April 2020 - Devel - libvirt List Archives

[PATCH] Add 'permissive' option for PCI devices
by Marek Marczykowski-Górecki 19 Apr '20

19 Apr '20

From: Simon Gaiser <simon(a)invisiblethingslab.com> By setting the permissive flag the guest access to the PCI config space is not filtered. This might be a security risk, but it's required for some devices and the IOMMU and interrupt remapping should (mostly?) contain it. Signed-off-by: Simon Gaiser <simon(a)invisiblethingslab.com> Signed-off-by: Marek Marczykowski-Górecki <marmarek(a)invisiblethingslab.com> --- docs/formatdomain.html.in | 3 +++ docs/schemas/domaincommon.rng | 5 +++++ src/conf/domain_conf.c | 12 ++++++++++++ src/conf/domain_conf.h | 1 + src/libxl/libxl_conf.c | 1 + 5 files changed, 22 insertions(+) diff --git a/docs/formatdomain.html.in b/docs/formatdomain.html.in index 6f43976815..79a5176ccd 100644 --- a/docs/formatdomain.html.in +++ b/docs/formatdomain.html.in @@ -5051,6 +5051,9 @@ or hot-plugging the device and <code>virNodeDeviceReAttach</code> (or <code>virsh nodedev-reattach</code>) after hot-unplug or stopping the guest. + When <code>permissive</code> is "yes" the pci config space access + will not be filtered. This might be a security issue. The default + is "no". </dd> <dt><code>scsi</code></dt> <dd>For SCSI devices, user is responsible to make sure the device diff --git a/docs/schemas/domaincommon.rng b/docs/schemas/domaincommon.rng index 65d6580434..9389eec3d8 100644 --- a/docs/schemas/domaincommon.rng +++ b/docs/schemas/domaincommon.rng @@ -3064,6 +3064,11 @@ <ref name="virYesNo"/> </attribute> </optional> + <optional> + <attribute name="permissive"> + <ref name="virYesNo"/> + </attribute> + </optional> <interleave> <element name="source"> <optional> diff --git a/src/conf/domain_conf.c b/src/conf/domain_conf.c index 8e8146374c..607cae61d4 100644 --- a/src/conf/domain_conf.c +++ b/src/conf/domain_conf.c @@ -8419,6 +8419,7 @@ virDomainHostdevDefParseXMLSubsys(xmlNodePtr node, virDomainHostdevSubsysSCSIVHostPtr scsihostsrc = &def->source.subsys.u.scsi_host; virDomainHostdevSubsysMediatedDevPtr mdevsrc = &def->source.subsys.u.mdev; g_autofree char *managed = NULL; + g_autofree char *permissive = NULL; g_autofree char *sgio = NULL; g_autofree char *rawio = NULL; g_autofree char *backendStr = NULL; @@ -8434,6 +8435,11 @@ virDomainHostdevDefParseXMLSubsys(xmlNodePtr node, if ((managed = virXMLPropString(node, "managed")) != NULL) ignore_value(virStringParseYesNo(managed, &def->managed)); + if ((permissive = virXMLPropString(node, "permissive")) != NULL) { + if (STREQ(permissive, "yes")) + def->permissive = true; + } + sgio = virXMLPropString(node, "sgio"); rawio = virXMLPropString(node, "rawio"); model = virXMLPropString(node, "model"); @@ -25942,6 +25948,8 @@ virDomainActualNetDefFormat(virBufferPtr buf, virDomainHostdevDefPtr hostdef = virDomainNetGetActualHostdev(def); if (hostdef && hostdef->managed) virBufferAddLit(buf, " managed='yes'"); + if (hostdef && hostdef->permissive) + virBufferAddLit(buf, " permissive='yes'"); } if (def->trustGuestRxFilters) virBufferAsprintf(buf, " trustGuestRxFilters='%s'", @@ -26130,6 +26138,8 @@ virDomainNetDefFormat(virBufferPtr buf, virBufferAsprintf(buf, "<interface type='%s'", typeStr); if (hostdef && hostdef->managed) virBufferAddLit(buf, " managed='yes'"); + if (hostdef && hostdef->permissive) + virBufferAddLit(buf, " permissive='yes'"); if (def->trustGuestRxFilters) virBufferAsprintf(buf, " trustGuestRxFilters='%s'", virTristateBoolTypeToString(def->trustGuestRxFilters)); @@ -27914,6 +27924,8 @@ virDomainHostdevDefFormat(virBufferPtr buf, if (def->mode == VIR_DOMAIN_HOSTDEV_MODE_SUBSYS) { virBufferAsprintf(buf, " managed='%s'", def->managed ? "yes" : "no"); + if (def->permissive) + virBufferAddLit(buf, " permissive='yes'"); if (def->source.subsys.type == VIR_DOMAIN_HOSTDEV_SUBSYS_TYPE_SCSI && scsisrc->sgio) diff --git a/src/conf/domain_conf.h b/src/conf/domain_conf.h index aad3f82db7..b81a3ce901 100644 --- a/src/conf/domain_conf.h +++ b/src/conf/domain_conf.h @@ -345,6 +345,7 @@ struct _virDomainHostdevDef { bool missing; bool readonly; bool shareable; + bool permissive; union { virDomainHostdevSubsys subsys; virDomainHostdevCaps caps; diff --git a/src/libxl/libxl_conf.c b/src/libxl/libxl_conf.c index b3f67f817a..55f2a09e3e 100644 --- a/src/libxl/libxl_conf.c +++ b/src/libxl/libxl_conf.c @@ -2249,6 +2249,7 @@ libxlMakePCI(virDomainHostdevDefPtr hostdev, libxl_device_pci *pcidev) pcidev->bus = pcisrc->addr.bus; pcidev->dev = pcisrc->addr.slot; pcidev->func = pcisrc->addr.function; + pcidev->permissive = hostdev->permissive; return 0; } -- 2.21.1

2 1

[libvirt PATCH] util: Do not include sys/wait.h on Win32
by Jiri Denemark 17 Apr '20

17 Apr '20

This fixes build on mingw broken by my previous commit 36e125296a. Signed-off-by: Jiri Denemark <jdenemar(a)redhat.com> --- Pushed. src/util/virdaemon.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/src/util/virdaemon.c b/src/util/virdaemon.c index 6182ca3c21..31cc24e703 100644 --- a/src/util/virdaemon.c +++ b/src/util/virdaemon.c @@ -22,7 +22,9 @@ #include <sys/types.h> #include <sys/stat.h> -#include <sys/wait.h> +#ifndef WIN32 +# include <sys/wait.h> +#endif #include <fcntl.h> #include <unistd.h> #include <stdbool.h> -- 2.26.1

1 0

[PATCH v2 0/2] docs: Further adjustments to pci-addresses.rst
by Boris Fiuczynski 17 Apr '20

17 Apr '20

Andrea Bolognani (1): docs: Update introduction in pci-addresses.rst Boris Fiuczynski (1): docs: Improve zPCI section in pci-addresses.rst docs/pci-addresses.rst | 31 ++++++++++++++++++------------- 1 file changed, 18 insertions(+), 13 deletions(-) -- 2.25.1

3 5

[PATCH 0/3] qemu: Fix restoring a domain from a block device
by Michal Privoznik 17 Apr '20

17 Apr '20

*** BLURB HERE *** Michal Prívozník (3): selinux: Don't remember label for restore path security: Introduce virSecurityManagerDomainSetIncomingPathLabel qemu: Label restore path outside of secdriver transactions src/libvirt_private.syms | 1 + src/qemu/qemu_security.c | 7 +++++++ src/security/security_driver.h | 4 ++++ src/security/security_manager.c | 29 +++++++++++++++++++++++++++++ src/security/security_manager.h | 4 ++++ src/security/security_selinux.c | 23 +++++++++++++++++------ src/security/security_stack.c | 21 +++++++++++++++++++++ 7 files changed, 83 insertions(+), 6 deletions(-) -- 2.24.1

2 8

[PATCH 0/2] docs: Further adjustments to pci-addresses.rst
by Boris Fiuczynski 17 Apr '20

17 Apr '20

Andrea Bolognani (1): docs: Update introduction in pci-addresses.rst Boris Fiuczynski (2): docs: Improve zPCI section in pci-addresses.rst docs/pci-addresses.rst | 24 ++++++++++++++---------- 1 file changed, 14 insertions(+), 10 deletions(-) -- 2.25.1

3 11

[libvirt PATCH] util: Fix virDaemonForkIntoBackground
by Jiri Denemark 17 Apr '20

17 Apr '20

This commit partially reverts commit c360ea28dc267802690e129fbad08ca2f22a44e9 Refs: v6.2.0-rc1-1-gc360ea28dc Author: Rafael Fonseca <r4f4rfs(a)gmail.com> AuthorDate: Fri Mar 27 18:40:47 2020 +0100 Commit: Michal Prívozník <mprivozn(a)redhat.com> CommitDate: Mon Mar 30 09:48:22 2020 +0200 util: virdaemon: fix compilation on mingw The daemons are not supported on Win32 and therefore were not compiled in that platform. However, with the daemon code sharing, all the code in utils *is* compiled and it failed because `waitpid`, `fork`, and `setsid` are not available. So, as before, let's not build them on Win32 and make the code more portable by using existing vir* wrappers. Not compiling virDaemonForkIntoBackground on Win32 is good, but the second part of the original patch incorrectly replaced waitpid and fork with our virProcessWait and virFork APIs. These APIs are more than just simple wrappers and we don't want any of the extra functionality. Especially virFork would reset any setup made before virDaemonForkIntoBackground is called, such as logging, signal handling, etc. As a result of the change the additional fix in v6.2.0-67-ga87e4788d2 (util: virdaemon: fix waiting for child processes) is no longer needed and it is effectively reverted by this commit. Signed-off-by: Jiri Denemark <jdenemar(a)redhat.com> --- src/util/virdaemon.c | 13 +++++++------ 1 file changed, 7 insertions(+), 6 deletions(-) diff --git a/src/util/virdaemon.c b/src/util/virdaemon.c index 99530fd146..6182ca3c21 100644 --- a/src/util/virdaemon.c +++ b/src/util/virdaemon.c @@ -20,7 +20,9 @@ #include <config.h> +#include <sys/types.h> #include <sys/stat.h> +#include <sys/wait.h> #include <fcntl.h> #include <unistd.h> #include <stdbool.h> @@ -30,8 +32,6 @@ #include "virfile.h" #include "virlog.h" #include "viralloc.h" -#include "virprocess.h" -#include "vircommand.h" #include "configmake.h" @@ -44,7 +44,7 @@ virDaemonForkIntoBackground(const char *argv0) if (virPipeQuiet(statuspipe) < 0) return -1; - pid_t pid = virFork(); + pid_t pid = fork(); switch (pid) { case 0: { @@ -73,7 +73,7 @@ virDaemonForkIntoBackground(const char *argv0) if (setsid() < 0) goto cleanup; - nextpid = virFork(); + nextpid = fork(); switch (nextpid) { case 0: /* grandchild */ return statuspipe[1]; @@ -97,14 +97,15 @@ virDaemonForkIntoBackground(const char *argv0) default: { /* parent */ - int exitstatus = 0; + int got, exitstatus = 0; int ret; char status; VIR_FORCE_CLOSE(statuspipe[1]); /* We wait to make sure the first child forked successfully */ - if (virProcessWait(pid, &exitstatus, 0) < 0 || + if ((got = waitpid(pid, &exitstatus, 0)) < 0 || + got != pid || exitstatus != 0) { goto error; } -- 2.26.1

2 1

[PATCH 0/5] qemu: Support rbd namespace attribute
by Han Han 17 Apr '20

17 Apr '20

QEMU introduced rbd namespace blockdev args since v5.0.0[1]. Implement rbd namespace to libvirt. It could be used for tenant isolation with in a pool after Ceph Nautilus. Note that since the aarch64 qemu capabilities replies is not updated for the namespace args, I didn't add capabilities test for this arch. The capabilities test will be updateid after the updated replies. https://bugzilla.redhat.com/show_bug.cgi?id=1816909 [1]: https://lists.gnu.org/archive/html/qemu-devel/2019-12/msg04344.html Han Han (5): qemu_capabilities: Add QEMU_CAPS_RBD_NAMESPACE conf: Support to parse rbd namespace attribute qemu: Implement rbd namespace attribute doc: rng schemas and html doc for rbd namespace attribute news: qemu: Support rbd namespace docs/formatdomain.html.in | 5 +++ docs/news.xml | 9 ++++ docs/schemas/domaincommon.rng | 3 ++ src/conf/domain_conf.c | 4 ++ src/qemu/qemu_block.c | 1 + src/qemu/qemu_capabilities.c | 2 + src/qemu/qemu_capabilities.h | 1 + src/qemu/qemu_command.c | 14 ++++++- src/util/virstoragefile.h | 1 + .../qemucapabilitiesdata/caps_5.0.0.ppc64.xml | 1 + .../caps_5.0.0.x86_64.xml | 1 + ...k-network-rbd-namespace.x86_64-latest.args | 41 +++++++++++++++++++ .../disk-network-rbd-namespace.xml | 33 +++++++++++++++ tests/qemuxml2argvtest.c | 1 + ...sk-network-rbd-namespace.x86_64-latest.xml | 41 +++++++++++++++++++ tests/qemuxml2xmltest.c | 1 + 16 files changed, 158 insertions(+), 1 deletion(-) create mode 100644 tests/qemuxml2argvdata/disk-network-rbd-namespace.x86_64-latest.args create mode 100644 tests/qemuxml2argvdata/disk-network-rbd-namespace.xml create mode 100644 tests/qemuxml2xmloutdata/disk-network-rbd-namespace.x86_64-latest.xml -- 2.25.0

2 7

[libvirt PATCH] docs: kbase: add a page about debugging
by Ján Tomko 16 Apr '20

16 Apr '20

Migrate the following wiki articles: https://wiki.libvirt.org/page/DebugLogs https://wiki.libvirt.org/page/Debugging With the syntax changed to rST and rewrapped. Signed-off-by: Ján Tomko <jtomko(a)redhat.com> --- I might've changed an article or two, too. Or rather: the article 'the'. docs/kbase.html.in | 3 + docs/kbase/debugging.rst | 303 +++++++++++++++++++++++++++++++++++++++ 2 files changed, 306 insertions(+) create mode 100644 docs/kbase/debugging.rst diff --git a/docs/kbase.html.in b/docs/kbase.html.in index c586e0f676..1a50428805 100644 --- a/docs/kbase.html.in +++ b/docs/kbase.html.in @@ -36,6 +36,9 @@ <dt><a href="kbase/virtiofs.html">Virtio-FS</a></dt> <dd>Share a filesystem between the guest and the host</dd> + + <dt><a href="kbase/debugging.html">Debugging libvirt</a></dt> + <dd>How to capture debug logs and use a debugger on libvirt</dd> </dl> </div> diff --git a/docs/kbase/debugging.rst b/docs/kbase/debugging.rst new file mode 100644 index 0000000000..a9bc02aa55 --- /dev/null +++ b/docs/kbase/debugging.rst @@ -0,0 +1,303 @@ +================= +Debugging libvirt +================= + +.. contents:: + + +If you `report a bug <https://libvirt.org/bugs.html>`_ against libvirt, in most +cases you will be asked to attach debug logs. These are bare text files which +tracks transition between different states of libvirtd, what it has tried to +achieve, etc. Because of client -- server schema used in libvirt, the logs can +be either client or server too. Usually, it's server side that matters as +nearly all interesting work takes place there. Moreover, libvirt catches stderr +of all running domains. These can be useful as well. + + +How to turn on debug logs for libvirt +===================================== + +Persistent setting +------------------ + +The daemon configuration files location is dependent on the `connection URI +<http://libvirt.org/uri.html>`_. For ``qemu:///system``: + +* open ``/etc/libvirt/libvirtd.conf`` in your favourite editor +* find & replace, or set these variables:: + + # LEGACY SETTINGS PRIOR LIBVIRT 4.4.0 SEE BELOW! # + log_level = 1 + log_filters="1:qemu 3:remote 4:event 3:util.json 3:rpc" + log_outputs="1:file:/var/log/libvirt/libvirtd.log" + + + # PREFERRED SETTINGS AFTER LIBVIRT 4.4.0 # + log_filters="3:remote 4:event 3:util.json 3:rpc 1:*" + log_outputs="1:file:/var/log/libvirt/libvirtd.log" + +* save and exit +* restart libvirtd service:: + + systemctl restart libvirtd.service + +In the config variables above, we have set logging level to 1 (debug level), +set some filters (to filter out noise), e.g. from rpc only warnings (=level 3) +and above will be reported. The logs are saved into +``/var/log/libvirt/libvirtd.log``. Since libvirt *4.4.0* log filters +support shell globbing, therefore the usage of ``log_level`` is considered +deprecated in favour of pure usage of ``log_filters``. + +In case you want to get the client logs, you need to set this environment variable:: + + export LIBVIRT_LOG_OUTPUTS="1:file:/tmp/libvirt_client.log" + +However, when you are using the session mode ``qemu:///session`` or you run the +``libvirtd`` as unprivileged user you will find configuration file under +``$XDG_CONFIG_HOME/libvirt/libvirt.conf``. + + +Runtime setting +--------------- + +Debugging anomalies can be very painful, especially when trying to reproduce it +after the daemon restarts, since the new session can make the anomaly +"disappear". Therefore, it's possible to enable the debug logs during runtime +using libvirt administration API. To use it conveniently, there's a ``virt-admin`` +client provided by the ``libvirt-admin`` package. Use the package manager provided +by your distribution to install this package. Once you have it installed, run +the following as root to see the set of log filters currently being active:: + + # virt-admin daemon-log-filters + Logging filters: 3:remote 4:util.json 4:rpc + +In order to change this set, run the same command as root, this time with your own set of filters:: + + ## LEGACY APPROACH ENUMERATING ALL THE DESIRED MODULES ## + # virt-admin daemon-log-filters "1:util 1:libvirt 1:storage 1:network 1:nodedev 1:qemu" + + ## CURRENT APPROACH USING SHELL GLOBBING ## + # virt-admin daemon-log-filters "3:remote 4:util.json 4:rpc 1:*" + +Analogically, the same procedure can be performed with log outputs:: + + # virt-admin daemon-log-outputs + Logging outputs: 3:syslog:libvirtd + # virt-admin daemon-log-outputs "1:file:/var/log/libvirt/libvirtd.log" + +NOTE: It's always good practice to return the settings to the original state +once you're finished debugging, just remember to save the original sets of +filters and outputs and restore them at the end the same way as described +above. + + +Removing filters and outputs +---------------------------- + +It's also possible to remove all the filters and produce an enormous log file, +but it is not recommended since some of libvirt's modules can produce a large +amount of noise. However, should you really want to do this, you can specify an +empty set of filters:: + + # virt-admin daemon-log-filters "" + Logging filters: + +The situation is a bit different with outputs, since libvirt always has to log +somewhere and resetting the outputs to an empty set will restore the default +setting which depends on the host configuration, ''journald'' in our case:: + + # virt-admin daemon-log-outputs + Logging outputs: 1:file:/var/log/libvirt/libvirtd.log + # virt-admin daemon-log-outputs "" + Logging outputs: 2:journald + + +What to attach? +--------------- + +Now you should go and reproduce the bug. Once you're finished, attach: + +* ``/var/log/libvirt/libvirtd.log`` or whatever path you set for the daemon logs. +* If the problem is related to a domain attach ``/var/log/libvirt/qemu/$dom.log`` + then. Or substitute ``qemu`` with whatever hypervisor you are using. +* If you are asked for client logs, ``/tmp/libvirt_client.log``. + + +Using a debugger +================ + +When trying to figure out what libvirt does, debug logs might not always be +enough. And sometimes you might want to get some information from a user, but +you do not want to waste both your and their time by explaining how to do stuff +in gdb to, for example, get a backtrace. Here are some useful tips that you +might use. + + +Prerequisites +------------- + +In cases where you want to see details of what is happening, you need to have +debugging symbols installed, at least for the package you are trying to debug. +Although having debugging symbols for all dependent libraries is usually +helpful as well. Usually ``gdb`` will tell you what you need to do in order to +get the proper data to your machine when you run it with a binary. + +=== Example: === + +Running this command on 32bit Fedora 29 tells us what to install in order to +get the proper debugging symbols:: + + # gdb $(which libvirtd) + GNU gdb (GDB) Fedora 8.2-6.fc29 + ... + Reading symbols from /usr/sbin/libvirtd...(no debugging symbols found)...done. + Missing separate debuginfos, use: dnf debuginfo-install libvirt-daemon-4.7.0-1.fc29.i686 + +When the package is installed, we can break on main and run until then (gdb's +command ``start`` is perfect for this):: + + # gdb $(which libvirtd) + GNU gdb (GDB) Fedora 8.2-6.fc29 + ... + Reading symbols from /usr/sbin/libvirtd...Reading symbols from /usr/lib/debug/usr/sbin/libvirtd-4.7.0-1.fc29.i386.debug...done. + done. + (gdb) start + Temporary breakpoint 1 at 0x18fc0: file remote/remote_daemon.c, line 1030. + Starting program: /usr/sbin/libvirtd + Missing separate debuginfos, use: dnf debuginfo-install glibc-2.28-26.fc29.i686 + Missing separate debuginfo for /lib/libvirt-lxc.so.0 + Try: dnf --enablerepo='*debug*' install /usr/lib/debug/.build-id/4d/16496b686ec54ca4201bd769b04293f6c756b3.debug + Missing separate debuginfo for /lib/libvirt-qemu.so.0 + Try: dnf --enablerepo='*debug*' install /usr/lib/debug/.build-id/ea/91d5346bd3e265ffb12ae641ca93643443e6e7.debug + Missing separate debuginfo for /lib/libvirt.so.0 + Try: dnf --enablerepo='*debug*' install /usr/lib/debug/.build-id/02/af3a96fc6227ed5e3a447344bcbb672bde14ba.debug + ... + Temporary breakpoint 1, main (argc=1, argv=0xbffff614) at remote/remote_daemon.c:1030 + 1030 int main(int argc, char **argv) { + Missing separate debuginfos, use: dnf debuginfo-install audit-libs-3.0-0.5.20181218gitbdb72c0.fc29.i686 avahi-libs-0.7-16.fc29.i686 brotli-1.0.5-1.fc29.i686 cyrus-sasl-lib-2.1.27-0.3rc7.fc29.i686 dbus-libs-1.12.12-1.fc29.i686 device-mapper-libs-1.02.154-1.fc29.i686 gmp-6.1.2-9.fc29.i686 gnutls-3.6.6-1.fc29.i686 keyutils-libs-1.5.10-8.fc29.i686 krb5-libs-1.16.1-25.fc29.i686 libacl-2.2.53-2.fc29.i686 libattr-2.4.48-3.fc29.i686 libblkid-2.32.1-1.fc29.i686 libcap-2.25-12.fc29.i686 libcap-ng-0.7.9-5.fc29.i686 libcom_err-1.44.4-1.fc29.i686 libcurl-7.61.1-10.fc29.i686 libffi-3.1-18.fc29.i686 libgcrypt-1.8.4-1.fc29.i686 libidn2-2.1.1a-1.fc29.i686 libmount-2.32.1-1.fc29.i686 libnghttp2-1.34.0-1.fc29.i686 libnl3-3.4.0-6.fc29.i686 libpsl-0.20.2-5.fc29.i686 libselinux-2.8-6.fc29.i686 libsepol-2.8-3.fc29.i686 libssh-0.8.7-1.fc29.i686 libssh2-1.8.1-1.fc29.i686 libtirpc-1.1.4-2.rc2.fc29.i686 libunistring-0.9.10-4.fc29.i686 libuuid-2.32.1-1.fc29.i686 libwsman1-2.6.5-8.fc29.i686 libxcrypt-4.4.4-2.fc29.i686 libxml2-2.9.8-5.fc29.i686 lz4-libs-1.8.3-1.fc29.i686 numactl-libs-2.0.12-1.fc29.i686 openldap-2.4.46-10.fc29.i686 openssl-libs-1.1.1b-3.fc29.i686 p11-kit-0.23.15-2.fc29.i686 pcre2-10.32-8.fc29.i686 xz-libs-5.2.4-3.fc29.i686 yajl-2.1.0-11.fc29.i686 zlib-1.2.11-14.fc29.i686 + +You might need to run the above commands for more complete output. It is very +dependent on the actually problem, whether you need this or not, but it will +never hurt to actually have all the data installed. + + +When libvirt hangs +------------------ + +When a process hangs, we usually ask for a backtrace. To avoid problems with +paging and so on, it is usually very helpful to just get a backtrace for one +instance of the particular process. For that you can use something like this:: + + # gdb -batch -p $(pidof libvirtd) -ex 't a a bt f' + +This command will attach to currently running libvirtd process and run ``t a a +bt f``, which is short for ``thread apply all backtrace full``, feel free to +combine with ``sudo`` for users. If you are using this for virsh, or any other +binary which might have multiple processes running, then make sure you supply +the right pid for the ``-p`` option. For more info, read below about how to +automate gdb. + + +When libvirt crashes +-------------------- + +Different distros have different mechanisms of catching and reporting crashes. +The automated ones are usually enabled only for the packaged binaries, but that +should be enough for users. Developers will have their own way of doing things +anyway. + +* **systemd-coredump** -- ``coredumpctl show`` shows all needed information + (even a backtrace) of the last crash, use ``coredumpctl ls`` to list all + crashes cordumpctl knows about. + +* **abrt** -- ``abrt-cli`` works similarly to the above (TBD: how to get the + backtrace using abrt-cli) + +* **setup your own** -- you can do one of these things: + + * set the ulimit for the service (depends on your init system) and look for + the file that gets created + * set kernel.core_pattern using sysctl to a command (rather than a filename + template) that gets ran with each core dump. This one does not need any + ulimit setting, but you need to know what to specify there. + +For more information see related documentation. + + +Automating gdb +-------------- + +When you need more specific behaviour from gdb, you can automate that, but for +multiline commands you need an input redirection or execute them from the file. + + +Multiline example +----------------- + +Simple example that will print backtrace when ``abort()`` is reached:: + + $ cat >/var/lib/libvirt/gdbabortscript <<EOF + start + break abort + commands + t a a bt full + end + continue + EOF + +This file instructs gdb to ``start`` the program (run until ``main()``), that +will load all the libraries so that we can setup a breakpoint for (p[retty +much) any existing function. It then sets up a breakpoint for the ``abort()`` +function and immediately sets up a list of ``commands`` that will run when that +breakpoint is hit (list of commands ends with ``end``). After that it allows +the process to ``continue`` its execution. + + +Systemd example +--------------- + +Let's say you need to debug an issue which happens only when the daemon is run +as a service as it does not happen when run manually. Ideally you would +connect to a running instance, but if the issue happens right after starting +the daemon. One option would be utilizing ``systemtap`` to add a ``sleep()`` +in one of the early functions (TBD: add an automated way of doing that or +remove this tip if it's not worth it). Another idea is to make the init system +run the gdb command we need. + +In systemd world we can do this easily by overriding the ``ExecStart`` parameter:: + + # cat >/etc/systemd/system/libvirtd.service.d/override.conf <<EOF + [Service] + ExecStart= + ExecStart=/usr/bin/gdb --batch -x /var/lib/libvirt/gdbabortscript /usr/sbin/libvirtd $LIBVIRTD_ARGS + EOF + +Daemon needs to be reloaded to know about this file:: + + # systemctl daemon-reload + +We also need to make sure that the file we created will be readable by the +service. DAC should be fine, SELinux might get tricky. By placing the file +under ``/var/lib/libvirt`` this should be readable by both the init system and +the libvirt daemon, but we need to make sure it has a proper context:: + + # restorecon -F /var/lib/libvirt/gdbabortscript /etc/systemd/system/libvirtd.service.d/override.conf + +We actually do not need this to be read by the init system, but gdb will most +probably run under the same SELinux context as init, the context for libvirtd +gets changed by a transition rule which depends on the current runnning context +and the context of the binary being executed, so that whould apply only when +libvirtd is being started. This ''should'' work most of the time. If it does +not work for you, please figure out a way and add it here. + +Now we need to restart the daemon:: + + # systemctl restart libvirtd.service + +Beware, the command will not end until libvirtd itself ends as systemd is +waiting for ``sd_notify()`` from gdb's PID, but that function is being called +by libvirtd. + +You should get the full backtrace in the output of:: + + # journalctl -u libvirtd.service -- 2.25.1

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[libvirt PATCH] docs: Add section about code blocks to styleguide.rst
by Andrea Bolognani 16 Apr '20

16 Apr '20

Signed-off-by: Andrea Bolognani <abologna(a)redhat.com> --- docs/styleguide.rst | 12 ++++++++++++ 1 file changed, 12 insertions(+) diff --git a/docs/styleguide.rst b/docs/styleguide.rst index 2998e90963..3162868fb7 100644 --- a/docs/styleguide.rst +++ b/docs/styleguide.rst @@ -24,6 +24,18 @@ Whitespace Blocks should be indented with 3 spaces, and no tabs +Code blocks +=========== + +Code blocks should be created using + +:: + + This is regular text. + + :: + + This is a code block. Headings ======== -- 2.25.2

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[libvirt PATCH 0/4] docs: A few adjustments to pci-addresses.rst
by Andrea Bolognani 16 Apr '20

16 Apr '20

Andrea Bolognani (4): docs: Use consistent style in pci-addresses.rst docs: Move sections around in pci-addresses.rst docs: Remove MAC addresses from pci-addresses.rst docs: Remove one example from pci-addresses.rst docs/pci-addresses.rst | 102 +++++++++++++++++------------------------ 1 file changed, 42 insertions(+), 60 deletions(-) -- 2.25.2

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