I think using __initdata during init_hypervisor_platform() + allocating during x86_init.hyper.guest_late_init() is a good approach. My only concern, it would mean we need to init/uinit/init clock for boot cpu. Does it mean the clock continuity is preserved during the transition? I believe so, but needs to be verified. Pavel On Fri, Jul 6, 2018 at 6:53 AM Thomas Gleixner <tglx@xxxxxxxxxxxxx> wrote: > > On Fri, 6 Jul 2018, Thomas Gleixner wrote: > > On Fri, 6 Jul 2018, Paolo Bonzini wrote: > > > On 06/07/2018 11:45, Thomas Gleixner wrote: > > > >> One possibility is to introduce another layer of indirection: in > > > >> addition to the percpu pvclock data, add a percpu pointer to the pvclock > > > >> data and initialize it to point to a page-aligned variable in BSS. CPU0 > > > >> (used by vDSO) doesn't touch the pointer and keeps using the BSS > > > >> variable, APs instead redirect the pointer to the percpu data. > > > > Yeah, thought about that, but the extra indirection is ugly. Instead of > > > > using per cpu data, I just can allocate the memory _after_ the allocators > > > > are up and running and use a single page sized static __initdata for the > > > > early boot. > > > > > > Either works for me. Assembly-wise, the indirection should be more or > > > less the same as what we have now; even more efficient because it > > > accesses a percpu pointer instead of computing it based on > > > smp_processor_id(). > > > > Good point. Let me try that. > > Duh, that either requires a static key or a static PER_CPU pointer thingy, > which then wastes 8 bytes per cpu instead of 64 byte if unused. > > Thanks, > > tglx -- To unsubscribe from this list: send the line "unsubscribe linux-s390" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
