Hello, I have found a source of the problem. In displ_be, BaseDump copies to the drm buffer with a size from i915 drm driver, but this size a bit more than a size of my frontend display buffer. I have made a quick and dirty fix, a copy a line of my display buffer to a middle of a line of the drm display buffer. Patch is attached. Best regards, Alexander >Четверг, 6 февраля 2020, 11:20 +03:00 от Oleksandr Andrushchenko ><oleksandr_andrushche...@epam.com>: > >On 2/5/20 8:59 PM, Santucco wrote: >> Hello, >> Ok, I commented out the memcpy call and run the test. >> displ_be hasn’t crached, I have seen FLIP events in the log. >> But there hasn’t been the black screen, just a blink effect every >> couple of seconds. >> Logs are attached. >Ok, so I believe that frontend - backend (displ_be) communication is ok >and there is nothing to do there. > >Next, I would start debugging the following in Xen: >(XEN) mm.c:2223:d2v0 Bad L1 flags 80 >and have a look at [1]. Probably, someone on Xen x86 side can tell >if this could be related to the flags at [2]. > >> Best regards, >> Alexander >> >> Среда, 5 февраля 2020, 9:31 +03:00 от Oleksandr Andrushchenko >> < oleksandr_andrushche...@epam.com >: >> 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_andrushche...@epam.com >> </compose?To=oleksandr_andrushche...@epam.com>>: >> > >> > >> > 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_andrushche...@epam.com >> </compose?To=oleksandr_andrushche...@epam.com> >> > > > </compose?To=oleksandr_andrushche...@epam.com>>: >> > > > 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!kZ1JQFRS2pXj_IuXBhvYhmP9Q_svcLyjCXK9465ULGB4MeiYPRz2cF7lepHggr9UxPU9zOBEUw$ >> > >> > >> < >> 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 >> > > >> > >> > >> ------------------------------------------------------------------------ >> >[1] https://elixir.bootlin.com/linux/v5.5/source/drivers/xen/gntdev.c#L300 >[2] https://elixir.bootlin.com/linux/v5.5/source/drivers/xen/gntdev.c#L319
patch
Description: Binary data
