Re: [PATCH] tools/hvmloader: move shared_info to reserved memory area

[Konrad Rzeszutek Wilk <konrad@kernel.org>]

On Thu, Oct 25, 2012 at 01:46:45PM +0200, Olaf Hering wrote:
> On Thu, Oct 25, Keir Fraser wrote:
> 
> > To be honest, given that the XenPVHVM extensions to Linux won't have been
> > tested on such old hypervisors, it wouldn't be a bad thing to bail on
> > setting up the extensions when you detect running on a really old Xen
> > version (e.g., earlier than 3.4.0) anyway. There's a fair chance of doing
> > more harm than good?
> 
> I could stick such a check into
> arch/x86/xen/enlighten.c:x86_hyper_xen_hvm->detect, by rearranging the
> code of xen_hvm_platform and init_hvm_pv_info.  Konrad, what do you
> think about that? Recent changes indicate that you did some testing on
> 3.4 based hosts.

Sure. It might make sense to streamline this a bit. Meaning after the
version check, have an int (or function) called 'xen_old_hypervisor()'
which your code and the XenBus code could call?

That way on ARM that function can just become a nop while on X86 we
do the cpuids (or if those had already been done - we just return
true or false).