On Tue, Feb 15, 2022 at 2:08 PM David Hildenbrand <da...@redhat.com> wrote: > > On 15.02.22 09:12, Ani Sinha wrote: > > On Tue, Feb 15, 2022 at 1:25 PM David Hildenbrand <da...@redhat.com> wrote: > >> > >> On 15.02.22 08:00, Ani Sinha wrote: > >>> > >>> > >>> On Mon, 14 Feb 2022, David Hildenbrand wrote: > >>> > >>>> On 14.02.22 13:36, Igor Mammedov wrote: > >>>>> On Mon, 14 Feb 2022 10:54:22 +0530 (IST) > >>>>> Ani Sinha <a...@anisinha.ca> wrote: > >>>>> > >>>>>> Hi Igor: > >>>>>> > >>>>>> I failed to spawn a 9 Tib VM. The max I could do was a 2 TiB vm on my > >>>>>> system with the following commandline before either the system > >>>>>> destabilized or the OOM killed killed qemu > >>>>>> > >>>>>> -m 2T,maxmem=9T,slots=1 \ > >>>>>> -object > >>>>>> memory-backend-file,id=mem0,size=2T,mem-path=/data/temp/memfile,prealloc=off > >>>>>> \ > >>>>>> -machine memory-backend=mem0 \ > >>>>>> -chardev file,path=/tmp/debugcon2.txt,id=debugcon \ > >>>>>> -device isa-debugcon,iobase=0x402,chardev=debugcon \ > >>>>>> > >>>>>> I have attached the debugcon output from 2 TiB vm. > >>>>>> Is there any other commandline parameters or options I should try? > >>>>>> > >>>>>> thanks > >>>>>> ani > >>>>> > >>>>> $ truncate -s 9T 9tb_sparse_disk.img > >>>>> $ qemu-system-x86_64 -m 9T \ > >>>>> -object > >>>>> memory-backend-file,id=mem0,size=9T,mem-path=9tb_sparse_disk.img,prealloc=off,share=on > >>>>> \ > >>>>> -machine memory-backend=mem0 > >>>>> > >>>>> works for me till GRUB menu, with sufficient guest kernel > >>>>> persuasion (i.e. CLI limit ram size to something reasonable) you can > >>>>> boot linux > >>>>> guest on it and inspect SMBIOS tables comfortably. > >>>>> > >>>>> > >>>>> With KVM enabled it bails out with: > >>>>> qemu-system-x86_64: kvm_set_user_memory_region: > >>>>> KVM_SET_USER_MEMORY_REGION failed, slot=1, start=0x100000000, > >>>>> size=0x8ff40000000: Invalid argument > >>>>> > >>> > >>> I have seen this in my system but not always. Maybe I should have dug > >>> deeper as to why i do see this all the time. > >>> > >>>>> all of that on a host with 32G of RAM/no swap. > >>>>> > >>> > >>> My system in 16 Gib of main memory, no swap. > >>> > >>>> > >>>> #define KVM_MEM_MAX_NR_PAGES ((1UL << 31) - 1) > >>>> > >>>> ~8 TiB (7,999999) > >>> > >>> That's not 8 Tib, thats 2 GiB. But yes, 0x8ff40000000 is certainly greater > >>> than 2 Gib * 4K (assuming 4K size pages). > >> > >> "pages" don't carry the unit "GiB/TiB", so I was talking about the > >> actual size with 4k pages (your setup, I assume) > > > > yes I got that after reading your email again. > > The interesting question now is how is redhat QE running 9 TiB vm with kvm? > > As already indicated by me regarding s390x only having single large NUMA > nodes, x86 is usually using multiple NUMA nodes with such large memory. > And QE seems to be using virtual numa nodes: > > Each of the 32 virtual numa nodes receive a: > > -object memory-backend-ram,id=ram-node20,size=309237645312,host- > nodes=0-31,policy=bind > > which results in a dedicated KVM memslot (just like each DIMM would) > > > 32 * 309237645312 == 9 TiB :)
ah, I should have looked closely at the other commandlines before shooting off the email. Yes the limitation is per mem-slot and they have 32 slots one per node. ok so should we do kvm_set_max_memslot_size(KVM_SLOT_MAX_BYTES); from i386 kvm_arch_init()?
