Re: Using virtio-gpu instead of virtwl

Thomas Leonard
2022-03-22T11:09:05Z

On Mon, 21 Mar 2022 at 16:05, Alyssa Ross <hi@alyssa.is> wrote:
>
> On Mon, Mar 21, 2022 at 12:10:43PM +0000, Thomas Leonard wrote:
> > Looking at the Linux virtio_gpu driver, it seems that using contexts
> > requires virgl:
> >
> > static int virtio_gpu_context_init_ioctl(struct drm_device *dev, void
> > *data, struct drm_file *file)
> > {
> > ...
> > if (!vgdev->has_context_init || !vgdev->has_virgl_3d)
> > return -EINVAL;
> >
> > https://github.com/torvalds/linux/blob/f443e374ae131c168a065ea1748feac6b2e76613/drivers/gpu/drm/virtio/virtgpu_ioctl.c#L732
> >
> > I think perhaps that crosvm is compiled without the "virgl_renderer"
> > feature (it's not in the default set), and this is causing it to crash
> > because that's also "self.default_component". I don't know how to
> > compile crosvm with virgl enabled, though.
>
> It wasn't easy, but I got it to build[1]. I hope that helps. It adds
> both virgl_renderer and virgl_renderer_next. I think virgl_renderer
> is on by default with --gpu, and virgl_renderer_next is used with the
> --gpu-render-server argument. Hopefully at least one of those does the
> right thing — let me know!
>
> [1]: https://github.com/NixOS/nixpkgs/pull/165128

Thanks, that is very helpful!

I gave it a try, and it got a little further. But now, doing `modprobe
virtio_gpu` in the VM crashes crosvm with:

Stack trace of thread 2:
#0 0x00007fa5fd0915f6 abort (libc.so.6 + 0x265f6)
#1 0x00007fa5fcfc6bfd get_dlopen_handle.part.0 (libepoxy.so.0 + 0xc7bfd)
#2 0x00007fa5fcfc7366 epoxy_egl_dlsym (libepoxy.so.0 + 0xc8366)
#3 0x00007fa5fcfbf870 egl_single_resolver (libepoxy.so.0 + 0xc0870)
#4 0x00007fa5fcfc1d2f epoxy_eglQueryString_global_rewrite_ptr
(libepoxy.so.0 + 0xc2d2f)
#5 0x0000561703e72ca1 virgl_egl_init (crosvm + 0x3deca1)
#6 0x0000561703e72221 vrend_winsys_init (crosvm + 0x3de221)
#7 0x0000561703e380dc virgl_renderer_init (crosvm + 0x3a40dc)
#8 0x0000561703e35e44
_ZN12rutabaga_gfx14virgl_renderer13VirglRenderer4init17h96573d71589e47fcE
(crosvm + 0x3a1e44)
#9 0x0000561703e23124
_ZN12rutabaga_gfx13rutabaga_core15RutabagaBuilder5build17h694f3c234f8787ffE
(crosvm + 0x38f124)
#10 0x0000561703cdfb0f
_ZN7devices6virtio3gpu10virtio_gpu9VirtioGpu3new17h43dded1b3497b0f1E
(crosvm + 0x24bb0f)
#11 0x0000561703d0feb2
_ZN7devices6virtio3gpu5build17hc6e82daf2d41f5feE (crosvm + 0x27beb2)
#12 0x0000561703cbee32
_ZN3std10sys_common9backtrace28__rust_begin_short_backtrace17h8f078e46fd25a72dE
(crosvm + 0x22ae32)
#13 0x0000561703cf5e0d
_ZN4core3ops8function6FnOnce40call_once$u7b$$u7b$vtable.shim$u7d$$u7d$17h5605b62669a02b38E
(crosvm + 0x261e0d)
#14 0x0000561703ee8b43
_ZN3std3sys4unix6thread6Thread3new12thread_start17h3f45e1fefa031d31E
(crosvm + 0x454b43)
#15 0x00007fa5fceb6d40 start_thread (libpthread.so.0 + 0x8d40)
#16 0x00007fa5fd16703f __clone (libc.so.6 + 0xfc03f)

Stack trace of thread 1:
#0 0x00007fa5fd1684b2 recvfrom (libc.so.6 + 0xfd4b2)
#1 0x0000561703ec7b0c
_ZN8sys_util3net13UnixSeqpacket20recv_as_vec_with_fds17hcc9cb638a4fdbca9E
(crosvm + 0x433b0c)
#2 0x0000561703b85b87 _ZN4base4tube4Tube4recv17hd85339bce7434d11E
(crosvm + 0xf1b87)
#3 0x0000561703b90395
_ZN7devices5proxy10child_proc17hde9579314b1fc020E (crosvm + 0xfc395)
#4 0x0000000103001400 n/a (n/a + 0x0)

It looks like it should be printing a message to stderr before calling
abort, but I don't see it
(https://github.com/anholt/libepoxy/blob/1.5.9/src/dispatch_common.c#L315).

I also tried with --gpu=backend=virglrenderer,egl=false, which crashes
instead with:

Stack trace of thread 2:
#0 0x0000000000000000 n/a (n/a + 0x0)
#1 0x00007fac70002b00 n/a (n/a + 0x0)

I think I'll give up on virtio_gpu for now and try again after a few months.

--
talex5 (GitHub/Twitter)