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1 files changed, 88 insertions, 3 deletions
@@ -1,6 +1,6 @@ # KVMX Documentation -Misc documentation on kvmx and qemu. +Misc documentation on kvmx and QEMU. ## USB hotplug support @@ -46,8 +46,7 @@ Misc documentation on kvmx and qemu. Nowadays this can be done with `kvmx growpart <device> <partition> <additional_size>`, but here goes some manual procedures if needed. -* Image resize action, doing something like this, thanks to - https://ahelpme.com/linux/online-resize-of-a-root-ext4-file-system-increase-the-space/ +Image resize can be manually done with a procedure like this thanks to [these docs][]: # poweroff kvmx poweroff $guest @@ -77,3 +76,89 @@ here goes some manual procedures if needed. kvmx ssh $guest sudo resize2fs /dev/vda2 kvmx ssh $guest sudo touch /forcefsck kvmx restart $guest + +[these docs]: https://ahelpme.com/linux/online-resize-of-a-root-ext4-file-system-increase-the-space/ + +## Folder sharing + +### Virtio + +References on virtio: + +* [Virtio on Linux — The Linux Kernel documentation](https://www.kernel.org/doc/html/v6.8/driver-api/virtio/virtio.html) + * [linux kernel - VIRTIO: How it increase performance - Stack Overflow](https://stackoverflow.com/questions/24737882/virtio-how-it-increase-performance) + * [Virtual I/O Device (VIRTIO) Version 1.1](https://docs.oasis-open.org/virtio/virtio/v1.1/cs01/virtio-v1.1-cs01.html#x1-240006) + +### With virtio and 9p + +* Status: works on kvmx. +* Limitations: performance is low on Linux (as of 2024-08-01), due to a + limitation in the kernel. +* Since fixes for CVE-2023-2861 were released, it's not possible anymore to set + UNIX sockets in shared folders. + +#### Details + +Some references on 9p folder sharing: + +* [v9fs: Plan 9 Resource Sharing for Linux — The Linux Kernel documentation](https://www.kernel.org/doc/html/latest/filesystems/9p.html) + * [Documentation/9p - QEMU](https://wiki.qemu.org/Documentation/9p) + * [Documentation/9psetup - QEMU](https://wiki.qemu.org/Documentation/9psetup) + * [v9fs · GitHub](https://github.com/v9fs) + +Support for opening sockets was removed with fixes for CVE-2023-2861: + +* [Os boot issues on 9p filesystem due to unix domain sockets open failure (#2337) · Issues · QEMU / QEMU · GitLab](https://gitlab.com/qemu-project/qemu/-/issues/2337) +* [9pfs: prevent opening special files (CVE-2023-2861) (f6b0de53) · Commits · QEMU / QEMU · GitLab](https://gitlab.com/qemu-project/qemu/-/commit/f6b0de53fb87ddefed348a39284c8e2f28dc4eda) +* [CVE - CVE-2023-2861](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2023-2861) +* [SECURITY DLA 3759-1 qemu security update](https://lists.debian.org/debian-lts-announce/2024/03/msg00012.html) + +#### Performance + +Performance limitations: + +* There's a limit in the Linux kernel, which is explained in [this + message](https://lists.gnu.org/archive/html/qemu-devel/2021-02/msg06850.html) + as being `.maxsize = PAGE_SIZE * (VIRTQUEUE_NUM - 3)`. +* The limit is present at `trans_virtio.c` (as of 2024-08-01): + [linux/net/9p/trans_virtio.c at master - L803 · torvalds/linux · + GitHub](https://github.com/torvalds/linux/blob/master/net/9p/trans_virtio.c#L803) +* [History for net/9p/trans_virtio.c - torvalds/linux · GitHub](https://github.com/torvalds/linux/commits/master/net/9p/trans_virtio.c) + +Discussion an proposals to overcome this limit: + +* [Can not set high msize with virtio-9p (Was: Re: virtiofs vs 9p performan](https://lists.gnu.org/archive/html/qemu-devel/2021-02/msg06343.html) + * [Re: Can not set high msize with virtio-9p (Was: Re: virtiofs vs 9p perfo](https://lists.gnu.org/archive/html/qemu-devel/2021-02/msg06850.html) +* [remove msize limit in virtio transport - LWN.net](https://lwn.net/Articles/901523/) + * [New Patches Aim To Boost Linux 9p Performance By ~10x - Phoronix](https://www.phoronix.com/news/Linux-9p-10x-Performance) + * [9p performance increase by ~10x reflected in WSL? · microsoft/WSL · Discussion #9412 · GitHub](https://github.com/microsoft/WSL/discussions/9412) + * [VM: 9p: degraded performance: a reasonable high msize should be chosen on client/guest side · Issue #10219 · canonical/lxd · GitHub](https://github.com/canonical/lxd/issues/10219) + * [Add msize configuration for windows-side 9P client (=higher WSL2 disk speed) · Issue #9125 · microsoft/WSL · GitHub](https://github.com/microsoft/WSL/issues/9125) + * [[Virtio-fs] Can not set high msize with virtio-9p (Was: Re: virtiofs vs 9p performance)](https://listman.redhat.com/archives/virtio-fs/2021-March/002811.html) + +Patches: + +* [[PATCH v6 00/11] remove msize limit in virtio transport [LWN.net]](https://lwn.net/ml/linux-kernel/cover.1657920926.git.linux_oss@crudebyte.com/) +* [[PATCH v5 00/11] remove msize limit in virtio transport - Christian Schoenebeck](https://lore.kernel.org/all/cover.1657636554.git.linux_oss@crudebyte.com/) +* [Performance fixes for 9p filesystem - LWN.net](https://lwn.net/Articles/918213/) +* Other (untriaged list): + * [Re: [PATCH v5 00/11] remove msize limit in virtio transport - Christian Schoenebeck](https://lore.kernel.org/all/7468612.NupLhYsxyy@silver/) + * [[PATCH v3 0/7] net/9p: remove msize limit in virtio transport - Christian Schoenebeck](https://lore.kernel.org/netdev/cover.1632327421.git.linux_oss@crudebyte.com/) + * [[PATCH v2 1/7] net/9p: show error message if user 'msize' cannot be satisfied — Netdev](https://www.spinics.net/lists/netdev/msg768036.html) + * [[PATCH v2 00/10] Performance fixes for 9p filesystem - Eric Van Hensbergen](https://lore.kernel.org/lkml/20221218232217.1713283-1-evanhensbergen@icloud.com/) + * [[Virtio-fs] [PATCH v2 0/3] virtio: increase VIRTQUEUE_MAX_SIZE to 32k](https://listman.redhat.com/archives/virtio-fs/2021-October/004135.html) + * [[v4,08/12] net/9p: limit 'msize' to KMALLOC_MAX_SIZE for all transports - Patchwork](https://patchwork.kernel.org/project/netdevbpf/patch/39f81db5e5b25a1e4f94ad3b05552044209aff21.1640870037.git.linux_oss@crudebyte.com/) + * [Thread: [V9fs-developer] [PATCH] Improve 9p performance for read operations | Plan 9 Resource Sharing for Linux](https://sourceforge.net/p/v9fs/mailman/v9fs-developer/thread/B272E6A0-C349-4B23-BE6F-7CBA8D6C4B6B%40icloud.com/) + +### With virtiofs + +* The `virtiofsd` implementation from upstream QUEMY was removed on [version + 8.0](https://wiki.qemu.org/ChangeLog/8.0), in favor of the [virtio-fs / + virtiofsd](https://gitlab.com/virtio-fs/virtiofsd) implementation. +* [virtiofs - shared file system for virtual machines](https://virtio-fs.gitlab.io/) + * [virtiofs - shared file system for virtual machines / Standalone usage](https://virtio-fs.gitlab.io/howto-qemu.html) + * [Debian -- Details of package virtiofsd in trixie](https://packages.debian.org/trixie/virtiofsd) + * [rust-virtiofsd - Debian Package Tracker](https://tracker.debian.org/pkg/rust-virtiofsd) + * [libvirt: Sharing files with Virtiofs](https://libvirt.org/kbase/virtiofs.html) + * [virtio-fs / virtiofsd · GitLab](https://gitlab.com/virtio-fs/virtiofsd) + * [VirtIO-FS Is Looking Quite Good For Shared File-System With VMs - Phoronix](https://www.phoronix.com/news/VirtIO-FS-Looking-Good-2020) |