Re: [Xen-devel] [PATCH v4] xen PVonHVM: move shared_info to reserved memory area

Jan Beulich
2012-10-31T08:02:17Z

>>> On 30.10.12 at 18:03, Olaf Hering <olaf@aepfle.de> wrote:
> On Tue, Oct 30, Jan Beulich wrote:
>
>> And iirc you're doing this relocation because otherwise the newly
>> booting kernel image may get overwritten at an (from its
>> perspective) arbitrary location. What I'm trying to point out is
>> that the shared info structure is not the only thing (potentially)
>> inside the kernel image that might get overwritten - the relocated
>> (by the old kernel) vCPU info may as well. Plus I think the new
>> kernel has no way of relocating it a second time (including back
>> into the shared info structure) with how the hypervisor works at
>> present.
>
> Thanks, I have not looked at this, nor was I aware of it until now.
> I will see what needs to be done.
>
> Is this also an issue with the xenlinux based PVonHVM code?

No - this code doesn't make use of that feature (yet, we've got
a feature request that would involve doing so), as it only ever
touches vCPU 0's info.

Jan