On 2/4/20 10:28 AM, Santucco wrote:
> Hello,
> displ_be was compiled without zero-copy support early.
> I have tried with the recompiled dom0 kernel, a result is the same.
> Logs and configs (+displ_be’s CMakeCache.txt ) are attached.
Ok, yet another test to localize the problem.
Could you please remove memcpy from
#1 0x000055e5a1f28bec in Drm::DumbDrm::copy (this=0x7f9338000e00) at
/home/santucco/tmp/xen-troops/displ_be/src/displayBackend/drm/Dumb.cpp:149
and just memset the destination with 0 or whatever.
I expect that system won't crash, nothing will be shown (black screen), but
displ_be will show page flip events in its logs.
> Best regards,
> Alexander
>
> Понедельник, 3 февраля 2020, 10:36 +03:00 от Oleksandr
> Andrushchenko <
oleksandr_andrushchenko@xxxxxxxx>:
>
>
> On 2/1/20 4:39 PM, Santucco wrote:
> > Hello again,
> > I have not yet made to work my drm client, so I have tried to run
> > linux like a domU (to see how it should work), it doesn’t work too
> > — displ_be catches SIGSEGV:
> >
> > #0 0x00007f4afed1c161 in ?? () from /lib64/libc.so.6
> > #1 0x000055723b9c5bec in Drm::DumbDrm::copy
> (this=0x7f4adc000e00) at
> >
> /home/santucco/tmp/xen-troops/displ_be/src/displayBackend/drm/Dumb.cpp:149
> > #2 0x000055723b9a8f51 in BuffersStorage::getFrameBufferAndCopy
> > (this=0x7f4ae00010e0, fbCookie=18446612682295083264) at
> >
> /home/santucco/tmp/xen-troops/displ_be/src/displayBackend/BuffersStorage.cpp:165
> > It tries to copy to mBuffer with non-accessible address.
> > For the moment I see a strange offset for mmap call of
> /dev/drm/card0
> > in the strace log — 0x100000000. Is that normal?
> > Any direction of which to dig will be very helpful.
> > Configuration details:
> > Xen 4.12.1 Dom0: Linux 4.20.17-gentoo #13 SMP Sat Dec 28
> 11:12:24 MSK
> > 2019 x86_64 Intel(R) Celeron(R) CPU N3050 @ 1.60GHz GenuineIntel
> GNU/Linux
> > DomU: Linux 4.20.17-gentoo
> > last xen-troops/libxenbe and xen-troops/displ_be
> > Logs (dmesg, xl dmesg, displ_be, strace log of displ_be), a
> backtrace
> > of gdb and kernel configs are attached.
> > Thanks in advance.
> Could you please try Dom0 kernel WITHOUT the options below:
> CONFIG_XEN_GNTDEV_DMABUF=y
> CONFIG_XEN_GRANT_DMA_ALLOC=y
>
> Then, just to make sure, did you build displ_be without zero-copy
> support?
>
> > On 1/8/20 5:38 PM, Santucco wrote:
> > > Thank you very much for all your answers.
> > >
> > > Среда, 8 января 2020, 10:54 +03:00 от Oleksandr Andrushchenko
> > > <
oleksandr_andrushchenko@xxxxxxxx> > > </compose?To=oleksandr_andrushchenko@xxxxxxxx>>:
> > > On 1/6/20 10:38 AM, Jürgen Groß wrote:
> > > > On 06.01.20 08:56, Santucco wrote:
> > > >> Hello,
> > > >>
> > > >> I’m trying to use vdispl interface from PV OS, it doesn’t work.
> > > >> Configuration details:
> > > >> Xen 4.12.1
> > > >> Dom0: Linux 4.20.17-gentoo #13 SMP Sat Dec 28 11:12:24 MSK
> > > 2019
> > > >> x86_64 Intel(R) Celeron(R) CPU N3050 @ 1.60GHz GenuineIntel
> > > GNU/Linux
> > > >> DomU: x86 Plan9, PV
> > > >> displ_be as a backend for vdispl and vkb
> > > >>
> > > >> when VM starts, displ_be reports about an error:
> > > >> gnttab: error: ioctl DMABUF_EXP_FROM_REFS failed: Invalid
> argument
> > > >> (displ_be.log:221)
> > > >>
> > > >> related Dom0 output is:
> > > >> [ 191.579278] Cannot provide dma-buf: use_ptemode 1
> > > >> (dmesg.create.log:123)
> > > >
> > > > This seems to be a limitation of the xen dma-buf driver. It was
> > > written
> > > > for being used on ARM initially where PV is not available.
> > > This is true and we never tried/targeted PV domains with this
> > > implementation,
> > > so if there is a need for that someone has to take a look on the
> > > proper
> > > implementation for PV…
> > >
> > > Have I got your right and there is no the proper
> implementation :-)?
> > There is no
> > >
> > > >
> > > > CC-ing Oleksandr Andrushchenko who is the author of that
> driver. He
> > > > should be able to tell us what would be needed to enable PV
> dom0.
> > > >
> > > > Depending on your use case it might be possible to use PVH
> dom0, but
> > > > support for this mode is "experimental" only and some features
> > > are not
> > > > yet working.
> > > >
> > > Well, one of the workarounds possible is to drop zero-copying
> use-case
> > > (this is why display backend tries to create dmu-bufs from grants
> > > passed
> > > by the guest domain and fails because of "Cannot provide dma-buf:
> > > use_ptemode 1")
> > > So, in this case display backend will do memory copying for the
> > > incoming
> > > frames
> > > and won't touch DMABUF_EXP_FROM_REFS ioctl.
> > > To do so just disable zero-copying while building the backend [1]
> > >
> > > Thanks, I have just tried the workaround. The backend has failed
> > > in an other place not corresponding with dma_buf.
> > > Anyway it is enough to continue debugging my
> frontend implementation.
> > > Do you know how big is performance penalty in comparison with
> > > the zero-copy variant?
> > Well, it solely depends on your setup, so I cannot tell what
> > would the numbers be in your case. Comparing to what I have doesn't
> > make any sense to me: one should compare apples to apples
> > > Does it make a sense if I make a dedicated HVM domain with
> linux only
> > > for the purpose of vdispl and vkbd backends? Is there a hope this
> > > approach will work?
> > You can try if this approach fits your design and requirements
> > >
> > > >
> > > > Juergen
> > > >
> > > [1]
> > >
> >
>
https://github.com/xen-troops/displ_be/blob/master/CMakeLists.txt#L12> <
https://urldefense.com/v3/__https://github.com/xen-troops/displ_be/blob/master/CMakeLists.txt*L12__;Iw!!GF_29dbcQIUBPA!kvDgy3X0IuSQk7D2DdsGtsjtyGroYbNKOrPG95OpyoAkuBVbFSmzozwfor05jkRl0ita0FumBw$>
> >
> <
https://urldefense.com/v3/__https://github.com/xen-troops/displ_be/blob/master/CMakeLists.txt*L12__;Iw!!GF_29dbcQIUBPA!gi81oZZNvWaFWUVnaZluA_mNBAItLMd4RZmnc-M_FmlpDojqeQQnS7aXSNlbo80re9uOl2wqFA$>
> > >
> >
> <
https://urldefense.com/v3/__https://github.com/xen-troops/displ_be/blob/master/CMakeLists.txt*L12__;Iw!!GF_29dbcQIUBPA!mz3gn1wQMX2DXeNuAV-1_dI7nxFYYZOgdPiJNSFMesCz9lAzOKlwVPlddbxbcLmUO44NOy0TFA$>
> > >
> > > Best regards,
> > > Alexander Sychev
> >
>
> ------------------------------------------------------------------------
