On Wed, Oct 18, 2017 at 7:38 AM, Stephen Bates <sba...@raithlin.com> wrote: > Hi All > > I am hoping someone can help shed some light on an issue I am seeing with my > attempt to add p2pmem [1] to the ppc64el kernel. p2pmem is a (currently) > out-of-tree patchset that allows one to add device memory with struct page > backing into the Linux kernel. It leverages MEMORY_HOTPLUG and ZONE_DEVICE > which were added to ppc64 in 4.14 so I thought it would be fun to try it out. > > We constructed a patchset based off 4.14-rc1 [1] and build a kernel based off > the pseries defconfig and ran this on upstream qemu-system-ppc64. The exact > command to run QEMU was: > > qemu-system-ppc64 \ > -machine pseries \ > -cpu power8 \ > -smp 1 -m 2048 \ > -kernel ~/kernel/linux-ppc64el/vmlinux \ > -append "nvme.use_cmb=24 console=hvc root=/dev/sda rootwait rw" \ > -serial mon:stdio -drive > file=image-ppc64el.img,if=scsi,format=raw,index=0 \ > -nographic \ > -drive file=../images/nvme.qcow2,if=none,id=nvme1,snapshot=on \ > -device nvme,drive=nvme1,serial=nvme1 \ > -drive file=../images/nvme2.qcow2,if=none,id=nvme2,snapshot=on \ > -device nvme,drive=nvme2,serial=nvme2,cmb_size_mb=64 > > This resulted in the following extract from dmesg when registering the p2pmem > associated with one of the NVMe SSDs. > > [ 3.508497] nvme 0000:00:03.0: enabling device (0100 -> 0102) > [ 3.510743] nvme 0000:00:03.0: Using 64-bit direct DMA at offset > 800000000000000 > [ 3.535706] p2pmem p2pmem0: registered > [ 3.537780] lpar: Attempting to resize HPT to shift 21 > [ 3.539251] Unable to resize hash page table to target order 21: -1
I am guessing that the hotplug of ZONE_DEVICE memory was done incorrectly as it lead to HPT resizing (the system thinking this is normal memory). Ideally one would expect that the driver would online ZONE_DEVICE memory and not go through the HOTPLUG path. Are you using devm_memremap_pages() path to add these pages? Balbir Singh.
