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Sergey Dyasli
5ed12565aa
When one core is loading ucode, handling NMI on sibling threads or on other cores in the system might be problematic. By rendezvousing all CPUs in NMI handler, it prevents NMI acceptance during ucode loading. Basically, some work previously done in stop_machine context is moved to NMI handler. Primary threads call in and load ucode in NMI handler. Secondary threads wait for the completion of ucode loading on all CPU cores. An option is introduced to disable this behavior. Control thread doesn't rendezvous in NMI handler by calling self_nmi() (in case of unknown_nmi_error() being triggered). The side effect is control thread might be handling an NMI while other threads are loading ucode. If an ucode is to update something shared by a whole socket, control thread may be accessing things that are being updating by the ucode loading on other cores. It is not safe. Update ucode on the control thread first to mitigate this issue. Signed-off-by: Sergey Dyasli <sergey.dyasli@citrix.com> Signed-off-by: Chao Gao <chao.gao@intel.com> Reviewed-by: Jan Beulich <jbeulich@suse.com>
Remus provides fault tolerance for virtual machines by sending continuous checkpoints to a backup, which will activate if the target VM fails. See the website at http://wiki.xen.org/wiki/Remus for details. Using Remus with libxl on Xen 4.5 and higher: To enable network buffering, you need libnl 3.2.8 or higher along with the development headers and command line utilities. If your distro does not have the appropriate libnl3 version, you can find the latest source tarball of libnl3 at http://www.carisma.slowglass.com/~tgr/libnl/ Disk replication: VMs protected by Remus need to use DRBD based disk backends. Specifically, you need a compile and install a custom version of DRBD, that is available publicly at https://github.com/rshriram/remus-drbd This code is based on DRBD 8.3.11 and uses a new replication protocol (named protocol D) for asynchronous disk checkpoint replication. A protected VM's DRBD disks on the primary and backup hosts need to be configured to use protocol D as the replication protocol. An example resource configuration file can be found in the aforementioned github repository.