On Wed, 2022-06-29 at 10:48 +0200, Igor Mammedov wrote: > > Hi Rafael, Igor, > > > > On my test machine, the acpi_memory_device_add() is not called for system > > memory. It probably because my machine doesn't have memory device in ACPI. > > > > I don't know whether we can have any memory device in ACPI if such memory is > > present during boot? Any comments here? > > I don't see anything in ACPI spec that forbids memory device being present at > boot. > Such memory may also be present in E820, but in QEMU is not done as linux used > to > online all E820 memory as normal which breaks hotplug. And I don't know if it > still true. > > Also NVDIMMs also use memory device, so they may be affected by this patch as > well. AFAICT NVDIMM uses different device ID so won't be impacted. But right there's no specification around "whether firmware will create ACPI memory device for boot-time present memory", so I guess we need to treat it is possible. So I agree having the check at the beginning of acpi_memory_device_add() looks incorrect. Also as Christoph commented I'll give up introducing new CC attribute. > > > > > And CC_ATTR_ACPI_MEMORY_HOTPLUG_DISABLED is only true on TDX bare-metal > > system, > > but cannot be true in Qemu guest. But yes if this flag ever becomes true in > > that's temporary, once TDX support lands in KVM/QEMU, this patch will silently > break usecase. I don't think so. KVM/Qemu won't expose TDX to guest, so this code won't be true in guest. -- Thanks, -Kai
