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Re: [PATCH v4 4/4] meson: Warn when TCI is selected but TCG backend is a
From: |
Alex Bennée |
Subject: |
Re: [PATCH v4 4/4] meson: Warn when TCI is selected but TCG backend is available |
Date: |
Wed, 27 Jan 2021 21:47:50 +0000 |
User-agent: |
mu4e 1.5.7; emacs 28.0.50 |
Stefan Weil <sw@weilnetz.de> writes:
> Am 27.01.21 um 20:52 schrieb Alex Bennée:
>
>> For example - debian-buster (arm64) running ffmpeg:
>>
>> alex.bennee@8cd150a4b35d:~/lsrc/qemu.git/builds/all.tci$ ./qemu-aarch64
>> /usr/bin/ffmpeg -i theora.mkv theora.webm
>> TODO ../../tcg/tci.c:882: tcg_qemu_tb_exec()
>> ../../tcg/tci.c:882: tcg fatal error
>> qemu: uncaught target signal 11 (Segmentation fault) - core dumped
>> Segmentation fault (core dumped)
>
>
> Thanks. All I tried to say is that I prefer to replace those TODO
> statements by working code as soon as there was a case which triggers
> them. Most of those TODO statements are very easy to implement, so
> anyone can add them when he/she detects a missing one. If I get
> information about a scenario which triggers a missing TODO, I'll fix
> that of course. I just don't want to add that missing code blindly.
Your just going to end up playing wack-a-mole:
TODO ../../tcg/tci.c:620: tcg_qemu_tb_exec()me=00:00:00.00 bitrate=N/A speed=
0x
../../tcg/tci.c:620: tcg fatal error
qemu: uncaught target signal 11 (Segmentation fault) - core dumped
Segmentation fault (core dumped)
> Using `make check-tcg` helped finding and fixing one of them, future
> improved CI checks can find more, and so can examples like the one
> above. The error message tci.c:882 is INDEX_op_ld8s_i64
> (https://github.com/qemu/qemu/blob/master/tcg/tci.c#L882). The missing
> code is nearly identical to the existing code for INDEX_op_ld8u_i64, but
> with *(int8_t *) instead of *(uint8_t *), so maybe you can try that and
> confirm whether it fixes the reported problem. Otherwise I'll try to
> reproduce it with any mkv file.
ffmpeg is a good application for working out the SIMD code because it
features quite a lot of optimised code for each architecture.
> I recently tried running tesseract with qemu-x86_64 because I had
> expected that it might trigger some unimplemented TCG opcodes.
qemu-x86-64 is a poor choice as a relatively under maintained front-end
doesn't emulate a particularly new CPU or take advantage of the new TCG
features. ARM64 is pretty good because the default cpu for linux-user is
CPU max which a) enables all ISA features we have and b) exposes them
fairly easily to guest detection routines which probe feature registers.
> Instead
> it showed a general problem for native TCG: qemu-x86_64 allocates too
> much memory for tesseract and gets killed by the Linux kernel OOM
> handler.
Do you have a command line? That sounds like something that should be
fixed.
>
> Regards,
>
> Stefan
--
Alex Bennée
- Re: [PATCH v4 4/4] meson: Warn when TCI is selected but TCG backend is available, (continued)
- Re: [PATCH v4 4/4] meson: Warn when TCI is selected but TCG backend is available, Stefan Weil, 2021/01/26
- Re: [PATCH v4 4/4] meson: Warn when TCI is selected but TCG backend is available, Alex Bennée, 2021/01/26
- Re: [PATCH v4 4/4] meson: Warn when TCI is selected but TCG backend is available, Stefan Weil, 2021/01/26
- Re: [PATCH v4 4/4] meson: Warn when TCI is selected but TCG backend is available, Paolo Bonzini, 2021/01/26
- Re: [PATCH v4 4/4] meson: Warn when TCI is selected but TCG backend is available, Stefan Weil, 2021/01/26
- Re: [PATCH v4 4/4] meson: Warn when TCI is selected but TCG backend is available, Richard Henderson, 2021/01/26
- Re: [PATCH v4 4/4] meson: Warn when TCI is selected but TCG backend is available, Stefan Weil, 2021/01/27
- Re: [PATCH v4 4/4] meson: Warn when TCI is selected but TCG backend is available, Richard Henderson, 2021/01/27
- Re: [PATCH v4 4/4] meson: Warn when TCI is selected but TCG backend is available, Alex Bennée, 2021/01/27
- Re: [PATCH v4 4/4] meson: Warn when TCI is selected but TCG backend is available, Stefan Weil, 2021/01/27
- Re: [PATCH v4 4/4] meson: Warn when TCI is selected but TCG backend is available,
Alex Bennée <=
- Re: [PATCH v4 4/4] meson: Warn when TCI is selected but TCG backend is available, Stefan Weil, 2021/01/27
- qemu user mode fails to run programs with large VM / built with address sanitizer (was: Re: [PATCH v4 4/4] meson: Warn when TCI is selected but TCG backend is available), Stefan Weil, 2021/01/28
- Re: qemu user mode fails to run programs with large VM / built with address sanitizer (was: Re: [PATCH v4 4/4] meson: Warn when TCI is selected but TCG backend is available), Richard Henderson, 2021/01/28
- Re: [PATCH v4 4/4] meson: Warn when TCI is selected but TCG backend is available, Daniel P . Berrangé, 2021/01/27
- Re: [PATCH v4 4/4] meson: Warn when TCI is selected but TCG backend is available, Alex Bennée, 2021/01/27
- Re: [PATCH v4 4/4] meson: Warn when TCI is selected but TCG backend is available, Daniel P . Berrangé, 2021/01/26
Re: [PATCH v4 0/4] meson: Try to clarify TCG / TCI options for new users, Paolo Bonzini, 2021/01/29