On Wed, Aug 13, 2008 at 01:19:42PM +0900, Jun Koi wrote: It'd be really good to have a driver for this for libvirt. QEMU does virtual->physical translation for us, through the guest's CR3 & page tables. [This discussion will concentrate on x86 for the moment :-)] If you look at the qemu source, file target-i386/ helper2.c, function cpu_get_phys_page_debug, you will see the code they use to navigate through the 3 or 4 levels of page tables for i386 & x86-64 respectively. The QEMU memsave command made it almost trivial to write virDomainMemoryPeek (...VIR_MEMORY_VIRTUAL...); On Xen things are a bit different. You can map in physical pages from another guest using the libxc call xc_map_foreign_range. Note that you cannot just call xc_map_foreign_range because the libxc & libvirt licenses are _not_ compatible. So instead you'd need to do the underlying sequence of mmap / ioctl / munmap. (See tools/libxc/ xc_linux.c in the Xen source). But you still need to do virtual to physical page translation, either using the qemu source as an example, or using xc_translate_foreign_address as a guide (or just using the Intel Programmers Reference Manual and doing it from first principles). Another alternative is to implement virDomainMemoryPeek (...VIR_MEMORY_PHYSICAL...). It is not possible to implement this for QEMU at all, at least not without changing QEMU. Implementing this for Xen would be much easier because you don't need to do address translation, but it does push the problem of address translation up to the callers. Places to look in the QEMU source for inspiration: monitor.c:do_memory_save target-i386/helper2.c:cpu_get_phys_page_debug Other places to look in the Xen source for inspiration: tools/libxc/xc_linux.c tools/libxc/xc_pagetab.c tools/xentrace/xenctx.c (thanks Mark McLoughlin) Rich. -- Richard Jones, Emerging Technologies, Red Hat http://et.redhat.com/~rjones virt-top is 'top' for virtual machines. Tiny program with many powerful monitoring features, net stats, disk stats, logging, etc. http://et.redhat.com/~rjones/virt-top