I also did a full review of all callers, and only the xen driver
forgot to call drm_dev_put in the failure path. Fix that up too.
v2: I noticed that xen has a drm_driver.release hook, and uses
drm_dev_alloc(). We need to remove the kfree from
xen_drm_drv_release().
bochs also has a release hook, but leaked the drm_device ever since
commit 0a6659bdc5
Author: Gerd Hoffmann <kraxel@redhat.com>
Date: Tue Dec 17 18:04:46 2013 +0100
drm/bochs: new driver
This patch here fixes that leak.
Same for virtio, started leaking with
commit b1df3a2b24
Author: Gerd Hoffmann <kraxel@redhat.com>
Date: Tue Feb 11 14:58:04 2020 +0100
drm/virtio: add drm_driver.release callback.
Acked-by: Gerd Hoffmann <kraxel@redhat.com>
Acked-by: Thomas Zimmermann <tzimmermann@suse.de>
Acked-by: Sam Ravnborg <sam@ravnborg.org>
Reviewed-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
Cc: Gerd Hoffmann <kraxel@redhat.com>
Cc: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
Cc: xen-devel@lists.xenproject.org
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Maxime Ripard <mripard@kernel.org>
Cc: Thomas Zimmermann <tzimmermann@suse.de>
Cc: David Airlie <airlied@linux.ie>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
Cc: xen-devel@lists.xenproject.org
Link: https://patchwork.freedesktop.org/patch/msgid/20200323144950.3018436-5-daniel.vetter@ffwll.ch
The atomic helpers automatically send out fake VBLANK events if no
vblanking has been initialized. This would apply to xen, but xen has
its own vblank logic. To avoid interfering with the atomic helpers,
disable automatic vblank events explicitly.
v5:
* update comment
v4:
* separate commit from core vblank changes
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Acked-by: Gerd Hoffmann <kraxel@redhat.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Reviewed-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200129120531.6891-16-tzimmermann@suse.de
The current code is a pretty good wtf moment, since we drop the
reference before we use it. It's not a big deal, because a) we only
use the pointer, so doesn't blow up and the real reason b) fb->obj[0]
already holds a full reference for us.
Might as well take the real pointer ins't of complicated games that
baffle.
Reviewed-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Cc: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
Cc: xen-devel@lists.xenproject.org
Link: https://patchwork.freedesktop.org/patch/msgid/20191115092120.4445-7-daniel.vetter@ffwll.ch
Passing the wrong type feels icky, everywhere else we use the pipe as
the first parameter. Spotted while discussing patches with Thomas
Zimmermann.
v2: Make xen compile correctly
Acked-By: Thomas Zimmermann <tzimmermann@suse.de> (v1)
Cc: Thomas Zimmermann <tzimmermann@suse.de>
Cc: Noralf Trønnes <noralf@tronnes.org>
Cc: Gerd Hoffmann <kraxel@redhat.com>
Cc: Eric Anholt <eric@anholt.net>
Cc: Emil Velikov <emil.velikov@collabora.com>
Cc: virtualization@lists.linux-foundation.org
Cc: Linus Walleij <linus.walleij@linaro.org>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191023101256.20509-1-daniel.vetter@ffwll.ch
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Merge tag 'for-linus-5.4-rc3-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip
Pull xen fixes from Juergen Gross:
- correct panic handling when running as a Xen guest
- cleanup the Xen grant driver to remove printing a pointer being
always NULL
- remove a soon to be wrong call of of_dma_configure()
* tag 'for-linus-5.4-rc3-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip:
xen: Stop abusing DT of_dma_configure API
xen/grant-table: remove unnecessary printing
x86/xen: Return from panic notifier
As the removed comments say, these aren't DT based devices.
of_dma_configure() is going to stop allowing a NULL DT node and calling
it will no longer work.
The comment is also now out of date as of commit 9ab91e7c5c ("arm64:
default to the direct mapping in get_arch_dma_ops"). Direct mapping
is now the default rather than dma_dummy_ops.
According to Stefano and Oleksandr, the only other part needed is
setting the DMA masks and there's no reason to restrict the masks to
32-bits. So set the masks to 64 bits.
Cc: Robin Murphy <robin.murphy@arm.com>
Cc: Julien Grall <julien.grall@arm.com>
Cc: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
Cc: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: Stefano Stabellini <sstabellini@kernel.org>
Cc: Christoph Hellwig <hch@lst.de>
Cc: xen-devel@lists.xenproject.org
Signed-off-by: Rob Herring <robh@kernel.org>
Acked-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Static structure fb_funcs, of type drm_framebuffer_funcs, is used only
when it is passed to drm_gem_fb_create_with_funcs() as its last
argument. drm_gem_fb_create_with_funcs does not modify its lst argument
(fb_funcs) and hence fb_funcs is never modified. Therefore make fb_funcs
constant to protect it from further modification.
Issue found with Coccinelle.
Signed-off-by: Nishka Dasgupta <nishkadg.linux@gmail.com>
Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
Reviewed-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190813062712.24993-1-nishkadg.linux@gmail.com
They're the default.
Aside: Would be really nice to switch the others over to
drm_gem_object_funcs.
Reviewed-by: Eric Anholt <eric@anholt.net>
Reviewed-by: Emil Velikov <emil.velikov@collabora.com>
Reviewed-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Cc: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
Cc: xen-devel@lists.xenproject.org
Link: https://patchwork.freedesktop.org/patch/msgid/20190614203615.12639-39-daniel.vetter@ffwll.ch
Add SPDX license identifiers to all Make/Kconfig files which:
- Have no license information of any form
These files fall under the project license, GPL v2 only. The resulting SPDX
license identifier is:
GPL-2.0-only
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This makes it possible to use drm_dev_unplug() with the upcoming
devm_drm_dev_init() which will do drm_dev_put() in its release callback.
Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: Christian König <christian.koenig@amd.com>
Cc: David (ChunMing) Zhou <David1.Zhou@amd.com>
Cc: Dave Airlie <airlied@redhat.com>
Cc: Sean Paul <sean@poorly.run>
Cc: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Noralf Trønnes <noralf@tronnes.org>
Acked-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20190208140103.28919-3-noralf@tronnes.org
When GEM backing storage is allocated those are normal pages,
so there is no point using pgprot_writecombine while mmaping.
This fixes mismatch of buffer pages' memory attributes between
the frontend and backend which may cause screen artifacts.
Fixes: c575b7eeb8 ("drm/xen-front: Add support for Xen PV display frontend")
Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
Suggested-by: Julien Grall <julien.grall@arm.com>
Acked-by: Julien Grall <julien.grall@arm.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190129150422.19867-1-andr2000@gmail.com
There is no need to have the 'struct drm_framebuffer *fb' variable
static since new value always be assigned before use it.
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Reviewed-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
Link: https://patchwork.freedesktop.org/patch/msgid/1548504338-114487-1-git-send-email-yuehaibing@huawei.com
Having the probe helper stuff (which pretty much everyone needs) in
the drm_crtc_helper.h file (which atomic drivers should never need) is
confusing. Split them out.
To make sure I actually achieved the goal here I went through all
drivers. And indeed, all atomic drivers are now free of
drm_crtc_helper.h includes.
v2: Make it compile. There was so much compile fail on arm drivers
that I figured I'll better not include any of the acks on v1.
v3: Massive rebase because i915 has lost a lot of drmP.h includes, but
not all: Through drm_crtc_helper.h > drm_modeset_helper.h -> drmP.h
there was still one, which this patch largely removes. Which means
rolling out lots more includes all over.
This will also conflict with ongoing drmP.h cleanup by others I
expect.
v3: Rebase on top of atomic bochs.
v4: Review from Laurent for bridge/rcar/omap/shmob/core bits:
- (re)move some of the added includes, use the better include files in
other places (all suggested from Laurent adopted unchanged).
- sort alphabetically
v5: Actually try to sort them, and while at it, sort all the ones I
touch.
v6: Rebase onto i915 changes.
v7: Rebase once more.
Acked-by: Harry Wentland <harry.wentland@amd.com>
Acked-by: Sam Ravnborg <sam@ravnborg.org>
Cc: Sam Ravnborg <sam@ravnborg.org>
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Acked-by: Benjamin Gaignard <benjamin.gaignard@linaro.org>
Acked-by: Jani Nikula <jani.nikula@intel.com>
Acked-by: Neil Armstrong <narmstrong@baylibre.com>
Acked-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
Acked-by: CK Hu <ck.hu@mediatek.com>
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Acked-by: Sam Ravnborg <sam@ravnborg.org>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Liviu Dudau <liviu.dudau@arm.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Cc: linux-arm-kernel@lists.infradead.org
Cc: virtualization@lists.linux-foundation.org
Cc: etnaviv@lists.freedesktop.org
Cc: linux-samsung-soc@vger.kernel.org
Cc: intel-gfx@lists.freedesktop.org
Cc: linux-mediatek@lists.infradead.org
Cc: linux-amlogic@lists.infradead.org
Cc: linux-arm-msm@vger.kernel.org
Cc: freedreno@lists.freedesktop.org
Cc: nouveau@lists.freedesktop.org
Cc: spice-devel@lists.freedesktop.org
Cc: amd-gfx@lists.freedesktop.org
Cc: linux-renesas-soc@vger.kernel.org
Cc: linux-rockchip@lists.infradead.org
Cc: linux-stm32@st-md-mailman.stormreply.com
Cc: linux-tegra@vger.kernel.org
Cc: xen-devel@lists.xen.org
Link: https://patchwork.freedesktop.org/patch/msgid/20190117210334.13234-1-daniel.vetter@ffwll.ch
UAPI Changes:
Cross-subsystem Changes:
- Turn dma-buf fence sequence numbers into 64 bit numbers
Core Changes:
- Move to a common helper for the DP MST hotplug for radeon, i915 and
amdgpu
- i2c improvements for drm_dp_mst
- Removal of drm_syncobj_cb
- Introduction of an helper to create and attach the TV margin properties
Driver Changes:
- Improve cache flushes for v3d
- Reflection support for vc4
- HDMI overscan support for vc4
- Add implicit fencing support for rockchip and sun4i
- Switch to generic fbdev emulation for virtio
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Merge tag 'drm-misc-next-2019-01-07-1' of git://anongit.freedesktop.org/drm/drm-misc into drm-next
drm-misc-next for 5.1:
UAPI Changes:
Cross-subsystem Changes:
- Turn dma-buf fence sequence numbers into 64 bit numbers
Core Changes:
- Move to a common helper for the DP MST hotplug for radeon, i915 and
amdgpu
- i2c improvements for drm_dp_mst
- Removal of drm_syncobj_cb
- Introduction of an helper to create and attach the TV margin properties
Driver Changes:
- Improve cache flushes for v3d
- Reflection support for vc4
- HDMI overscan support for vc4
- Add implicit fencing support for rockchip and sun4i
- Switch to generic fbdev emulation for virtio
Signed-off-by: Dave Airlie <airlied@redhat.com>
[airlied: applied amdgpu merge fixup]
From: Maxime Ripard <maxime.ripard@bootlin.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190107180333.amklwycudbsub3s5@flea
Use page directory based shared buffer implementation
now available as common code for Xen frontend drivers.
Remove flushing of shared buffer on page flip as this
workaround needs a proper fix.
Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
Reviewed-by: Noralf Trønnes <noralf@tronnes.org>
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Dan Carpenter has reported that there is the following static checker
warning:
drivers/gpu/drm/drm_prime.c:317 drm_gem_map_dma_buf()
warn: 'sgt' can also be NULL
314 sgt = obj->dev->driver->gem_prime_get_sg_table(obj);
315
316 if (!IS_ERR(sgt)) {
317 if (!dma_map_sg_attrs(attach->dev, sgt->sgl, sgt->nents, dir,
Problematic functions are xen_drm_front_gem_get_sg_table and
drm_gem_cma_prime_get_sg_table. Fix those by replacing NULL with error value.
Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Dan Carpenter <dan.carpenter@oracle.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180719093713.3643-1-andr2000@gmail.com
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Merge tag 'drm-next-2018-06-06-1' of git://anongit.freedesktop.org/drm/drm
Pull drm updates from Dave Airlie:
"This starts to support NVIDIA volta hardware with nouveau, and adds
amdgpu support for the GPU in the Kabylake-G (the intel + radeon
single package chip), along with some initial Intel icelake enabling.
Summary:
New Drivers:
- v3d - driver for broadcom V3D V3.x+ hardware
- xen-front - XEN PV display frontend
core:
- handle zpos normalization in the core
- stop looking at legacy pointers in atomic paths
- improved scheduler documentation
- improved aspect ratio validation
- aspect ratio support for 64:27 and 256:135
- drop unused control node code.
i915:
- Icelake (ICL) enabling
- GuC/HuC refactoring
- PSR/PSR2 enabling and fixes
- DPLL management refactoring
- DP MST fixes
- NV12 enabling
- HDCP improvements
- GEM/Execlist/reset improvements
- GVT improvements
- stolen memory first 4k fix
amdgpu:
- Vega 20 support
- VEGAM support (Kabylake-G)
- preOS scanout buffer reservation
- power management gfxoff support for raven
- SR-IOV fixes
- Vega10 power profiles and clock voltage control
- scatter/gather display support on CZ/ST
amdkfd:
- GFX9 dGPU support
- userptr memory mapping
nouveau:
- major refactoring for Volta GV100 support
tda998x:
- HDMI i2c CEC support
etnaviv:
- removed unused logging code
- license text cleanups
- MMU handling improvements
- timeout fence fix for 50 days uptime
tegra:
- IOMMU support in gr2d/gr3d drivers
- zpos support
vc4:
- syncobj support
- CTM, plane alpha and async cursor support
analogix_dp:
- HPD and aux chan fixes
sun4i:
- MIPI DSI support
tilcdc:
- clock divider fixes for OMAP-l138 LCDK board
rcar-du:
- R8A77965 support
- dma-buf fences fixes
- hardware indexed crtc/du group handling
- generic zplane property support
atmel-hclcdc:
- generic zplane property support
mediatek:
- use generic video mode function
exynos:
- S5PV210 FIMD variant support
- IPP v2 framework
- more HW overlays support"
* tag 'drm-next-2018-06-06-1' of git://anongit.freedesktop.org/drm/drm: (1286 commits)
drm/amdgpu: fix 32-bit build warning
drm/exynos: fimc: signedness bug in fimc_setup_clocks()
drm/exynos: scaler: fix static checker warning
drm/amdgpu: Use dev_info() to report amdkfd is not supported for this ASIC
drm/amd/display: Remove use of division operator for long longs
drm/amdgpu: Update GFX info structure to match what vega20 used
drm/amdgpu/pp: remove duplicate assignment
drm/sched: add rcu_barrier after entity fini
drm/amdgpu: move VM BOs on LRU again
drm/amdgpu: consistenly use VM moved flag
drm/amdgpu: kmap PDs/PTs in amdgpu_vm_update_directories
drm/amdgpu: further optimize amdgpu_vm_handle_moved
drm/amdgpu: cleanup amdgpu_vm_validate_pt_bos v2
drm/amdgpu: rework VM state machine lock handling v2
drm/amdgpu: Add runtime VCN PG support
drm/amdgpu: Enable VCN static PG by default on RV
drm/amdgpu: Add VCN static PG support on RV
drm/amdgpu: Enable VCN CG by default on RV
drm/amdgpu: Add static CG control for VCN on RV
drm/exynos: Fix default value for zpos plane property
...
Building for a 32-bit target results in warnings from casting
between a 32-bit pointer and a 64-bit integer. Fix the warnings
by casting those pointers to uintptr_t first.
Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
Reviewed-by: Juergen Gross <jgross@suse.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180523113630.29811-1-andr2000@gmail.com
If the loop times out then we want to exit with "to" set to zero, but in
the current code it's set to -1.
Fixes: c575b7eeb8 ("drm/xen-front: Add support for Xen PV display frontend")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180508092829.GC661@mwanda
The xen_drm_front_shbuf_alloc() function was returning a mix of error
pointers and NULL and the the caller wasn't checking correctly. I've
changed it to always return error pointer consistently.
Fixes: c575b7eeb8 ("drm/xen-front: Add support for Xen PV display frontend")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180508092739.GB661@mwanda
It turns out this was only needed to paper over a bug in the CMA
helpers, which was addressed in
commit 998fb1a0f4
Author: Liviu Dudau <Liviu.Dudau@arm.com>
Date: Fri Nov 10 13:33:10 2017 +0000
drm: gem_cma_helper.c: Allow importing of contiguous scatterlists with nents > 1
Without this the following pipeline didn't work:
domU:
1. xen-front allocates a non-contig buffer
2. creates grants out of it
dom0:
3. converts the grants into a dma-buf. Since they're non-contig, the
scatter-list is huge.
4. imports it into rcar-du, which requires dma-contig memory for
scanout.
-> On this given platform there's an IOMMU, so in theory this should
work. But in practice this failed, because of the huge number of sg
entries, even though the IOMMU driver mapped it all into a dma-contig
range.
With a guest-contig buffer allocated in step 1, this problem doesn't
exist. But there's technically no reason to require guest-contig
memory for xen buffer sharing using grants.
Given all that, the xen-front cma support is not needed and should be
removed.
Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
Suggested-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20180417074012.21311-1-andr2000@gmail.com
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
