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? https://bugzilla-attachments.redhat.com/attachment.cgi?id=1795945
