On Tue, Feb 15, 2022 at 5:56 PM Akihiko Odaki <akihiko.odaki@gmail.com
<mailto:akihiko.odaki@gmail.com>> wrote:
On Tue, Feb 15, 2022 at 10:32 PM Marc-André Lureau
<marcandre.lureau@gmail.com <mailto:marcandre.lureau@gmail.com>> wrote:
>
> Hi
>
> On Tue, Feb 15, 2022 at 7:09 AM Akihiko Odaki
<akihiko.odaki@gmail.com <mailto:akihiko.odaki@gmail.com>> wrote:
>>
>>
>>
>> On 2022/02/15 4:49, Marc-André Lureau wrote:
>> > Hi
>> >
>> > On Mon, Feb 14, 2022 at 5:15 PM Akihiko Odaki
<akihiko.odaki@gmail.com <mailto:akihiko.odaki@gmail.com>
>> > <mailto:akihiko.odaki@gmail.com
<mailto:akihiko.odaki@gmail.com>>> wrote:
>> >
>> > On Mon, Feb 14, 2022 at 9:07 PM Marc-André Lureau
>> > <marcandre.lureau@gmail.com
<mailto:marcandre.lureau@gmail.com>
<mailto:marcandre.lureau@gmail.com
<mailto:marcandre.lureau@gmail.com>>> wrote:
>> > >
>> > > Hi Akihiko
>> > >
>> > > On Sun, Feb 13, 2022 at 6:44 AM Akihiko Odaki
>> > <akihiko.odaki@gmail.com <mailto:akihiko.odaki@gmail.com>
<mailto:akihiko.odaki@gmail.com <mailto:akihiko.odaki@gmail.com>>>
wrote:
>> > >>
>> > >> ui/dbus required to have multiple DisplayChangeListeners
>> > (possibly with OpenGL)
>> > >> for a console but that caused several problems:
>> > >> - It broke egl-headless, an unusual display which
implements
>> > OpenGL rendering
>> > >> for non-OpenGL displays. The code to support multiple
>> > DisplayChangeListeners
>> > >> does not consider the case where non-OpenGL displays
listens
>> > OpenGL consoles.
>> > >
>> > >
>> > > Can you provide instructions on what broke? Even better
write a
>> > test, please.
>> >
>> > The following command segfaults. Adding a test would be
nice, but it
>> > would need a binary which uses OpenGL.
>> > qemu-system-x86_64 -device virtio-gpu-gl-pci -display
egl-headless
>> > -vnc :0 -m 8G -cdrom
Fedora-Workstation-Live-x86_64-34-1.2.iso -accel
>> > kvm
>> >
>> >
>> > Thanks!
>> >
>> > This is clearly a mistake from commit 7cc712e98 ("ui: dispatch
GL events
>> > to all listener").
>> >
>> > It should have taken into account that some listeners do not
have GL
>> > callbacks, and guard the call.
>> >
>> > We should wrap the missing ops->dpy_gl_call() with a if
>> > (ops->dpy_gl_call) ? I'll send a patch for that.
>>
>>
>> The assumption that OpenGL DisplayChangeListener and non-OpenGL
>> DisplayChangeListener are exclusive is now broken so we have to
examine
>
>
> Before the changes, there was already such a GL & non-GL listener
mixed situation. It's only because the first listener with GL would
be registered in register_displaychangelistener() that it "worked".
I mean the dbus patch series should be reexamined since it does not
seem to consider the case.
That's what I am doing, with your very good help.
>
>> if the whole patch series works correct without the assumption.
Other
>> problem I have found (and forgot to mention) is:
>> - that console_select and register_displaychangelistener may not
call
>> dpy_gfx_switch and call dpy_gl_scanout_texture instead. It is
>> incompatible with non-OpenGL displays and
>
>
> Can you translate that to a reproducible test with expected outcome?
vnc has the feature to switch consoles with Ctrl+Alt+[1-9] if it is
not bound to a particular console. Invoking the functionality with
egl-headless enabled would trigger the problem.
That doesn't seem to happen after the fixes ([PATCH 0/3] GL console
related fixes) I posted.
>
>>
>> - that the compatibility check breaks if egl-headless is present
and a
>> non-OpenGL DisplayChangeListener with con field is being added.
>>
>
> Same, thanks
The following command should do:
qemu-system-x86_64 -device virtio-gpu-gl-pci,id=d -display
egl-headless -vnc :0,display=d -m 8G -cdrom
Fedora-Workstation-Live-x86_64-34-1.2.iso -accel kvm
Thanks, that helps! I didn't realize DCL had "dynamic" consoles and the
compatibility checks were bypassed without specifying a specific display=d.
I'll address this in the v2 of my patch fixes series. Please check it.
>
>>
>> By the way, dbus registers a DisplayChangeListener for the size
>> detection, apparently it fails to set "con" field, making it an
>> accidental user of console_select.
>
>
> I need more details, please.
A DisplayChangeListener without con field set is passed to
register_displaychangelistener in dbus_display_console_new.
Good catch, should be fixed too.
>
>>
>>
>> >
>> > >
>> > > "make check-avocado
AVOCADO_TESTS=tests/avocado/virtio-gpu.py",
>> > which covers egl-headless usage, works.
>> > >
>> > >>
>> > >> - Multiple OpenGL DisplayChangeListeners of dbus
shares one
>> > DisplaySurface and
>> > >> modifies its texture field, causing OpenGL texture
leak and
>> > use-after-free.
>> > >
>> > >
>> > > Again, please provide instructions. I have regularly
run -display
>> > dbus with multiple clients and qemu compiled with
sanitizers. I
>> > don't see any leak or use after free.
>> >
>> > I doubt sanitizers can find this because it is an OpenGL
texture. You
>> > may add a probe around surface_gl_create_texture and
>> > surface_gl_destroy_texture.
>> >
>> >
>> > Indeed, a surface is created on each frame, because we create a 2d
>> > surface on each qemu_console_resize(), which is called at each
virgl
>> > scanout. This is a regression introduced by commit ebced09185
("console:
>> > save current scanout details"). I can propose an easy fix,
please check it.
>> >
>> > And the root of the leak is actually
surface_gl_create_texutre(), it
>> > should be idempotent, just like destroy().
>>
>> That is not enough since it may leave the texture present after
>> unregister_displaychangelistener. And calling
>> surface_gl_destroy_texture() before
unregister_displaychangelistener may
>> break the other listeners.
>
>
> The texture is shared, but owned by the console. It is not leaked.
>
> However, given that it is shared, it would be indeed better to
refcount the users to avoid destroying the texture by one listener
going away.
Nobody destroys the texture in the case so it is a leak. Particularly
after dpy_gfx_replace_surface, even the reference which remains in
DisplaySurface will be gone.
We need a QemuConsole finalizer to call qemu_free_displaysurface().
The UI code needs to evolve to become more robust in dynamic situations.
Let's do that.
>
>>
>> >
>> >
>> > >
>> > >>
>> > >> - Introduced extra code to check the compatibility of
OpenGL
>> > context providers
>> > >> and OpenGL texture renderers where those are often
inherently
>> > tightly coupled
>> > >> since they must share the same hardware.
>> > >
>> > >
>> > > So code checks are meant to prevent misusage. They
might be too
>> > limited or broken in some ways, but reverting is likely
going to
>> > introduce other regressions I was trying to fix.
>> >
>> > The misuse will not occur because DisplayChangeListeners
will be
>> > merged with OpenGL context providers.
>> >
>> >
>> > Ok, but aren't the checks enough to prevent it already? I have
to check
>> > the use cases and differences of design, but you might be
right that we
>> > don't need such a split after all.
>>
>> Yes, the point is that it requires extra code.
>>
>> >
>> >
>> > >
>> > >> - Needed extra work to broadcast the same change to
multiple
>> > dbus listeners.
>> > >>
>> > >
>> > > Compared to what?
>> >
>> > Compared to sharing one DisplayChangeListener for multiple
dbus
>> > listeners.
>> >
>> >
>> > Well, you just moved the problem to the dbus display, not
removed any work.
>> >
>> > What we have currently is more generic, you should be able to
add/remove
>> > various listeners (in theory, we only really do it for dbus at
this point).
>>
>> The each DisplayChangeListeners have to upload the
DisplaySurface to the
>> graphics accelerator, create a DMA-BUF file descriptor, and make it
>> suitable for D-Bus delivery. The duplicate work can be just done
once if
>> we have only one DisplayChangeListener for one console.
>
>
> And we should avoid duplicating the texture/resources if
possible. This is not specific to DBus, it's the reason why I would
rather have the logic in the console code so we avoid code
duplication and we can do further improvement at the lower-level.
The resources created are specific to D-Bus. Not all displays have
GUnixFDList, DMA-BUF file descriptors and OpenGL textures.
GUnixFDList is in dbus code. dmabuf fd & opengl textures are not
specific to dbus, they are used by spice as well, for example.
Regards,
Akihiko Odaki
>
>>
>>
>> >
>> >
>> > >
>> > >>
>> > >> This series solve them by implementing the change
broadcast in
>> > ui/dbus, which
>> > >> knows exactly what is needed. Changes for the common
code to
>> > support multiple
>> > >> OpenGL DisplayChangeListeners were reverted to fix
egl-headless
>> > and reduce
>> > >> the code size.
>> > >
>> > >
>> > > Thanks a lot for your work, I am going to take a look
at your
>> > approach. But please help us understand better what the
problem
>> > actually is, by giving examples & tests to avoid future
regressions
>> > and document the expected behaviour.
>> >
>> > The thing is really complicated and I may miss details so
please feel
>> > free to ask questions or provide suggestions.
>> >
>> >
>> > Reverting changes and proposing an alternative implementation
requires
>> > detailed explanation and convincing arguments. It may take a
while, but
>> > we will try to get through the problems and evaluate the
alternative
>> > designs. Thanks again for your help!
>>
>> Rather, I think proposing a large change to common console code
requires
>> thorough examination and it should be reverted before it reaches the
>> release if it is doubtful that it is correct and reduces the
complexity
>> of a few displays (possibly in the future). "No regression"
should come
>> first before fix and feature. We can always revisit the change
land it
>> in a proper form even after reverting the change.
>>
>
> That's not how we usually work, there was a long RFC&PATCH review
period during which testing was done. It's true that Gerd, the
maintainer, didn't do a thorough review though. If we have to
revert, we can do it before the release. However, I would rather fix
the current design since it is meant to be more generic & flexible.
We still have some time.
>
> Thanks again for your help
>
>> Regards,
>> Akihiko Odaki
>>
>> >
>> > Regards,
>> > Akihiko Odaki
>> >
>> >
>> > >
>> > >>
>> > >> Akihiko Odaki (6):
>> > >> ui/dbus: Share one listener for a console
>> > >> Revert "console: save current scanout details"
>> > >> Revert "ui: split the GL context in a different object"
>> > >> Revert "ui: dispatch GL events to all listeners"
>> > >> Revert "ui: associate GL context outside of display
listener
>> > >> registration"
>> > >> Revert "ui: factor out
qemu_console_set_display_gl_ctx()"
>> > >>
>> > >> include/ui/console.h | 60 +-----
>> > >> include/ui/egl-context.h | 6 +-
>> > >> include/ui/gtk.h | 11 +-
>> > >> include/ui/sdl2.h | 7 +-
>> > >> include/ui/spice-display.h | 1 -
>> > >> ui/console.c | 258 +++++++----------------
>> > >> ui/dbus-console.c | 109 ++--------
>> > >> ui/dbus-listener.c | 417
>> > +++++++++++++++++++++++++++----------
>> > >> ui/dbus.c | 22 --
>> > >> ui/dbus.h | 36 +++-
>> > >> ui/egl-context.c | 6 +-
>> > >> ui/egl-headless.c | 20 +-
>> > >> ui/gtk-egl.c | 10 +-
>> > >> ui/gtk-gl-area.c | 8 +-
>> > >> ui/gtk.c | 25 +--
>> > >> ui/sdl2-gl.c | 10 +-
>> > >> ui/sdl2.c | 14 +-
>> > >> ui/spice-display.c | 19 +-
>> > >> 18 files changed, 498 insertions(+), 541 deletions(-)
>> > >>
>> > >> --
>> > >> 2.32.0 (Apple Git-132)
>> > >>
>> > >>
>> > >
>> > >
>> > > --
>> > > Marc-André Lureau
>> >
>> >
>> >
>> > --
>> > Marc-André Lureau
>
>
>
> --
> Marc-André Lureau
--
Marc-André Lureau