July 2022 - Users - libvirt List Archives

systemtap stapvirt tool
by Stan Cox 07 Jul '22

07 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 01 Jul '22

01 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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