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. Best regards, Alexander >Понедельник, 3 февраля 2020, 10:36 +03:00 от Oleksandr Andrushchenko < >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 >>: >> > 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!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 >> ----------------------------------------------------------------------
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