, and any future revisions\\
 	\phantomsection\label{intro:PCI}\textbf{[PCI]} &
-- 
2.25.0.341.g760bfbb309-goog

[RFC PATCH v3 2/2] virtio-gpu: add the ability to export resources

[David Stevens]

Signed-off-by: David Stevens <stevensd@chromium.org>
---
 virtio-gpu.tex | 29 +++++++++++++++++++++++++++++
 1 file changed, 29 insertions(+)

diff --git a/virtio-gpu.tex b/virtio-gpu.tex
index af4ca61..e950ad3 100644
--- a/virtio-gpu.tex
+++ b/virtio-gpu.tex
@@ -186,12 +186,16 @@ \subsubsection{Device Operation: Request header}\label{sec:Device Types / GPU De
         VIRTIO_GPU_CMD_UPDATE_CURSOR = 0x0300,
         VIRTIO_GPU_CMD_MOVE_CURSOR,
 
+        /* misc commands */
+        VIRTIO_GPU_CMD_RESOURCE_ASSIGN_UUID = 0x0400,
+
         /* success responses */
         VIRTIO_GPU_RESP_OK_NODATA = 0x1100,
         VIRTIO_GPU_RESP_OK_DISPLAY_INFO,
         VIRTIO_GPU_RESP_OK_CAPSET_INFO,
         VIRTIO_GPU_RESP_OK_CAPSET,
         VIRTIO_GPU_RESP_OK_EDID,
+        VIRTIO_GPU_RESP_OK_RESOURCE_ASSIGN_UUID,
 
         /* error responses */
         VIRTIO_GPU_RESP_ERR_UNSPEC = 0x1200,
@@ -454,6 +458,31 @@ \subsubsection{Device Operation: controlq}\label{sec:Device Types / GPU Device /
 This detaches any backing pages from a resource, to be used in case of
 guest swapping or object destruction.
 
+\item[VIRTIO_GPU_CMD_RESOURCE_ASSIGN_UUID] Creates an exported object from
+  a resource. Request data is \field{struct
+    virtio_gpu_resource_assign_uuid}.  Response type is
+  VIRTIO_GPU_RESP_OK_RESOURCE_ASSIGN_UUID, response data is \field{struct
+    virtio_gpu_resp_resource_assign_uuid}.
+
+\begin{lstlisting}
+struct virtio_gpu_resource_assign_uuid {
+        struct virtio_gpu_ctrl_hdr hdr;
+        le32 resource_id;
+        le32 padding;
+};
+
+struct virtio_gpu_resp_resource_assign_uuid {
+        struct virtio_gpu_ctrl_hdr hdr;
+        u8 uuid[16];
+};
+\end{lstlisting}
+
+The response contains a UUID which identifies the exported object created from
+the host private resource. Note that if the resource has an attached backing,
+modifications made to the host private resource through the exported object by
+other devices are not visible in the attached backing until they are transferred
+into the backing.
+
 \end{description}
 
 \subsubsection{Device Operation: cursorq}\label{sec:Device Types / GPU Device / Device Operation / Device Operation: cursorq}
-- 
2.25.0.341.g760bfbb309-goog

Re: [RFC PATCH v3 2/2] virtio-gpu: add the ability to export resources

[Gerd Hoffmann]

On Fri, Feb 07, 2020 at 04:40:33PM +0900, David Stevens wrote:
> Signed-off-by: David Stevens <stevensd@chromium.org>
> ---
>  virtio-gpu.tex | 29 +++++++++++++++++++++++++++++
>  1 file changed, 29 insertions(+)
> 
> diff --git a/virtio-gpu.tex b/virtio-gpu.tex
> index af4ca61..e950ad3 100644
> --- a/virtio-gpu.tex
> +++ b/virtio-gpu.tex
> @@ -186,12 +186,16 @@ \subsubsection{Device Operation: Request header}\label{sec:Device Types / GPU De
>          VIRTIO_GPU_CMD_UPDATE_CURSOR = 0x0300,
>          VIRTIO_GPU_CMD_MOVE_CURSOR,
>  
> +        /* misc commands */
> +        VIRTIO_GPU_CMD_RESOURCE_ASSIGN_UUID = 0x0400,

I'd suggest to move that to the "2d commands" section (which isn't
really "2d" but more "not 3d").

We also need a feature flag signaling support for the new command.

Otherwise this looks ok to me.

Are there any patches and/or attempts to merge/discuss upstream?
Specifically for handling the uuids for dma-bufs in linux (guest side)?
I suspect there will be some discussions on this and having at least
some plan upstream can agree on would be good.

cheers,
  Gerd