# KVMX Documentation Misc documentation on kvmx and QEMU. ## USB hotplug support * Good to have `usbutils` package in the guest. * Docs: * https://qemu.readthedocs.io/en/latest/system/usb.html * https://github.com/qemu/qemu/blob/master/docs/usb2.txt * https://wiki.gentoo.org/wiki/QEMU/Windows_guest * https://www.linux-kvm.org/page/USB_Host_Device_Assigned_to_Guest * https://en.wikibooks.org/wiki/QEMU/Devices/USB/Root * https://wiki.archlinux.org/index.php/QEMU#Pass-through_host_USB_device * Issues: * https://serverfault.com/questions/666210/attaching-usb-dongle-to-kvm-vm * https://unix.stackexchange.com/questions/119335/how-can-i-simulate-usb-storage-device-connection-with-qemu#119530 * https://unix.stackexchange.com/questions/452934/can-i-pass-through-a-usb-port-via-qemu-command-line#452946 kvm - Can I pass through a USB Port via qemu Command Line? - Unix & Linux Stack Exchange * https://unix.stackexchange.com/questions/310271/camera-passthrough-in-qemu-kvm-linux-guest-machine Camera passthrough in QEMU/KVM (linux) guest machine - Unix & Linux Stack Exchange * https://bugs.launchpad.net/qemu/+bug/1377163/ Bug #1377163 “Does not add usb-host devices as they are hotplugg...” : Bugs : QEMU * https://bugzilla.redhat.com/show_bug.cgi?id=955438 955438 – qemu should fail to boot guest when speed mismatch trying to attach low speed usb device to xHCI high speed controller * https://bugs.launchpad.net/qemu/+bug/1550743 Bug #1550743 “connect low speed host devices to qemu ehci does n...” : Bugs : QEMU * https://bugzilla.redhat.com/show_bug.cgi?id=949505 949505 – Assign 3.0 usb device to ehci and uhci or usb hub got applied anyway with warning but fails to function * https://www.reddit.com/r/linuxadmin/comments/7a7bgl/when_adding_usb_redirection_in_a_vm_it_resets_the/ When adding USB redirection in a vm it resets the USB device and errors with speed mismatch. Any idea how to change speed? : linuxadmin * https://bugs.launchpad.net/qemu/+bug/1810000 qemu system emulator crashed when using xhci usb controller ## Manually resizing an image Nowadays this can be done with `kvmx growpart `, 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/ # poweroff kvmx poweroff $guest # resize image qemu-img resize `kvmx list_image $guest` +5G # power up kvmx up $guest # ensure parted is installed #sudo apt-get install -y parted kvmx ssh $guest sudo apt-get install -y cloud-guest-utils # resize virtual machine root fs - while the partition is mounted! # this parted command currently need to be done manually #echo resizepart 2 -1 | kvmx ssh $guest sudo parted /dev/vda # See https://unix.stackexchange.com/questions/373063/auto-expand-last-partition-to-use-all-unallocated-space-using-parted-in-batch-m # https://unix.stackexchange.com/questions/190317/gnu-parted-resizepart-in-script#202872 # https://bugs.launchpad.net/ubuntu/+source/parted/+bug/1270203 # https://techtitbits.com/2018/12/using-parteds-resizepart-non-interactively-on-a-busy-partition/ # https://serverfault.com/questions/870594/resize-partition-to-maximum-using-parted-in-non-interactive-mode #kvmx ssh $guest sudo parted /dev/vda resizepart 2 -1 Yes kvmx ssh $guest sudo growpart /dev/vda 2 kvmx ssh $guest sudo resize2fs /dev/vda2 kvmx ssh $guest sudo touch /forcefsck kvmx restart $guest ## Folder sharing ### With virtio and 9p 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) 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) Performance limitations: * [linux/net/9p/trans_virtio.c at master · torvalds/linux · GitHub](https://github.com/torvalds/linux/blob/master/net/9p/trans_virtio.c) * [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) * [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) Discussion an proposals to overcome this limit: * [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 * [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)