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Julien Grall
abb234b5ac
Per the Arm ARM (D4.5 in ARM DDI 0487E.a), SError may be precise or imprecise. Imprecise means the state presented to the exception handler is not guaranteed to be consistent with any point in the excution stream from which the exception was taken. In other words, they are likely to be fatal as you can't return safely from them. Without the RAS extension, the Arm architecture does not provide a way to differentiate between imprecise and precise SError. Furthermore Xen has no support for RAS yet. So from a software POV, there is not much we can do. More generally, forwarding blindly SErrors to the guest is likely to be the wrong thing to do. Indeed, Xen is not able to know what is the content of the SError. This may be a critical device used by the hypervisor that is about to fail. In a nutshell, the option serrors=forward is not safe to use in any environment with the current state of Xen. Therefore the option and any code related to it are completely removed. Take the opportunity to rework the comment in do_trap_data_abort() as all SErrors/External Abort generated by the hypervisor will result in a crash of the system no matter what the user passed on the command line. Signed-off-by: Julien Grall <julien.grall@arm.com> Reviewed-by: Stefano Stabellini <sstabellini@kernel.org> Release-acked-by: Juergen Gross <jgross@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.