On Thursday, March 09, 2017 02:37:55 PM Dan Williams wrote: > On Thu, Mar 9, 2017 at 2:22 PM, Rafael J. Wysocki <[email protected]> wrote: > > On Thursday, March 09, 2017 11:15:47 PM Rafael J. Wysocki wrote: > >> On Thursday, March 09, 2017 10:10:31 AM Dan Williams wrote: > >> > On Thu, Mar 9, 2017 at 5:39 AM, Rafael J. Wysocki <[email protected]> > >> > wrote: > [..] > >> > I *think* we're ok in this case because unplugging the CPU package > >> > that contains a persistent memory device will trigger > >> > devm_memremap_pages() to call arch_remove_memory(). Removing a pmem > >> > device can't fail. It may be held off while pages are pinned for DMA > >> > memory, but it will eventually complete. > >> > >> What about the offlining, though? Is it guaranteed that no memory from > >> those > >> ranges will go back online after the acpi_scan_try_to_offline() call in > >> acpi_scan_hot_remove()? > > > > My point is that after the acpi_evaluate_ej0() in acpi_scan_hot_remove() the > > hardware is physically gone, so if anything is still doing DMA to that > > memory at > > that point, then the user is going to be unhappy. > > Hmm, ACPI 6.1 does not have any text about what _EJ0 means for ACPI0012.
ACPI0012 is exceptional, but in general _EJ0 does not have to be present under a particular device for it to be affected. It can be under the device's parent, for example, in which case the entire subtree under a device with _EJ0 goes away in one go. And that very well may mean disconnect at the physical level (voltage goes away IOW). Thanks, Rafael
