[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [Xen-devel] [XEN-devel] arm64: fix incorrect pa_range_info table to support 42 bit PA systems.


On 15/05/17 18:11, Feng Kan wrote:
On Mon, May 15, 2017 at 7:53 AM, Julien Grall <julien.grall@xxxxxxx> wrote:
Hello Feng,

On 13/05/17 01:26, Feng Kan wrote:

The pa_range_info table contain incorrect root_order and t0sz which
prevent 42 bit PA systems from booting dom0.

As I mentioned in the previous thread [1], this is not a bug. What you
configure below is the stage-2 page table and not the hypervisor page-table.

It is perfectly fine to expose less IPA (Intermediate Physical Address) bits
than the number of PA (Physical Address) bits as long as all the address
wired are below 40 bits (assumption made by the patch who added this code).
Does your hardware have devices/RAM above 40 bits?
Yes,  the APM X-Gene series have all been 42 bit PA systems.
Particularly X-Gene 3, which
has its PCIe0 all the way up starting at 41 bit.

Thank you for the information.

If so, then you need to
mention in the commit message.
I will be more clear in the commit message.

This bring another question, now you will allocate 8 pages by default for
both DOM0 and guests. Exposing 42 bits IPA to a guest does not sound
necessary, so we would waste memory here. How are you going to address that?
To be honest, I hadn't thought of that. I had assume system such as
these would have
plenty of memory. I will take a look regarding this. If you have any
suggestions that would
be greatly appreciated

I am not totally against using 8 pages. Although a TODO will be useful in the code and the commit message.


Julien Grall

Xen-devel mailing list



Lists.xenproject.org is hosted with RackSpace, monitoring our
servers 24x7x365 and backed by RackSpace's Fanatical Support®.