drm/xen-front: Add support for Xen PV display frontend
Add support for Xen para-virtualized frontend display driver.
Accompanying backend [1] is implemented as a user-space application
and its helper library [2], capable of running as a Weston client
or DRM master.
Configuration of both backend and frontend is done via
Xen guest domain configuration options [3].
Driver limitations:
1. Only primary plane without additional properties is supported.
2. Only one video mode supported which resolution is configured
via XenStore.
3. All CRTCs operate at fixed frequency of 60Hz.
1. Implement Xen bus state machine for the frontend driver according to
the state diagram and recovery flow from display para-virtualized
protocol: xen/interface/io/displif.h.
2. Read configuration values from Xen store according
to xen/interface/io/displif.h protocol:
- read connector(s) configuration
- read buffer allocation mode (backend/frontend)
3. Handle Xen event channels:
- create for all configured connectors and publish
corresponding ring references and event channels in Xen store,
so backend can connect
- implement event channels interrupt handlers
- create and destroy event channels with respect to Xen bus state
4. Implement shared buffer handling according to the
para-virtualized display device protocol at xen/interface/io/displif.h:
- handle page directories according to displif protocol:
- allocate and share page directories
- grant references to the required set of pages for the
page directory
- allocate xen balllooned pages via Xen balloon driver
with alloc_xenballooned_pages/free_xenballooned_pages
- grant references to the required set of pages for the
shared buffer itself
- implement pages map/unmap for the buffers allocated by the
backend (gnttab_map_refs/gnttab_unmap_refs)
5. Implement kernel modesetiing/connector handling using
DRM simple KMS helper pipeline:
- implement KMS part of the driver with the help of DRM
simple pipepline helper which is possible due to the fact
that the para-virtualized driver only supports a single
(primary) plane:
- initialize connectors according to XenStore configuration
- handle frame done events from the backend
- create and destroy frame buffers and propagate those
to the backend
- propagate set/reset mode configuration to the backend on display
enable/disable callbacks
- send page flip request to the backend and implement logic for
reporting backend IO errors on prepare fb callback
- implement virtual connector handling:
- support only pixel formats suitable for single plane modes
- make sure the connector is always connected
- support a single video mode as per para-virtualized driver
configuration
6. Implement GEM handling depending on driver mode of operation:
depending on the requirements for the para-virtualized environment,
namely requirements dictated by the accompanying DRM/(v)GPU drivers
running in both host and guest environments, number of operating
modes of para-virtualized display driver are supported:
- display buffers can be allocated by either
frontend driver or backend
- display buffers can be allocated to be contiguous
in memory or not
Note! Frontend driver itself has no dependency on contiguous memory for
its operation.
6.1. Buffers allocated by the frontend driver.
The below modes of operation are configured at compile-time via
frontend driver's kernel configuration.
6.1.1. Front driver configured to use GEM CMA helpers
This use-case is useful when used with accompanying DRM/vGPU driver
in guest domain which was designed to only work with contiguous
buffers, e.g. DRM driver based on GEM CMA helpers: such drivers can
only import contiguous PRIME buffers, thus requiring frontend driver
to provide such. In order to implement this mode of operation
para-virtualized frontend driver can be configured to use
GEM CMA helpers.
6.1.2. Front driver doesn't use GEM CMA
If accompanying drivers can cope with non-contiguous memory then, to
lower pressure on CMA subsystem of the kernel, driver can allocate
buffers from system memory.
Note! If used with accompanying DRM/(v)GPU drivers this mode of operation
may require IOMMU support on the platform, so accompanying DRM/vGPU
hardware can still reach display buffer memory while importing PRIME
buffers from the frontend driver.
6.2. Buffers allocated by the backend
This mode of operation is run-time configured via guest domain
configuration through XenStore entries.
For systems which do not provide IOMMU support, but having specific
requirements for display buffers it is possible to allocate such buffers
at backend side and share those with the frontend.
For example, if host domain is 1:1 mapped and has DRM/GPU hardware
expecting physically contiguous memory, this allows implementing
zero-copying use-cases.
Note, while using this scenario the following should be considered:
a) If guest domain dies then pages/grants received from the backend
cannot be claimed back
b) Misbehaving guest may send too many requests to the
backend exhausting its grant references and memory
(consider this from security POV).
Note! Configuration options 1.1 (contiguous display buffers) and 2
(backend allocated buffers) are not supported at the same time.
7. Handle communication with the backend:
- send requests and wait for the responses according
to the displif protocol
- serialize access to the communication channel
- time-out used for backend communication is set to 3000 ms
- manage display buffers shared with the backend
[1] https://github.com/xen-troops/displ_be
[2] https://github.com/xen-troops/libxenbe
[3] https://xenbits.xen.org/gitweb/?p=xen.git;a=blob;f=docs/man/xl.cfg.pod.5.in;h=a699367779e2ae1212ff8f638eff0206ec1a1cc9;hb=refs/heads/master#l1257
Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20180403112317.28751-2-andr2000@gmail.com
2018-04-03 05:23:17 -06:00
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/* SPDX-License-Identifier: GPL-2.0 OR MIT */
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/*
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* Xen para-virtual DRM device
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*
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* Copyright (C) 2016-2018 EPAM Systems Inc.
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*
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* Author: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
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*/
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#ifndef __XEN_DRM_FRONT_H_
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#define __XEN_DRM_FRONT_H_
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#include <drm/drmP.h>
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#include <drm/drm_simple_kms_helper.h>
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#include <linux/scatterlist.h>
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#include "xen_drm_front_cfg.h"
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/**
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* DOC: Driver modes of operation in terms of display buffers used
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*
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* Depending on the requirements for the para-virtualized environment, namely
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* requirements dictated by the accompanying DRM/(v)GPU drivers running in both
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2018-04-17 01:40:12 -06:00
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* host and guest environments, display buffers can be allocated by either
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* frontend driver or backend.
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drm/xen-front: Add support for Xen PV display frontend
Add support for Xen para-virtualized frontend display driver.
Accompanying backend [1] is implemented as a user-space application
and its helper library [2], capable of running as a Weston client
or DRM master.
Configuration of both backend and frontend is done via
Xen guest domain configuration options [3].
Driver limitations:
1. Only primary plane without additional properties is supported.
2. Only one video mode supported which resolution is configured
via XenStore.
3. All CRTCs operate at fixed frequency of 60Hz.
1. Implement Xen bus state machine for the frontend driver according to
the state diagram and recovery flow from display para-virtualized
protocol: xen/interface/io/displif.h.
2. Read configuration values from Xen store according
to xen/interface/io/displif.h protocol:
- read connector(s) configuration
- read buffer allocation mode (backend/frontend)
3. Handle Xen event channels:
- create for all configured connectors and publish
corresponding ring references and event channels in Xen store,
so backend can connect
- implement event channels interrupt handlers
- create and destroy event channels with respect to Xen bus state
4. Implement shared buffer handling according to the
para-virtualized display device protocol at xen/interface/io/displif.h:
- handle page directories according to displif protocol:
- allocate and share page directories
- grant references to the required set of pages for the
page directory
- allocate xen balllooned pages via Xen balloon driver
with alloc_xenballooned_pages/free_xenballooned_pages
- grant references to the required set of pages for the
shared buffer itself
- implement pages map/unmap for the buffers allocated by the
backend (gnttab_map_refs/gnttab_unmap_refs)
5. Implement kernel modesetiing/connector handling using
DRM simple KMS helper pipeline:
- implement KMS part of the driver with the help of DRM
simple pipepline helper which is possible due to the fact
that the para-virtualized driver only supports a single
(primary) plane:
- initialize connectors according to XenStore configuration
- handle frame done events from the backend
- create and destroy frame buffers and propagate those
to the backend
- propagate set/reset mode configuration to the backend on display
enable/disable callbacks
- send page flip request to the backend and implement logic for
reporting backend IO errors on prepare fb callback
- implement virtual connector handling:
- support only pixel formats suitable for single plane modes
- make sure the connector is always connected
- support a single video mode as per para-virtualized driver
configuration
6. Implement GEM handling depending on driver mode of operation:
depending on the requirements for the para-virtualized environment,
namely requirements dictated by the accompanying DRM/(v)GPU drivers
running in both host and guest environments, number of operating
modes of para-virtualized display driver are supported:
- display buffers can be allocated by either
frontend driver or backend
- display buffers can be allocated to be contiguous
in memory or not
Note! Frontend driver itself has no dependency on contiguous memory for
its operation.
6.1. Buffers allocated by the frontend driver.
The below modes of operation are configured at compile-time via
frontend driver's kernel configuration.
6.1.1. Front driver configured to use GEM CMA helpers
This use-case is useful when used with accompanying DRM/vGPU driver
in guest domain which was designed to only work with contiguous
buffers, e.g. DRM driver based on GEM CMA helpers: such drivers can
only import contiguous PRIME buffers, thus requiring frontend driver
to provide such. In order to implement this mode of operation
para-virtualized frontend driver can be configured to use
GEM CMA helpers.
6.1.2. Front driver doesn't use GEM CMA
If accompanying drivers can cope with non-contiguous memory then, to
lower pressure on CMA subsystem of the kernel, driver can allocate
buffers from system memory.
Note! If used with accompanying DRM/(v)GPU drivers this mode of operation
may require IOMMU support on the platform, so accompanying DRM/vGPU
hardware can still reach display buffer memory while importing PRIME
buffers from the frontend driver.
6.2. Buffers allocated by the backend
This mode of operation is run-time configured via guest domain
configuration through XenStore entries.
For systems which do not provide IOMMU support, but having specific
requirements for display buffers it is possible to allocate such buffers
at backend side and share those with the frontend.
For example, if host domain is 1:1 mapped and has DRM/GPU hardware
expecting physically contiguous memory, this allows implementing
zero-copying use-cases.
Note, while using this scenario the following should be considered:
a) If guest domain dies then pages/grants received from the backend
cannot be claimed back
b) Misbehaving guest may send too many requests to the
backend exhausting its grant references and memory
(consider this from security POV).
Note! Configuration options 1.1 (contiguous display buffers) and 2
(backend allocated buffers) are not supported at the same time.
7. Handle communication with the backend:
- send requests and wait for the responses according
to the displif protocol
- serialize access to the communication channel
- time-out used for backend communication is set to 3000 ms
- manage display buffers shared with the backend
[1] https://github.com/xen-troops/displ_be
[2] https://github.com/xen-troops/libxenbe
[3] https://xenbits.xen.org/gitweb/?p=xen.git;a=blob;f=docs/man/xl.cfg.pod.5.in;h=a699367779e2ae1212ff8f638eff0206ec1a1cc9;hb=refs/heads/master#l1257
Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20180403112317.28751-2-andr2000@gmail.com
2018-04-03 05:23:17 -06:00
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*/
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/**
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* DOC: Buffers allocated by the frontend driver
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*
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2018-04-17 01:40:12 -06:00
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* In this mode of operation driver allocates buffers from system memory.
|
drm/xen-front: Add support for Xen PV display frontend
Add support for Xen para-virtualized frontend display driver.
Accompanying backend [1] is implemented as a user-space application
and its helper library [2], capable of running as a Weston client
or DRM master.
Configuration of both backend and frontend is done via
Xen guest domain configuration options [3].
Driver limitations:
1. Only primary plane without additional properties is supported.
2. Only one video mode supported which resolution is configured
via XenStore.
3. All CRTCs operate at fixed frequency of 60Hz.
1. Implement Xen bus state machine for the frontend driver according to
the state diagram and recovery flow from display para-virtualized
protocol: xen/interface/io/displif.h.
2. Read configuration values from Xen store according
to xen/interface/io/displif.h protocol:
- read connector(s) configuration
- read buffer allocation mode (backend/frontend)
3. Handle Xen event channels:
- create for all configured connectors and publish
corresponding ring references and event channels in Xen store,
so backend can connect
- implement event channels interrupt handlers
- create and destroy event channels with respect to Xen bus state
4. Implement shared buffer handling according to the
para-virtualized display device protocol at xen/interface/io/displif.h:
- handle page directories according to displif protocol:
- allocate and share page directories
- grant references to the required set of pages for the
page directory
- allocate xen balllooned pages via Xen balloon driver
with alloc_xenballooned_pages/free_xenballooned_pages
- grant references to the required set of pages for the
shared buffer itself
- implement pages map/unmap for the buffers allocated by the
backend (gnttab_map_refs/gnttab_unmap_refs)
5. Implement kernel modesetiing/connector handling using
DRM simple KMS helper pipeline:
- implement KMS part of the driver with the help of DRM
simple pipepline helper which is possible due to the fact
that the para-virtualized driver only supports a single
(primary) plane:
- initialize connectors according to XenStore configuration
- handle frame done events from the backend
- create and destroy frame buffers and propagate those
to the backend
- propagate set/reset mode configuration to the backend on display
enable/disable callbacks
- send page flip request to the backend and implement logic for
reporting backend IO errors on prepare fb callback
- implement virtual connector handling:
- support only pixel formats suitable for single plane modes
- make sure the connector is always connected
- support a single video mode as per para-virtualized driver
configuration
6. Implement GEM handling depending on driver mode of operation:
depending on the requirements for the para-virtualized environment,
namely requirements dictated by the accompanying DRM/(v)GPU drivers
running in both host and guest environments, number of operating
modes of para-virtualized display driver are supported:
- display buffers can be allocated by either
frontend driver or backend
- display buffers can be allocated to be contiguous
in memory or not
Note! Frontend driver itself has no dependency on contiguous memory for
its operation.
6.1. Buffers allocated by the frontend driver.
The below modes of operation are configured at compile-time via
frontend driver's kernel configuration.
6.1.1. Front driver configured to use GEM CMA helpers
This use-case is useful when used with accompanying DRM/vGPU driver
in guest domain which was designed to only work with contiguous
buffers, e.g. DRM driver based on GEM CMA helpers: such drivers can
only import contiguous PRIME buffers, thus requiring frontend driver
to provide such. In order to implement this mode of operation
para-virtualized frontend driver can be configured to use
GEM CMA helpers.
6.1.2. Front driver doesn't use GEM CMA
If accompanying drivers can cope with non-contiguous memory then, to
lower pressure on CMA subsystem of the kernel, driver can allocate
buffers from system memory.
Note! If used with accompanying DRM/(v)GPU drivers this mode of operation
may require IOMMU support on the platform, so accompanying DRM/vGPU
hardware can still reach display buffer memory while importing PRIME
buffers from the frontend driver.
6.2. Buffers allocated by the backend
This mode of operation is run-time configured via guest domain
configuration through XenStore entries.
For systems which do not provide IOMMU support, but having specific
requirements for display buffers it is possible to allocate such buffers
at backend side and share those with the frontend.
For example, if host domain is 1:1 mapped and has DRM/GPU hardware
expecting physically contiguous memory, this allows implementing
zero-copying use-cases.
Note, while using this scenario the following should be considered:
a) If guest domain dies then pages/grants received from the backend
cannot be claimed back
b) Misbehaving guest may send too many requests to the
backend exhausting its grant references and memory
(consider this from security POV).
Note! Configuration options 1.1 (contiguous display buffers) and 2
(backend allocated buffers) are not supported at the same time.
7. Handle communication with the backend:
- send requests and wait for the responses according
to the displif protocol
- serialize access to the communication channel
- time-out used for backend communication is set to 3000 ms
- manage display buffers shared with the backend
[1] https://github.com/xen-troops/displ_be
[2] https://github.com/xen-troops/libxenbe
[3] https://xenbits.xen.org/gitweb/?p=xen.git;a=blob;f=docs/man/xl.cfg.pod.5.in;h=a699367779e2ae1212ff8f638eff0206ec1a1cc9;hb=refs/heads/master#l1257
Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20180403112317.28751-2-andr2000@gmail.com
2018-04-03 05:23:17 -06:00
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*
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* Note! If used with accompanying DRM/(v)GPU drivers this mode of operation
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* may require IOMMU support on the platform, so accompanying DRM/vGPU
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* hardware can still reach display buffer memory while importing PRIME
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* buffers from the frontend driver.
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*/
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/**
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* DOC: Buffers allocated by the backend
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*
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* This mode of operation is run-time configured via guest domain configuration
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* through XenStore entries.
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*
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* For systems which do not provide IOMMU support, but having specific
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* requirements for display buffers it is possible to allocate such buffers
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* at backend side and share those with the frontend.
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* For example, if host domain is 1:1 mapped and has DRM/GPU hardware expecting
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* physically contiguous memory, this allows implementing zero-copying
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* use-cases.
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*
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* Note, while using this scenario the following should be considered:
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*
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* #. If guest domain dies then pages/grants received from the backend
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* cannot be claimed back
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*
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* #. Misbehaving guest may send too many requests to the
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* backend exhausting its grant references and memory
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* (consider this from security POV)
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*/
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/**
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* DOC: Driver limitations
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*
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* #. Only primary plane without additional properties is supported.
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*
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* #. Only one video mode per connector supported which is configured
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* via XenStore.
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*
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* #. All CRTCs operate at fixed frequency of 60Hz.
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*/
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/* timeout in ms to wait for backend to respond */
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#define XEN_DRM_FRONT_WAIT_BACK_MS 3000
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#ifndef GRANT_INVALID_REF
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/*
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* Note on usage of grant reference 0 as invalid grant reference:
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* grant reference 0 is valid, but never exposed to a PV driver,
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* because of the fact it is already in use/reserved by the PV console.
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*/
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#define GRANT_INVALID_REF 0
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#endif
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struct xen_drm_front_info {
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struct xenbus_device *xb_dev;
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struct xen_drm_front_drm_info *drm_info;
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/* to protect data between backend IO code and interrupt handler */
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spinlock_t io_lock;
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int num_evt_pairs;
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struct xen_drm_front_evtchnl_pair *evt_pairs;
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struct xen_drm_front_cfg cfg;
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/* display buffers */
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struct list_head dbuf_list;
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};
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struct xen_drm_front_drm_pipeline {
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struct xen_drm_front_drm_info *drm_info;
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int index;
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struct drm_simple_display_pipe pipe;
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struct drm_connector conn;
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/* These are only for connector mode checking */
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int width, height;
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struct drm_pending_vblank_event *pending_event;
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struct delayed_work pflip_to_worker;
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bool conn_connected;
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};
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struct xen_drm_front_drm_info {
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struct xen_drm_front_info *front_info;
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struct drm_device *drm_dev;
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struct xen_drm_front_drm_pipeline pipeline[XEN_DRM_FRONT_MAX_CRTCS];
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};
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static inline u64 xen_drm_front_fb_to_cookie(struct drm_framebuffer *fb)
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{
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2018-05-23 05:36:30 -06:00
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return (uintptr_t)fb;
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drm/xen-front: Add support for Xen PV display frontend
Add support for Xen para-virtualized frontend display driver.
Accompanying backend [1] is implemented as a user-space application
and its helper library [2], capable of running as a Weston client
or DRM master.
Configuration of both backend and frontend is done via
Xen guest domain configuration options [3].
Driver limitations:
1. Only primary plane without additional properties is supported.
2. Only one video mode supported which resolution is configured
via XenStore.
3. All CRTCs operate at fixed frequency of 60Hz.
1. Implement Xen bus state machine for the frontend driver according to
the state diagram and recovery flow from display para-virtualized
protocol: xen/interface/io/displif.h.
2. Read configuration values from Xen store according
to xen/interface/io/displif.h protocol:
- read connector(s) configuration
- read buffer allocation mode (backend/frontend)
3. Handle Xen event channels:
- create for all configured connectors and publish
corresponding ring references and event channels in Xen store,
so backend can connect
- implement event channels interrupt handlers
- create and destroy event channels with respect to Xen bus state
4. Implement shared buffer handling according to the
para-virtualized display device protocol at xen/interface/io/displif.h:
- handle page directories according to displif protocol:
- allocate and share page directories
- grant references to the required set of pages for the
page directory
- allocate xen balllooned pages via Xen balloon driver
with alloc_xenballooned_pages/free_xenballooned_pages
- grant references to the required set of pages for the
shared buffer itself
- implement pages map/unmap for the buffers allocated by the
backend (gnttab_map_refs/gnttab_unmap_refs)
5. Implement kernel modesetiing/connector handling using
DRM simple KMS helper pipeline:
- implement KMS part of the driver with the help of DRM
simple pipepline helper which is possible due to the fact
that the para-virtualized driver only supports a single
(primary) plane:
- initialize connectors according to XenStore configuration
- handle frame done events from the backend
- create and destroy frame buffers and propagate those
to the backend
- propagate set/reset mode configuration to the backend on display
enable/disable callbacks
- send page flip request to the backend and implement logic for
reporting backend IO errors on prepare fb callback
- implement virtual connector handling:
- support only pixel formats suitable for single plane modes
- make sure the connector is always connected
- support a single video mode as per para-virtualized driver
configuration
6. Implement GEM handling depending on driver mode of operation:
depending on the requirements for the para-virtualized environment,
namely requirements dictated by the accompanying DRM/(v)GPU drivers
running in both host and guest environments, number of operating
modes of para-virtualized display driver are supported:
- display buffers can be allocated by either
frontend driver or backend
- display buffers can be allocated to be contiguous
in memory or not
Note! Frontend driver itself has no dependency on contiguous memory for
its operation.
6.1. Buffers allocated by the frontend driver.
The below modes of operation are configured at compile-time via
frontend driver's kernel configuration.
6.1.1. Front driver configured to use GEM CMA helpers
This use-case is useful when used with accompanying DRM/vGPU driver
in guest domain which was designed to only work with contiguous
buffers, e.g. DRM driver based on GEM CMA helpers: such drivers can
only import contiguous PRIME buffers, thus requiring frontend driver
to provide such. In order to implement this mode of operation
para-virtualized frontend driver can be configured to use
GEM CMA helpers.
6.1.2. Front driver doesn't use GEM CMA
If accompanying drivers can cope with non-contiguous memory then, to
lower pressure on CMA subsystem of the kernel, driver can allocate
buffers from system memory.
Note! If used with accompanying DRM/(v)GPU drivers this mode of operation
may require IOMMU support on the platform, so accompanying DRM/vGPU
hardware can still reach display buffer memory while importing PRIME
buffers from the frontend driver.
6.2. Buffers allocated by the backend
This mode of operation is run-time configured via guest domain
configuration through XenStore entries.
For systems which do not provide IOMMU support, but having specific
requirements for display buffers it is possible to allocate such buffers
at backend side and share those with the frontend.
For example, if host domain is 1:1 mapped and has DRM/GPU hardware
expecting physically contiguous memory, this allows implementing
zero-copying use-cases.
Note, while using this scenario the following should be considered:
a) If guest domain dies then pages/grants received from the backend
cannot be claimed back
b) Misbehaving guest may send too many requests to the
backend exhausting its grant references and memory
(consider this from security POV).
Note! Configuration options 1.1 (contiguous display buffers) and 2
(backend allocated buffers) are not supported at the same time.
7. Handle communication with the backend:
- send requests and wait for the responses according
to the displif protocol
- serialize access to the communication channel
- time-out used for backend communication is set to 3000 ms
- manage display buffers shared with the backend
[1] https://github.com/xen-troops/displ_be
[2] https://github.com/xen-troops/libxenbe
[3] https://xenbits.xen.org/gitweb/?p=xen.git;a=blob;f=docs/man/xl.cfg.pod.5.in;h=a699367779e2ae1212ff8f638eff0206ec1a1cc9;hb=refs/heads/master#l1257
Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20180403112317.28751-2-andr2000@gmail.com
2018-04-03 05:23:17 -06:00
|
|
|
}
|
|
|
|
|
|
|
|
static inline u64 xen_drm_front_dbuf_to_cookie(struct drm_gem_object *gem_obj)
|
|
|
|
{
|
2018-05-23 05:36:30 -06:00
|
|
|
return (uintptr_t)gem_obj;
|
drm/xen-front: Add support for Xen PV display frontend
Add support for Xen para-virtualized frontend display driver.
Accompanying backend [1] is implemented as a user-space application
and its helper library [2], capable of running as a Weston client
or DRM master.
Configuration of both backend and frontend is done via
Xen guest domain configuration options [3].
Driver limitations:
1. Only primary plane without additional properties is supported.
2. Only one video mode supported which resolution is configured
via XenStore.
3. All CRTCs operate at fixed frequency of 60Hz.
1. Implement Xen bus state machine for the frontend driver according to
the state diagram and recovery flow from display para-virtualized
protocol: xen/interface/io/displif.h.
2. Read configuration values from Xen store according
to xen/interface/io/displif.h protocol:
- read connector(s) configuration
- read buffer allocation mode (backend/frontend)
3. Handle Xen event channels:
- create for all configured connectors and publish
corresponding ring references and event channels in Xen store,
so backend can connect
- implement event channels interrupt handlers
- create and destroy event channels with respect to Xen bus state
4. Implement shared buffer handling according to the
para-virtualized display device protocol at xen/interface/io/displif.h:
- handle page directories according to displif protocol:
- allocate and share page directories
- grant references to the required set of pages for the
page directory
- allocate xen balllooned pages via Xen balloon driver
with alloc_xenballooned_pages/free_xenballooned_pages
- grant references to the required set of pages for the
shared buffer itself
- implement pages map/unmap for the buffers allocated by the
backend (gnttab_map_refs/gnttab_unmap_refs)
5. Implement kernel modesetiing/connector handling using
DRM simple KMS helper pipeline:
- implement KMS part of the driver with the help of DRM
simple pipepline helper which is possible due to the fact
that the para-virtualized driver only supports a single
(primary) plane:
- initialize connectors according to XenStore configuration
- handle frame done events from the backend
- create and destroy frame buffers and propagate those
to the backend
- propagate set/reset mode configuration to the backend on display
enable/disable callbacks
- send page flip request to the backend and implement logic for
reporting backend IO errors on prepare fb callback
- implement virtual connector handling:
- support only pixel formats suitable for single plane modes
- make sure the connector is always connected
- support a single video mode as per para-virtualized driver
configuration
6. Implement GEM handling depending on driver mode of operation:
depending on the requirements for the para-virtualized environment,
namely requirements dictated by the accompanying DRM/(v)GPU drivers
running in both host and guest environments, number of operating
modes of para-virtualized display driver are supported:
- display buffers can be allocated by either
frontend driver or backend
- display buffers can be allocated to be contiguous
in memory or not
Note! Frontend driver itself has no dependency on contiguous memory for
its operation.
6.1. Buffers allocated by the frontend driver.
The below modes of operation are configured at compile-time via
frontend driver's kernel configuration.
6.1.1. Front driver configured to use GEM CMA helpers
This use-case is useful when used with accompanying DRM/vGPU driver
in guest domain which was designed to only work with contiguous
buffers, e.g. DRM driver based on GEM CMA helpers: such drivers can
only import contiguous PRIME buffers, thus requiring frontend driver
to provide such. In order to implement this mode of operation
para-virtualized frontend driver can be configured to use
GEM CMA helpers.
6.1.2. Front driver doesn't use GEM CMA
If accompanying drivers can cope with non-contiguous memory then, to
lower pressure on CMA subsystem of the kernel, driver can allocate
buffers from system memory.
Note! If used with accompanying DRM/(v)GPU drivers this mode of operation
may require IOMMU support on the platform, so accompanying DRM/vGPU
hardware can still reach display buffer memory while importing PRIME
buffers from the frontend driver.
6.2. Buffers allocated by the backend
This mode of operation is run-time configured via guest domain
configuration through XenStore entries.
For systems which do not provide IOMMU support, but having specific
requirements for display buffers it is possible to allocate such buffers
at backend side and share those with the frontend.
For example, if host domain is 1:1 mapped and has DRM/GPU hardware
expecting physically contiguous memory, this allows implementing
zero-copying use-cases.
Note, while using this scenario the following should be considered:
a) If guest domain dies then pages/grants received from the backend
cannot be claimed back
b) Misbehaving guest may send too many requests to the
backend exhausting its grant references and memory
(consider this from security POV).
Note! Configuration options 1.1 (contiguous display buffers) and 2
(backend allocated buffers) are not supported at the same time.
7. Handle communication with the backend:
- send requests and wait for the responses according
to the displif protocol
- serialize access to the communication channel
- time-out used for backend communication is set to 3000 ms
- manage display buffers shared with the backend
[1] https://github.com/xen-troops/displ_be
[2] https://github.com/xen-troops/libxenbe
[3] https://xenbits.xen.org/gitweb/?p=xen.git;a=blob;f=docs/man/xl.cfg.pod.5.in;h=a699367779e2ae1212ff8f638eff0206ec1a1cc9;hb=refs/heads/master#l1257
Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20180403112317.28751-2-andr2000@gmail.com
2018-04-03 05:23:17 -06:00
|
|
|
}
|
|
|
|
|
|
|
|
int xen_drm_front_mode_set(struct xen_drm_front_drm_pipeline *pipeline,
|
|
|
|
u32 x, u32 y, u32 width, u32 height,
|
|
|
|
u32 bpp, u64 fb_cookie);
|
|
|
|
|
2018-04-17 01:40:12 -06:00
|
|
|
int xen_drm_front_dbuf_create(struct xen_drm_front_info *front_info,
|
|
|
|
u64 dbuf_cookie, u32 width, u32 height,
|
|
|
|
u32 bpp, u64 size, struct page **pages);
|
drm/xen-front: Add support for Xen PV display frontend
Add support for Xen para-virtualized frontend display driver.
Accompanying backend [1] is implemented as a user-space application
and its helper library [2], capable of running as a Weston client
or DRM master.
Configuration of both backend and frontend is done via
Xen guest domain configuration options [3].
Driver limitations:
1. Only primary plane without additional properties is supported.
2. Only one video mode supported which resolution is configured
via XenStore.
3. All CRTCs operate at fixed frequency of 60Hz.
1. Implement Xen bus state machine for the frontend driver according to
the state diagram and recovery flow from display para-virtualized
protocol: xen/interface/io/displif.h.
2. Read configuration values from Xen store according
to xen/interface/io/displif.h protocol:
- read connector(s) configuration
- read buffer allocation mode (backend/frontend)
3. Handle Xen event channels:
- create for all configured connectors and publish
corresponding ring references and event channels in Xen store,
so backend can connect
- implement event channels interrupt handlers
- create and destroy event channels with respect to Xen bus state
4. Implement shared buffer handling according to the
para-virtualized display device protocol at xen/interface/io/displif.h:
- handle page directories according to displif protocol:
- allocate and share page directories
- grant references to the required set of pages for the
page directory
- allocate xen balllooned pages via Xen balloon driver
with alloc_xenballooned_pages/free_xenballooned_pages
- grant references to the required set of pages for the
shared buffer itself
- implement pages map/unmap for the buffers allocated by the
backend (gnttab_map_refs/gnttab_unmap_refs)
5. Implement kernel modesetiing/connector handling using
DRM simple KMS helper pipeline:
- implement KMS part of the driver with the help of DRM
simple pipepline helper which is possible due to the fact
that the para-virtualized driver only supports a single
(primary) plane:
- initialize connectors according to XenStore configuration
- handle frame done events from the backend
- create and destroy frame buffers and propagate those
to the backend
- propagate set/reset mode configuration to the backend on display
enable/disable callbacks
- send page flip request to the backend and implement logic for
reporting backend IO errors on prepare fb callback
- implement virtual connector handling:
- support only pixel formats suitable for single plane modes
- make sure the connector is always connected
- support a single video mode as per para-virtualized driver
configuration
6. Implement GEM handling depending on driver mode of operation:
depending on the requirements for the para-virtualized environment,
namely requirements dictated by the accompanying DRM/(v)GPU drivers
running in both host and guest environments, number of operating
modes of para-virtualized display driver are supported:
- display buffers can be allocated by either
frontend driver or backend
- display buffers can be allocated to be contiguous
in memory or not
Note! Frontend driver itself has no dependency on contiguous memory for
its operation.
6.1. Buffers allocated by the frontend driver.
The below modes of operation are configured at compile-time via
frontend driver's kernel configuration.
6.1.1. Front driver configured to use GEM CMA helpers
This use-case is useful when used with accompanying DRM/vGPU driver
in guest domain which was designed to only work with contiguous
buffers, e.g. DRM driver based on GEM CMA helpers: such drivers can
only import contiguous PRIME buffers, thus requiring frontend driver
to provide such. In order to implement this mode of operation
para-virtualized frontend driver can be configured to use
GEM CMA helpers.
6.1.2. Front driver doesn't use GEM CMA
If accompanying drivers can cope with non-contiguous memory then, to
lower pressure on CMA subsystem of the kernel, driver can allocate
buffers from system memory.
Note! If used with accompanying DRM/(v)GPU drivers this mode of operation
may require IOMMU support on the platform, so accompanying DRM/vGPU
hardware can still reach display buffer memory while importing PRIME
buffers from the frontend driver.
6.2. Buffers allocated by the backend
This mode of operation is run-time configured via guest domain
configuration through XenStore entries.
For systems which do not provide IOMMU support, but having specific
requirements for display buffers it is possible to allocate such buffers
at backend side and share those with the frontend.
For example, if host domain is 1:1 mapped and has DRM/GPU hardware
expecting physically contiguous memory, this allows implementing
zero-copying use-cases.
Note, while using this scenario the following should be considered:
a) If guest domain dies then pages/grants received from the backend
cannot be claimed back
b) Misbehaving guest may send too many requests to the
backend exhausting its grant references and memory
(consider this from security POV).
Note! Configuration options 1.1 (contiguous display buffers) and 2
(backend allocated buffers) are not supported at the same time.
7. Handle communication with the backend:
- send requests and wait for the responses according
to the displif protocol
- serialize access to the communication channel
- time-out used for backend communication is set to 3000 ms
- manage display buffers shared with the backend
[1] https://github.com/xen-troops/displ_be
[2] https://github.com/xen-troops/libxenbe
[3] https://xenbits.xen.org/gitweb/?p=xen.git;a=blob;f=docs/man/xl.cfg.pod.5.in;h=a699367779e2ae1212ff8f638eff0206ec1a1cc9;hb=refs/heads/master#l1257
Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20180403112317.28751-2-andr2000@gmail.com
2018-04-03 05:23:17 -06:00
|
|
|
|
|
|
|
int xen_drm_front_fb_attach(struct xen_drm_front_info *front_info,
|
|
|
|
u64 dbuf_cookie, u64 fb_cookie, u32 width,
|
|
|
|
u32 height, u32 pixel_format);
|
|
|
|
|
|
|
|
int xen_drm_front_fb_detach(struct xen_drm_front_info *front_info,
|
|
|
|
u64 fb_cookie);
|
|
|
|
|
|
|
|
int xen_drm_front_page_flip(struct xen_drm_front_info *front_info,
|
|
|
|
int conn_idx, u64 fb_cookie);
|
|
|
|
|
|
|
|
void xen_drm_front_on_frame_done(struct xen_drm_front_info *front_info,
|
|
|
|
int conn_idx, u64 fb_cookie);
|
|
|
|
|
|
|
|
#endif /* __XEN_DRM_FRONT_H_ */
|