Your message dated Tue, 5 Oct 2021 21:45:12 +0300 with message-id <[email protected]> and subject line Re: Bug#939413: qemu-system: Regression: `-drive file=/dev/fdset/$FD` fails with EPERM has caused the Debian Bug report #939413, regarding qemu-system: Regression: `-drive file=/dev/fdset/$FD` fails with EPERM to be marked as done.
This means that you claim that the problem has been dealt with. If this is not the case it is now your responsibility to reopen the Bug report if necessary, and/or fix the problem forthwith. (NB: If you are a system administrator and have no idea what this message is talking about, this may indicate a serious mail system misconfiguration somewhere. Please contact [email protected] immediately.) -- 939413: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=939413 Debian Bug Tracking System Contact [email protected] with problems
--- Begin Message ---Package: qemu-system-x86 Version: 1:4.1-1 Severity: normal File: qemu-system Dear Maintainer, Using a pre-opened file descriptor to a disk image no longer work as documented (and as it used to with ≤1:3.1+dfsg-8~deb10u1): $ touch /tmp/disk.img $ qemu-system-x86_64 -display none \ -add-fd "fd=3,set=0" \ -drive "file=/dev/fdset/0,format=raw,media=disk" \ 3<>/tmp/disk.img qemu-system-x86_64: -drive file=/dev/fdset/0,format=raw,media=disk: Could not open '/dev/fdset/0': Permission denied Interestingly, for read-only media it does work if the file descriptor is opened in read-only mode: $ qemu-system-x86_64 -display none \ -add-fd "fd=3,set=0" \ -drive "file=/dev/fdset/0,format=raw,media=cdrom,readonly" \ 3</tmp/disk.img -- Guilhem. -- System Information: Debian Release: bullseye/sid APT prefers unstable APT policy: (500, 'unstable'), (1, 'experimental') Architecture: amd64 (x86_64) Kernel: Linux 5.2.0-2-amd64 (SMP w/2 CPU cores) Locale: LANG=en_US.UTF-8, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8), LANGUAGE=en_US:en (charmap=UTF-8) Shell: /bin/sh linked to /bin/dash Init: systemd (via /run/systemd/system) Versions of packages qemu-system-x86 depends on: ii ipxe-qemu 1.0.0+git-20190125.36a4c85-1 ii libaio1 0.3.112-5 ii libasound2 1.1.8-1 ii libbluetooth3 5.50-1+b1 ii libbrlapi0.6 5.6-11 ii libc6 2.28-10 ii libcacard0 1:2.6.1-1 ii libcapstone3 4.0.1+really+3.0.5-1+b1 ii libepoxy0 1.5.3-0.1 ii libfdt1 1.5.0-2 ii libgbm1 19.1.4-1 ii libgcc1 1:9.2.1-6 ii libglib2.0-0 2.60.6-2 ii libgnutls30 3.6.9-4 ii libibverbs1 24.0-2 ii libjpeg62-turbo 1:1.5.2-2+b1 ii libncursesw6 6.1+20190803-1 ii libnettle6 3.5.1+really3.4.1-1 ii libnuma1 2.0.12-1+b1 ii libpixman-1-0 0.36.0-1 ii libpng16-16 1.6.37-1 ii librdmacm1 24.0-2 ii libsasl2-2 2.1.27+dfsg-1 ii libseccomp2 2.4.1-2 ii libspice-server1 0.14.2-3 ii libtinfo6 6.1+20190803-1 ii libusb-1.0-0 2:1.0.23-1 ii libusbredirparser1 0.8.0-1+b1 ii libvdeplug2 2.3.2+r586-2.2+b1 ii libvirglrenderer0 0.7.0-2 ii libxendevicemodel1 4.11.1+92-g6c33308a8d-2+b1 ii libxenevtchn1 4.11.1+92-g6c33308a8d-2+b1 ii libxenforeignmemory1 4.11.1+92-g6c33308a8d-2+b1 ii libxengnttab1 4.11.1+92-g6c33308a8d-2+b1 ii libxenmisc4.11 4.11.1+92-g6c33308a8d-2+b1 ii libxenstore3.0 4.11.1+92-g6c33308a8d-2+b1 ii libxentoolcore1 4.11.1+92-g6c33308a8d-2+b1 ii qemu-system-common 1:4.1-1 ii qemu-system-data 1:4.1-1 ii seabios 1.12.0-1 ii zlib1g 1:1.2.11.dfsg-1+b1 Versions of packages qemu-system-x86 recommends: pn ovmf <none> ii qemu-system-gui 1:4.1-1 pn qemu-utils <none> Versions of packages qemu-system-x86 suggests: pn qemu-block-extra <none> pn samba <none> pn sgabios <none> pn vde2 <none> -- no debconf information
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--- Begin Message ---Again, this is a feature without any documentation (an irony: the first non-source-code hit on google for "qemu fdset" leads to this very bugreport! :), which is non-obvious at first. An fdset supposed to have at least two file descriptors: one opened read-only and another opened read-write. Internally qemu does more than one open of a given file. First it tries to open it read-only (controllable by another not-as-well-documented flag auto-read-only=off (default is on). And when you give it an fdset with a single file descriptor open for read-write, it fails to find readonly version of it. In order to fix this issue, you either have to give it two file descriptors (for the SAME file!) - one rw and one ro, or you can tell it to always open files in read-write mode. I'm closing this bug report since it is about wrong usage which leads to wrong results. But the actual issue here, as far as I can tell, is the lack of documentation. The whole thing, as far as I can see, is supposed to be used within libvirt or some other management tool, since the concept is quite difficult to use from command line, especially with this huge amount of documentation... Thanks, /mjt
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