James Morse <james.morse@xxxxxxx> writes: > Hello! > > arm64 recently queued support for memory hotremove, which led to some > new corner cases for kexec. > > If the kexec segments are loaded for a removable region, that region may > be removed before kexec actually occurs. This causes the first kernel to > lockup when applying the relocations. (I've triggered this on x86 too). > > The first patch adds a memory notifier for kexec so that it can refuse > to allow in-use regions to be taken offline. > > > This doesn't solve the problem for arm64, where the new kernel must > initially rely on the data structures from the first boot to describe > memory. These don't describe hotpluggable memory. > If kexec places the kernel in one of these regions, it must also provide > a DT that describes the region in which the kernel was mapped as memory. > (and somehow ensure its always present in the future...) > > To prevent this from happening accidentally with unaware user-space, > patches two and three allow arm64 to give these regions a different > name. > > This is a change in behaviour for arm64 as memory hotadd and hotremove > were added separately. > > > I haven't tried kdump. > Unaware kdump from user-space probably won't describe the hotplug > regions if the name is different, which saves us from problems if > the memory is no longer present at kdump time, but means the vmcore > is incomplete. > > > These patches are based on arm64's for-next/core branch, but can all > be merged independently. So I just looked through these quickly and I think there are real problems here we can fix, and that are worth fixing. However I am not thrilled with the fixes you propose. Eric
