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 > > all of that on a host with 32G of RAM/no swap. >
#define KVM_MEM_MAX_NR_PAGES ((1UL << 31) - 1) ~8 TiB (7,999999) In QEMU, we have static hwaddr kvm_max_slot_size = ~0; And only s390x sets kvm_set_max_memslot_size(KVM_SLOT_MAX_BYTES); with #define KVM_SLOT_MAX_BYTES (4UL * TiB) -- Thanks, David / dhildenb
