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Mon, 20 Oct 2025 14:40:22 -0400 (EDT) Message-ID: Date: Mon, 20 Oct 2025 19:40:21 +0100 Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: 9P change breaks bpftrace running in qemu+9p? To: Song Liu , v9fs@lists.linux.dev Cc: Eric Van Hensbergen , Dominique Martinet , Latchesar Ionkov , Christian Schoenebeck , =?UTF-8?Q?Micka=C3=ABl_Sala=C3=BCn?= , bpf References: Content-Language: en-US From: Tingmao Wang In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Hi Song, On 10/20/25 18:40, Song Liu wrote: > Hi, > > I noticed a new error in the upstream kernel when I run bpftrace with > vmtest [2]: > > $ vmtest -k arch/x86/boot/bzImage "bpftrace.real -e > 'fexit:cmdline_proc_show {exit();}'" > => bzImage > ===> Booting > ===> Setting up VM > ===> Running command > [ 5.610741] id (178) used greatest stack depth: 11592 bytes left > Parse error: Input/output error > Command failed with exit code: 2 > [root@(none) /]# > > git bisect points to patch 1/3 of this set [1]. > > Any idea what is happening here? I have attempted to reproduce this but couldn't yet: > git log --format=short -1 commit 211ddde0823f1442e4ad052a2f30f050145ccada (HEAD, tag: v6.18-rc2, origin/master, origin/HEAD) Author: Linus Torvalds Linux 6.18-rc2 (0.067s) linux-devbox-2 (mao; ; ?) ~/9pfs > vmtest -k arch/x86/boot/bzImage "bpftrace -e 'fexit:cmdline_proc_show {exit();}'" => bzImage ===> Booting ===> Setting up VM ===> Running command Attached 1 probe ^C⏎ (130) (14.421s) linux-devbox-2 (mao; ; ?) ~/9pfs > vmtest -k arch/x86/boot/bzImage "(sleep 2; cat /proc/cmdline) & bpftrace -e 'fexit:cmdline_proc_show {exit();}'" => bzImage ===> Booting ===> Setting up VM ===> Running command Attached 1 probe rootfstype=9p rootflags=trans=virtio,cache=mmap,msize=1048576 rw earlyprintk=serial,0,115200 printk.devkmsg=on console=0,115200 loglevel=7 ra... (5.29s) linux-devbox-2 (mao; ; ?) ~/9pfs > qemu-system-x86_64 -version QEMU emulator version 10.1.1 Copyright (c) 2003-2025 Fabrice Bellard and the QEMU Project developers (0.011s) linux-devbox-2 (mao; ; ?) ~/9pfs > bpftrace --version bpftrace v0.24.1 I'm happy to take a further look - is there anything special about your setup, what version of QEMU / bpftrace are you running? > > Thanks, > Song > > [1] https://lore.kernel.org/v9fs/cover.1743956147.git.m@maowtm.org/ > [2] https://github.com/danobi/vmtest