Re: Translate virtual address to physical address

[Wei Liu <wei.liu2@citrix.com>]

Please don't top-posting.

On Sun, 2012-01-01 at 14:59 +0000, lmingcsce wrote:
> Thanks for your reply.
> "Establishing a new array in the tools directory" means that I declare
> a new array in /tools/libxc/xc_domain_save.c and want to pass the
> physical address of this array to the hypervisor.
> I have already tried copy_to_user and copy_to_guest and from the
> experiment, I find that there is size limit for these two functions.

What size limit? I don't quite get it. I've never seen an array large
enough to bloat whole address space.

> By the way, I also want to ask the code organization of xen. What's
> the function of stubdom directory? 

stubdom is used to boost HVM performance. It is based on minios, with
qemu compiled in. It is not mandatory though.

> When the virtual machines execute, the function in tools will execute
> in the Dom0 space? Can you illustrate that for me or give me some
> specific material? I have already seen some explanation, and don't
> find the answer.
> Thanks.

Of course tools run in Dom0, they are just normal user programs.
However, every functionality requires hypervisor to do the actual job. A
normal work flow is like:

toolstack ---(syscall)--> kernel ---(hypercall)--> hypervisor

The kernel entry is /proc/xen/privcmd, whose source code is in Linux
tree drivers/xen/xenfs.



Wei.