[Qemu-discuss] Backing Guest RAM by a file

[Binh Pham]

Hi folks,

I am working on a task that requires replicating the page table walk process in QEMU to a timing model, which is plugged in QEMU. In order to do so, I want to back guest RAM by a file on my host system, so that I can perform the walk off the mapped file. I am playing with mem-path option in QEMU, and here is what I did:

1. Create a file big enough to back the guest RAM:

dd if=guest.img bs=4k count=1000000 guest.img

2. Run qemu with mem-path
%>qemu-system-aarch64 -mem-path=/path/to/guest.img

I got this warning:

Warning: path not on HugeTLBFS: /prj/crdral/usr01/binhp/miramar/guest-ram/guest.img

qemu-system-aarch64: unable to create backing store for hugepages: Not a directory

I tried to search around, and it seems like mem-path was created to back guest RAM by huge pages on the host only, which is not what I want.

Does anyone know if my understanding is right? And if so, I would appreciate any kind of suggestions for me in doing this task.

Thanks,

-Binh