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The default USB controller of pc machine type
by Han Han 15 Jul '22

15 Jul '22

Hello, I found that the default USB controller for q35 machine type is qemu-xhci while for pc it is piix3-uhci. Here are the results(on qemu-kvm-7.0.0 qemu-kvm-7.0.0): ➜ ~ cat /tmp/usb.xml <domain type="kvm"> <name>USB</name> <uuid>1a81d4ef-6537-4ae8-b257-8a15e0c0525f</uuid> <memory>2097152</memory> <currentMemory>2097152</currentMemory> <vcpu>1</vcpu> <os> <type arch="x86_64" machine="q35">hvm</type> <boot dev="hd"/> </os> <devices> <emulator>/usr/libexec/qemu-kvm</emulator> </devices> </domain> ➜ ~ virsh define /tmp/usb.xml && virsh dumpxml USB|grep usb Domain 'USB' defined from /tmp/usb.xml <controller type='usb' index='0' model='qemu-xhci'> ➜ ~ cat /tmp/usb-pc.xml <domain type="kvm"> <name>USB</name> <uuid>1a81d4ef-6537-4ae8-b257-8a15e0c0525f</uuid> <memory>2097152</memory> <currentMemory>2097152</currentMemory> <vcpu>1</vcpu> <os> <type arch="x86_64" machine="pc">hvm</type> <boot dev="hd"/> </os> <devices> <emulator>/usr/libexec/qemu-kvm</emulator> </devices> </domain> ➜ ~ virsh define /tmp/usb-pc.xml && virsh dumpxml USB|grep usb Domain 'USB' defined from /tmp/usb-pc.xml <controller type='usb' index='0' model='piix3-uhci'> And the default usb controller for q35 has been added since: ed2049ea19 qemu: auto-add generic xhci rather than NEC xhci to Q35 domains As I know, pc machine supports qemu-xhci as well. Morever, the performance of qemu-xhci is better than piix3-uhci. So why not update the default usb controller of pc machine type to qemu-xhci? I think we can improve it here.

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Why can not get the expected cpu topology after setting the maxcpu in xml?
by liang chaojun 15 Jul '22

15 Jul '22

Hello all, I hit a issue that I'm not able to see the expected cpu topology in VM after setting the maxcpu arrtribute in domain. the xml look like below: <vcpu placement='static' current='4'>8</vcpu> <cpu mode='host-passthrough' check='none' migratable='on'> <topology sockets='2' dies='1' cores='4' threads='1'/> </cpu> I notice that the cpu topoloy looked like below capture output from 'lscpu' tool which is totally different with my setting. CPU(s): 4 On-line CPU(s) list: 0-3 Thread(s) per core: 1 Core(s) per socket: 4 Socket(s): 1 NUMA node(s): 1 Vendor ID: GenuineIntel CPU family: 6 Model: 63 Model name: Intel(R) Xeon(R) CPU E5-2699 v3 @ 2.30GHz Besides i found it looked correct if i relpace 'vcpu' line with "<vcpu placement='static'>8</vcpu>" that remove maxcpu value. Could you give me some information? Any comments are appreciated. Thanks

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systemtap stapvirt tool
by Stan Cox 08 Jul '22

08 Jul '22

I am having a quandary with libvirt and am wondering if someone can shed some light. Systemtap converts a probing and instrumentation language into a kernel module. The module can optionally be run remotely via ssh or libvirt. The libvirt mechanism is not working (not yet sure of timing of regression) The systemtap stap command pipes to a stapvirt command that is the libvirt interface. The remote is running a stapsh tool that receives the requests. The initial commands are sent and received okay (strace output on remote) but never receives the stap kernel module: # local sent option data request [pid 11959] read(3, "option data\n", 4096) = 12 # remote says OK [pid 11959] write(3, "OK\n", 3) = 3 [pid 11959] poll([{fd=3, events=POLLIN}, {fd=0, events=0}, {fd=0, events=0}], 3, -1) = 1 ([{fd=3, revents=POLLIN}]) [pid 11959] --- SIGIO {si_signo=SIGIO, si_code=SI_KERNEL} --- [pid 11959] poll([{fd=3, events=POLLHUP}], 1, 0) = 0 (Timeout) [pid 11959] rt_sigreturn({mask=[]}) = 1 # local sent file ... request to download the module [pid 11959] read(3, "file 926928 stap_1f18b4b54e74602"..., 4096) = 58 # remote opens the module [pid 11959] openat(AT_FDCWD, "stap_1f18b4b54e74602a0a1f0685f2f7333e_1006.ko", O_WRONLY|O_CREAT|O_TRUNC, 0666) = 4 # but never receives it [pid 11959] read(3, "", 4096) = 0 The local sets up callbacks for stdin, stdout, stream: ctxt.stdin_w = virEventAddHandle(STDIN_FILENO, VIR_EVENT_HANDLE_READABLE, stdin_event, &ctxt, NULL); ... ctxt.stdout_w = virEventAddHandle(STDOUT_FILENO, 0, stdout_event, &ctxt, NULL); ... virStreamEventAddCallback(ctxt.st, VIR_STREAM_EVENT_READABLE | VIR_EVENT_HANDLE_WRITABLE, stream_event, &ctxt, NULL) < 0) Then starts an even loop while (!disconnect) { if (virEventRunDefaultImpl() != 0) break; } stream_event is notified for the command requests, but is not notified for the kernel module chunks: stdin_event excerpt: bytes_read = read(fd, ctxt->termbuf + ctxt->termbuf_off, sizeof(ctxt->termbuf) - ctxt->termbuf_off); ... ctxt->termbuf_off += bytes_read; ... if (ctxt->termbuf_off) { // we have stuff to write to the stream virStreamEventUpdateCallback(ctxt->st, VIR_STREAM_EVENT_READABLE | VIR_STREAM_EVENT_WRITABLE); } stream_event excerpt: if ((events & VIR_STREAM_EVENT_READABLE) && (ctxt->stbuf_off < sizeof(ctxt->stbuf))) { int bytes_recv = virStreamRecv(st, ctxt->stbuf + ctxt->stbuf_off, sizeof(ctxt->stbuf) - ctxt->stbuf_off); I notice https://libvirt.org/html/libvirt-libvirt-stream.html has an example using virStreamSend. Is that the preferred way to do the above?

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Incomplete information in the website Wiki for libvirt.org
by Uriel Emmanuel Pelaez Hernández 04 Jul '22

04 Jul '22

Dear Web Marster from wiki.libvirt.org, I tried to look for the libvirtd, the demon that is suppose to run under Linux/Unix environment, but your site didn't show any information. Only a statement appeared: "Create the page libvirtd " Please, update your site or suggest any other weblink with the information. In theory CygWin use your package, but the information is incomplete too, about this issue. I send this mail to these both Email address by the information displayed in your wiki, about the contact address to solve this kind of problems. By now, Google Service in my region is deprecated, so the information that the WebBrowser display is not the best. I send this request from my Email of Graduated Student form the University domain. Best Regards, Mr. Peláez Uriel. Mexico City

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Storage Pool - NFS v4.1
by Charles Koprowski 02 Jul '22

02 Jul '22

Hello, In order to use pNFS which is only available in NFS version 4.1, I'm trying to create a netfs storage pool specifying the protocol version to be used : <pool type="netfs"> <name>vms</name> <source> ... <format type="nfs"/> <protocol ver='4.1'/> </source> <target> ... </pool> But the storage pool XML documentation [1] states that : protocol For a netfs Storage Pool provide a mechanism to define which NFS protocol version number will be used to contact the server's NFS service. The attribute ver accepts an unsigned *integer* as the version number to use. And indeed, when I try to virsh pool-define I get : error: Failed to define pool from pool.xml error: XML error: storage pool protocol ver '4.1' is malformed How can I specify the desired NFS minor version to libvirt ? I could mount the NFS share myself and build a dir storage pool on top of it but that's not very pretty. Thank you, [1] https://libvirt.org/formatstorage.html -- Charles

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libvirt and Ledger Nano or hotswappable single USB port with virt-manager - almost there?
by Anonymous Aardvark 28 Jun '22

28 Jun '22

Hi I am holding off on a full VFIO system (with a host just used for hosting and main hardware forwarded) until after a build a new PC for the coming generation of graphics cards but I have started using virt-manager to partition my workspaces. My host is Ubuntu 20.04 running QEMU v 5.0 on and Intel i5-4690K CPU and GA-Z97X-Gaming 5 motherboard. Guest is Debian 11. I am trying to solve the issue of how the Ledger Nano X changes its product ID when using different applications <https://imil.net/blog/posts/2020/ledger_on_kvm/>. Unfortunately all ports seem to be in the same IOMMU group so I cannot just forward a controller. I have learned that although my temporary fallback Virtualbox allows forwarding by vendor ID without a product ID <https://www.reddit.com/r/ledgerwallet/comments/mf872x/how_can_you_run_ledge…>, and I have seen some libvirt references to this, including mention of a patch that apparently should have been implemented I have not been able to make it work: from QEMU to libvirt(virsh) - add USB-port <https://stackoverflow.com/questions/46421962/from-qemu-to-libvirtvirsh-add-…> Can I pass through a USB Port via qemu Command Line? <https://unix.stackexchange.com/questions/452934/can-i-pass-through-a-usb-po…> Detail on on my comprehensive hotplugger attempts to forward a single port here <https://www.reddit.com/r/VFIO/comments/lbvgpr/comment/idzml1k/?utm_source=s…> . Can you please tell me if there is some way I can edit either my debian.xml or how hotplugger interacts with the socket so that I can forward a single port that is hotswapable and/or so that Ledger Nano X will stay visible on the guest even after it changes product ID? Thanks Aard.

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Domain XML and VLAN tagging
by Gionatan Danti 20 Jun '22

20 Jun '22

Hi all, from here [1]: "Network connections that support guest-transparent VLAN tagging include 1) type='bridge' interfaces connected to an Open vSwitch bridge Since 0.10.0 , 2) SRIOV Virtual Functions (VF) used via type='hostdev' (direct device assignment) Since 0.10.0 , and 3) SRIOV VFs used via type='direct' with mode='passthrough' (macvtap "passthru" mode) Since 1.3.5 . All other connection types, including standard linux bridges and libvirt's own virtual networks, do not support it." I read it correctly that when used on a classical linux bridge these vlan tags does nothing? If so, it is due to something related to the underlying bridge device (ie: incomplete support for vlan filtering) or it is because libvirt lacks the necessary "plumbing" to use advanced bridge features? Thanks. [1] https://libvirt.org/formatdomain.html#setting-vlan-tag-on-supported-network… -- Danti Gionatan Supporto Tecnico Assyoma S.r.l. - www.assyoma.it email: g.danti(a)assyoma.it - info(a)assyoma.it GPG public key ID: FF5F32A8

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managed save returns "migration with virtiofs device is not supported"
by Francesc Guasch 16 Jun '22

16 Jun '22

Hello. I have a virtual machine with a virtiofs entry configured. When I try to do a managed save it fails with this message: libvirt error code: 55, message: Requested operation is not valid: migration with virtiofs device is not supported This is libvirt 8.0.0 that comes with Ubuntu 22.04. I have seen the current release in git is libvirt 8.5 . I will try to build from source and try again if you think this was not the expected behaviour. This is the filesystem entry: <filesystem type='mount' accessmode='passthrough'> <driver type='virtiofs'/> <source dir='/home/shared'/> <target dir='home_shared'/> <address type='pci' domain='0x0000' bus='0x01' slot='0x00' function='0x0'/> </filesystem> Sorry if this is not the right place to ask. I can write an issue in gitlab or whatever is more appropriate. Thanks !

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managed save returns "migration with virtiofs device is not supported"
by Francesc Guasch 16 Jun '22

16 Jun '22

Hello. I have a virtual machine with a virtiofs entry configured. When I try to do a managed save it fails with this message: libvirt error code: 55, message: Requested operation is not valid: migration with virtiofs device is not supported This is libvirt 8.0.0 that comes with Ubuntu 22.04. I have seen the current release in git is libvirt 8.5 . I will try to build from source and try again if you think this was not the expected behaviour. This is the filesystem entry: <filesystem type='mount' accessmode='passthrough'> <driver type='virtiofs'/> <source dir='/home/shared'/> <target dir='home_shared'/> <address type='pci' domain='0x0000' bus='0x01' slot='0x00' function='0x0'/> </filesystem> Sorry if this is not the right place to ask. I can write an issue in gitlab or whatever is more appropriate. Thanks !

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After restarted libvirtd service, live migration VM hit an issue 'Target CPU check default does not match source none'
by 梁朝军 15 Jun '22

15 Jun '22

Hi All, After restarted the libvirtd service on the source host, we start live migration VM to destination host and often hit an issue 'unsupported configuration: Target CPU check default does not match source none’ We don’t configure any special setting for CPU model when start VM and I think it should be ‘custom’ mode by default . Furthermore , those two hosts for doing live migration have almost the same capabilities as below. It’s confused me why failed to check the cpu configuration after restart libvitd service on source host? The libvirt version is 7.9.0, package: 1.el8 (Unknown, 2021-11-28-22:35:11) private build Host OS version : rhat8.4 QEMU version: QEMU 5.1 private build Any comments are appreciated. Thanks

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