On Sat, Apr 15, 2023 at 01:44:13AM +0200, Thomas Gleixner wrote: > Background > ---------- > > The reason why people are interested in parallel bringup is to shorten > the (kexec) reboot time of cloud servers to reduce the downtime of the > VM tenants. There are obviously other interesting use cases for this > like VM startup time, embedded devices... ... > There are two issue there: > > a) The death by MCE broadcast problem > > Quite some (contemporary) x86 CPU generations are affected by > this: > > - MCE can be broadcasted to all CPUs and not only issued locally > to the CPU which triggered it. > > - Any CPU which has CR4.MCE == 0, even if it sits in a wait > for INIT/SIPI state, will cause an immediate shutdown of the > machine if a broadcasted MCE is delivered. When doing kexec, CR4.MCE should already have been set to 1 by the prior kernel, no?
