Emre Can Sezer wrote:
> Hi,
>
> I'm trying to communicate some information from an HVM guest to Xen. 
> Passing a pointer to a buffer would suffice and the communication will be
> single sided. What is the best way to do this?
>
> I've looked into making a hypercall from an HVM guest and came across this
> post on this mailing list by Steve Ofsthun:
>
> http://lists.xensource.com/archives/html/xen-devel/2006-04/msg00526.html 
This code is quite old and much has changed since then. You should probably 
use the pv on hvm driver code as an example these days 
(xen/unmodified_drivers/linux-2.6/platform-pci).
What hypercalls are you trying to use? Note that HVM guests are restricted to 
a subset of the normal PV guest hypercalls.
Steve
>
> However, I'm unable to get this code to work. I'm running a 64-bit system
> with the linux-2.6.26 kernel downloaded from kernel.org on top of
> xen-3.2.2. When I compile, I get compilation errors resulting from
> hypercall.h. I believe this code is intended for 32 bit guests only as
> the structure definitions are different fot the pte_t type.
>
> The error was:
> In file included from include/asm/xen/hypervisor.h:53,
> from /home/ecsezer/kernels/vmcall/./features.c:11:
> include/asm/xen/hypercall.h: In function 'HYPERVISOR_update_va_mapping':
> include/asm/xen/hypercall.h:230: error: 'pte_t' has no member named 'pte_low'
>
> I tried to modify this code to get rid of compilation errors but a final
> warning still persists and loading the module causes a seg fault. The
> warning I get is:
> CC [M] /home/ecsezer/kernels/hyper/./hypercall.o
> {standard input}: Assembler messages:
> {standard input}:149: Warning: indirect call without `*'
>
> So I tried to compile with mercurial repository version linux-2.6.18-xen
> and that compiles fine. However, due to being a different version, I
> can't use the resulting module.
>
> I would appreciate any insight as to how to proceed. What could be the
> problem? Perhaps there is an easier way of passing the information I want
> without a full blown hypercall interface?
>
> Thanks,
>
> John
>
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