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Libvirt provides a portable, long term stable C API for managing the virtualization technologies provided by many operating systems. It includes support for QEMU, KVM, Xen, LXC, bhyve, Virtuozzo, VMware vCenter and ESX, VMware Desktop, Hyper-V, VirtualBox and the POWER Hypervisor.
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2eabac008e
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Eric Blake 2eabac008e blockjob: fix block-stream bandwidth race 
With RHEL 6.2, virDomainBlockPull(dom, dev, bandwidth, 0) has a race
with non-zero bandwidth: there is a window between the block_stream
and block_job_set_speed monitor commands where an unlimited amount
of data was let through, defeating the point of a throttle.

This race was first identified in commit a9d3495e, and libvirt was
able to reduce the size of the window for that race.  In the meantime,
the qemu developers decided to fix things properly; per this message:
https://lists.gnu.org/archive/html/qemu-devel/2012-04/msg03793.html
the fix will be in qemu 1.1, and changes block-job-set-speed to use
a different parameter name, as well as adding a new optional parameter
to block-stream, which eliminates the race altogether.

Since our documentation already mentioned that we can refuse a non-zero
bandwidth for some hypervisors, I think the best solution is to do
just that for RHEL 6.2 qemu, so that the race is obvious to the user
(anyone using stock RHEL 6.2 binaries won't have this patch, and anyone
building their own libvirt with this patch for RHEL can also rebuild
qemu to get the modern semantics, so it is no real loss in behavior).

Meanwhile the code must be fixed to honor actual qemu 1.1 naming.
Rename the parameter to 'modern', since the naming difference now
covers more than just 'async' block-job-cancel.  And while at it,
fix an unchecked integer overflow.

* src/qemu/qemu_monitor.h (enum BLOCK_JOB_CMD): Drop unused value,
rename enum to match conventions.
* src/qemu/qemu_monitor.c (qemuMonitorBlockJob): Reflect enum rename.
* src/qemu_qemu_monitor_json.h (qemuMonitorJSONBlockJob): Likewise.
* src/qemu/qemu_monitor_json.c (qemuMonitorJSONBlockJob): Likewise,
and support difference between RHEL 6.2 and qemu 1.1 block pull.
* src/qemu/qemu_driver.c (qemuDomainBlockJobImpl): Reject
bandwidth during pull with too-old qemu.
* src/libvirt.c (virDomainBlockPull, virDomainBlockRebase):
Document this.
2012-04-27 13:00:56 -06:00
.gnulib@bb2f5640d5 build: fix bootstrap on RHEL 2012-04-25 16:25:49 -06:00
daemon The policy kit and HAL node device drivers both require a 2012-04-19 17:03:10 +01:00
docs docs: Serialize running apibuild.py 2012-04-27 12:37:47 -04:00
examples Revert "Refactor the libvirt RPM daemon pieces" 2012-04-03 14:49:31 +08:00
gnulib build: fix fresh checkout on RHEL5 2012-04-19 17:11:43 -06:00
include blockjob: add new API flags 2012-04-23 07:44:29 -06:00
m4 Enable all warnings permanently & default to -Werror for GIT builds 2012-03-27 17:08:06 +01:00
po The policy kit and HAL node device drivers both require a 2012-04-19 17:03:10 +01:00
python python: Fix doc directory name for stable releases 2012-04-27 12:41:05 -04:00
src blockjob: fix block-stream bandwidth race 2012-04-27 13:00:56 -06:00
tests blockjob: enhance xml to track mirrors across libvirtd restart 2012-04-23 08:43:33 -06:00
tools blockjob: add 'blockcopy' to virsh 2012-04-23 07:44:30 -06:00
.dir-locals.el maint: let emacs avoid tabs in rng files 2011-08-13 08:56:26 -06:00
.gitignore docs: Serialize running apibuild.py 2012-04-27 12:37:47 -04:00
.gitmodules
.mailmap maint: prune duplicate listings in AUTHORS 2012-02-03 09:56:45 -07:00
AUTHORS esx: Fix segfault in esxConnectToHost 2012-04-21 14:13:22 +02:00
autobuild.sh Enable all warnings permanently & default to -Werror for GIT builds 2012-03-27 17:08:06 +01:00
autogen.sh build: allow for local gnulib diffs 2011-11-09 09:03:33 -07:00
bootstrap build: fix bootstrap on RHEL 2012-04-25 16:25:49 -06:00
bootstrap.conf build: fix bootstrap on RHEL 2012-04-25 16:25:49 -06:00
cfg.mk build: avoid strtol and strtod 2012-04-19 17:42:53 -06:00
ChangeLog-old virterror.c: Fix several spelling mistakes 2012-02-03 11:32:51 -07:00
configure.ac configure: Use ustar format for dist tarball 2012-04-27 12:36:30 -04:00
COPYING.LIB
HACKING Document STREQ_NULLABLE and STRNEQ_NULLABLE 2011-10-06 16:50:38 +02:00
libvirt.pc.in Fix typos in API XML file paths 2012-02-15 11:29:38 +00:00
libvirt.spec.in Fix initial hypervisor conditionals 2012-04-04 10:54:20 +01:00
Makefile.am maint: add missing copyright notices 2011-07-28 15:01:17 -06:00
Makefile.nonreentrant Ban use of all inet_* functions 2010-10-22 11:59:23 +01:00
mingw32-libvirt.spec.in Fix typos in API XML file paths 2012-02-15 11:29:38 +00:00
README
README-hacking
TODO Update todo list file to point at bugzilla/website 2010-10-13 16:45:26 +01:00

README 

         LibVirt : simple API for virtualization

  Libvirt is a C toolkit to interact with the virtualization capabilities
of recent versions of Linux (and other OSes). It is free software
available under the GNU Lesser General Public License. Virtualization of
the Linux Operating System means the ability to run multiple instances of
Operating Systems concurrently on a single hardware system where the basic
resources are driven by a Linux instance. The library aim at providing
long term stable C API initially for the Xen paravirtualization but
should be able to integrate other virtualization mechanisms if needed.

Daniel Veillard <veillard@redhat.com>